Die Autoren danken der Deutschen Forschungsgemeinschaft, Bayer Pharma AG, Chemtura Organometallics GmbH Bergkamen, Bayer Services GmbH, BASF AG, und Sasol GmbH für die finanzielle Unterstützung.

1. Herstellung von Titan (IV)-tert-Lösung -butoxide/Triethylchlorosilane <ol><li> Man löst 400 mg (400 ul), Titan (IV)-tert-butylat (1 mmol) in 10 ml trockenem Dichlormethan. In 150 mg (170 ul) Triethylchlorsilan (1 mmol) zu dieser Lösung bei RT. 1 ml des Dichlormethan-Lösung 0,1 mmol Titan (IV)-tert-butoxid und 0,1 mmol Triethylchlorsilan. </li></ol> 2. Pinakol-Reaktion von Tetraphenyl-1 ,2-Ethandiol (1) mit 2-Ethylbutyraldehyd <ol><li> Löse 366 mg Tetraphenyl-1 ,2-Ethandiol (1, 1 mmol) und 300 mg (370 &amp;mgr; l) frisch destilliertes 2-Ethylbutyraldehyd (3 mmol) in 3 ml trockenem Dichlormethan. </li><li> 0,5 ml der separat hergestellten Titan (IV)-tert -butoxide/triethylchlorosilane Lösung (0,05 mmol). </li><li> Die resultierende Mischung wurde bei RT in einem verschlossenen Reaktionsröhrchen. </li><li> Konfiauf Kieselgel-DC-Platten (60 F254): - (9/1 Hexan / Aceton-Elutionsmittel) rm die Reaktion durch Dünnschichtchromatographie abgeschlossen. Das Ende der Reaktion zu dem Zeitpunkt, Tetraphenyl-1 ,2-Ethandiol-1 nicht mehr festgestellt werden (~ 12 h) erreicht. Der Rf-Wert des Produkts ist 0,3 14. </li><li> Verdünnt das erhaltene Reaktionsgemisch mit 50 ml Dichlormethan. </li><li> Nacheinander Waschen des verdünnten Reaktionsgemisch mit 20 ml gesättigter wässriger Ammoniumchlorid-und Natriumhydrogencarbonat-Lösung in einen Scheidetrichter. </li><li> Isolieren Sie die organische Schicht durch einen Scheidetrichter. </li><li> Die organische Schicht wird durch Rühren über trockenem Magnesiumsulfat. </li><li> Filtrat der Suspension durch einen Faltenpapierfilter und sammeln die Filtrate. </li><li> Entfernen Dichlormethan aus dem Filtrat im Vakuum bei 40 ° C unter Verwendung eines Rotationsverdampfers (10-30 mmHg). Abdampfen der Lösungsmittel werden 20 min erforderlich. </li><li> Reinige den verbleibenden Restdurch Flash-Säulenchromatographie mit einer Säule aus Kieselgel (0,035-0,070 mm, ACROS) mit einem Gradienten von Hexan / Aceton (19:1 ab und gehen bis 16,4) und 280 mg 1,2-diol 2f erwerben (0,99 mmol). </li><li> Bestätigen der Identität des 1,2-Diol 2f durch 1 H-Kernresonanzspektroskopie (NMR) unter Verwendung von CDCl 3 als Lösungsmittel. Für einen 300-MHz-NMR-Spektrometer, das 1 H-NMR-Spektrum des Diols wie folgt: δ = 0,78 (t, 3H, J = 7,4 Hz), 0,87 (t, 3H, J = 7,3 Hz), 1,18-1,40 (m , 4H), 1,75-1,81 (m, 1H), 1,91 (s, 1H, OH), 3.12 (s, 1H, OH), 4,68 (d, 1H, J = 1,2 Hz), 7,19-7,37 (m, 6H ), 7,44-7,46 (m, 2H), 7,61 bis 7,63 (m, 2H). </li></ol> 3. Pinakol-Reaktion von Tetraphenyl-1 ,2-Ethandiol (1) mit Diethylketon <ol><li> Löse 366 mg Tetraphenyl-1 ,2-Ethandiol (1, 1 mmol) und 345 mg (423 ul), Diethylketon (4 mmol) in 3ml trockenem Dichlormethan. </li><li> 1 ml der getrennt hergestellten Titan (IV)-tert -butoxide/triethylchloro-silane Lösung (0,1 mmol). </li><li> Die resultierende Mischung wurde bei RT in einem verschlossenen Reaktionsröhrchen. </li><li> Bestätigen Sie die Reaktion vollständig durch Dünnschicht-Chromatographie (Laufmittel: Hexan / Aceton, 9:1) auf Kieselgel-DC-Platten (60 F254). Das Ende der Reaktion zu dem Zeitpunkt erreicht wird, wenn Tetraphenyl-1 ,2-Ethandiol 1 nicht erkannt werden kann (~ 12 h). Der Rf des Produkts 0,3 14. </li><li> Verdünnt das erhaltene Reaktionsgemisch mit 50 ml Dichlormethan. </li><li> Nacheinander Waschen des verdünnten Reaktionsgemisch mit 20 ml gesättigter wässriger Ammoniumchlorid-und Natriumcarbonat-Lösung in einen Scheidetrichter. </li><li> Isolieren Sie die organische Schicht durch einen Scheidetrichter. </li><li> Die organische Schicht wird durch Rühren über trockenem Magnesiumsulfat. </li><li> Filtrat der Suspension durch einen Faltenfilter Papierter und sammeln die Filtrate. </li><li> Entfernen Dichlormethan im Vakuum bei 40 ° C unter Verwendung eines Rotationsverdampfers (10-30 mmHg). Verdunsten von flüchtigen Bestandteilen wird 30 min benötigen. </li><li> Reinige den verbleibenden Rückstand durch Flash-Chromatographie über eine Kolonne mit Kieselgel (0,035-0,070 mm, ACROS) mit einem Gradienten von Hexan / Aceton (19:1 ab und gehen bis 16,4), um 250 mg von 1 zu erwerben, 2-diol 4f (0.93 mmol). </li><li> Bestätigen die Identität des Produkts durch 1 H-Kernresonanzspektroskopie (NMR) unter Verwendung von CDCl 3 als Lösungsmittel. Für einen 300-MHz-NMR-Spektrometer, das 1 H-NMR-Spektrum des Diols 4f wie folgt: δ = 0,92 (t, 6H, J = 7,6 Hz), 1,78 (m, 4H), 2,03 (s, 1H, OH), 2,83 (s, 1H, OH), 7,26-7,35 (m, 6H), 7,69-7,71 (m, 4H). </li></ol>

<ol>
	<li>Hirao, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catalytic+reductive+coupling+of+carbonyl+compounds+-+The+pinacol+coupling+reaction+and.">Catalytic reductive coupling of carbonyl compounds - The pinacol coupling reaction and.</a> 279, 53-75 (2007).</li><li>Chatterjee, A., Joshi, N. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+the+stereoselective+pinacol+coupling+reaction.">Evolution of the stereoselective pinacol coupling reaction.</a> Tetrahedron. 62, 12137-12158 (2006).</li><li>Ladipo, F. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-valent+titanium-mediated+reductive+coupling+of+carbonyl+compounds.">Low-valent titanium-mediated reductive coupling of carbonyl compounds.</a> Curr. Org. Chem. 10, 965-980 (2006).</li><li>Gans&#228;uer, A., Bluhm, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reagent-controlled+transition-metal-catalyzed+radical+reactions.">Reagent-controlled transition-metal-catalyzed radical reactions.</a> Chem. Rev. 100, 2771-2788 (2000).</li><li>Duan, X. -. F., Feng, J. X., Zi, G. -. F., Zhang, Z. -. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Convenient+synthesis+of+unsymmetrical+pinacols+by+coupling+of+structurally+similar+aromatic+aldehydes+mediated+by+low-valent+titanium.">A Convenient synthesis of unsymmetrical pinacols by coupling of structurally similar aromatic aldehydes mediated by low-valent titanium.</a> Synthesis. , 277-282 (2009).</li><li>Paquette, L. A., Lai, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pinacol+macrocyclization-based+route+to+the+polyfused+medium-sized+CDE+ring+system+of+lancifodilactone.">Pinacol macrocyclization-based route to the polyfused medium-sized CDE ring system of lancifodilactone.</a> G. Org. Lett. 10, 3781-3784 (2008).</li><li>Maekawa, H., Yamamoto, Y., Shimada, H., Yonemura, K., Nishiguchi, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mg-+promoted+mixed+pinacol+coupling.">Mg- promoted mixed pinacol coupling.</a> Tetrahedron Lett. 45, 3869-3872 (2004).</li><li>Kang, M., Park, J., Pedersen, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pinacol+cross+coupling+reactions+of+ethyl+2-alkyl-2-formylpropionates.+stereoselective+synthesis+of+2,2,4-+trialkyl-3-hydroxy-&#947;-butyrolactones.">Pinacol cross coupling reactions of ethyl 2-alkyl-2-formylpropionates. stereoselective synthesis of 2,2,4- trialkyl-3-hydroxy-&#947;-butyrolactones.</a> Syn. Lett. , 41-43 (1997).</li><li>Askham, F. R., Carroll, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anionic+zirconaoxiranes+as+nucleophilic+aldehyde+equivalents.+application+to+intermolecular+pinacol+cross+coupling.">Anionic zirconaoxiranes as nucleophilic aldehyde equivalents. application to intermolecular pinacol cross coupling.</a> J. Org. Chem. 58, 7328-7329 (1993).</li><li>Hou, Z., Takamine, K., Aoki, O., Shiraishi, H., Fujiwara, Y., Taniguchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nucleophilic+Addition+of+lanthanoid+metal+umpoled+diaryl+ketones+to+electrophiles.">Nucleophilic Addition of lanthanoid metal umpoled diaryl ketones to electrophiles.</a> J. Org. Chem. 53, 6077-6084 (1988).</li><li>Groth, U., Jung, M., Vogel, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intramolecular+chromium(II)-catalyzed+pinacol+cross+coupling+of+2-Mmethylene-&#945;,&#969;-dicarbonyls.">Intramolecular chromium(II)-catalyzed pinacol cross coupling of 2-Mmethylene-&#945;,&#969;-dicarbonyls.</a> Syn. Lett. , 1054-1058 (2004).</li><li>Appendino, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+Modified+Ingenol+Esters.">Synthesis of Modified Ingenol Esters.</a> Eur. J. Org. Chem. , 3413-3420 (1999).</li><li>Spaccini, R., Pastori, N., Clerici, A., Punta, C., Porta, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Key+role+of+Ti(IV)+in+the+selective+radical-radical+cross-coupling+mediated+by+the+Ingold-Fischer+effect.">Key role of Ti(IV) in the selective radical-radical cross-coupling mediated by the Ingold-Fischer effect.</a> J. Am. Chem. Soc. 130, 18018-18024 (2008).</li><li>Leonard, J., Lyfo, B., Procter, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Advanced Practical Organic Chemistry. , (2013).</li><li>Scheffler, U., Stoesser, R., Mahrwald, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retropinacol+/+cross-pinacol+coupling+reactions+-+a+catalytic+access+to+1,2-unsymmetrical+diols.">Retropinacol / cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols.</a> Adv. Synth. Cat. 354, 2648-2652 (2012).</li></ol>

Die Autoren erklären, keine finanziellen Interessen konkurrieren.

Eine allgemeine Abnahme der Reaktionszeiten und höhere Erträge durch Einsatz von elektronenreichen Carbonylverbindungen (vgl. Nr. 3 mit 17, Tabelle 1 oder Eintrag 19 mit 13, Tabelle 2). Zusätzlich wird in Reaktionen von Ketonen mit sperrigen Substituenten eine Abnahme der Ausbeuten unter vergleichbaren Bedingungen beobachtet (vergleiche Nr. 12 mit 11, Tabelle 2). Obwohl eine Vielzahl von Carbonylverbindungen k?...

Die Pinakol-Kupplung ist eine allgemeine und häufig verwendete Methode zur Herstellung von vicinalen Diolen symmetrisch (1,2-Diolen, Pinakolen). Für eine umfassende Bewertungen in diesem Bereich siehe Referenzen Hirao 1, Chatterjee und Joshi 2, Ladipo 3 und 4 Gansäuer und Bluhm. Im Gegensatz dazu wurden nur wenige Berichte veröffentlicht, um eine effiziente Realisierung von Cross-Pinakolkupplung Reaktionen beziehen sich auf die entsprechenden unsymmetrischen 1,2-Diole (Titan (IV)-chlorid / Mangan-5, Samarium (II)-Iodid-6-, Magnesium-Ausbeute / Trimethylchlorsilan 7, Vanadium (II) 8, Zirkonium / Zinn-9 und Ytterbium 10). So bleibt immer noch die intermolekulare Quer Pinakolkupplung Reaktion eine große Herausforderung in der organischen Chemie, insbesondere die katalytische Ausführung dieser Transformation. Die Bildung von Querkoppelprodukte ist kinetisch benachteiligtunter den Bedingungen einer klassischen Pinakolkupplung. Um ausreichende Mengen der unsymmetrischen Produkt zu erhalten verzögerten Zugabe einer Carbonylverbindung ist möglich. Es gibt einige Beispiele, die das Konzept entwickelt werden, sie werden jedoch auf verschiedene spezifische experimentelle Manipulationen auf und können daher nicht verallgemeinert werden. Darüber hinaus ist die erforderliche Überschuß einer Carbonylverbindung in dieser Transformationen zu einer mühsamen Trennung eines komplexen Produktgemisches 11. Eine Alternative hierzu ist durch die Präkomplexierung eines Reaktanten Rendering äquimolaren Mengen eines zusätzlichen Reagenzes erforderlich dargestellt. Verschiedene Beispiele einer reversiblen Pinakolreaktion beschrieben worden 12. Diese führen zu der Überlegung, dass solche Bedingungen könnte ein optimaler Ausgangspunkt für die selektive Synthese von Kreuzkupplungsprodukte sein. Da ein niedervalentes Metall sowie eine reaktive Radikalspezies gleichzeitig in situ gebildetKönnte unsymmetrischen Diole ausschließlich in der Gegenwart eines geeigneten Carbonylreaktant gebildet werden. Zu bestem Wissen solches Verfahren wurde nicht berichtet vor (Porta et al. Beschrieben eine vergleichbare Pinakol-Spaltung und anschließende Kupplung mit dem zusätzlichen Einsatz stöchiometrischer Mengen von AIBN (2,2 &#39;-Azo-bis-isobutyronitril) zu erzeugen, die erforderlichen Radikale) 13. Hier ein Protokoll visualisiert, die eine schnelle und operativ einfachen Zugang zu unsymmetrischen 1,2-Diole bietet. Die unsymmetrischen Pinakol-Produkte sind meist zugänglich in hervorragenden Ausbeuten (&gt; 95%). Unerwünschte symmetrisch Pinakol-Produkte werden nicht beobachtet. Diese neue Quer pinacol Methodik beruht auf einem retropinacol / Quer Pinakolkupplung Sequenz. Es wird im folgenden durch repräsentative Reaktionen Benzpinakol (1,1,2,2-Tetraphenyl-1 ,2-Ethandiol, 1), 2-Ethylbutyraldehyd (im Aldehyd-Serie) und w gezeigt werdenith Diethylketon (in dem Keton-Reihe).

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">1.2-Dichloromethane</td>
			<td style="width:179px;">Sigma-Aldrich</td>
			<td style="width:137px;">319929</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Titanium(IV)tert-butoxide</td>
			<td>VWR International</td>
			<td>200014-852</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-Ethylbutyraldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>110094</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzopinacol</td>
			<td>Aldrich</td>
			<td>B9807</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triethylchlorosilane</td>
			<td>Aldrich</td>
			<td>&#160;235067</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hexane, certified ACS</td>
			<td>Fisher scientific</td>
			<td>H29220</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">acetone, certified ACS</td>
			<td>ACROS</td>
			<td>42324</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium chloride</td>
			<td>ACROS</td>
			<td>19997</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium hydrogen carbonate</td>
			<td>ACROS</td>
			<td>12336</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium sulphate</td>
			<td>ACROS</td>
			<td>41348</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">silica gel 60 F254 TLC plates</td>
			<td>VWR International</td>
			<td>1,057,140,001</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;silica gel, 0.035-0.070 for flash-chromatography</td>
			<td>ACROS</td>
			<td>240360300</td>
			<td style="width:79px;"></td>
		</tr>
	</tbody>
</table>

retropinacol/cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols

Unsymmetrische 1,2-Diole sind durch reduktive Pinakolkupplung Prozesse kaum zugänglich. Eine erfolgreiche Durchführung einer solchen Transformation zu einer klaren Anerkennung und strikte Unterscheidung von zwei ähnlichen Carbonylverbindungen (Aldehyde → sekundäre 1,2-Diole oder Ketonen → tertiären 1,2-Diole) gebunden. Diese Feinabstimmung ist immer noch eine Herausforderung und ein ungelöstes Problem für einen organischen Chemiker. Es gibt mehrere Berichte über die erfolgreiche Ausführung dieser Transformation aber nicht verallgemeinert werden kann. Hier beschreiben wir eine katalytische Direkt Pinakolkupplung Prozess, der über einen retropinacol / Quer Pinakolkupplung Ablauf erfolgt. Somit kann unsymmetrisch substituierten 1,2-Diolen mit fast quantitativen Ausbeuten durch eine technisch einfache Leistung unter sehr milden Bedingungen zugänglich. Kunsttechniken wie Spritzen-Pumptechniken oder verzögerte Zugaben von Reaktanten sind nicht erforderlich. Das Verfahren beschreiben wir eine sehr schnellen Zugriff aufQuer Pinakol Produkte (1,2-Diolen, vicinalen Diolen). Eine weitere Erweiterung dieses neuen Verfahrens, z. B. einer enantioselektiven Leistung könnte ein sehr nützliches Werkzeug für die Synthese von unsymmetrischen chiralen 1,2-Diolen bereitzustellen.

Bei Umsetzungen von Tetraphenyl-1 ,2-Ethandiol 1 und Aceton in Gegenwart von katalytischen Mengen von Titan (IV)-alkoxide wir ,2-diol 4a beobachtet die Bildung von 1,1-Diphenyl-1 und zur gleichen Zeit die Bildung Benzophenon 3 (Schema 1). Die entsprechenden symmetrischen 1,2-Diol durch einen kompetitiven Pinakolkupplung Aceton gebildet wurde nicht nachgewiesen. Jedoch wurden quantitative Umsätze zu erzielen extrem langen Reaktionszeiten und inakzeptabel unter diesen Be...

Watch this Scientific Journal Video about Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols at JoVE.com

Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

Eine neue Konto für die Synthese von unsymmetrischen 1,2-Diole auf Basis eines retropinacol / Quer Pinakolkupplung Mechanismus beschrieben. Aufgrund der katalytischen Durchführung dieser Reaktion eine erhebliche Verbesserung im Vergleich zu herkömmlichen Quer Pinakol Kupplungen erreicht wird.

Retropinacol / Quer Pinakol-Kupplungen - Ein katalytischer Zugang zu 1,2-Diole unsymmetrische

Unsymmetrical 1,2-diols are hardly accessible by reductive pinacol coupling processes. A successful execution of such a transformation is bound to a clear ...

retropinacolcross-pinacol-coupling-reactions-catalytic-access-to-12

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12.9K Aufrufe.  Humboldt University of Berlin.  Eine neue Konto für die Synthese von unsymmetrischen 1,2-Diole auf Basis eines retropinacol / Quer Pinakolkupplung Mechanismus beschrieben. Aufgrund der katalytischen Durchführung dieser Reaktion eine erhebliche Verbesserung im Vergleich zu herkömmlichen Quer Pinakol Kupplungen erreicht wird. 

Serie: Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

Mizoroki-Heck-Kreuzkupplungsreaktionen von Dichloro {bis [1,1 &#39;, 1&#39;&#39; - (phosphinetriyl) tripiperidine]} katalysierte Palladium unter milden Reaktionsbedingungen

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

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Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as an intrinsic probe to characterize virtually every chemical process. Nowadays, this technique is extensively applied to determine thermodynamic parameters of biomolecular binding equilibria. In addition, ITC has been demonstrated to be able of directly measuring kinetics and thermodynamic parameters (kcat, KM, &#916;H) of enzymatic reactions, even though this application is still underexploited. As heat changes spontaneously occur during enzymatic catalysis, ITC does not require any modification or labeling of the system under analysis and can be performed in solution. Moreover, the method needs little amount of material. These properties make ITC an invaluable, powerful and unique tool to study enzyme kinetics in several applications, such as, for example, drug discovery.
In this work an experimental ITC-based method to quantify kinetics and thermodynamics of enzymatic reactions is thoroughly described. This method is applied to determine kcat and KM of the enzymatic hydrolysis of urea by Canavalia ensiformis (jack bean) urease. Calculation of intrinsic molar enthalpy (&#916;Hint) of the reaction is performed. The values thus obtained are consistent with previous data reported in literature, demonstrating the reliability of the methodology.

Isothermal titration calorimetry measures heat flow released or absorbed in chemical reactions. This method can be used to quantify enzyme-catalysis. In this paper, the protocol for instrumental setup, experiment running, and data analysis is generally described, and applied to the characterization of enzymatic urea hydrolysis by jack bean urease.

Hot Biologische Katalyse: Isotherme Titrationskalorimetrie zu Enzymreaktionen Charakterisieren

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as ...

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Amid-Kupplung für die Synthese von Bispyridin basierten Liganden und ihre Komplexierung Platinum als zweikernige Antikrebsmittel

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

Echtzeit-Überwachung von Reaktionen durchgeführt mit Continuous-Flow-Verarbeitung: Die Herstellung von 3-Acetylcoumarin als Beispiel

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form catalytically active N-Heterocyclic Carbenes (NHCs). Here we have used ILs as precatalysts in the addition of &#945;,&#946;-unsaturated aldehydes to chalcones to form 1,6-ketoesters, incorporating an anti-diphenyl moiety in a highly stereoselective fashion. The reaction has a broad substrate scope and several functional groups and heteroaromatics can be integrated into the ketoester backbone in generally good yields with maintained stereoselectivity. The reaction protocol is robust and scalable. The starting materials are inexpensive and the products can be obtained after simple filtration, avoiding solvent-demanding chromatography. Furthermore, the IL can be recycled up to 5 times without any loss of reactivity. Moreover, the 1,6-ketoester end product is a potent gelator in several hydrocarbon based solvents. The method enables rapid access to and evaluation of a new class of low molecular weight gelators (LMWGs) from recyclable and inexpensive starting materials.

Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents.

Hochstereoselektive Synthese von 1,6-Ketoester durch Ionische Flüssigkeiten vermittelte: Ein Dreikomponentenreaktion zur raschen Zugang zu einer neuen Klasse von niedermolekularen Gelbildner

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form ...

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

Eine einfache, kostengünstige und robuste System das Volumen an Wasserstoff durch chemische Reaktionen mit wässrigen Lösungen Evolved messen

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

Laboratory Production of Biofuels and Biochemicals from a Rapeseed Oil through Catalytic Cracking Conversion

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil (HGO) for production of transportation fuels through a fluid catalytic cracking (FCC) route. Cracking experiments are performed with a fully automated reaction unit at a fixed weight hourly space velocity (WHSV) of 8 hr-1, 490-530 &#176;C, and catalyst/oil ratios of 4-12 g/g. When a feed is in contact with catalyst in the fluid-bed reactor, cracking takes place generating gaseous, liquid, and solid products. The vapor produced is condensed and collected in a liquid receiver at -15 &#176;C. The non-condensable effluent is first directed to a vessel and is sent, after homogenization, to an on-line gas chromatograph (GC) for refinery gas analysis. The coke deposited on the catalyst is determined in situ by burning the spent catalyst in air at high temperatures. Levels of CO2 are measured quantitatively via an infrared (IR) cell, and are converted to coke yield. Liquid samples in the receivers are analyzed by GC for simulated distillation to determine the amounts in different boiling ranges, i.e., IBP-221 &#176;C (gasoline), 221-343 &#176;C (light cycle oil), and 343 &#176;C+ (heavy cycle oil). Cracking of a feed containing canola oil generates water, which appears at the bottom of a liquid receiver and on its inner wall. Recovery of water on the wall is achieved through washing with methanol followed by Karl Fischer titration for water content. Basic results reported include conversion (the portion of the feed converted to gas and liquid product with a boiling point below 221 &#176;C, coke, and water, if present) and yields of dry gas (H2-C2's, CO, and CO2), liquefied petroleum gas (C3-C4), gasoline, light cycle oil, heavy cycle oil, coke, and water, if present.

This paper presents an experimental method to produce biofuels and biochemicals from canola oil mixed with a fossil-based feed in the presence of a catalyst at mild temperatures. Gaseous, liquid, and solid products from a reaction unit are quantified and characterized. Conversion and individual product yields are calculated and reported.

Labor Produktion von Biokraftstoffen und Biochemikalien aus Rapsöl durch Catalytic Cracking-Umwandlung

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil ...

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

We describe the catalytic insertion polymerization of 5-norbornene-2-carboxylic acid and 5-vinyl-2-norbornene to form functional polymers with a very high glass transition temperature.

Ein einfaches und effizientes Protokoll für die katalytische Insertion Polymerisation von Functional Norbornene

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Ein Protokoll für sichere Lithiierungen Mit Organolithiumreagentien

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Palladium<em&gt; N.</em&gt; -Heterocyclische Carbenkomplexe: Synthese aus Benzimidazoliumsalzen und katalytische Aktivität bei Kohlenstoff-Kohlenstoff-Bindungs-bildenden Reaktionen

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...

Retropinacol / Quer Pinakol-Kupplungen - Ein katalytischer Zugang zu 1,2-Diole unsymmetrische

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