Name: controlled photoredox ring-opening polymerization of o-carboxyanhydrides mediated by ni/zn complexes
Uploaded: 2017-11-21T15:00:00.000+00:00
Duration: 5 min 48 s
Description: Watch this Scientific Journal Video about Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes at JoVE.com

Bu eser Virginia Politeknik Enstitüsü ve Eyalet Üniversitesi açılış fon tarafından desteklenmiştir. Q.F. destek Ulusal Doğa Bilimleri Vakfı Çin (21504047), Jiangsu Province, Doğa Bilimleri Vakfı (BK20150834), Nanjing Üniversitesi Mesajını ve telekomünikasyon bilimsel Vakfı NUPTSF (NY214179) kabul eder.

Dikkat: Tüm malzeme güvenlik bilgi formları (MSDS) kullanmadan önce lütfen danışın. Sentezinde kullanılan birçok akut toksik ve kanserojen kimyasallardır. Lütfen tüm uygun güvenlik uygulamaları (duman hood ve torpido) mühendislik kontrolleri ve kişisel koruyucu ekipman (koruyucu gözlük, eldiven, önlük, tam uzunlukta pantolon, kapalı-toe ayakkabı, mavi ışık kullanımı dahil tepki yerine getirirken kullanın Emanet engelleme gözlükler). Aşağıdaki yordamlar bir eldiven kutusunda Standart serbest yayını işleme teknikleri içerir. Tüm çözümler pipet kullanarak transfer edilir.
1. hazırlanması katalizör ve başlatıcı
Not: Tüm süreç ile soğuk bir tuzak bir torpido gözünde yapılır. Tüm kimyasallar kurutulmuş veya kutuya geçmeden önce saf. 13 tüm şişeleri ve Züccaciye Mağazaları kuru ve kutuya geçmeden önce fırında ısıtılmış.
<ol><li>
(Bpy)Ni(COD) çözelti hazırlanması Not: (bpy)Ni(COD) taze hazırlanmış situ içinde. Torpido dondurucu (-35 ° C) depolanan ve bir hafta içinde kullanılan gerekir. Tüm diğer katalizörler ve başlatıcı çözümleri torpido buzlukta 1 ay depolanabilir.<ol>
<li>Ni(COD)2 (3.5 mg, 12,7 µmol, 1.0 eq) 7-mL mercek şişe tartın.</li>
		<li>2, 2 '-bipyridine (5.9 mg, 37.8 µmol) 7-mL mercek şişe içine tartın.</li>
		<li>2, 2 '-bipyridine susuz tetrahydrofuran (THF) 1 ml geçiyoruz.</li>
		<li>Elde edilen 2, 2'bipyridine çözüm (337 µL) içeren Ni(COD)2şişe içine ekleyin.</li>
		<li>Susuz THF 1 mL karışımı sulandırmak.</li>
		<li>Şişeyi kap ve 2 h için oda sıcaklığında tepki karışımı yerleştirin. Not: Ni(COD)2 THF içinde çözünür değildir Oysa (bpy)Ni(COD) THF içinde çözünür. Mor çözüm yok yağış 2 h sonra olmalıdır.</li>
		<li>Mağaza (bpy)Ni(COD)-35 ° C dondurucu.</li>
	</ol>
</li>
	<li>
Zn(HMDS)2 çözüm hazırlanması
	<ol>
<li>Zn(HMDS)2 (3.3 mg, 4 µL, 8,5 µmol) 7-mL mercek şişe ekleyin.</li>
		<li>Susuz THF 1 ml Zn(HMDS)2 geçiyoruz.</li>
		<li>Zn(HMDS)2 çözüm-35 ° C dondurucuda saklayın.</li>
	</ol>
</li>
	<li>
BnOH çözüm hazırlanması
	<ol>
<li>BnOH (4,0 mg, 4 µL, 37,0 µmol) 7-mL mercek şişe ekleyin.</li>
		<li>Susuz THF 4 ml BnOH geçiyoruz.</li>
		<li>BnOH çözüm-35 ° C dondurucuda saklayın.</li>
	</ol>
</li>
	<li>
IR-1 çözüm hazırlanması
	<ol>
<li>Torpido Işığı söndür. Dikkat: Daha önce polimerizasyon IR-1 , etkinliğini önlemek için torpido ışığı kapatmak gereklidir.</li>
		<li>IR-1 (2.9 mg, 2.6 µmol) 7-mL mercek şişe ekleyin.</li>
		<li>Susuz THF 3 ml IR-1 geçiyoruz.</li>
		<li>IR-1 çözüm-35 ° C dondurucuda saklayın.</li>
	</ol>
</li>
</ol>2. Photoredox yüzük-açılış polimerizasyon l-1
Not: Tüm süreç ile soğuk bir tuzak bir torpido gözünde yapılır. Tüm OCA monomerleri kullanmadan önce torpido gözünde recrystallized. 13 burada polimerizasyon örneği DP vermek = 500 ([l -1] /[(bpy)Ni(COD)]/[Zn(HMDS)2] / [BnOH] / [IR-1] 500/1/1/1/0.1 =). Polimerler, farklı DPs monomer kitle buna göre ayarlayarak da hazırlanabilir.
<ol><li>
Polimerizasyon için l-1 çözüm hazırlanması
	<ol>
<li>L-1 (72.2 mg, 375.7 µmol) 7-mL mercek şişe ekleyin.</li>
		<li>722 µL susuz THF içinde l-1 geçiyoruz.</li>
		<li>L-1 çözüm 200 µL olan heyecan çubuk donatılmış başka bir 7-mL mercek şişe içine ekleyin.</li>
		<li>Susuz THF 100 µL 7-mL mercek şişe ekleyin.</li>
		<li>Şişeyi kap ve l-1 çözüm soğuk köşeye yerleştirin.</li>
		<li>Torpido Işığı söndür. Dikkat: Daha önce polimerizasyon IR-1 , etkinliğini önlemek için torpido ışığı kapatmak gereklidir.</li>
	</ol>
</li>
	<li>
Soğuk tuzak soğutma
	<ol>
<li>Kutunun içine bir termometre soğuk tuzağın içine koymak.</li>
		<li>Ve kutunun dışında ca. 500 mL etanol dewar şişesi ekleyin.</li>
		<li>Sıvı azot dewar şişesi ekleyin.</li>
		<li>KGW dewar flask soğuk tuzak için yükleyin.</li>
		<li>-50 ° c soğuk tuzak serin</li>
		<li>Yerine bir heyecan plaka underneath soğuk tuzak (bkz. şekil 1).</li>
	</ol>
</li>
	<li>
Photoredox yüzük-açılış polimerizasyon gerçekleştirmek Not: polimerizasyon başlamadan önce koruyucu gözlük blok mavi ışığı ulaşmak içinde yerleştirin. Tüm catalyst sistem çözümleri hemen dondurucudan çıkarılan ve art arda 20 mg l-1 Duraklat veya kesintileri olmadan 30 'un üzerinde içeren 7-mL mercek şişeyi eklendi s.<ol>
<li>Ekle (bpy)Ni(COD) çözüm (16,4 µL, 0,208 µmol) l-1 (2.1 hazır) içeren 7-mL mercek şişe içine.</li>
		<li>Zn(HMDS)2 çözüm (24,4 µL, 0,208 µmol) şişe ekleyin.</li>
		<li>BnOH çözüm (22.5 µL, 0,208 µmol) şişe ekleyin.</li>
		<li>IR-1 çözüm (24,2 µL, 0.0208 µmol) şişe ekleyin ve şişeyi kap.</li>
		<li>Mavi LED ışık engelleme koruyucu gözlük takıyorum. Dikkat: mavi LED ışık göreli yüksek yoğunluğu ile kullanılır, koruyucu gözlük tüm işlemi sırasında giymek.</li>
		<li>Mavi LED ışık (34 W) ve LED tarafından üretilen ısı dağılımı için fan hafif açın. Işık soğuk tuzak şişede doğru yönlendirin. (Şekil 1)</li>
		<li>Karıştırıcı üzerinde açın.</li>
		<li>Alüminyum folyo ile soğuk tuzak kapağı.</li>
		<li>Reaksiyon sıcaklığı tutmak-15 ± 5 ° C ve sıvı azot her 15-20 dakika ekleyin. Not: Tepki sıcaklık bakımından polimerizasyon ve MW kontrolü için önemlidir.</li>
	</ol>
</li>
</ol>3. monitör Fourier dönüşümü kızılötesi spectra monomer dönüştürme
Not: Fourier dönüşümü kızılötesi spectra (FTIR) elmas ATR ve iletim örnekleme aksesuar ile donatılmış bir FT-IR Spektrometre kaydedilirler.
<ol><li>Zaman belirli noktalarda, polimer çözüm (20 µL) küçük bir aliquot 7-mL mercek şişe ekleyin ve şapkalı.</li>
	<li>Şişeyi torpido dışarı çıkarın.</li>
	<li>Hemen çözüm (3 µL) FTIR-ATR elmas örnekleyici üzerine bırakın. Bir film 10 içinde çözüm formları s spektrum ölçümü için.</li>
	<li>Örnek FTIR spektrum ölçmek. Not: 1760 cm-1 ve 1805s cm-1arasında yoğunluk oranı monomer dönüşüm kararlıydı: dönüşüm % =1760/ (Ben1760 +1805) (temsilcisi sonuçları Şekil 2' de). Genel olarak, polimerizasyon 200 den 1000'e kadar DP için yaklaşık 1-8 h alır (detaylı Kinetik başvuru 13' te ele alınmıştır).</li>
</ol>4. polimer'ın molekül ağırlığı jel-Permeasyon Kromatografi tarafından ölçümü
Not: Bir isocratic pompa ile degasser, multiangle lazer ışık saçılma (MALS) dedektörü ile donatılmış bir sistemde jel-Permeasyon Kromatografi (GPC) deneyler yapılmaktadır (GaAs 30 mW lazer λ = 690 nm) ve fark Kırılma indisi (DRI) dedektörü 690 nm ışık kaynağı ile. Renk ayrımlarını seri olarak bağlı boyut dışlama sütunları kullanarak gerçekleştirilir (100 Å, 500 Å, 103 Å ve 104 Å sütunlar, 5 mikron, 300 × 4.6 mm) 35 ° c THF 0,35 mL/dk a akış hızında mobil faz olarak kullanarak. Polimer molekül ağırlığı (MW) ve moleküler Ağırlık dağılımı (Ð) Zimm modelini kullanarak uygun MALS-DRI veri türlerini belirler. Metal polimer içinde karmaşık varlığı GPC ölçüm sonuçları etkilemez.
<ol><li>Küçük bir aliquot polimer çözüm (50 µL) eldiven kutusundan kaldırın.</li>
	<li>THF 100 µL şişe içine ekleyin.</li>
	<li>Örnek GPC örnekleyici enjekte.</li>
	<li>GPC çalışma tamamlandıktan sonra sonuç analiz. Not: Monodispersed dar Đ ile polimer olmalıdır (temsilcisi sonuçları şekil 3' te). Polimer (20 mg) kurutulmuş ve 1 mL Dietil eter kaldırmak için % 87'ni ve Zn kompleksleri, İndüktif eşleşmiş plazma kütle spektrometresi (ICP-MS) tarafından belirlenen % 50'si % 1 HOAc ve 1 mL metanol, içeren tarafından yıkanmış.</li>
</ol>

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Yazarlar hiçbir rakip mali çıkarlarının bildirin. Geçici bir patent (ABD Patent uygulama No: 62/414,016) ve sonuçları bu raporda sunulan ilgili dava açtı.

İletişim kuralına kritik adım-15 ± tepki sıcaklığında bakımı 5 ° C. Tüm katalizörler çözümleri ve OCA monomerleri bir torpido dondurucu-35 ° c polimerizasyon önce depolanması var. Reaksiyon şişeleri soğuk tuzakta önceden soğutulmuş olmak zorunda. Isı, LED ışık kalır çünkü reaksiyonu sırasında bu tepki her 15-20 dakika izlemek gereklidir. Sıcaklık oluşturulur bir kez yukarı-10 ° C ile sıvı azot tuzak soğumasını dewar eklenmelidir. Düşük sıcaklık Ni(CO) oda sıcaklığınd...

Poli (α-hidroksi asit) (PAHA) biyolojik olarak parçalanabilen ve Biyouyumlu polimerler Biyomedikal cihazlar için ambalaj malzemeleri arasında değişen uygulamalar ile önemli bir sınıf ediyor. 1 , 2 her ne kadar PAHAs doğrudan α-hidroksi asitler polikondenzasyon tarafından hazırlanmış olabilir, sonuçta elde edilen PAHAs moleküler ağırlıkları (MWs) genellikle düşüktür. 3 halka açılış polimerizasyon (ROP) lactones (örneğin, lactide ve glycolide), ma ve moleküler Ağırlık dağılımı (Đ) üzerinde daha iyi kontrol polikondenzasyon daha sağlayan alternatif sentetik yaklaşımıdır. Ancak, yan zinciri işlevselliği PAHAs ve lactones eksikliği fiziksel ve kimyasal özellikleri ve uygulamaları çeşitliliği sınırı. 4 , 5 2006 yılından bu yana 1,3-dioxolane-2,4-date, sözde O- yan zinciri işlevleri, zengin çeşitli6,7,8, ile hazırlanan carboxyanhydrides (OCAs), 9 , 10 , 11 , 12 , 13 son derece etkin monomerleri polyester polimerizasyon için alternatif bir sınıf olarak ortaya çıktı. 14 , 15
OCAs ROP için katalitik sistemleri organocatalysts,8,12,16,17 Organometalik katalizörler12,18,19 sınıflandırılabilir ,20,21 ve Biyokatalizörler. 22 genellikle, tarafından organocatalyst terfi OCAs ROP için elektron çekilmesi grupları,8,17 taşıyan OCAs epimerization (yani, stereoregularity eksikliği) gibi az ya da kontrolsüz bir şekilde devam eder öngörülemeyen MWs, ya da yavaş polimerizasyon Kinetik. 13 bu sorunları gidermek için etkin bir Zn-alkoxide kompleksi OCAs ROP için geliştirilmiştir. 12 well-controlled ROPs polimerizasyon (DP) epimerization olmadan düşük bir derece elde edildi. Ancak, bu Zn-alkoxide katalizör polimerler ile polimerizasyon (DP ≥ 300) yüksek derecede verimli bir şekilde üretemez. 13
Son zamanlarda büyük customizability ve PAHA sentezi (şekil 1) verimliliğini geliştirir umut verici bir yaklaşım bildirdin. 13 OCA decarboxylation yüzük-açılış polimerizasyon OCAs, arabuluculuk çinko alkoxide ile teşvik photoredox Ni/IR katalizörler birleştirme. Düşük sıcaklık (-15 ° C) ve photoredox Ni/IR kalıtımda kullanımı sinerjik yüzük-açılış ve OCA decarboxylation istenmeyen yan reaksiyonlar, kaçınırken zinciri yayma Örneğin, Ni-karbonil oluşumu için hızlandırır. 23 , 24 transmetalation Ni karmaşık ile üzerine etkin Zn alkoxide zinciri terminus zinciri yayma için yer alır. 13
Bu protokol için biz taze hazırlanan eklemek (bpy)Ni(COD) (bpy = 2, 2'-bipyridyl, COD = 1,5-cyclooctadiene), Zn(HMDS)2 (HMDS hexamethyldisilazane =),25 Benzil alkol (BnOH) ve IR [dF (CF3) ppy]2(dtbbpy) PF6 () IR-1, dF (CF3) ppy 2-(2,4-difluorophenyl) -5 =-(trifluoromethyl) pyridine, dtbbpy = 4, 4' - di -tert- butil-2, 2'-bipyridine) soğuk bir tuzakta varlığı ile bir eldiven kutusunda monomer l-1 çözüm26 içine bir mavi LED ışık (400-500 nm) ve sıcaklık (şekil 1) korumak için bir fan. Sıcaklık 5 ° C-15 ° C ± polimerizasyon sırasında tutulur. OCA dönüşüm Fourier dönüşümü kızılötesi spektroskopi tarafından izlenir. Elde edilen polimer ma ve Đs bir jel Permeasyon Kromatografi (GPC) ile karakterizedir. Homodecoupling 1H NMR çalışmada elde edilen polimer isotactic olup olmadığını belirler. Çoğu kimyasal neme çok hassas olduğundan, detaylı video protokolü yeni uygulayıcıları OCAs ROP photoredox ile ilişkili tuzaklardan kaçınmak yardımcı olmak içindir.

<table><tbody><tr><td>Ni(COD)&lt;sub&gt;2&lt;/sub&gt;</td><td>Strem</td><td>28-0010</td><td>Stored in the glove box freezer.</td></tr><tr><td>2,2&amp;prime;-bipyridine</td><td>Strem</td><td>07-0290</td><td>Stored in the glove box freezer.</td></tr><tr><td>Zn(HMDS)&lt;sub&gt;2&lt;/sub&gt;</td><td>N/A</td><td>N/A</td><td>Synthesized following reported procedures.&lt;sup class=&quot;xref&quot;&gt;25&lt;/sup&gt; Stored in the glove box freezer.</td></tr><tr><td>Benzyl alcohol</td><td>Sigma-Aldrich</td><td>402834</td><td>Stored with 4&amp;Aring; molecular sieve</td></tr><tr><td>Ir[dF(CF&lt;sub&gt;3&lt;/sub&gt;)ppy]&lt;sub&gt;2&lt;/sub&gt;(dtbbpy)PF&lt;sub&gt;6&lt;/sub&gt;</td><td>Strem</td><td>77-0425</td><td>Stored in the glove box freezer.</td></tr><tr><td>THF</td><td>Sigma-Aldrich</td><td>34865</td><td>Dried by alumina columns and stored with 4&amp;Aring; molecular sieve in the dark bottle in the glove box.</td></tr><tr><td>Ethanol</td><td>Sigma-Aldrich</td><td>793175</td><td></td></tr><tr><td>GPC with an isocratic pump</td><td>Agilent</td><td>Agilent 1260 series</td><td></td></tr><tr><td>Dawn Heleos II Light Scatterer</td><td>Wyatt</td><td></td><td></td></tr><tr><td>Optilab rEX differential refractive index detector</td><td>Wyatt</td><td></td><td></td></tr><tr><td>Size exclusion columns</td><td>Phenomenex</td><td></td><td></td></tr><tr><td>Glass Scintillation Vials - 7 ml</td><td>VWR</td><td></td><td></td></tr><tr><td>FTIR spectrometer</td><td>Agilent</td><td></td><td></td></tr><tr><td>Stir bars</td><td>VWR</td><td>58948-091</td><td></td></tr><tr><td>Balance</td><td></td><td></td><td></td></tr><tr><td>Glove box</td><td>Mbraun</td><td>Labstar Pro</td><td></td></tr></tbody></table>

controlled photoredox ring-opening polymerization of o-carboxyanhydrides mediated by ni/zn complexes

Burada, photoredox Ni/IR kataliz Zn alkoxide kullanım için isotactic Poli (α-hidroksi asitler) sentezi için izin verimli yüzük-açılış polimerizasyonu ile beklenen moleküler ağırlıkları ile birleştiren etkili bir iletişim kuralı tanımlamak (> 140 kDa) ve dar moleküler ağırlık Dağılımları (Mw/Mn < 1.1). Bu yüzük-açılış polimerizasyon Ni ve Zn kompleksleri varlığında alkol başlatıcı ve mavi LED (400-500 nm) ile ışınlanmış bir photoredox IR katalizör, aracılık ettiği. Polimerizasyon istenmeyen yan reaksiyonları önlemek için bir düşük sıcaklıkta (-15 ° C) gerçekleştirilir. Tam monomer tüketimi 4-8 saat içinde beklenen molekül ağırlığı yakın bir polimer ile dar moleküler Ağırlık dağılımı sağlayarak elde edilebilir. Neden sayı ortalama molekül ağırlığı kadar 1000 polimerizasyon derecesine ile doğrusal bir ilişki gösterir. Homodecoupling 1H NMR çalışmada elde edilen polimer isotactic epimerization olmadan olduğunu onaylar. Burada bildirilen bu polimerizasyon stereoregular Poli (α-hidroksi asitler) ve çeşitli işlevsel yan zinciri grupları taşıyan onun kopolimerler hazırlamak için hızlı, kontrollü O- carboxyanhydrides polimerizasyon elde etmek için bir strateji sunmaktadır.

OCA çevrimi Şekil 2' de gösterildiği gibi Fourier dönüşümü kızılötesi spektroskopi tarafından izlenir. 1805 cm-1 zirve anhidrit bond streç Oca'da olarak atanır; 1760 cm-1 zirve polimer ester bağı oluşumu karşılık gelir. Bir kez 1805 cm-1 monomer'ın zirvesinde tamamen kaybolur, polimerizasyon sona erdi.
MW ve Đ elde edilen polimer taraf...

Watch this Scientific Journal Video about Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes at JoVE.com

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

O- carboxyanhydrides Ni/Zn kompleksleri tarafından aracılı kontrollü photoredox yüzük-açılış polimerizasyon için bir protokol sunulmuştur.

Photoredox yüzük-açılış polimerizasyon O- Carboxyanhydrides Ni/Zn kompleksleri tarafından aracılı ile kontrol

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

controlled-photoredox-ring-opening-polymerization-o-carboxyanhydrides

Research

JoVE Journal

Chemistry

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

8.0K Görüntüleme.  Nanjing University of Posts and Telecommunications. O- carboxyanhydrides Ni/Zn kompleksleri tarafından aracılı kontrollü photoredox yüzük-açılış polimerizasyon için bir protokol sunulmuştur.

Video: Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

We demonstrate a method for high-throughput catalyst screening using a parallel pressure reactor starting from the initial synthesis of a nickel &#945;-diimine ethylene polymerization catalyst. Initial polymerizations with the catalyst lead to optimized reaction conditions, including catalyst concentration, ethylene pressure and reaction time. Using gas-uptake data for these reactions, a procedure to calculate the initial rate of propagation (kp) is presented. Using the optimized conditions, the ability of the nickel &#945;-diimine polymerization catalyst to undergo chain transfer with diethylzinc (ZnEt2) during ethylene polymerization was investigated. A procedure to assess the ability of the catalyst to undergo chain transfer (from molecular weight and 13C NMR data), calculate the degree of chain transfer, and calculate chain transfer rates (ke) is presented.

A protocol for the high-throughput analysis of polymerization catalyst, chain transfer polymerizations, polyethylene characterization, and reaction kinetic analysis is presented.

Paralel Basınç Reaktörleri ve Zincir Transferi Polimerizasyon bir Kinetik Analizi Etilen Polimerizasyonlar

We demonstrate a method for high-throughput catalyst screening using a parallel pressure reactor starting from the initial synthesis of a nickel ...

Kimya

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

Bir görünür ışık fotokatalistinin olarak Perylene kullanarak Fonksiyonlu Vinil Monomer Atom Transfer Radikal Polimerizasyonu

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of solid-phase synthesis, regenerating Michael (REM) linker strategies, and 1,3-dipolar cycloaddition, a library of structurally similar heterocycles, both with and without a spirocyclic center, can be constructed. The main advantages of the solid-support synthesis are as follows: first, each reaction step can be driven to completion using a large excess of reagents resulting in high yields; next, the use of commercially available starting materials and reagents keep the costs low; finally, the reaction steps are easy to purify via simple filtration. The REM linker strategy is attractive because of its recyclability and traceless nature. Once a reaction scheme is completed, the linker can be reused multiple times. In a typical solid-phase synthesis, the product contains either a part of or the whole linker, which can prove undesirable. The REM linker is &#34;traceless&#34; and the point of attachment between the product and the polymer is indistinguishable. The high diastereoselectivity of the intramolecular 1,3-dipolar cycloaddition is well documented. Limited by the insolubility of the solid support, the reaction progression can only be monitored by a change in the functional groups (if any) via infrared (IR) spectroscopy. Thus, the structural identification of intermediates cannot be characterized by conventional nuclear magnetic resonance (NMR) spectroscopy. Other limitations to this method stem from the compatibilities of the polymer/linker to the desired chemical reaction scheme. Herein we report a protocol that allows for the convenient production of spirocyclic heterocycles that, with simple modifications, can be automated with high-throughput techniques.

Here we present a protocol to demonstrate an efficient method for the synthesis of spirocyclic heterocycles. The five-step process utilizes solid-phase synthesis and regenerating Michael linker strategies. Generally difficult to synthesize, we present a customizable method for the synthesis of spirocyclic molecules otherwise inaccessible to other modern approaches.

Katı faz [4.4] Spirocyclic Oximes sentezi

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of ...

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes and determine the corresponding photochemical mechanism. Then, we describe a protocol to perform ring-opening metathesis polymerization (ROMP) in solution and in miniemulsion using this NHC-photogenerating system. To photogenerate IMes, a system comprising 2-isopropylthioxanthone (ITX) as the sensitizer and 1,3-dimesitylimidazolium tetraphenylborate (IMesH+BPh4-) as the protected form of NHC is employed. IMesH+BPh4- can be obtained in a single step by anion exchange between 1,3-dimesitylimidazolium chloride and sodium tetraphenylborate. A real-time steady-state photolysis setup is described, which hints that the photochemical reaction proceeds in two consecutive steps: 1) ITX triplet is photo-reduced by the borate anion and 2) subsequent proton transfer takes place from the imidazolium cation to produce the expected NHC IMes. Two separate characterization protocols are implemented. Firstly, CS2 is added to the reaction media to evidence the photogeneration of NHC through formation of the IMes-CS2 adduct. Secondly, the amount of NHC released in situ is quantified using acid-base titration. The use of this NHC photo-generating system for the ROMP of norbornene is also discussed. In solution, a photopolymerization experiment is conducted by mixing ITX, IMesH+BPh4-, [RuCl2(p-cymene)]2 and norbornene in CH2Cl2, then irradiating the solution in a UV reactor. In a dispersed medium, a monomer miniemulsion is first formed then irradiated inside an annular reactor to produce a stable poly(norbornene) latex.

We describe a protocol to photogenerate N-heterocyclic carbenes (NHCs) by UV irradiation of a 2-isopropylthioxanthone/imidazolium tetraphenylborate salt system. Methods to characterize the photoreleased NHC and elucidate the photochemical mechanism are proposed. The protocols for ring-opening metathesis photopolymerization in solution and miniemulsion illustrate the potential of this 2-component NHC photogenerating system.

N oluşur Carbenes Photogeneration: Photoinduced yüzük-açılış sentezde polimerizasyon uygulamada

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes ...

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium- and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF6, as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford&#160;4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

[(DPEPhos) (bcp) cu] PF6: genel ve geniş uygulanabilir bakır bazlı Photoredox katalizörü

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the ...

Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions

The interest on nitrogen-containing heterocycles has expanded rapidly in the synthetic community since they are important motifs for new drugs. Traditionally, they were synthesized through thermal cycloaddition reactions, whereas today, photocatalysis is preferred due to the mild and efficient conditions. With this focus, a new photocatalytic method for the synthesis of nitrogen-containing heterocycles is highly desired. Here, we report a protocol for the biosynthesis of cercosporin, which could function as a metal-free photocatalyst. We then illustrate cercosporin-photocatalyzed protocols for the synthesis of nitrogen-containing heterocycles 1,2,3-thiadiazoles through annulation of azoalkenes with KSCN, and synthesis of 1,4,5,6-tetrahydropyridazines [4+2] through cyclodimerization of azoalkenes under mild conditions, respectively. As a result, there is a new bridge between the microbial fermentation method and organic synthesis in a mild, cost-effective, environmentally friendly and sustainable manner.

New routes for the synthesis of nitrogen-containing heterocycles utilizing cercosporin as a metal-free photocatalyst were developed.

Cercosporin-Photocatalyzed [4+1]- ve [4+2]-Hafif Koşullarda Azoalkenlerin Annülasyonları

The interest on nitrogen-containing heterocycles has expanded rapidly in the synthetic community since they are important motifs for new drugs. ...

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. Achieving a closed-loop polymer economy via chemical recycling to monomer (CRM) is one such promising route. Our group recently reported a new CRM system based on polymers prepared by ring-opening metathesis polymerization (ROMP) of trans-cyclobutane fused cyclooctene (tCBCO) monomers. This system offers several key advantages, including the ease of polymerization at ambient temperatures, quantitative depolymerization to monomers under mild conditions, and a broad range of functionalities and thermomechanical properties. Here, we outline detailed protocols for the preparation of tCBCO-based monomers and their corresponding polymers, including the preparation of elastic polymer networks and compression molding of linear thermoplastic polymers. We also outline the preparation of high ring strain E-alkene tCBCO monomers and their living polymerization. Finally, the procedures for the depolymerization of linear polymers and polymer networks are also demonstrated.

Here, we describe protocols for the preparation of trans-cyclobutane fused cyclooctenes (tCBCO),&#160;their polymerization to prepare depolymerizable olefinic polymers, and the depolymerization of these polymers under mild conditions. Additionally, protocols for the preparation of depolymerizable networks and compression molding of rigid linear plastics based on this system are described.

Kaynaşmış Halka Siklookten Monomerlerine Dayanan Depolimerize Edilebilir Olefinik Polimerler

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. ...

Photochemical Initiation Of Radical Polymerization Reactions

Source: David C. Powers, Tamara M. Powers, Texas A&#38;M
In this video, we will carry out the photochemically initiated polymerization of styrene to generate polystyrene, which is an important commodity plastic. We will learn the fundamentals of photochemistry and use simple photochemistry to initiate radical polymerization reactions. Specifically, in this module we will examine the photochemistry of benzoyl peroxide and its role as a photo-initiator of styrene polymerization reactions. In the described experiments, we will investigate the role of wavelength, photon absorption, and excited state structure on the efficiency (measured as quantum yield) of photochemical reactions.

Source: David C. Powers, Tamara M. Powers, Texas A&#38;M
In this video, we will carry out the photochemically initiated polymerization of styrene to ...

Education

JoVE Science Education

İnorganik Kimya

Acid-Catalyzed Ring-Opening of Epoxides

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The reaction follows the SN2 mechanism, and the protonated oxygen, unlike other leaving groups, does not detach from the molecule. The regiochemistry of the products formed is governed by either steric or electronic effects. In the case of an asymmetrical epoxide bearing a primary and a secondary carbon, the steric effect dominates and favors the nucleophilic attack at a less-hindered carbon. However, in epoxides where one of the carbons is tertiary, the electronic effect comes into play and favors the attack at a more-hindered carbon. The stereochemistry of the products is similar to an SN2 reaction, where the nucleophile attacks anti to the leaving group. Notably, the anti-attack at a chiral carbon causes an inversion of configuration.

Epoksitlerin Asit Katalizli Halka Açılması

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the ...

JoVE Core

Organik Kimya

Unit 1

Eterler, Epoksitler, Sülfitler

KEY TERMS AND CONCEPTS

Base-Catalyzed Ring-Opening of Epoxides

Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile or a base. A variety of nucleophiles like sodium hydroxide, sodium alkoxide, sodium hydrosulfide, sodium cyanide, lithium aluminum hydride, and Grignard reagent can open the epoxide ring. The nucleophilic attack on the epoxide ring proceeds via an SN2 mechanism and involves an alkoxide intermediate. The product formed in base-catalyzed reactions shows SN2-like stereoselectivity and regioselectivity. The nucleophile attacks at the less-hindered carbon and anti to the leaving group, leading to the inversion of configuration at a chiral center. In contrast to epoxides, acyclic ethers do not undergo direct nucleophilic substitutions, as the reaction is thermodynamically unfavorable.

Epoksitlerin baz katalizli halka açılması

Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of ...