Name: protocol for the synthesis of ortho-trifluoromethoxylated aniline derivatives
Uploaded: 2016-01-19T15:00:00
Description: Watch this Scientific Journal Video about Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives at JoVE.com

We acknowledge generous start-up funds from the State University of New York at Stony Brook in support of this work. We also thank TOSOH F-Tech, Inc. for providing us TMSCF3 reagent for the synthesis of Togni reagent II.

1. Precursor Preparation: Synthesis of Methyl 4-(N-hydroxyacetamido)benzoate (1a)
<ol>
	<li>Reduction of methyl 4-nitrobenzoate.
	<ol>
		<li>Add 5.00 g of methyl 4-nitrobenzoate (27.6 mmol, 1.00 equiv), 159 mg of 5% Rhodium on carbon (Rh/C, 0.300 mol% Rh), and a magnetic stir-bar into an oven-dried 250 ml two-neck round-bottom flask (dried at 150 &#176;C for 18 hr). 
		NOTE: Reagents can be weighed out under ambient atmosphere. However, the reaction needs to be carried out under nitrogen ...

<ol>
	<li>Yagupolskii, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sintez+proizvodnykh+feniltriftormetilovogo+efira.">Sintez proizvodnykh feniltriftormetilovogo efira.</a> Dokl. Akad. Nauk SSSR. 105, 100-102 (1955).</li><li>Booth, H. S., Burchfield, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorination+of+halogeno+methyl+ethers.+I.+Fluorination+of+trichlorodimethyl+ether.">Fluorination of halogeno methyl ethers. I. Fluorination of trichlorodimethyl ether.</a> J. Am. Chem. Soc. 57, 2070 (1935).</li><li>McClinton, M. A., McClinton, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trifluoromethylations+and+related+reactions+in+organic-chemistry.">Trifluoromethylations and related reactions in organic-chemistry.</a> Tetrahedron. 48, 6555-6666 (1992).</li><li>Hansch, C., Leo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Substituent Constants for Correlation Analysis in Chemistry and Biology. , (1979).</li><li>Leroux, F., Jeschke, P., Schlosser, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alpha-fluorinated+ethers,+thioethers,+and+amines:+Anomerically+biased+species.">Alpha-fluorinated ethers, thioethers, and amines: Anomerically biased species.</a> Chem. Rev. 105, 827-856 (2005).</li><li>Jeschke, P., Baston, E., Leroux, F. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alpha-fluorinated+ethers+as+'exotic'+entity+in+medicinal+chemistry.">Alpha-fluorinated ethers as 'exotic' entity in medicinal chemistry.</a> Mini-Rev. Med. Chem. 7, 1027-1034 (2007).</li><li>Leroux, F. R., Manteau, B., Vors, J. P., Pazenok, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trifluoromethyl+ethers+-+synthesis+and+properties+of+an+unusual+substituent.">Trifluoromethyl ethers - synthesis and properties of an unusual substituent.</a> Beilstein J. Org. Chem. 4, (2008).</li><li>Fantasia, S., Welch, J. M., Togni, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactivity+of+a+hypervalent+iodine+trifluoromethylating+reagent+toward+THF:+ring+opening+and+formation+of+trifluoromethyl+ethers.">Reactivity of a hypervalent iodine trifluoromethylating reagent toward THF: ring opening and formation of trifluoromethyl ethers.</a> J. Org. Chem. 75, 1779-1782 (2010).</li><li>Manteau, B., Pazenok, S., Vors, J. P., Leroux, F. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+trends+in+the+chemistry+of+alpha-fluorinated+ethers,+thioethers,+amines+and+phosphines.">New trends in the chemistry of alpha-fluorinated ethers, thioethers, amines and phosphines.</a> J. Fluorine Chem. 131, 140-158 (2010).</li><li>Landelle, G., Panossian, A., Leroux, F. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trifluoromethyl+ethers+and+-thioethers+as+tools+for+medicinal+chemistry+and+drug+discovery.">Trifluoromethyl ethers and -thioethers as tools for medicinal chemistry and drug discovery.</a> Curr. Top. Med. Chem. 14, 941-951 (2014).</li><li>Liang, T., Neumann, C. N., Ritter, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Introduction+of+fluorine+and+fluorine-containing+functional+groups.">Introduction of fluorine and fluorine-containing functional groups.</a> Angew. Chem. Int. Ed. 52, 8214-8264 (2013).</li><li>Yarovenko, N. N., Vasileva, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+method+for+the+introduction+of+trihalomethyl+groups+into+organic+molecules.">A new method for the introduction of trihalomethyl groups into organic molecules.</a> Zh. Obshch. Khim. 28, 2502-2504 (1958).</li><li>Yagupols, L., Troitskaya, V. I. <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+phenyl+trifluoromethyl+ether+derivatives.">Synthesis of phenyl trifluoromethyl ether derivatives.</a> Zh. Obshch. Khim. 31, 915-924 (1961).</li><li>Yagupolskii, L. M., Orda, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bis(triftormetoksi+I+triftormetilmerkapto)-proizvodnye+benzola.">Bis(triftormetoksi I triftormetilmerkapto)-proizvodnye benzola.</a> Zh. 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Chem. 29, 1-11 (1964).</li><li>Kuroboshi, M., Suzuki, K., Hiyama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidative+desulfurization-fluorination+of+xanthates+-+a+convenient+synthesis+of+trifluoromethyl+ethers+and+difluoro(methylthio)methyl+ethers.">Oxidative desulfurization-fluorination of xanthates - a convenient synthesis of trifluoromethyl ethers and difluoro(methylthio)methyl ethers.</a> Tetrahedron Lett. 33, 4173-4176 (1992).</li><li>Kanie, K., Tanaka, Y., Suzuki, K., Kuroboshi, M., Hiyama, T. <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+trifluoromethyl+ethers+by+oxidative+desulfurization-fluorination+of+dithio+carbonates.">A convenient synthesis of trifluoromethyl ethers by oxidative desulfurization-fluorination of dithio carbonates.</a> Bull. Chem. Soc. 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Rev. 96, 1757-1777 (1996).</li><li>Umemoto, T., Adachi, K., Ishihara, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CF3+oxonium+salts,+O-(trifluoromethyl)dibenzofuranium+salts:+in+situ+synthesis,+properties,+and+application+as+a+real+CF3++species+reagent.">CF3 oxonium salts, O-(trifluoromethyl)dibenzofuranium salts: in situ synthesis, properties, and application as a real CF3+ species reagent.</a> J. Org. Chem. 72, 6905-6917 (2007).</li><li>Stanek, K., Koller, R., Togni, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactivity+of+a+10-I-3+hypervalent+iodine+trifluoromethylation+reagent+with+phenols.">Reactivity of a 10-I-3 hypervalent iodine trifluoromethylation reagent with phenols.</a> J. Org. Chem. 73, 7678-7685 (2008).</li><li>Koller, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zinc-mediated+formation+of+trifluoromethyl+ethers+from+alcohols+and+hypervalent+iodine+trifluoromethylation+reagents.">Zinc-mediated formation of trifluoromethyl ethers from alcohols and hypervalent iodine trifluoromethylation reagents.</a> Angew. Chem. Int. Ed. 48, 4332-4336 (2009).</li><li>Trainor, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+preparation+of+O-trifluoromethyl+carbohydrates.">The preparation of O-trifluoromethyl carbohydrates.</a> J. Carbohydr. Chem. 4, 545-563 (1985).</li><li>Nishida, M., Vij, A., Kirchmeier, R. L., Shreeve, J. M. <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+polyfluoro+aromatic+ethers+-+a+facile+route+using+polyfluoroalkoxides+generated+from+carbonyl+and+trimethysilyl+compounds.">Synthesis of polyfluoro aromatic ethers - a facile route using polyfluoroalkoxides generated from carbonyl and trimethysilyl compounds.</a> Inorg. Chem. 34, 6085-6092 (1995).</li><li>Kolomeitsev, A. A., Vorobyev, M., Gillandt, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Versatile+application+of+trifluoromethyl+triflate.">Versatile application of trifluoromethyl triflate.</a> Tetrahedron Lett. 49, 449-454 (2008).</li><li>Marrec, O., Billard, T., Vors, J. P., Pazenok, S., Langlois, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+deeper+insight+into+direct+trifluoromethoxylation+with+trifluoromethyl+triflate.">A deeper insight into direct trifluoromethoxylation with trifluoromethyl triflate.</a> J. Fluorine Chem. 131, 200-207 (2010).</li><li>Marrec, O., Billard, T., Vors, J. P., Pazenok, S., Langlois, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+and+direct+trifluoromethoxylation+of+aliphatic+substrates+with+2,4-dinitro(trifluoromethoxy)benzene.">A new and direct trifluoromethoxylation of aliphatic substrates with 2,4-dinitro(trifluoromethoxy)benzene.</a> Adv. Synth. Catal. 352, 2831-2837 (2010).</li><li>Huang, C. H., Liang, T., Harada, S., Lee, E., Ritter, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silver-mediated+trifluoromethoxylation+of+aryl+stannanes+and+arylboronic+acids.">Silver-mediated trifluoromethoxylation of aryl stannanes and arylboronic acids.</a> J. Am. Chem. Soc. 133, 13308-13310 (2011).</li><li>Rozen, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+fluorinations+by+reagents+containing+the+OF+group.">Selective fluorinations by reagents containing the OF group.</a> Chem. Rev. 96, 1717-1736 (1996).</li><li>Venturini, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+trifluoro-methoxylation+of+aromatics+with+perfluoro-methyl-hypofluorite.">Direct trifluoro-methoxylation of aromatics with perfluoro-methyl-hypofluorite.</a> J. Fluorine Chem. 140, 43-48 (2012).</li><li>Hojczyk, K. N., Feng, P., Zhan, C., Ngai, M. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trifluoromethoxylation+of+arenes:+synthesis+of+ortho-trifluoromethoxylated+aniline+derivatives+by+OCF3+migration.">Trifluoromethoxylation of arenes: synthesis of ortho-trifluoromethoxylated aniline derivatives by OCF3 migration.</a> Angew. Chem. Int. Ed. 53, 14559-14563 (2014).</li><li>Still, W. C., Kahn, M., Mitra, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+chromatographic+technique+for+preparative+separations+with+moderate+Resolution.">Rapid chromatographic technique for preparative separations with moderate Resolution.</a> J. Org. Chem. 43, 2923-2925 (1978).</li><li>Fiederling, N., Haller, J., Schramm, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Notification+about+the+Explosive+Properties+of+Togni's+Reagent+II+and+One+of+Its+Precursors.">Notification about the Explosive Properties of Togni's Reagent II and One of Its Precursors.</a> Org. Process Res. 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Due to the lack of a general and user-friendly procedure for the synthesis of trifluoromethoxylated arenes, many OCF3-containing aromatic compounds are extremely expensive.34 Our strategy displaces a broad functional group tolerance and provides an easy access to various trifluoromethoxylated arenes. These compounds could serve as valuable building blocks for the discovery and development of new pharmaceuticals, agrochemicals, and materials.
Hydrazine was used as a hydrog...

The trifluoromethoxy (OCF3) group has made a profound impact on life and materials science research since the first synthesis of trifluoromethyl ether in 1935.2 Due to its unique combination of high electronegativity (&#967; = 3.7)3 and excellent lipophilicity (&#928;x = 1.04),4 the trifluoromethoxy group has found broad applications in medicine, agriculture, and materials industry.5-10 However, facile introduction of the OCF3 group into organic molecules, especially aromatic compounds, remains a major challenge in synthetic chemistry.
Over the last few decades, efforts to address this challenge led to the development of a handful of transformations for the synthesis of trifluoromethoxylated arenes.5-7,9-11 These include (i) chlorine/fluorine exchange on trichlorinated precursors;1,12-17 (ii) deoxyfluorination of fluoroformates;18 (iii) oxidative fluorodesulfurization;19-21 (iv) electrophilic trifluoromethylation of alcohols;22-25 (v) nucleophilic trifluoromethoxylation;26-30, (vi) transition metal-mediated trifluoromethoxylation of aryl borates and stannanes;31 and (vii) radical trifluoromethoxylation.32,33 Nevertheless, many of these approaches either suffer from poor substrate scope or require use of highly toxic and/or thermally labile reagents. Therefore, due to the lack of a general and user-friendly method to synthesize OCF3-containing compounds, the potential of the OCF3 group has not been fully exploited in chemistry.
As part of our interest in trifluoromethoxylation reactions,34 we describe herein a two-step protocol (i.e., radical&#160;O-trifluoromethylation and thermally induced OCF3-migration) for the synthesis of methyl 4-acetamido-3-(trifluoromethoxy)benzoate (3a) from methyl 4-(N-hydroxyacetamido)benzoate (1a). The strategy is easy-to-operate and applicable to the synthesis of a wide range of ortho-trifluoromethoxylated aniline derivatives.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">5% Rhodium on carbon</td>
			<td style="width:71px;">Aspira Scientific</td>
			<td style="width:119px;">300835</td>
			<td style="width:167px;">5% wt% dry loading</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">hydrazine monohydrate</td>
			<td style="width:71px;">Sigma-Alderich</td>
			<td style="width:119px;">13696HMV</td>
			<td style="width:167px;">Reagent grade, 98%</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Acetyl chloride</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td style="width:119px;">10176887</td>
			<td style="width:167px;">98%</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Sodium bicarbonate</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">134826</td>
			<td style="width:167px;">Chemical pure</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Cesium carbonate</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td style="width:119px;">12887</td>
			<td style="width:167px;">99.9%, metals basis</td>
		</tr>
		<tr height="148">
			<td height="148" style="height:148px;width:216px;">Togni Reagent II</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Prepared according to the literature procedure (ref 37). Caution: Pure Togni reagent II is impact and friction sensitive, treat it with great care (see ref. 36).</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Tetrahydrofuran</td>
			<td style="width:71px;">BDH</td>
			<td style="width:119px;">BDH1149-4LG</td>
			<td style="width:167px;">Distilled from deep purple sodium benzophenone ketyl.</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Diethyl Ether</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">148221</td>
			<td style="width:167px;">Distilled from deep purple sodium benzophenone ketyl.</td>
		</tr>
		<tr height="47">
			<td height="47" style="height:47px;width:216px;">Chloroform</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">141739</td>
			<td style="width:167px;">Dried over CaH2 and distilled</td>
		</tr>
		<tr height="47">
			<td height="47" style="height:47px;width:216px;">nitro methane</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td style="width:119px;">J03z053</td>
			<td style="width:167px;">Dried over CaSO4 and distilled</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Silica gel</td>
			<td style="width:71px;">SILICYCLE</td>
			<td style="width:119px;">60514</td>
			<td style="width:167px;">40-63 &#181;m (230-400 mesh)</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Cilite</td>
			<td style="width:71px;">EMD</td>
			<td style="width:119px;">2012040674</td>
			<td style="width:167px;">Not acid washed</td>
		</tr>
	</tbody>
</table>

protocol for the synthesis of ortho-trifluoromethoxylated aniline derivatives

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of trifluoromethoxylated aromatic compounds remains a formidable challenge in organic synthesis. Conventional approaches often suffer from poor substrate scope, or require use of highly toxic, difficult-to-handle, and/or thermally labile reagents. Herein, we report a user-friendly protocol for the synthesis of methyl 4-acetamido-3-(trifluoromethoxy)benzoate using 1-trifluoromethyl-1,2-benziodoxol-3(1H)-one (Togni reagent II). Treating methyl 4-(N-hydroxyacetamido)benzoate (1a) with Togni reagent II in the presence of a catalytic amount of cesium carbonate (Cs2CO3) in chloroform at RT afforded methyl 4-(N-(trifluoromethoxy)acetamido)benzoate (2a). This intermediate was then converted to the final product methyl 4-acetamido-3-(trifluoromethoxy)benzoate (3a) in nitromethane at 120 &#176;C. This procedure is general and can be applied to the synthesis of a broad spectrum of ortho-trifluoromethoxylated aniline derivatives, which could serve as useful synthetic building blocks for the discovery and development of new pharmaceuticals, agrochemicals, and functional materials.

Methyl 4-(N-hydroxyacetamido)benzoate (1a) was synthesized in 92% isolated yield through a two-step procedure (i.e., reducing methyl 4-nitrobenzoate with hydrazine using 5% Rh/C as a catalyst to form methyl 4-(N-hydroxyamino)benzoate, followed by acetyl protection of the resulting hydroxylamine). O-Trifluoromethylation of 1a with Togni reagent II in the presence of catalytic amount of cesium carbonate (Cs2CO<...

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Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

An operationally simple procedure for the synthesis of ortho-trifluoromethoxylated aniline derivatives via a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxyacetamide followed by thermally induced intramolecular OCF3-migration is reported.

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of ...

The overall goal of this protocol is to synthesize novel ortho-trifluoromethoxylated anilines with the discovery and development of new drugs, agrochemicals, and functional materials. This method can help to answer key questions in the field of foreign chemistry such as how incorporation of trifluoromethoxy group into a molecule effects its physical, chemical, and biological properties. The main advantage of this technique that our method uses easy-to-handle reagents.It's amendable to gram-scale synthesized and it has broad substrate scope and high tolerance of functional groups. For the reduction of methyl 4-nitrobenzoate, add 5.00 grams of methyl 4-nitrobenzoate, 159 milligrams of 5%Rhodium on carbon, and a magnetic stir-bar into an oven-dried 250 milliliter two-neck round-bottom flask. Connect one neck of the flask to a nitrogen-vacuum manifold and cap the other neck with a septum.Perform three vacuum-refill cycles to replace the air in the flask with nitrogen gas, then add 138 milliliters of anhydrous tetrahydrofuran to the reaction flask using an airtight syringe. Cool and stir the reaction mixture at zero degrees Celsius for 15 minutes. Next, add 1.47 milliliters of hydrazine monohydrate drop-wise to the reaction mixture at zero degrees Celsius using an airtight syringe.At this point, Rhodium on carbon will start aggregation to form larger particles. Monitor the reaction using thin-layer chromatography or TLC. Use a mixture of hexane and ethyl acetate as an element to develop the TLC.When methyl 4-nitrobenzoate is completely consumed, filter the reaction mixture through a short pad of Celite in a 60 milliliter frit Buchner funnel using vacuum filtration. Wash the filter with 20 milliliters of ethyl acetate three times. Concentrate the filtrate in vacuo using a rotary evaporator to afford the crude methyl 4-hydroxyamino benzoate which is used directly without further purification.To perform acetyl protection of methyl 4-hydroxyamino benzoate, add 2.55 grams of sodium bicarbonate, all the crude methyl 4-hydroxyamino benzoate obtained in the previous step, and a stir-bar into an oven-dried 500 milliliter two-neck round-bottom flask. Cap one neck with a septum, and connect another neck to a nitrogen-vacuum manifold. Perform three vacuum-refill cycles to replace the air in the flask with nitrogen gas.Add 138 milliliters of anhydrous diethyl ether to the reaction flask using an airtight syringe. Cool and stir the reaction mixture at zero degrees Celsius for 15 minutes. Prepare a solution of 2.17 milliliters of acetyl chloride and 138 milliliters of anhydrous diethyl ether.Add the solution to the reaction mixture at zero degrees Celsius using a syringe pump at a rate of 10.0 milliliters per hour. At the end of the addition, filter the reaction mixture through a short pad of Celite in a 16 milliliter frit Buchner funnel using vacuum filtration. After washing the filter with 20 milliliters of ethyl acetate three times, concentrate the filtrate in vacuo using a rotary evaporator.Purify the crude product with flash-column chromatography eluting with a mixture of hexane and ethyl acetate to afford 5.31 grams of methyl 4-hydroxy acetamido benzoate as a light yellow solid. Add 2.00 grams of methyl 4-hydroxy acetamido benzoate, 311 milligrams of cesium carbonate 3.63 grams of Togni reagent II, and a magnetic stir-bar into an oven-dried 250 milliliter round-bottom flask inside a glove box. This reaction can also be performed using Schlenk techniques outside the glove box, then add 95.6 milliliters of dried and degassed chloroform to the reaction flask.Cap the flask with a septum and stir the reaction mixture at 23 degrees Celsius under nitrogen atmosphere either inside or outside the glove box for 16 hours. Filter the reaction mixture through a filter funnel to remove any solid residue before concentrating the filtrate in vacuo using a rotary evaporator. Next, purify the crude product using flash-column chromatography eluting with a mixture of hexane and dichloromethane to afford 2.51 grams of methyl 4-trifluoromethoxy acetamido benzoate To synthesize the final product at 2.51 grams of methyl 4-trifluoromethoxy acetamido benzoate, a magnetic stir-bar, and 9.05 milliliters of anhydrous nitromethane into a 15 milliliter pressure vessel.Cap the vessel with a screw cap, stir the reaction mixture at 120 degree Celsius behind the safety shield for 20 hours. After cooling the reaction mixture to room temperature, transfer to a 100 milliliter round-bottom flask. Concentrate the reaction mixture in vacuo using a rotary evaporator.Purify the crude product with flash-column chromatography eluding with a mixture of hexanes and ethyl acetate to afford 2.13 grams of methyl 4-acetamido 3-trifluoromethoxy benzoate. Characterize all the new compounds by proton-carbon-13 nuclear magnetic resonance or NMR spectroscopy and high-resolution mass spectroscopy. Use fluorine-19 NMR spectroscopy to characterize compounds containing fluorine atoms.Representative results of Togni reagent II mediated intermolecular trifluoromethoxylation of arenes are shown here. This protocol is general and applicable to a wide array of aromatic compounds. The reaction tolerates a broad spectrum of functional groups.In addition, high levels of ortho over para selectivity are observed, for example, substrates, 3f, 3k, and 3l. In the presence of two non-identical ortho positions, low levels of Regio-control are obtained as in substrates, 3d.3e. 3k, and 3m.Furthermore, the reaction temperature for the trifluoromethoxy migration step depends on the electronic nature of the arenes. Generally, more electron-deficient arenes require higher reaction temperature. After its development, this technique paved the way for researchers in the field of chemistry and biology to explore trifluoromethoxylated arenes, and the discovery, and the development of new technique molecules.

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Aromatic Compounds

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