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Kang Y.-W.,Ajou University | Jang H.-Y.,Ajou University | Jang H.-Y.,Korea Carbon Capture and Sequestration Randnter
RSC Advances | Year: 2014

A combination of N-heterocyclic carbene (NHC) catalysts and 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) was proposed for the synthesis of allylic esters from allylic alcohols. The yield of one-pot conversion of allylic alcohols to esters increased when hexafluoroisopropanol (HFIP) was used. The effect of HFIP in this tandem reaction was investigated by monitoring the reaction using gas chromatographic analysis. Control experiments using oxoammonium showed that the oxidative esterification occurred via a single-electron transfer mechanism. © 2014 the Partner Organisations. Source


Ji M.,Ajou University | Lim S.,Ajou University | Jang H.-Y.,Ajou University | Jang H.-Y.,Korea Carbon Capture and Sequestration Randnter
RSC Advances | Year: 2014

N-heterocyclic carbene-catalyzed oxidation using TEMPO is reported for the conversion of aldehydes to amides. A wide range of amides were synthesized in good yields (up to 72%) via a one-pot, sequential protocol involving oxidative esterification of aldehydes and subsequent aminolysis. To promote efficient aminolysis, various alkoxide leaving groups were evaluated. © 2014 the Partner Organisations. Source


Lee C.,Ajou University | Wang X.,Ajou University | Jang H.-Y.,Ajou University | Jang H.-Y.,Korea Carbon Capture and Sequestration Randnter
Organic Letters | Year: 2015

Despite the remarkable success of the copper-catalyzed oxidative coupling reaction, direct cross-coupling of amines and thiols for the synthesis of N-sulfenylimines has not been previously reported. Using commercially available copper catalysts (CuI) and oxygen as an environmentally benign oxidant, synthetically useful N-sulfenylimines were prepared from amines and thiols in good yields without overoxidation of sulfur atoms. © 2015 American Chemical Society. Source


Lee C.,Ajou University | Lim Y.N.,Ajou University | Jang H.-Y.,Ajou University | Jang H.-Y.,Korea Carbon Capture and Sequestration Randnter
European Journal of Organic Chemistry | Year: 2015

Recent remarkable success of copper-catalyzed oxidative bond formations led us to develop an environmentally benign copper-catalyzed sulfur-nitrogen bond-forming reaction to provide synthetically and industrially useful electron-deficient sulfenamides. The low nucleophilicity of N-formyl/acyl- and sulfonylamides was overcome by introducing a 1,5,7-triazabicyclo[4.4.0]dec-5-ene additive. A variety of N-formyl/acylsulfenamides and -thiosulfonamides were synthesized in good yields without over-oxidation of sulfur. Related mechanistic studies supported the proposed reaction mechanism. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Ji M.,Ajou University | Wang X.,Ajou University | Lim Y.N.,Ajou University | Kang Y.-W.,Ajou University | And 2 more authors.
European Journal of Organic Chemistry | Year: 2013

A versatile carbene-catalysed oxidation protocol involving N-heterocyclic carbene catalysts and 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) is described for the synthesis of esters, cinnamic acids, and thioesters. A wide range of esters, thioesters, and cinnamic acids were obtained by metal-free coupling of aldehydes with aliphatic, allylic and aromatic alcohols, benzyl mercaptan, and water. In addition to the oxidative coupling of aldehydes with nucleophiles, dehydrogenation of saturated aldehydes and oxidation of allylic alcohols were found under our oxidative coupling conditions. Unlike other TEMPO-mediated oxidative esterification reactions, this reaction does not proceed through a TEMPO ester intermediate to form esters and thioesters. N-Heterocyclic carbene complexes catalyse various oxidative coupling reactions in the presence of TEMPO. A variety of α,β-unsaturated and saturated esters, and aromatic esters and thioesters were synthesised. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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