Julia–Kocienski approach to trifluoromethyl-substituted alkenes
摘要:
A Julia-Kocienski approach to trifluoromethyl-substituted alkenes was evaluated in the reactions of 1,3-benzothiazol-2-yl, 1-phenyl-1H-tetrazol-5-yl, and 1-tbutyl-1H-tetrazol-5-yl 2,2,2-trifluoroethyl sulfones with aldehydes. Among the various conditions tested, the best yields were obtained with 1-phenyl-1H-tetrazol-5-yl 2,2,2-trifluoroethyl sulfone, in CsF-mediated, room temperature olefinations in DMSO. Aromatic aldehydes gave (trifluoromethyl)vinyl derivatives in 23-86% yields, with generally moderate stereoselectivity. Straightforward synthesis of the Julia-Kocienski reagent, and conversion to trifluoromethyl-substituted alkenes under mild reaction conditions, are the advantages of this approach. (C) 2013 Elsevier Ltd. All rights reserved.
Synthesis of CF<sub>3</sub>-Substituted Olefins by Julia-Kocienski Olefination Using 2-[(2,2,2-Trifluoroethyl)sulfonyl]benzo[<i>d</i>]thiazole as Trifluoromethylation Agent
作者:Andreas Hafner、Tobias S. Fischer、Stefan Bräse
DOI:10.1002/ejoc.201301070
日期:2013.12
A modified Julia–Kocienski protocol was investigated for the synthesis of CF3-substituted terminal olefins. By employing a simple one-step procedure, aldehydes were converted into the corresponding CF3-substitutedolefinsusing2-[(2,2,2-trifluoroethyl)sulfonyl]benzo[d]thiazole as the trifluoromethylationagent. This sulfone was prepared on a gram scale in two steps from inexpensive and commercially
of 1°, 2°, and 3° alkyl radicals through the single-electron transfer of sulfones under mild reaction conditions. These alkyl radicals generated via the reductive desulfonylation of readily synthesized and stable alkylsulfones were engaged to forge C–C bonds. A detailed study was also carried out to shed light on the mechanism.