1-Ethoxy-3-trifluoromethyl-1,3-butadiene and Congeners as Diels−Alder Components Opening an Entry to Functionalized (Trifluoromethyl)benzenes and -pyridines
作者:Jean-Noël Volle、Manfred Schlosser
DOI:10.1002/1099-0690(200205)2002:9<1490::aid-ejoc1490>3.0.co;2-1
日期:2002.5
1-Ethoxy-3-trifluoromethyl-1,3-butadiene and its 2-bromo- and 2-phenyl-substituted derivatives have been prepared by Wittig methylenation of the corresponding 4-ethoxy-1,1,1-trifIuoro-3-buten-2-ones, which in turn are readily accessible from trifluoroacetic acid. The electron-rich/electron-poor dienes combine smoothly with dimethyl acetylenedicarboxylate and methyl propiolate to provide trifluoromethyl-substituted phthalates (2, 6 and 10) or benzoates (3, 7, 8 and 11). Satisfactory yields [of 4-(trifluoromethyl)pyridinecarboxylic acids 4 and 12] can even be achieved with methyl cyanoformate, a less reactive dienophile, if a large excess of the dienophile is employed.((C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).