A Convenient Synthetic Route to Functionalized 5-Trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2<i>H</i>-pyrans: Hetero-Diels-Alder Reaction of β,β-Bis(trifluoroacetyl)vinyl Ethers with Electron-Rich Alkenes
作者:Masaru Hojo、Ryōichi Masuda、Etsuji Okada
DOI:10.1055/s-1990-26874
日期:——
Hetero-Diels-Alder reaction of β,β-bis(trifluoroacetyl)vinyl ethers, which are prepared by acylation of vinyl ethers with trifluoroacetic anhydride, with electron-rich alkenes such as vinyl ethers, ethyl vinyl sulfide and 1,1-diphenoxyethylene proceed quite easily under mild conditions to afford 2,4-dialkoxy-, 2-ethoxy-4-phenoxy-, 2-ethylthio-4-alkoxy-, 2,2-diphenoxy-4-ethoxy- and, 4-diaryloxy-5-trifluoroacetyl-6-trifluoromethyl-3,4dihydro-2H-pyrans in excellent yields.
β,β-二(trifluoroacetyl)乙烯醚的异源Diels-Alder反应,采用三氟乙酸酐对乙烯醚进行酰化后制备而成,与电子富含的烯烃(如乙烯醚、乙基乙烯硫醚和1,1-二苯氧乙烯)在温和条件下进行反应,反应十分顺利,获得了2,4-二烷氧基、2-乙氧基-4-苯氧基、2-乙基硫-4-烷氧基、2,2-二苯氧基-4-乙氧基和4-二芳氧-5-三氟乙酰基-6-三氟甲基-3,4-二氢-2H-吡喃类化合物,并且产率极高。