Regioslective preparation of 2,4-, 3,4-, and 2,3,4-substituted furan rings. 2. Regioselective lithiation of 2-silylated-3-substituted furan rings

摘要

A new method for the preparation of 3,4-and 2,5-disubstituted furan rings is described. A variety of 2-silylated-3-(hydroxymethyl)furans and 2-silylated-3-furioc acids lithiate exclusively at C-4 when treated with 2.2 equivs of BuLi. The resulting dianions with variety of electrophiles to provide 2-silylated-3-(hydroxymethyl)-4-substituted furans and 2-silylated-4-substituted 3-furoic acids in good to excellent yields. Removal of the silyl group (n-Bu_4NF) provided a variety of 4-substituted-3-(hydroxymethyl)furans and methyl 4-substituted-3-furoates, respectively.