T. Nakajima et al., RING-ENLARGEMENT OF CYCLOPROPYLACYLSILANES WITH SULFURIC OR TRIFLIC ACID - SELECTIVE FORMATION OF CYCLOBUTANONES OR 2-SILYL-4,5-DIHYDROFURANS, Tetrahedron letters, 36(10), 1995, pp. 1667-1670
Reaction of cyclopropylacylsilanes with sulfuric or triflic acid in ap
rotic solvent affords the corresponding cyclobutanone or 2-silyl-4,5-d
ihydrofuran derivatives, depending upon the substituents on the three-
membered ring or acid used. The use of triflic acid results in the sel
ective formation of the dihydrofurans.