Ring-enlargement of cyclopropylacylsilanes with sulfuric or triflic acid. Selective formation of cyclobutanones or 2-silyl-4,5-dihydrofurans
摘要:
Reaction of cyclopropylacylsilanes with sulfuric or triflic acid in aprotic solvent affords the corresponding cyclobutanone or 2-silyl-4,5-dihydrofuran derivatives, depending upon the substituents on the three-membered ring or acid used. The use of triflic acid results in the selective formation of the dihydrofurans.
γ-butyrolactones are obtained in good yields from 4-trimethylsilyl-3-alkyn-1-ols via Wacker-type oxidation reaction. A mechanism is proposed for this transformation: it involves two successive trans-hydroxypalladations followed by a [PdXSiMe3] syn-elimination and explains why the presence of the silyl group is essential in such a process.
Treatment of cyclopropyl silyl ketones with trimethylsilyl trifluoromethanesulfonate as a strong acid having low nucleophilic counter anion gives the corresponding 5-silyl-2,3-dihydrofuran derivatives, exclusively, regardless of substituents on the cyclopropane ring or silicon atom. The resulting 5-silyl-2,3-dihydrofuran derivatives exhibit both reactivities of the vinylsilane and the cyclic enolether in the