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.
RING OPENING AND ENLARGEMENT OF CYCLOPROPYL TRIMETHYLSILYL KETONES BY ACIDS
作者:Tadashi Nakajima、Hiroyuki Miyaji、Masahito Segi、Sohei Suga
DOI:10.1246/cl.1986.181
日期:1986.2.5
The reaction of a series of cyclopropyl trimethylsilyl ketones with acids proceeds under milder conditions compared to that of their carbonanalogs to give either the ring opening products, 3-chloropropyl trimethylsilyl ketones, or the ringenlargement products, 2-trimethylsilyl-4,5-dihydrofuran derivatives.
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
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.