アリルシランを用いた新規合成反応の開発

Abstract

Reported herein is the formation of both heterocycles and carbocycles by means of the nudeophilic attack of the hetero-atom onto the β-silyl carbocation intermediate generated from allylsilane. Thus, on treatment of β-keto ester with allylsilane bearing bulky silyl group in the presence of Lewis acid, [3+2] or [2+2] cycloaddition took place smoothly to afford silyl-substituted tetrahydrofuran or oxetane in good yield.ZrCl4 mediated [3+2] cycloannulation of allyldiisopropylphenylsilane with α, β-unsaturated diesters proceeded smoothly to afford silyl-substituted cyclopentanes highly stereoselectively in good yields. Subsequent oxidative cleavage of the carbon-silicon furnised cyclopentanols. Allyldiisopropylphenylsilane was found to work effectively as 2-hydroxy-1, 3-dipole equivalent in the [3+2] cycloaddition reactions.Bronsted acid catalyzed silicon-directed cyclization of allylsilane bearing hydroxy or sulfonamide moiety furnished silyl-substituted tetrahydrofuran or pyrrolidine derivatives stereoselectively in high yields. Chiral synthesis of pyrrolidine was achieved starting from enantiomerically pure aziridines.