Formal 2+1 Annulation (Spiro-Cyclopropanation) Reaction between Sulfur Ylides Derived from Baylis-Hillman Bromides and Arylidene Indane-1,3-Dione

摘要

abstract_textpThe sulfonium salts derived from the Baylis-Hillman bromides have been successfully employed for the selective cycloproporanation of arylidene indane-1,3-diones to synthesize densely substituted spiro-cyclopropanes in good to excellent yields (upto 94). Products were obtained mostly in 1:1 diastereomeric ratio and were isolated in pure form. Diastereoselectivity has been improved by using suitably substituted starting materials. In this case a formal 2+1 annulation reaction competes over a probable 3+2 cycloaddition reaction. The reaction proceeds through a Michael initiated ring closure process of S-ylides to the activated olefins for the formation of structurally strained spiro-cyclopropanes./p/abstract_text