AN EFFECTIVE AND SELECTIVE CONJUGATE PROPARGYLATION REACTION OF STANNYLALLENES TO ALPHA-BETA-UNSATURATED CARBONYL-COMPOUNDS AND ALPHA-NITRO OLEFINS

Stannylallenes (1) reacted with a,β-unsaturated carbonyl compounds and a-nitro olefins in the presence of TiCl4 to give the corresponding conjugate propargylation products. Thus, the reaction of 1 with cyclic and acyclic a,β-unsaturated carbonyl compounds (2) gave 0-propargylic ketones (3) in high yields. With a-nitro olefins (4), two types of products, β-propargylic nitroalkanes (5) and a-propargylic ketones (6), were obtained selectively depending on the presence or absence of the a-substituent of 4. Transformations of the products (6) to cy-clopentenone derivatives (10 and 12) are also described. © 1990, American Chemical Society. All rights reserved.