Allylic tributyltins add to aromatic alakhydes to afford regioreversed a-a&iuct predominantly with almost complete retention of the stereochemistry of the allylic groups under photochemical conditions. The photoinduced single ekctron transfer mechanism is proposed.
The addition of allyltin reagents to aldehydes has been extensively developed for the useful carbon-carbon bond construction in organic synthesis over the past decade.1 The addition reaction has been promoted by Lewis acids? heat? and high pressure.* In general, the reaction of aldehydes with the substituted allylic stamtanes under these conditions results in the products in which the allylic group is attached at the more highly substituted position (y-adduct). On the other hand, the regioreversed addition of the allylic stannanes to aldehydes to produce linear homoallylic alcohols (a&duct) has been scarcely studied.5 but the stereoselective addition with retention of the double-bond geometry of the allylic group in the tin reagents is totally unprecedented despite their gmat potential importance in organic synthesis. 6 Recently, we found that the addition maction of allyltrialkyltins to carbonyl compounds such as benzophenone, enone, and benxil could be also promoted by light7 Herein. we report that the photoinduced a-m&selective and stereospecific allylation of aromatic aldehydes using (I?)-and (Z)-allylic tributyltins.