Synthesis of 2-tributylstannyl-1-alkenes from 2-tributylstannyl-2-propen-1-yl acetate

Abstract

2-Tributylstannyl-2-propen-1-yl acetate ( 2), which can be easily prepared from ethyl propynoate ( 5), represents a useful precursor to a variety of 2-tributylstannyl-1-alkenes of general formula 1. Thus, treatment of 2 with complex organocopper species of general formula RCu·MgBrX·LiBr ( 4) (R = alkyl, aryl, benzyl, allyl) affords compounds 1 in fair to excellent yields. However, this procedure is unsuccessful for the preparation of 2- tributylstannyl-1,4-pentadiene ( 1e) and 2,3-bis(tributylstannyl)-1-propene ( 1g). Nevertheless, compound 1g contaminated by hexabutylditin ( 13) can be synthetized by palladium-catalyzed reaction between 2 and (tributylstannyl)diethylaluminum ( 15). The reactions of ( E)-2-tributylstannyl-2-octen-1-yl acetate ( 22) with compounds 4h (R = i-Bu; X = Br) and 4b (R = Ph; X = Br) have been also investigated. These reactions, when carried out in THF solution, provide mixtures of two regioisomers of general formula 23 and 1, respectively, in which the prevailing components are those derived from a γ-substitution reaction. Compound 23b, free of the corresponding regioisomer 1k, has been synthesized in low yield by palladium-catalyzed cross-coupling reaction between 22 and phenyltrimethylstannane ( 25). Moreover, two N-substituted derivatives of 3-amino-2-tributylstannyl-1-propene, i.e. compounds 11 and 1m have been prepared by palladium-catalyzed amination of 2.