PHENYL-SUBSTITUTED VINYLSTANNANES - SYNTHESIS AND REACTIVITY IN ELECTROPHILIC SUBSTITUTION-REACTIONS

Seven phenyl-substituted vinylstannanes have been prepared. (Z)-beta-(trimethylstannyl)styrene, alpha-(trimethylstannyl)styrene, and 1,1-diphenyl-2-(trimethylstannyl)ethene were prepared by Grignard coupling between the appropriate phenyl-substituted vinyl bromide and chlorotrimethylstannane. (E)-beta-(Trimethylstannyl)styrene and (Z)-(trimethylstannyl)stilbene were prepared by AIBN catalyzed hydrostannation of the appropriate phenyl-substituted acetylene. (E)-(Trimethylstannyl)stilbene and methyl (E)-2-(trimethylstannyl)cinnamate were prepared by palladium(0) catalyzed hydrostannation of diphenylacetylene and methyl phenylpropiolate, respectively. Each compound was characterized by H-1, C-13, and Sn-119 NMR. Reactivity of each compound to protodestannylation was determined by spectrophotometric or H-1 NMR measurement of second order rate constants. The relative reactivity is interpreted on the basis of the electronic and steric effects of the phenyl substituents. The stereochemistry of destannylation resulted in retention of configuration for four of the compounds, consistent with an S(E)2 mechanism. However, methyl (E)-2-(trimethylstannyl)cinnamate gave an E/Z product ratio of essentially. This result is consistent with an allenol mechanism for protodestannylation of this compound.