摘要:
Six substituted vinylstannanes have been prepared. (E)- and (Z)-2-trimethylstannyl-2-butene, (1) and (2), respectively, 2-methyl-1-(trimethylstannyl) propene, (3), and 3-methyl-2-trimethylstannyl-2-butene, (4), were prepared by coupling the appropriate lithium or Grignard. reagent with chlorotrimethylstannane. 3-Trimethylstannyl-3-butene-2-one, (5), and (Z)-3-trimethylstannyl-3-hexene-2-one, (6), were prepared by palladium(O) catalyzed hydrostannation of the appropriate ynone. This reaction was regiospecific such that the trimethylstannyl and carbonyl groups were bonded at the same vinyl carbon. The reaction was also stereospecific giving syn addition in each case. However, isomerization to a mixture of isomers was observed for the reaction of (5) with Me3SnD and complete isomerization of E-(6) to Z-(6). Each compound was characterized by H-1, C-13, and Sn-119 NMR. The reactivity to protodestannylation was determined for each compound by spectrophotometric measurement of second order rate constants. The reactivity of the multimethyl-substituted vinylstannanes was consistent with the reactivity determined previously for monomethyl-substituted vinylstannanes. However, two methyl groups at the remote vinyl carbon exhibited a synergistic activating effect on the protodestannylation reactivity. The acyl group was found to be deactivating for protodestannylation. The stereochemistry of the reaction was found to take place with retention of configuration.