Pd(0)-catalyzed addition of Me3SnSnMe3 to α,β-alkynic aldehydes and ketones. Synthesis of (Z)-β-trimethylstannyl α,β-alkenic aldehydes and ketones. Preparation and synthetic uses of substituted (Z)-4-trimethylstannyl-1,3-butadienes

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Abstract
Treatment (dry tetrahydrofuran, reflux) of the α,β-alkynic aldehydes 26–28 and ketones 29–36 with Me3SnSnMe3 in the presence of a catalytic amount of (Ph3P)4Pd provides fair to excellent yields of the corresponding (Z)-β-trimethylstannyl α,β-alkenic aldehydes 41–43 and ketones 44–51. The carbonyl compounds 41–51, upon reaction with methylenetriphenylphosphorane under suitable conditions, are smoothly converted into the (Z)-4-trimethylstannyl-1,3-butadienes 61–71, respectively. Treatment of the aldehyde 41 with the anion of trimethyl phosphonoacetate and the aldehyde 42 with the anion of the phosphonoacetate 73 produces excellent yields of the 5-trimethylstannyl-2,4-heptadienoates 72 and 74, respectively. The synthetic potential of (Z)-4-trimethylstannyl-1,3-butadienes is illustrated by the conversion of 62 into the functionalized, stereodefined conjugated dienes 76 and 78 and by transformation of 87 into the structurally novel diene 84. Diels–Alder reactions of 84 with tetracyanoethylene and dimethyl acetylenedicarboxylate provide the spiro[3.5]nonane derivatives 88 and 89, respectively. Key words: Diels–Alder cycloaddition, organocopper(I), transmetallation, alkylidenecyclobutane, (E)-4-lithio-1,3-butadienes, spiro[3.5]nonane.