Allenylations 3-trimethylsilyl-1 -propyne

Organo-silanes and -stannanes possessing sp caibon-metal bonds also add to carbonyls in the presence of Lewis acids. Alkynylation with silyl- and stannyl-alkynes is promoted by AICI3 or ZtiGz (equations 9 and 10). " Notably, the reaction of l,3-bis(trimethylsilyl)-l-propyne with chloral affords alkynic alcohol instead of allenylic alcohol, showing the preferential cleavage of sp C—Si bonds (equation 11). ... 

Wang et al [2] have reported that treatment of the readily available 3-(fert-butyl-dimethylsilyl)-l-(trimethylsilyl)-l-propyne [4] with n-butyllithium, followed by B-MeO-9-BBN and 4/3 BFj-OEtj [5] yields B-allenyl-9-BBN. The condensation of B-allenyl-9-BBN with hexanal or benzaldehyde and followed by the elimination step of the Peterson olefination [3] affords the conjugated enynes (Scheme 24.15) [2]. 

Methoxy-l-phenyl-l-propyne in anhydrous ether added at -75° under argon to 2 moles butyllithium in the same solvent, stirred 15 min., 1 mole ethyl bromide in ether added slowly, stirred 15 min., then trimethylsilyl chloride in ether added, allowed to warm to room temp, with stirring, the soln. of the intermediate allenyl ether (Y 82% if isolated) treated with 20%-HCl, and refluxed 5 hrs. product. Y 76%. F. e. s. Y. Leroux and R. Mantione, J. Organometal. Chem. 30, 295 (1971). 

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