The hydroalumination of diethynes with di(tert-butyl)aluminium hydride: a facile method for the synthesis of organometallic dialuminium compounds

Di(tert-butyl)aluminium hydride reacted with the diynes 1,4-bis(trimethylsilyl)-1,3-butadiyne and 1,4-bis(trimethylsilylethynyl)benzene by hydroalumination and addition of one Al–H bond to each CC triple bond. A selective cis addition was observed in both cases to yield alkenes with Z configuration exclusively. The aluminium atoms were attached to those carbon atoms which bear the trimethylsilyl groups. While the butadiyne product (1) decomposed upon heating in benzene solution, the diene (2), obtained by the twofold hydroalumination of 1,4-bis(trimethylsilylethynyl)benzene, showed a remarkable rearrangement and gave the thermodynamically favoured product (4) almost quantitatively, which has two alkenes in E configuration. All products were characterized by crystal structure determinations.