Hydroalumination reactions employing the bulky dialkylaluminum hydride [(Me3Si)2HC]2Al-H -: Prevention of secondary reactions

Usually, the hydroalumination of alkynes results in secondary reactions under release of the corresponding trialkylaluminum compounds. In contrast, the monoaddition products of R2Al-H to C≡ C triple bonds [R2Al-(R')C=C(R")-H] could be isolated in high yields now by employing the bulky dialkylaluminum hydride [(Me3Si)(2)HC](2)Al-H (1). This is shown here by two reactions starting with a monoalkyne (Me3C-C≡ C-C6H5) and a dialkyne (Me3C-C≡ C-C6H4-C=C-CMe3). Both products have the aluminium atoms attached to those carbon atoms of the C=C double bonds which are in the a-position with respect to the phenyl groups. The configuration of the alkenyl groups verifies the cis-addition of the Al-H bonds in all cases.