Chemo- and Regioselective Dimerization of Terminal Alkynes Promoted by Methylaluminoxane.

Methylalumoxane (MAO) was found to be an active catalytic precursor for the chemo- and regioselective dimerization of a wide range of aryl- and alkyl-substituted terminal alkynes yielding the corresponding geminal dimers A. For an olefin-functionalized terminal alkyne (RC&tbd1;CH, R = MeC=CH(2)), the geminal dimer undergoes an intermolecular [4 + 2] cycloaddition forming compound B.