Assessing the utility of HAlCl2 derived vinylalanes for Michael addition

Rare alkenylalanes are prepared by Cp2TiCl2 or Cp*2ZrCl2 (Cp = η-C5H5; Cp* = η-C5Me5) catalysed addition of HAlCl2·(THF)2 to terminal alkynes (R1CCH; R1 = alkyl). Use of minimum head-volume sealed vials maximises the hydroalumination yields of volatile alkynes. Facile 1,4-addition of the resultant alkenylalanes to unsaturated malonates R2CHC(CO2R3)2 (R2 = alkyl, aryl, R3 = alkyl) is observed providing rapid and convenient access to the addition products.