Carboalumination internal alkynes

Carboalumination of alkynes is possible in the presence of the zirconium catalyst Cp2ZrCl2. The method is particularly attractive for methylalumination using Me3 A1 and can tolerate a wide variety of functional groups. Terminal alkynes react with very good regioselectivity ( 95 5) and excellent stereoselectivity (>98%) in favour of the alkenyl aluminium species, such as 58 (2.69). Mixtures of regioisomers often result when using internal alkynes with two different substituents. 

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