Diastereoselective addition of organocerium(III) reagents derived from 3-substituted propargyl bromides to aldehydes

Various cerium allenyl reagents were generated by transmetallation of allenyl Grignard compounds with CeCl3 and subsequent conversion into homopropargylic alcohols by addition to various aliphatic and aromatic aldehydes. The a-acetylenic alcohols were obtained with regioselectivities and diastereoselectivities up to 98% de in favor of the threo-diastereomers.