Metal-Free Synthesis of Homopropargylic Alcohols from Aldehydes.

The synthesis of homopropargylic alcohols under metal-free and mild condition is described. This transformation is based on a one-pot procedure involving sequential α-alkynylation of acyclic aldehydes using hypervalent iodine reagents and borohydride reduction. The chemistry exhibits broad substrate scope and good scalability, providing a convenient route for the α-alkynylation of aldehydes along with the formation of a quaternary carbon center. The applicability of the method is demonstrated by the gram-scale synthesis of the key synthetic precursor of botulinum toxin inhibitors.