Fluoride-Assisted Activation of Calcium Carbide: A Simple Method for the Ethynylation of Aldehydes and Ketones

The fluoride-assisted ethynylation of ketones and aldehydes is described using commercially available calcium carbide with typically 5 mol % of TBAF center dot 3H(2)O as the catalyst in DMSO. Activation of calcium carbide by fluoride is thought to generate an acetylide ate-complex that readily adds to carbonyl groups. Aliphatic aldehydes and ketones generally provide high yields, whereas aromatic carbonyls afford propargylic alcohols with moderate to good yields. The use of calcium carbide as a safe acetylide ion source along with economic amounts of TBAF center dot 3H(2)O make this procedure a cheap and operationally simple method for the preparation of propargylic alcohols.