Two-Carbon Homologation of Aldehydes: An Efficient Route to Difluoromethyl Alkynes

We report a simple and efficient two-carbon homologation method to directly convert aldehydes into difluoromethyl alkynes by using the readily accessible and stable trifluoroethyl phosphine oxide Ph2P=O(CH2CF3). This reaction condition is compatible with a broad range of aldehydes. Deuterium-labeling experiments suggest that the reaction likely involve a key rearrangement of in-situ generated aryl difluoroallenes.