Difluoromethylation of Terminal Alkynes by Fluoroform

The difluoromethylation of terminal
alkynes through the use of
fluoroform as a source of difluorocarbene is described. The choice
of solvents and bases was found to be crucial for the transformation.
A series of terminal alkynes 1 were nicely converted
into the corresponding difluoromethyl alkynes 2 using
potassium tert-butoxide in n-decane
in moderate to good yields. Functional groups such as methoxy, dimethylamino,
and bromo as well as phenyl, heteroaryl, and sterically demanding
naphthyl were well tolerated under the reaction conditions. One-step
transformations of difluoromethyl alkynes 2 to difluoromethylated
isoxazoles 3 and 1,2,3-triazoles 4 were
also achieved.