A FACILE PREPARATION METHOD FOR ALPHA,ALPHA-DIFLUOROALKANECARBOXYLIC ACIDS AND ESTERS - A FORMAL DIFLUOROMETHYLENE INSERTION TO ALKANECARBOXYLIC ACIDS USING RADICAL REACTION

Various alkyl radicals generated by the photoreaction of a series of B arton esters reacted with 1,1-dichloro-2,2-difluoroethene to give radi cal adducts as the major product accompanied with self-trapping produc ts. Primary, secondary, tertiary, benzyl, and some unsaturated alkyl r adicals as well as those with another functional group such as ether, carbonyl, and azide were applicable. Barton esters of diacids also aff ord 1:2 adducts with a small amount of 1:1 adducts and his-self-trappi ng products except for the succinic case. These adducts were hydrolyze d with AgNO3/H2O-THF to alpha,alpha-difluoroalkanecarboxylic acids and methanolyzed with AgNO3/MeOH to the corresponding methyl esters. 4-Az ido-2,2-difluorobutylic acid and the methyl ester were converted to di fluoro-GABA and difluoro-gamma-lactams.