Practical and Efficient Synthesis of Alkyl, Alkenyl and Aryl-alkyl α,α-Difluoro Esters as Precursors of Potential Inhibitors of the Pheromone Catabolism in Insects

Abstract

An efficient method for the synthesis of long chain alkyl, alkenyl and aryl-alkyl α,α-difluoro esters through reductive cleavage of the corresponding S-methyl dithiocarbonates with diphenylphosphine oxide and di-tert-butyl peroxide as initiator is reported. The α,α-difluoro esters 4a-j have been obained for the first time and in good overall yields. A limitation of the method is the presence of radical-sensitive functions, such as disubstituted double or triple bonds, in the substrate since the concomitant addition of the phosphonyl radical to the unsaturated carbons may induce isomerization of the double bond or polymerization. If stereomerically pure alkenyl α,α-difluoro esters are required, it is suggested to run the reductive cleavage on the S-methyl dithiocarbonate of the acetylenic precursor followed by stereoselective hydrogenation to the alkene.