Systematic synthesis of multifluorinated α,α-difluoro-γ-lactones through intramolecular radical cyclization

Article abstract of DOI:10.1021/jo982035b

Carbon radicals from allyl O-(trimethylsilyl)-α-bromo-α,α- difluoroacetal can cyclize onto the olefinic part regiospecifically to give γ-lactols in good yield. The lactols are then converted to the corresponding α,α-difluoro-γ-lactones. Systematic synthesis of multifluorinated-α,α- difluoro-γ-lactones has thus been accomplished through intramolecular radical cyclization as a key reaction. Semiempirical MO calculation study suggested a unique nature of α,α-difluoroacetate in that complete delocalization of the electrons in the SOMO orbital of α,α-difluoroacetyl radical occurred; this caused unsuccessful cyclization. To apply the present radical reaction, the first synthesis of both enantiomers of difluoroeldanolide, analogues of the sex pheromone of the male African sugarcane borer, has been demonstrated. Electrophysiological tests revealed that the difluorinated analogues were as active as the natural eldanolide on the olfactory receptors.