Hypervalent-iodine mediated one-pot synthesis of isoxazolines and isoxazoles bearing a difluoromethyl phosphonate moiety.

A one-pot, regioselective 1,3-dipolar cycloaddition of in situ generated (diethoxyphosphoryl)difluoromethyl nitrile oxide toward selected alkenes and alkynes is reported. This protocol enables facile access to 3,5-disubstituted isoxazolines and isoxazoles bearing a CF2P(O)(OEt)2 moiety in good to excellent yields, under mild reaction conditions.

Synthesis of (α,α-difluoropropargyl)phosphonates via aldehyde-to-alkyne homologation.

An efficient synthetic methodology to a series of novel alkynes bearing a difluoromethylenephosphonate function via a Corey-Fuchs-type sequence starting from (diethoxyphosphoryl)difluoroacetic aldehyde is described. Dehydrobromination of the intermediate (3,3-dibromodifluoroallyl)phosphonate with potassium tert-butoxide gave rise to the corresponding bromoalkyne, whereas upon treatment with lithium base, the generation of ((diethoxyphosphoryl)difluoropropynyl)lithium has been achieved for the first time. The synthetic potential of this lithium reagent was further demonstrated by its reactions with selected electrophiles such as aldehydes, ketones, triflates, chlorophosphines, and chlorosilanes, leading to the corresponding propargyl phosphonates in good to excellent yields.