Additive-free regio- and diastereoselective construction of fully-substituted isoxazolidines employing diazo compounds

An efficient additive-free three-component reaction of trifluorodiazoethane, nitrosobenzene, and allenic esters has been uncovered. This protocol provides easy access to a variety of trifluoromethylated isoxazolidines with good functional group tolerance. Moreover, this methodology was found to be extendable to α-diazomethylphosphonate providing phosphonylated isoxazolidines. The utility of these products has been demonstrated by the expedient synthesis of trifluoromethylated lactam.