“…As a matter of fact, when the added alkyl halide is different from the halide formed during the reaction, a mixture of the two corresponding phosphonopyrrolidines is obtained. 180 One example of 1,4-addition was described under modified conditions. In the presence of a Lewis acid, ring contraction of 6H-1,2-oxazine 396 occurs with the formation of an R,β-unsaturated nitrone 397.…”