Synthesis of the spiro derivatives of 1,2-oxaphosphetes by [2+2] cycloaddition of cyclic 1-(2,4,6-triisopropylphenyl)phosphine oxides with dimethyl acetylenedicarboxylate

Members of a new heterocyclic family, 1,2-oxaphosphetes were prepared by th e unexpected [2+2] cycloaddition of the P=O group of 1-(2,4,6-triisopropylp henyl) P-heterocycles with the acetylene moiety of dimethyl acetylenedicarb oxylate. The new oxaphosphetes are spiro derivatives of the starting hetero cycles and exhibit a phosphorus atom with trigonal bipyramidal geometry. PM 3 semiempirical calculations justified the novel reaction path and suggeste d a stepwise reaction mechanism. (C) 2000 Elsevier Science Ltd. All rights reserved.