A new method is developed for the synthesis of 2-substituted 2-oxo-1,2 lambda (5)-thiaphospholanes and thiaphosphorinanes (thiolphostones) on the basis of intramolecular Pishchimuka rearrangement of thiophosphonic and thiophosphinic esters with omega -chloroalkyl substituentsat the phosphorus atom. Intermediate compound in the Pishchimuka rearrangement, 2-ethyl-2-ethoxy-1,2 lambda (4)-thiaphospholanium perchlorate, was isolated.