Derivatives of new bicyclic systems-1H-thieno[3,2-c][1,5,2]oxazaphosphinine and 1,2-dihydrothieno[2,3-b][1,4]azaphosphinine have been obtained by phosphorylation of N-substituted derivatives of 5-amino-2-methoxycarbonylthiophene with phosphorus (III) tribromide. These heterocyclizations can be carried out in the basic medium and under mild conditions. The end reaction products were studied by means of chemical analysis, 1 H and 31 P NMR spectroscopy.