Formation of the P–C and C–C bonds in the Reaction of 2-(5-Methyl-2-phenyl-2H-1,2,3-diazaphosphol-4-yl)-4H-benzo[e]-1,3,2-dioxaphosphorin-4-one with Dimethyl Acetylenedicarboxylate under Mild Conditions

2-(5-Methyl-2-phenyl-2 H -1,2,3-diazaphosphol-4-yl)-4 H -benzo[ e ]-1,3,2-dioxaphosphorin-4-one reacts under mild conditions with dimethyl acetylenedicarboxylate with the participation by only threecoordinated phosphorus atom and the formation of 2-(5-methyl-2-phenyl-2 H -1,2,3-diazaphosphol-4-yl)-3,4-dimethoxycarbonylbenzo[f]-1,2-oxaphosphepine-2,5-dione. During the process, simultaneous formation of the P–C and C–C bonds takes place.