1,1-Phosphinoboration of diazomethanes

The reactions of the phosphinoboranes Ph₂PBMes₂, Ph₂PBpin, and Ph₂PBcat with the diazomethanes Ph₂CN₂, C₁₂H₈CN₂, and EtO₂CCHN₂ are shown to give products of 1,1-phosphinoboration. The products (1–6) are shown to have PNB linkages with three-coordinate boron centers, whereas the products (EtOOC)CNN(PR₂)(Bpin) (R = Ph 7, tBu 8) form zwitterionic heterocycles resulting from chelation of the ester carbonyl to boron. DFT calculations show that the reactions are initiated by N-to-B addition followed by 1,2-phosphinyl shift.