1,1-Phosphinoboration of diazomethanes

The reactions of the phosphinoboranes Ph 2 PBMes 2 , Ph 2 PBpin, and Ph 2 PBcat with the diazomethanes Ph 2 CN 2 , C 12 H 8 CN 2 , and EtO 2 CCHN 2 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(PR 2 )(Bpin) (R = Ph 7, t Bu 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. The reactions of the phosphinoboranes Ph 2 PBMes 2 , Ph 2 PBpin, and Ph 2 PBcat with the diazomethanes Ph 2 CN 2 , C 12 H 8 CN 2 , and EtO 2 CCHN 2 are shown to give products of 1,1-phosphinoboration.