PNPCB heterocycles via thermal and Lewis acid catalyzed trans-hydroborations

The compounds iPr(2)P(BH3)N-3 1, tBu(2)PC=CR (R = Ph 2, tBu 3, Cy 4) and Ph2PC=CR (R = Ph 5, tBu 6, Cy 7) were reacted to give the products tBu(2)P(C=CR)NP(BH3)iPr(2) (R = Ph 8, tBu 9, Cy 10) and Ph2P(C=CR)NP(BH3)iPr(2) (R = Ph 11, tBu 12, Cy 13). Subsequent thermally induced or Lewis acid catalyzed intramolecular hydroboration of 8 and 11 afforded the PNPCB heterocyclic compounds Ph2P(C-CHPh)NP (BH2)iPr(2) 14 and tBu(2)P(C-CHPh)NP(BH2)iPr(2) 15, respectively. Compounds 8-11 and 13-15 were crystallographically characterized and the mechanisms and implications for the synthesis of inorganic heterocycles are considered.