PNPCB heterocycles via thermal and Lewis acid catalyzed trans-hydroborations

Abstract

The compounds iPr₂P(BH₃)N₃1, tBu₂PCCR (R = Ph 2, tBu 3, Cy 4) and Ph₂PCCR (R = Ph 5, tBu 6, Cy 7) were reacted to give the products tBu₂P(CCR)NP(BH₃)iPr₂ (R = Ph 8, tBu 9, Cy 10) and Ph₂P(CCR)NP(BH₃)iPr₂ (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(CCHPh)NP(BH₂)iPr₂14 and tBu₂P(CCHPh)NP(BH₂)iPr₂15, respectively. Compounds 8–11 and 13–15 were crystallographically characterized and the mechanisms and implications for the synthesis of inorganic heterocycles are considered.