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.