Synthesis and Characterization of R₂PNP(ⁱBuNCH₂CH₂)₃N: A New Bulky Electron-Rich Phosphine for Efficient Pd-Assisted Suzuki−Miyaura Cross-Coupling Reactions

Pro-azaphosphatrane 1a [P(iBuNCH2CH2)3N] reacts with iodine under mild conditions to give [IP(iBuNCH2CH2)3N]I in excellent yield, which on subsequent reaction with ammonia followed by deprotonation with KOtBu provided HNP(iBuNCH2CH2)3N (3a) in quantitative yield. Reaction of 3a with R‘2PCl afforded sterically bulky electron-rich phosphines of the type R‘2PNP(iBuNCH2CH2)3N (4) [R‘ = Ph (4a), iPr (4b), tBu (4c)]. The Pd(OAc)2/4c catalyst system was particularly efficient for the coupling of arylboronic acids with aryl bromides as well as aryl chlorides to give biaryls in excellent yields.