Synthesis and Characterization of R2PNP(iBuNCH2CH2)3N: A New Bulky Electron-Rich Phosphine for Efficient Pd-Assisted Suzuki−Miyaura Cross-Coupling Reactions
摘要:
Pro-azaphosphatrane 1a [P((BuNCH2CH2)-Bu-i)(3)N] reacts with iodine under mild conditions to give [IP((BuNCH2CH2)-Bu-i)(3)N]I in excellent yield, which on subsequent reaction with ammonia followed by deprotonation with (KOBu)-Bu-t provided HN=P((BuNCH2CH2)-Bu-i)(3)N (3a) in quantitative yield. Reaction of 3a with R'2PCl afforded sterically bulky electron-rich phosphines of the type R'2PN=P((BuNCH2CH2)-Bu-i)(3)N (4) [R' = Ph (4a), Pr-i (4b), Bu-t (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.