There are many different alkyl triphenyl phosphonium salts that are used as phase-transfer catalysts for high temperature reactions and for the second step of producing epoxy resins to build molecular weight. One attempt to use methyl triphenyl phosphonium bromide is described in this month’s PTC Reaction of the Month for a Fluoride-Halex Reaction.
A patent was issued this month (Watanabe, T.; Miyake, Y.; Kinsho, T.; (Shin-Etsu Chemical) US Patent 10,737,999, 11-Aug-2020) describing the preparation of pentyltriphenylphosphonium bromide. Even though this was for a Wittig reaction for an agrochemical intermediate and not as a phase-transfer catalyst, we are highlighting here how simple it is to synthesize these salts.
The synthesis is simply: To a reactor were charged 1-bromopentane (185 g, 1.20 mol), triphenylphosphine (321 g, 1.20 mol) and N,N-dimethylformamide (225 g), and the resulting mixture was stirred at 110 C to 115 C for 6 hours to prepare pentyltriphenylphosphonium bromide.
About Marc Halpern
Dr. Halpern is founder and president of PTC Organics, Inc., the only company dedicated exclusively to developing low-cost high-performance green chemistry processes for the manufacture of organic chemicals using Phase Transfer Catalysis. Dr. Halpern has innovated PTC breakthroughs for pharmaceuticals, agrochemicals, petrochemicals, monomers, polymers, flavors & fragrances, dyes & pigments and solvents. Dr. Halpern has provided PTC services on-site at more than 260 industrial process R&D departments in 37 countries and has helped chemical companies save > $200 million. Dr. Halpern co-authored five books including the best-selling “Phase-Transfer Catalysis: Fundamentals, Applications and Industrial Perspectives” and has presented the 2-day course “Practical Phase-Transfer Catalysis” at 50 locations in the US, Europe and Asia.
Dr. Halpern founded the journal “Industrial Phase-Transfer Catalysis” and “The PTC Tip of the Month” enjoyed by 2,100 qualified subscribers, now beyond 130 issues. In 2014, Dr. Halpern is celebrating his 30th year in the chemical industry, including serving as a process chemist at Dow Chemical, a supervisor of process chemistry at ICI, Director of R&D at Sybron Chemicals and founder and president of PTC Organics Inc. (15 years) and PTC Communications Inc. (20 years). Dr. Halpern also co-founded PTC Interface Inc. in 1989 and PTC Value Recovery Inc. in 1999. His academic breakthroughs include the PTC pKa Guidelines, the q-value for quat accessibility and he has achieved industrial PTC breakthroughs for a dozen strong base reactions as well as esterifications, transesterifications, epoxidations and chloromethylations plus contributed to more than 100 other industrial PTC process development projects.
Dr. Halpern has dedicated his adult life to his family and to phase-transfer catalysis (in that order!).
