Phase-transfer catalysis is often used to improve transition metal catalyzed reactions. We have been reporting a lot of phase-transfer catalyzed Suzuki applications in recent years but not too many hydrogenations, though we teach some in our 2-day course “Industrial Phase-Transfer Catalysis.”
This month, Dr. Schnatterrer’s process R&D department at Bayer, that frequently develops PTC applications, screened nine tetramethyl-, tetraethyl- and tetrabutylammonium salts to enhance hydrogenation using 15 different palladium catalysts. The reaction shown in the diagram uses TBAB with palladium hydroxide on carbon (Noblyst P1071) in methanol. The product was isolated as a 20% solution in methanol. The methanolic solution of the amine product was used in te next step which was a N-benzoylation.
Other PTC palladium co-catalyzed hydrogenations we have seen use Aliquat 336 as the phase-transfer catalyst and toluene as the solvent.
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!).
This month, Dr. Schnatterrer’s process R&D department at Bayer, that frequently develops PTC applications, screened nine tetramethyl-, tetraethyl- and tetrabutylammonium salts to enhance hydrogenation using 15 different palladium catalysts. The reaction shown in the diagram uses TBAB with palladium hydroxide on carbon (Noblyst P1071) in methanol. The product was isolated as a 20% solution in methanol. The methanolic solution of the amine product was used in te next step which was a N-benzoylation.