In last month’s PTC Tip of the Month, we showed how using PTC can save money by reducing the excess amount of borohydride for the reduction of a ketone to a secondary alcohol shown in the figure. We promised to highlight another clever aspect of this patent, so here it is.
When performing the reduction of terfenadone to terfenadine using ethanolic borohydride, the product is obtained as the low melting polymorph. The product must be recrystallized from xylene to obtain the high melting polymorph for formulation. The clever inventor, Dr. Magni, decided to use xylene as the solvent for the reaction when shifting to the PTC system. He knew that he could transfer borohydride into a variety of organic solvents when using a quaternary ammonium phase-transfer catalyst, so he chose to use the recrystallization solvent as the reaction solvent! It worked and he eliminated a solvent exchange unit operation, thereby obtaining the desired polymorph directly from the reaction solvent.
The flexible choice of solvent is one of the many great advantages that you enjoy when using phase-transfer catalysis.
If you have any chance of streamlining a process using PTC and you’re not sure if it will work, feel free to contact Marc Halpern to get an estimate of the probability of success of your potential PTC application. Don’t let your company waste precious money that could be turned into profit by using phase-transfer catalysis!
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!).
