The reaction conditions for this reaction are a bit surprising at first glance since there are many PTC reactions that use dichlorodiphenylsulfone as the substrate for nucleophilic aromatic substitution (mostly by GE/SABIC) but are usually performed at higher temperature and use “special” thermally stable phase-transfer catalysts.
In this case, the inventors simply used TBAB and kept the temperature at a moderate 60 deg C which TBAB can withstand. It is possible that the mercaptide is sufficiently nucleophilic that higher temperature is not needed. In addition, the mercaptide anion doesn’t hydrate very much, so its nucleophilicity is not reduced very much. Moreover, aqueous mercaptide used in many other PTC patents is usually around 15% in water. This patent uses 32% aqueous mercaptide which starves the system for water more than usual. It is possible that by combining these various factors enables working at 60 deg C instead of over 100 deg C which would be challenging for TBAB stability.
If your process development program needs to improve process performance and R&D efficiency to achieve low-cost, high-performance green chemistry, now contact Marc Halpern to integrate the highly specialized expertise of PTC Organics in industrial phase-transfer catalysis with your company’s commercial goals.
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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!).
