When working with active alkylating agent, especially benzyl halides and allyl halides, one can often produce an effective quaternary ammonium phase-transfer catalyst by adding a trialkylamine to the alkylating agent forming the PTC in-situ or in advance.
In the patent shown here, the inventors used tributylamine to quaternize methylallyl chloride that was the alkylating agent to etherify a phenol followed by a Claisen rearrangement. The methylallyl chloride served as both alkylating agent for the etherification and source for the alkyl group of the in-situ PTC quat.
An interesting and practical aspect of forming in-situ quat salts as phase-transfer catalysts from benzyl chloride or allyl chloride derivatives is that if they decompose by nucleophilic attack of the nucleophile present in the PTC system, they actually form the desired benzylated or allylated product and liberate the triakylamine that can requaternize to form more phase-transfer catalyst. This is not only elegant, it saves money since tributylamine is less expensive than TBAB. In fact, this in-situ phase-transfer catalyst was compared to TBAB in this patent and they had similar performance.
If you can benefit from optimal choice of phase-transfer catalyst, now contact Marc Halpern of PTC Organics Inc. to explore collaborative consulting to achieve the highest performance lowest cost processes for your company.
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!).
