This patent that was issued last week describes a PTC esterification of benzoic acid to produce chloromethyl benzoate.
Chloromethyl chlorosulfate has been used for chloromethylation, including in the synthesis of chloromethyl esters, without generation of the highly carcinogenic bischloromethyl ether as a by-product. Chloromethyl chlorosulfate was chosen to produce chloromethyl benzoate by the inventors in this patent.
Interestingly, the inventors thought about using PTC for this esterification but did not use PTC for the next reaction to replace chloride with iodide, in which PTC should excel and would not require isolation of the intermediate if performed in a well chosen solvent.
Even more surprising is that the inventors chose to perform an esterification of benzoic acid with an iodomethyl carbonate using silver oxide and not a simple PTC procedure. Furthermore, the inventors did not use PTC for another esterification and an N-alkylation. All of these reactions are shown in Scheme 1 in columns 103 and 104 of the patent.
We often find it surprising when inventors use PTC for one reaction in a sequence in which PTC excels but do not use PTC for other reactions in the sequence in which PTC also excels. Then again, we recognize that the best applications of PTC are not always obvious to non-experts outside of the highly specialized nihe of phase-transfer catalysis.
If you are not sure whether you should or can use phase-transfer catalysis for an application for which you must achieve low-cost high-performance green chemistry, now contact Marc Halpern of PTC Organics and/or complete the form at www.phasetransfer.com/projectform.pdf to obtain a free estimate of the probability of success for using PTC to meet your performance targets.
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!).
