PTC demethylation of ethers is known using HCl, HBr and HI. In this Sept 2015 patent, the authors used boron tribromide as the demethylating agent catalyzed by tetrabutylammonium iodide. The mechanism of demethylation with boron tribromide is shown in this link.
We may assume that the role of the iodide is to attack the methyl group to form methyl iodide which should be faster than the attack of the bromide, liberated from the BBr3, on the methyl group. The iodide can then be displaced by the excess bromide to form methyl bromide and release the iodide for another catalytic cycle.
The isolated yield reported is only 35% which may be low due handling losses after column chromatography.
If this reaction needed to be scaled up for commercial purposes, we would recommend exploring replacing the toxic and expensive boron tribromide with HCl or HBr ad a phase-transfer catalyst.
If your company wants to reduce the cost of acid reactions such as demethylation, HCl addition across a double bond or other acid reactions or acid-catalyzed reactions, now contact Marc Halpern of PTC Organics to integrate highly specialized expertise in industrial phase-transfer catalyze into your process development and optimization programs.
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!).
