Phase-transfer catalysis excels in transferring and reacting all kinds of oxidizing agents including permanganate and dichromate. Permanganate has a very high affinity for quaternary ammonium cations that enhances the extractability of this anionic oxidant. The first publication that launched the field of PTC, authored by Charles Starks, explicitly cited the use of Aliquat 336 with potassium permanganate (taught on page 197 of our PTC course manual). Another of the earliest PTC publications in the 1970’s was entitled “Purple Benzene” to describe what happens when you mix a quaternary ammonium salt with potassium permanganate and benzene (yes…we used benzene as a solvent in the 70’s!).
We don’t often see patents recently that cite the use of PTC with permanganate, but this August 2019 patent shows the reaction in the diagram that oxidizes a geminal alkene to a ketone using bicarbonate for pH control. A full equivalent of tetrabutylammonium hydrogen sulfate was used instead of catalytic quantity and it is not clear why so much was chosen to be used by the inventors.
PTC-permanganate oxidation of alkenes can produce a variety of products including diols, aldehydes, ketones, carboxylic acids and hydroxy-ketones depending on [1] the structure of the substrate [2] the pH of the aqueous phase in liquid-liquid PTC-permanganate systems and [3] and whether using aqueous workup or dry workup for solid-liquid PTC-permanganate systems. For more details, contact Marc Halpern of PTC Organics to explore PTC consulting to achieve your company’s process development goals.
One challenge of the use of PTC-permanganate reactions for commercial applications is the formation of manganese dioxide precipitate that is difficult to filter as a finely divided solid.
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!).
