PTC has been reported for several oxidations using TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy, free radical). In such oxidations, TEMPO is used catalytically and the phase-transfer catalyst is used to transfer the stoichiometric oxidant to regenerate the active TEMPO oxidant. In this case, the oxidant is hypochlorite used in 21.5 mole% excess. The reaction was performed until full conversion of starting material was observed by HPLC (in-process control).
The inventors also reported the use of silica-supported TEMPO and polystyrene-supported TEMPO.
The mechanism for TEMPO oxidation: https://www.organic-chemistry.org/chemicals/oxidations/tempo-2,2,6,6-tetramethylpiperidinyloxy.shtm
The purpose of synthesizing the ketone was to serve as a starting material for the asymmetric transfer hydrogenation of the substituted bicyclic pyridine ketone in presence of a chiral ruthenium catalyst.
In the past, we described PTC oxidations with TEMPO in the following examples.
http://phasetransfercatalysis.com/ptc_tip/ptc-oxidation-with-hypochlorite-and-hydroxy-tempo/
http://phasetransfercatalysis.com/ptc_tip/ptc-tempo-hypochlorite-oxidation/
http://phasetransfercatalysis.com/ptc_tip/combining-ptc-with-high-shear/
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!).
