Even veteran PTC chemists should be surprised to see the name of this compound as a phase-transfer catalyst. The inventors were looking for a catalyst for chiral PTC that would be both effective to achieve high ee and high yield as well as be produced from inexpensive raw materials.
The term “pentanidium compounds” refers to alkylated salts of pentanidines that contain five nitrogen atoms in conjugation. The key starting material is one of the diasteromers of a simple material 1,2-diphenyl-1,2-diaminoethane which is subsequently converted to the chiral phase-transfer catalyst in five very simple steps that use rather inexpensive reactants. In fact, it appears that the most expensive reaction in the sequence is the simple N-alkylation of an imidazolidin-2-one that uses NaH/THF! As a PTC expert, it bothers me that such reactions that are obviously made for PTC use expensive and hazardous strong base. However as a PTC businessperson, this means that there is still so much opportunity to expand the use of PTC, even in obvious cases.
In any case, the pentanidium salt is effective for the chiral Michael addition described in the May 2014 PTC Reaction of the Month. It will be interesting to see if these pentanidium salts gain popularity for chiral PTC reactions.
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!).
