As we teach in our 2-day course “Industrial Phase-Transfer Catalysis,” PTC works well for thiocyanate reactions because the polarizable thiocyanate anion has a high affinity for quaternary ammonium cations.
In the diagram are shown two PTC-thiocyanate reactions.
First, the cyclopropane ring is extremely sensitive to reactants and/or experimental conditions (thermal, photochemical, metal-catalyzed, free radicals) leading to rearranged or opened products. See https://www.sciencedirect.com/topics/chemistry/cyclopropane-ring.
Acids are known to open cyclopropyl rings. In the first reaction shown in the diagram, thiocyanate is present in the reaction mixture from the outset and ring expansion is observed.
In the second reaction sequence shown in the diagram, the chloropropyl intermediate is produced and isolated then the thiocyanate added to form the propyl thiocyanate.
While TBAB and other quat salts are known to solubilize inorganic acids in non-polar organic solvents, it is not known if the TBAB plays a role in transferring the acids into the polar solvents shown in the diagram.
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!).
