Oxazoline-based organocatalyst for enantioselective strecker reactions: a protocol for the synthesis of levamisole
Arghya Sadhukhan1, Debashis Sahu, Bishwajit Ganguly
1Discipline of Inorganic Materials and Catalysis, Central Salt & Marine Chemicals Research Institute (CSIR-CSMCRI), G.B. Marg, Bhavnagar, 364002 (India).
Abstract:
A chiral oxazoline-based organocatalyst has been found to efficiently catalyze asymmetric Strecker reactions of various aromatic and aliphatic N-benzhydrylimines with trimethylsilyl cyanide (TMSCN) as a cyanide source at -20 °C to give α-aminonitriles in high yield (96 %) with excellent chiral induction (up to 98 % ee). DFT calculations have been performed to rationalize the enantioselective formation of the product with the organocatalyst in these reactions. The organocatalyst has been characterized by single-crystal X-ray diffraction analysis, as well as by other analytical methods. This protocol has been extended to the synthesis of the pharmaceutically important drug molecule levamisole in high yield and with high enantioselectivity.
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