Potassium Phosphate-Catalyzed Chemoselective Reduction of alpha-Keto Amides: Route to Synthesize Passerini Adducts and 3-Phenyloxindoles

摘要

A chemoselective reduction of -keto amides to biologically important -hydroxy amides (mandelamides) by polymethylhydrosiloxane (PMHS) using 5mol% potassium phosphate (K3PO4) as catalyst has been developed. This transition metal-free protocol discloses excellent chemoselectivity for the ketone reduction of -keto amides in the presence of other reducible functionalities like ketone, nitro, halides, nitrile and amide. Also, the chemoselectively reduced -hydroxy amide has been derivatized to isocyanide-free Passerini adducts. The N-alkyl--hydroxy amides have been successfully converted to 3-phenyloxindole derivatives by treatment with methanesulfonyl cholride and triethylamine.