Smallridge, Andrew John, Trewhella, Maurice Arthur, Wilkinson, Kylie Anne (2007) Methods for the synthesis of amines such as ephedrine and intermediates. United States Patent 7176332.

Abstract

A method for the preparation of a compound of formula (VI): in which R2 is an optionally substituted C1–C6 alkyl; R4 is H, OH, an optionally substituted C1–C6 alkyl or an optionally substituted C1–C6 alkoxy; R5 is an optionally substituted aryl, an optionally substituted aralkyl, or an optionally substituted alkyl; and R6 is H or an optionally substituted C1–C6 alkyl; the method including the step of subjecting a ketone of formula (V) in which R2, R4 and R5 are as defined above, to reductive amination with an amine of formula R3NH2 in which R3 is an optionally substituted alkyl, and a reductant to form the compound of formula (VI), wherein the reaction is conducted in the presence of a supercritical fluid or a liquefied gas.

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