Oxidation and Deprotection of Primary Benzylamines by Visible Light Flavin Photocatalysis

Abstract

We report a photocatalytic oxidation procedure that can be used to convert benzylamines into their corresponding aldehydes under mild conditions without over-oxidation, using riboflavin tetraacetate as photocatalyst and blue emitting LEDs (440 nm) as light source. Oxygen is the terminal oxidant and H2O2 and NH3 appear as the only byproducts of the oxidation of primary benzylamines. Furthermore, we have developed a photocatalytic protocol for 4-methoxybenzyl (Mob) group deprotection of primary amines and alcohols. Double bonds, benzyl-protected esters and alcohols are tolerated under the applied conditions, whereas the deprotection of protected secondary amines is not applicable. Mob-protected carboxylic acids and carboxybenzoyl (Cbz) protected amines are inert under the photodeprotection conditions.