The synthetic utility of tertiary amines to oxidatively generate α-amino radicals is well established, however, primary amines remain challenging because of competitive side reactions. This report describes the site-selective α-functionalization of primary amine derivatives through the generation of α-amino radical intermediates. Employing visible-light photoredox catalysis, primary sulfonamides are coupled with electron-deficient alkenes to efficiently and mildly construct C-C bonds. Interestingly, a divergence between intermolecular hydrogen-atom transfer (HAT) catalysis and intramolecular [1,5] HAT was observed through precise manipulation of the protecting group. This dichotomy was leveraged to achieve excellent α/δ site-selectivity.
Keywords: amines; photochemistry; radicals; reaction mechanisms; synthetic methods.
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