Photoredox-HAT catalysed α-C–H alkylation of primary amines with vinyl phosphine oxides: New building blocks for spiropyrrolidine synthesis

Abstract

We report a dual photoredox and hydrogen atom transfer (HAT) catalysed α-C–H alkylation of unprotected, aliphatic primary amines with diphenyl(vinyl)phosphine oxide. This simple protocol, which can be run on gram-scale in continuous flow, enables the direct synthesis of γ-amino phosphine oxide building blocks. By condensation with aromatic aldehydes and base-induced 5-endo-trig cyclisation, the latter compounds can be converted into α-arylated, spirocyclic pyrrolidines. Finally, we show that attempted deprotonation of γ-amino phosphine oxides with strong base leads to an unexpected cyclisation to afford cyclic phosphinamide products.