Hydroaminoalkylation of 1,3-Dienes by Dual Photoredox and Nickel Catalysis

Abstract

A dual nickel/photoredox catalyzed hydroaminoalkylation of 1,3-dienes is presented. In this atom-economic and energetic protocol, the bulk industrial raw material isoprene and derivatives are employed as allylic electrophile surrogates, which undergo a coupling with photoredox-generated α-amino alkyl radical species to produce the valuable homoallylic amines efficiently. Preliminary mechanism experiments support the intervention of Ni-hydride species that undergo diene insertion to form Ni-allyl intermediates. Amines-containing chemical architectures are important and sought-after motifs with wide-ranging applications across the pharmaceutial and agrochemical sectors into natural product chemistry and also fine chemical research.1-4 As one of the typical amines, homoallylic amines are admitted as a class of versatile synthetic building blocks for diverse amines construction.5-8 Although the nucleophilic addition of allylmetal reagents to imine has been always dominating the preparation of homoallylic amines, to some extent, the need for stoichiometric metals and the tedious pre-preparation of allyl metal reagents limit their usefulness (Scheme 1a).9 Hydroaminoalkylation (HAA) of simple and bulk dienes, alkynes or allenes proves an efficient approach to access homoallylic amines.10-12 Nevertheless, controlling the reaction regioselectivity remains extremely challenging.13-16 For instance, isoprene would likely undergo various possible addition pathways in coupling reactions for it's electronically unbiased property, which makes it cumbersome to modulate the product distributions (Scheme 1b).17 Therefore, achieving the HAA of unactive dienes in a selective mode is still an inherent problematic.