Visible light-promoted Pd-catalyzed regioselective 1,4-dicarbofunctionalization of 1,3-butadiene with unactivated bromides and malononitriles

Abstract

As a versatile synthetic transformation, the dicarbofunctionalization of 1,3-butadiene enables the rapid assembly of structurally diverse allylic scaffolds. Herein, the selective 1,4-dicarbofunctionalization of 1,3-butadiene with organobromides (alkyl and aryl bromides) and malononitrile nucleophiles has been developed using a photoinduced Pd-catalyzed three-component coupling strategy. This process relies on photoexcited Pd(0) activation of both substrates through a single-electron transfer (SET) process, accommodating alkyl and aryl radicals of contrasting electronic character through precisely optimized reaction conditions. Under mild conditions, the protocol furnishes 74 functionalized malononitrile derivatives in high yields (up to 88%) and excellent regioselectivity (>20 : 1 rr), highlighting its broad scope and efficiency.