A strategy for the synthesis of α-carboline derivatives from indole-3-carboxaldehydes and 3-aminocyclohex-2-enones under metal-free conditions has been developed. The combination use of phenyliodine (III) diacetate (PIDA) and benzoic acid could significantly facilitate the corresponding [3 ​+ ​3] annulation process. This newly developed strategy featured unextraordinary chemoselectivity, good functional group tolerance and the preservation of the carbonyl group of the ketone substrates, which offers the possibility for further transformation of the products.