Copper-Catalyzed Selective 1,2-Difunctionalization of N-Heteroaromatics through Cascade C-N/C═C/C═O Bond Formation

This study presents an efficient strategy for constructing 1,2-difunctionalized quinoline derivatives via the multicomponent cascade coupling of N-heteroaromatics with alkyl halides and different terminal alkynes. This reaction was achieved through sequential functionalization at the one- and two-positions of quinolines, which displayed a broad substrate scope, environmental friendliness, excellent functional group tolerance, high atom efficiency, and chemoselectivity. The multicomponent coupling involved the abnormal construction of new C-N, C═C, and C═O bonds in one pot. The applicability of this method was further demonstrated by the late-stage functionalization of complex drug molecules under the established conditions.

Calcium-Catalyzed Stereoselective Tandem [4+2] and [3+2] Annulation Reaction for the Synthesis of Dihydropyrrolo[1,2-a]quinolines

Calcium-catalyzed highly facile one-pot, A⁴ annulation of aldehyde, amine, alkene, and alkyne to form fused 4,5-dihydropyrrolo[1,2-a]quinolines with exclusive syn diastereoselectivity is reported. This selectivity arises from an inverse electron demand [4+2] aza-Diels-Alder cycloaddition, and the adduct further undergoes a formal [3+2] cyclization with activated alkynes. This diversity-oriented protocol is highly general and furnishes the dihydropyrrolo[1,2-a]quinoline derivatives with a broad substrate scope in good to excellent yields.