Contractions of 1,4-Diazepines to Pyrroles Triggered by Valence Tautomerization: A One-Pot Approach and Mechanism

Herein, we describe the valence tautomerizations of fused 1,4-diazepines, which are reconstructed to give pyrrole derivatives and HCN gas. Several factors that influence the equilibrium between each valence tautomer of an 8π-electron diazepine skeleton are demonstrated. On the basis of these mechanistic studies, a cascade strategy for the construction of diazepines followed by ring contraction is developed to afford aryl- or alkyl-substituted pyrrolo[1,2-a]quinolines that are otherwise challenging to fabricate. In addition, further transformations of the obtained products highlight the advantages of the developed methodology.

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.

Encapsulating Au-Fe3 O4 Nanodots into AIE-active Supramolecular Assemblies: Ambient Visible-light Harvesting "Dip-Strip" Photocatalyst for C-C/C-N Bond Formation Reactions

The present study demonstrates the development of a supramolecular porous ensemble consisting of hetero-oligophenylene derivative 6 and Au-Fe₃ O₄ nanodots. Supramolecular assemblies of AIE-active hetero-oligophenylene derivative 6 served as reactors for the generation of Au-Fe₃ O₄ nanodots. The as prepared supramolecular ensemble functioned as an efficient recyclable photocatalytic system for C(sp² )-H bond activation of anilines for the construction of quinoline carboxylates. Interestingly, the "dip catalyst" prepared by depositing PTh-co-PANI-6: Au-Fe₃ O₄ nanodots on a filter paper served as a recyclable strip (up to 10 cycles) for C-C/C-N bond formation reaction.