Regiodivergent Synthesis of Penta-Substituted Pyrroles through a Cascade [3 + 2] Cyclization of C-Acylimines with Activated Alkynes and Aromatic Nucleophiles.

Highly robust one-pot, four-component cascade cyclization reaction of α-keto aldehydes, anilines, activated alkynes, and aromatic nucleophiles is developed to synthesize a diverse range of pharmaceutically important penta-substituted pyrroles. The reaction proceeds through the cascade cyclization of acylimines (in situ formed) with activated alkynes and aromatic nucleophiles such as indoles, pyrroles, and naphthols at room temperature under calcium(II) catalysis with high yields and broad substrate diversity.

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.

Highly Regioselective Synthesis of Oxindolyl-Pyrroles and Quinolines via a One-Pot, Sequential Meyer-Schuster Rearrangement, Anti-Michael Addition/C(sp3)-H Functionalization, and Azacyclization.

A one-pot, sequential Meyer-Schuster (MS) rearrangement of oxindole-derived propargyl alcohols to the corresponding α,ß-unsaturated enones and their anti-Michael addition, followed by intramolecular azacyclization is described in a highly regioselective manner using Ca(OTf)2 as the promoter. Further, we described the one-pot MS rearrangement, followed by C(sp3)-H functionalization of 2-methyl azaarenes at α-carbon of these doubly activated alkenes. Control experiments and computational calculations were performed to propose the reaction mechanism.

Iodo-Cycloisomerization of Aryl(indol-3-yl)methane-Tethered Propargyl Alcohols to 3-Iodocarbazoles via Selective 1,2-Alkyl Migration.

Herein, we disclose the first report on iodo-cycloisomerization of 1-(indol-3-yl)-1-arylbut-3-yn-2-ols to form 3-iodocarbazoles. The synthesis proceeds through a cascade 5-endo-spirocyclization, followed by selective 1,2-alkyl migration. This method governs the green synthesis principles such as open-flask reaction, AcOEt as the solvent, rt reaction with short time, use of iodine, and broad substrate scope with atom and step economy.

Correction to "Highly Regioselective Synthesis of Oxindolyl-Pyrroles and Quinolines via a One-Pot, Sequential Meyer-Schuster Rearrangement, Anti-Michael Addition/C(sp3)-H Functionalization, and Azacyclization".

[This corrects the article DOI: 10.1021/acsomega.8b00147.].

Amine-Triggered Highly Facile Oxidative Benzannulation Reaction for the Synthesis of Anthranilates under Solvent-Free Calcium(II) Catalysis.

An amine-triggered facile synthetic approach of anthranilates has been described through benzannulation of readily available chemicals under one-pot solvent-free conditions using Ca(OTf)2 as the sustainable catalyst. In this regioselective approach, we described a reasonably longer cascade, which proceeds through ß-enamino ester formation/Michael addition/intramolecular aldol reaction/elimination/aromatization/oxidative debenzylation/lactonization with a broad substrate scope and high yields. The isolation of intermediates authenticated the mechanism, and the synthetic utility of the products was also demonstrated.