Cu(I)-catalyzed intramolecular cyclization of ene-carbamates: synthesis of indoles and pyrrolo[2,3-c]pyridines

Rhodium-catalysed additive-free alkoxycarbonylation of indoles: 2,4,6-trimethylbenzoic acid-based carbonate anhydrides as a versatile alkoxycarboxyl source

We report a CO-free approach to indole-2-carboxylic esters: rhodium-catalysed C(2)-alkoxycarbonylation of indoles with 2,4,6-trimethylbenzoic acid-based carbonate anhydrides. Selective C-O bond cleavage of the anhydrides facilitates the introduction of various alkoxycarbonyl groups. Control experiments suggest that merging a rhodium catalyst and KI promotes the in situ formation of the RhI species.

Copper-catalysed N-arylation of 5-aminopyrazoles: a simple route to pyrazolo[3,4-b]indoles

A copper-catalysed intramolecular N-arylation of 5-aminopyrazoles is demonstrated for the first time. Highly substituted pyrazolo[3,4-b]indoles are synthesized. In particular, the indole core is decorated with halogens and alkyl and methoxy groups. Furthermore, a selective N-arylation of unsymmetrical diaryl bromide containing pyrazoles is exemplified, resulting in valuable pyrazolo[1,5-a]benzimidazoles.

Copper Catalyzed Intramolecular N-Arylation of Ketene Aminals at Room Temperature: Synthesis of 2-Amino-3-cyanoindoles

Various 2-amino-3-cyanoindoles are synthesized through copper catalyzed intramolecular N-arylations of ketene aminals at room temperature for the first time with 60-99% yields within 0.1-2 h. Controlled regioselective N-arylations of unsymmetrical ketene aminals are also studied. Further, a new double heteroannulation approach is demonstrated for the synthesis of 11-aminoindolo[2,3- b]quinolines from acyclic and nonheterocyclic precursors.

Mild one-pot Horner-Wadsworth-Emmons olefination and intramolecular N-arylation for the syntheses of indoles, all regio-isomeric azaindoles, and thienopyrroles

The syntheses of various N-protected aromatic-ring fused pyrrole-2-carboxylate derivatives have been accomplished using mild one-pot Horner-Wadsworth-Emmons olefination and Cu-catalyzed intramolecular N-arylation reactions. The optimized mild one-pot reaction conditions of various 2-bromo arylcarboxaldehydes with commercially available N-protected phosphonoglycine trimethylesters gave the desired aromatic-ring fused pyrrole-2-carboxylates, such as substituted indole-, all regio-isomeric azaindole-, and thienopyrrole-2-carboxylates, in good to excellent yields. These conditions showed broad substrate compatibility, without the loss of the protecting group.

Heterocycle synthesis by copper facilitated addition of heteroatoms to alkenes, alkynes and arenes

The de novo synthesis of small organic heterocyclic molecules has benefited from recent protocols for copper-facilitated additions of heteroatoms to alkenes, alkynes and arenes. This tutorial review summarizes a number of these recent contributions. Copper salts can facilitate bond formations due to their ability to serve as Lewis acids, oxidizing agents and transition metal catalysts. The current understanding of the mechanisms of these reactions is presented. This review should be of interest to chemists involved in the synthesis of heterocycles and those investigating transition metal facilitated reactions.