Azirine-triazole hybrids: selective synthesis of 5-(2-azirin-2-yl)-, 5-(1-pyrrol-2-yl)-1-1,2,3-triazoles and 2-(5-(2-azirin-2-yl)-1-1,2,3-triazol-1-yl)pyridines.

Azirine-triazole hybrids, 1--5-(3-aryl-2-azirin-2-yl)-1-1,2,3-triazoles, were selectively synthesized by reaction of 1-(3-aryl-2-azirin-2-yl)-2-(triphenylphosphoranylidene)ethanones with tosyl and ()-2-benzoylvinyl azides in high yields at rt. The reaction with 2-azidopyridine makes it possible to obtain azirine-triazole-pyridine hybrids, albeit in moderate yields, at 170 °C. The mechanism and selectivity of the reaction of α-carbonylphosphoranes with azides are discussed on the basis of DFT calculations.

An isoxazole strategy for the synthesis of alkyl 5-amino-4-cyano-1-pyrrole-2-carboxylates - versatile building blocks for assembling pyrrolo-fused heterocycles.

A full atom-economical domino method has been developed for the preparation of alkyl 5-amino-4-cyano-1H-pyrrole-2-carboxylates by transannulation of 5-alkoxyisoxazoles with malononitrile under Fe(ii) catalysis. Alkyl 5-amino-4-cyano-1H-pyrrole-2-carboxylates are excellent building blocks for various annulation reactions, leading to new derivatives of 1H-pyrrolo[1,2-a]imidazole and pyrrolo[2,3-d]pyrimidine. The DFT calculations of mechanistic details of alkyl 5-amino-4-cyano-1H-pyrrole-2-carboxylate formation are presented.

2-Azirine-2-carbonyl Azides: Preparation and Use as N-Heterocyclic Building Blocks.

2-Azirine-2-carbonyl azides, new reactive heterocyclic building blocks, were synthesized in high yield by the reaction of sodium azide with 2-azirine-2-carbonyl chlorides, generated by the Fe(II)-catalyzed isomerization of 5-chloroisoxazoles. 2-(Azidocarbonyl)-1-pyrroles, prepared by the Ni(II)-catalyzed reaction of 2-(azidocarbonyl)-2-azirines with 1,3-diketones, easily undergo the Curtius rearrangement in boiling BuOH to give Boc-protected α-aminopyrroles in high yield. Heating of 2-(azidocarbonyl)-1-pyrroles for a short time in inert solvents leads to the high-yield formation of benzo- and hetero-fused 1-pyrrolo[2,3-]pyridin-6(7)-ones, which are formed via a 6π electrocyclization involving the vicinal aryl or hetaryl substituent and the N═C bond of isocyanate, generated by the Curtius rearrangement of the azidocarbonyl group.

Novel homogeneous photocatalyst for oxygen to hydrogen peroxide reduction in aqueous media.

An isoquinolinium-pyrrole donor-acceptor dyad was found to exhibit photocatalytic activity in oxygen-to-peroxide photoreduction with oxalate as a sacrificial electron donor. The concentration of hydrogen peroxide was shown to reach a plateau of 0.57 mM.

Synthesis of Pyrrolotriazoloisoquinoline Frameworks by Intramolecular Cu-Mediated or Free Radical Arylation of Triazoles.

The cyclization of (2-bromophenyl)pyrrolyl-1,2,4-triazoles via copper-mediated intramolecular direct C-arylation of 1,2,4-triazoles was first accomplished under triazole-NHC control to give unknown fused heterocyclic skeletons, pyrrolo[3,2-c][1,2,4]triazolo[5,1-a] or [3,4-a]isoquinolines. The primary products underwent a triazole ring opening under the basic arylation conditions, providing N-(1H-pyrrolo[3,2-c]isoquinolin-5-yl)cyanamides. The formation of the cyanamides from isomeric pyrrolo[3,2-c][1,2,4]triazolo[3,4-a]isoquinolines involves, besides the triazole ring opening, the unusual migration of the cyano group.