Regioselective Ring Opening of Aziridines by Oximes via C-C Bond Cleavage: Access to a Library of Oxime-Ethers.

A series of sulfonamido-substituted oxime-ethers have been synthesized by the reaction of donor-acceptor aziridines with aldo- and keto-oximes through C-C bond cleavage. Nucleophilic attack by an oxime hydroxyl group on the -generated azomethine ylide rather than the routine cycloaddition reaction draws the novelty of the developed methodology. Selective protection of the oxime hydroxyl group is observed in the presence of phenolic -OH, which made the protocol enriched.

Solvent- and Catalyst-Controlled Regioselective - and -Alkylation of 2-Pyridones by 2-Azirines.

The synthesis of -substituted 2-hydroxypyridines and -substituted 2-pyridones, crucial for many bioactive compounds and drugs, faces challenges due to the tautomeric nature of 2-pyridones, which complicates selective alkylation. Here we developed an efficient method for regioselective - and -alkylation of 2-pyridones using Bro̷nsted acid-catalyzed ring opening of 2-azirines. The process involves triflic acid for -alkylation and -toluenesulfonic acid for alkylation, achieving high yields under optimized conditions.

Bi(III)-Catalyzed Michael Addition of Tautomerizable Heterocycles with α,β-Unsaturated Carbonyl Compounds: Regioselective Construction of C-N Bonds.

A Bi(III)-catalyzed synthetic strategy for regioselective construction of C-N bonds via a simple Michael addition reaction is reported. A wide range of tautomerizable heterocycles such as benzoxazolones, benzothiazolones, benzimidazolinones, indolinones, and 2-pyridones along with α,β-unsaturated carbonyls (ketones and esters) are employed to create a library of corresponding -alkylated derivatives exclusively. High regioselectivity, high atom economy, and the participation of a range of tautomerizable heterocycles highlight the uniqueness and generality of the developed methodology.

Regioselective Brønsted acid catalyzed ring opening of aziridines by phenols and thiophenols; a gateway to access functionalized indolines, indoles, benzothiazines, dihydrobenzo-thiazines, benzo-oxazines and benzochromenes.

Brønsted acid catalyzed regioselective ring opening of aziridines by phenols and thiophenols have been reported. Involvement of a series of aziridines with a range of phenols and thiophenols offer the generality of the reported protocol. Completion of the reaction at room temperature within very short time brings the uniqueness of the developed technique.

Brønsted acid-catalyzed regioselective ring opening of 2-azirines by 2-mercaptopyridines and related heterocycles; one pot access to imidazo[1,2-]pyridines and imidazo[2,1-]thiazoles.

A catalytic and versatile synthetic method for the synthesis of imidazo[1,2-]pyridines has been developed. Brønsted acid-catalysis plays a major role in the regioselective ring opening of 2-azirines. Nucleophilic attack the -centre of mercaptopyridines and their analogues, followed by cyclisation by cleaving the C-S bond, allowed a library of imidazo[1,2-]pyridines and related heterocycles to be built.

Methyltrifluoromethanesulfonate Catalyst in Direct Nucleophilic Substitution of Alcohols; One-Pot Synthesis of 4-Chromene Derivatives.

The catalytic activity of methyltrifluoromethanesulfonate (MeOTf) has been explored toward direct nucleophilic substitution of the hydroxyl group of nonmanipulated alcohols such as benzylic, allylic, propargylic, and tertiary alcohols with a wide range of uncharged nucleophiles such as 1,3-dicarbonyl compounds, amides, alkynes, and indoles to generate functionalized 1,3-dicarbonyl compounds, amides, alkynes, and indoles, respectively. Thus, the present protocol defines an alternate pathway to construct new C-C, C-N, and C-O bonds with the formation of water as the byproduct under mild conditions without any acids or metals. A completely different mechanism was established through several control experiments to explain the reaction methodology.

Regioselective Transition Metal-Free Catalytic Ring Opening of 2-Azirines by Phenols and Naphthols; One-Pot Access to Benzo- and Naphthofurans.

Benzofuran and naphthofuran derivatives are synthesized from readily available phenols and naphthols. Regioselective ring openings of 2-azirine followed by in situ aromatization using a catalytic amount of Brønsted acid have established the novelty of the methodology. The involvement of a series of 2-azirines with a variety of phenols, 1-naphthols, and 2-naphthols showed the generality of the protocol.

(3 + 2) cycloaddition of 2-alkoxynaphthalenes with azaoxyallyl cations: access to benzo[]indolones.

A reaction between 2-alkoxynaphthalene and an formed azaoxyallyl cation has been reported under ambient reaction conditions. The (3 + 2) cycloaddition reaction followed by aryl C-OMe/C-OEt bond cleavage produces a variety of benzo[]indolone derivatives. Based on the isolated intermediate from the control experiment and previous results, a possible mechanism has been drawn.