Solvent-Controlled Regioselective Reaction of 2-Methyleneaziridines with Acrylic/Propargylic Acids: Synthesis of Carboxylate Aziridine/Acetone Esters

Herein, we report a convenient solvent-controlled regioselective esterification to access two types of carboxylate esters without any additive or non-green activation strategy. In this transformation, 2-methyleneaziridines served as an ester reagent, providing two alternative electrophilic carbon centers. Notably, this protocol is suitable for some structure-complicated clinical molecules with a carboxylic acid group, presenting remarkable application potential.

Synthesis and applications of methyleneaziridines

Methyleneaziridines (MAs) are a special subset of aziridines featuring an exocyclic C–C double bond on the three-membered ring. They have found great potential in organic synthesis. In this review, the structural characterization of MAs, synthetic methods, chemical transformations and mechanisms, especially the advances achieved over the past decade are comprehensively summarized.

This review surveys the structural characterization, synthetic methods, chemical transformations and mechanisms of methyleneaziridines, especially the advances achieved over the past decade.

Biomimetic 2-Imino-Nazarov Cyclizations via Eneallene Aziridination

Amidoallyl cations are appealing three-carbon synthons for the preparation of complex amine-containing carbocycles; however, methods to generate and utilize these reactive species are limited and underexplored compared to those for oxallyl cations. Here we disclose a bioinspired strain-driven ring opening of bicyclic methyleneaziridines to 2-amidopentadienyl cation intermediates that readily engage in Nazarov cyclizations. Advantages of this strategy include ease of generation and improved reactivity compared to 3-pentadienyl cations, control over the ultimate position of the alkene, the potential for high dr between vicinal stereocenters, and the ability to further elaborate the products to fully substituted aminocyclopentanes. Experimental and computational studies support a dual role for the Rh₂L_n complex as both a nitrene transfer catalyst and a Lewis acid promoter, insight that provides a framework for the future development of asymmetric 2-imino-Nazarov cyclizations.

Oxidative Cascade Reaction of N-Aryl-3-alkylideneazetidines and Carboxylic Acids: Access to Fused Pyridines

A versatile silver-promoted oxidative cascade reaction of N-aryl-3-alkylideneazetidines with carboxylic acids is reported, providing a very efficient pathway to functionalized fused pyridines. This method allows introduction of fused pyridine ring systems to heterocycles, drugs, and natural products. A mechanistic study revealed that silver salt is essential for the chemo- and regioselective ring expansion, sequential oxidative nucleophilic additions, and oxidative aromatization. This approach represents the first example of the strained N-heterocycles undergoing a cascade reaction with a π bond and a nucleophile together.

Stereocontrolled lithiation/trapping of chiral 2-alkylideneaziridines: investigation into the role of the aziridine nitrogen stereodynamics

The origin of the stereoselectivity in the lithiation/trapping of 2-alkylideneaziridines bearing a chiral group as the nitrogen substituent was investigated.