Catalyst-Controlled Multicomponent Aziridination of Chiral Aldehydes

Recent updates and future perspectives in aziridine synthesis and reactivity

In this review, selected recent advances in the preparation and reactivity of aziridines using modern synthetic approaches are highlighted, while comparing these new strategies with more classical approaches. This critical analysis is designed to help identify current gaps in the field and is showcasing new and exciting opportunities to move the chemistry of aziridines forward in the future.

Stereoselective Multicomponent Reactions in the Synthesis or Transformations of Epoxides and Aziridines

Small ring heterocycles, such as epoxides and aziridines, are present in several natural products and are also highly versatile building blocks, frequently involved in the synthesis of numerous bioactive products and pharmaceuticals. Because of the potential for increased efficiency and selectivity, along with the advantages of environmentally benign synthetic procedures, multicomponent reactions (MCRs) have been explored in the synthesis and ring opening of these heterocyclic units. In this review, the recent advances in MCRs involving the synthesis and applications of epoxides and aziridines to the preparation of other heterocycles are discussed emphasizing the stereoselectivity of the reactions.

Chiral Diol-Based Organocatalysts in Enantioselective Reactions

Organocatalysis has emerged as a powerful synthetic tool in organic chemistry in the last few decades. Among various classes of organocatalysis, chiral diol-based scaffolds, such as BINOLs, VANOLs, and tartaric acid derivatives, have been widely used to induce enantioselectivity due to the ability of the hydroxyls to coordinate with the Lewis acidic sites of reagents or substrates and create a chiral environment for the transformation. In this review, we will discuss the applications of these diol-based catalysts in different types of reactions, including the scopes of reactions and the modes of catalyst activation. In general, the axially chiral aryl diol BINOL and VANOL derivatives serve as the most competent catalyst for most examples, but examples of exclusive success using other scaffolds, herein, suggests that they should not be overlooked. Lastly, the examples, to date, are mainly from tartrate and biaryl diol catalysts, suggesting that innovation may be available from new diol scaffolds.

Facile synthesis of α-alkoxyl amides via scandium-catalyzed oxidative reaction between ynamides and alcohols

A novel and efficient scandium-catalyzed oxidative reaction between ynamides and alcohols for the facile synthesis of various α-alkoxyl amides is reported in this paper. The reaction avoids the need for the use of α-diazo carbonyls which are unstable and may cause some safety concerns. Instead, by using alkynes as the starting materials, this protocol features readily available substrates, compatibility with a broad range of functional groups, simple procedure, mild reaction conditions, and high chemoselectivity.

Preparation of Chiral Contiguous Epoxyaziridines and Their Regioselective Ring-Opening for Drug Syntheses

Synthetically valuable chiral (aziridin-2-yl)oxirane-3-carbaldehydes bearing three consecutive functional groups including aziridine, epoxide, and aldehyde were prepared from the stereoselective epoxidation of (aziridin-2-yl)acrylaldehydes with H₂ O₂ using organocatalyst (2R)- or (2S)-[diphenyl(trimethylsilyloxy)methyl]pyrrolidine as organocatalyst. The regioselective ring opening of aziridines and epoxides enabled us to achieve the highly efficient asymmetric synthesis of the antibiotic edeine D fragment 3-hydroxy-4,5-diaminopenatanoic acid, an intermediate for the formal synthesis of non-proteinogenic amino acid (-)-galantinic acid, and for potent antifungal agent (+)-preussin, and the medicinally important framework 3-hydroxy-2-hydroxymethylpyrrolidine.