Asymmetric 1,3-Dipolar Cycloaddition Reactions

Acyclic stereochemical control in free-radical reactions

This critical review, which is relevant to researchers in synthetic organic chemistry, focuses on asymmetric 1,3-dipolar cycloadditions with acrylamides. The use of chiral acrylamides as dipolarophiles leads to high levels of stereocontrol, due to conformational constraint in the acrylamides. Employment of chiral tertiary acrylamides containing nitrogen heterocycles is particularly effective in controlling the stereoselectivity. Following a general overview of 1,3-dipolar cycloadditions, the main body of the review focuses on asymmetric 1,3-dipolar cycloadditions of acrylamides with nitrile oxides, nitrones, diazoalkanes and azomethine ylides, with particular emphasis on the rationale for the observed stereocontrol (215 references).

Asymmetric 1,3-dipolar cycloadditions of acrylamides

The nitroso ene reaction: a regioselective and stereoselective allylic nitrogen functionalization of mechanistic delight and synthetic potential

Cycloaddition reactions have figured prominently in both synthetic and mechanistic organic chemistry.1,2 Current understanding of the underlying principles in this area has grown from a fruitful interplay between theory and experiment.3 The monumental work of Huisgen and coworkers in the early 1960s led to the general concept of 1,3-dipolar cycloaddition.4–7 Few reactions rival this process in the number of bonds that undergo transformation during the reaction, producing products considerably more complex than the reactants. Over the years this reaction has developed into a generally useful method of five-membered heterocyclic ring synthesis, since many 1,3-dipolar species are readily available and react with a wide variety of dipolarophiles. 1,3-Dipolar cycloadditions are bimolecular in nature and involve the addition of a 1,3-dipole (1) to a multiple π-bond system (2) leading to five-membered heterocycles (3; equation 1).

4.9 – Intermolecular 1,3-Dipolar Cycloadditions

The preparation of optically active δ2- isoxazolines. A model for asymmetric induction in the non lewis acid catalyzed reactions of oppolzer's chiral sultam

Good diastereoselectivity (ca. 90 10 ) is reported in the cycloaddition reactions of Oppolzer's chiral sultam with nitrile oxides. A model is proposed which may apply to other non Lewis acid promoted reactions of this sultam.

The Preparation of Optically Active δ2-Isoxazolines. A Model for Asymmetric Induction in the Non Lewis Acid Catalyzed Reactions of Oppolzer′s Chiral Sultam.

James Daugherty

Papers

The preparation of optically active δ2- isoxazolines. A model for asymmetric induction in the non lewis acid catalyzed reactions of oppolzer's chiral sultam

The Preparation of Optically Active δ2-Isoxazolines. A Model for Asymmetric Induction in the Non Lewis Acid Catalyzed Reactions of Oppolzer′s Chiral Sultam.