Copper-mediated synthesis of N-alkenyl-α,ß-unsaturated nitrones and their conversion to tri- and tetrasubstituted pyridines.

A Chan-Lam reaction has been used to prepare N-alkenyl-α,ß-unsaturated nitrones, which undergo a subsequent thermal rearrangement to the corresponding tri- and tetrasubstituted pyridines. The optimization and scope of these transformations is discussed. Initial mechanistic experiments suggest a reaction pathway involving oxygen transfer followed by cyclization.

Preparation of α-imino aldehydes by [1,3]-rearrangements of O-alkenyl oximes.

The synthesis of α-imino aldehydes has been achieved through the thermal [1,3]-rearrangement of O-alkenyl benzophenone oximes. A copper-mediated C-O bond coupling between benzophenone oxime and alkenyl boronic acids provides facile access to the required O-alkenyl oximes and a Horner-Wadsworth-Emmons olefination can be applied to the α-imino aldehyde products to give γ-imino-α,ß-unsaturated esters. The scope of the method is described and mechanistic experiments are discussed.

Improved method for the synthesis of beta-carbonyl silyl-1,3-dithianes by the double conjugate addition of 1,3-dithiol to propargylic carbonyl compounds.

Base-mediated double conjugate addition of 1,3-propane dithiol to various silylated propargylic aldehydes and ketones allows for an efficient and scalable synthesis of beta-carbonyl silyl-1,3-dithianes.