Oxidation of azidoalkyl furans

Asymmetric Synthesis of Functionalized 2-Isoxazolines

The asymmetric synthesis of the isoxazoline skeleton was achieved by the oxidation of hydroxylaminoalkyl furan prepared from simple starting materials: 2-methylfuran and (S)-epichlorohydrin. The synthesis features an NBS-mediated oxidation of hydroxylaminoalkyl furan to give an α,β-unsaturated ketone intermediate which cyclized to the isoxazoline. The α,β-unsaturated double bond was successfully cleaved with RuCl3·xH2O catalysis en route to the isoxazoline skeleton bearing alcohol, aldehyde, and carboxylic acid functionalities.

Synthesis of Pyrrolidine-2-ylidenes from Isoxazolines and Allenes

A diastereoselective addition and rearrangement reaction has been developed for the synthesis of pyrrolidine-2-ylidenes from NH-isoxazolines and electron-deficient allenes. This method proceeds via the rearrangement of a proposed N-alkenylisoxazoline intermediate to generate densely functionalized pyrrolidine-2-ylidenes under simple catalyst-free conditions that tolerate ketone substituents and install relative stereochemistry at positions 3 and 4 of the heterocycle. Reaction optimization and the substrate scope are described in addition to studies evaluating the reactivity of the gem-dione and enaminone groups of the products.