Heterocycle Synthesis via Radical Addition-Cyclization of Oxime Ethers

Abstract

Oxime ethers connected by a tether to aldehydes or ketones efficiently cyclized via stannyl radical addition-cyclization to give a new entry to heterocyclic amino alcohols. The SmI₂-induced radical cyclization was found to be effective for preparing cyclic trans-amino alcohols. These radical reactions provide a novel method for the synthesis of (-) -balanol, aminocyclitols, 1-deoxynojirimycin, 2-substituted 5-amino-4-piperidinol, and nucleoside analogs. The sulfanyl radical addition-cyclization-elimination reaction was developed, which was successfully applied to the synthesis of (-) -kainic acid. The sulfanyl radical addition-cyclization of oxime ethers gave a method for synthesis of rigidified cyclic β-amino acids. The carbon radical addition-cyclization reaction of substrates having two different radical acceptors such as acrylate and aldoxime ether moieties proceeded even in aqueous media via a diastereoselective tandem C-C bond-forming process, providing a method for asymmetric synthesis of γ-butyrolactones and γ-amino acids.