Addition of Electrophilic and Heterocyclic Carbon-Centered Radicals to Glyoxylic Oxime Ethers

Abstract

[reaction: see text] Stabilized primary radicals can be formed from alkyl halides in an atom transfer process with Et(3)B. This process depends on the strength of the carbon-halogen bond and the stability of the resulting primary radical. Radicals formed from benzyl iodide and ethyl iodoacetate add to glyoxylic oxime ethers; however, more electrophilic radicals do not. Glyoxylic oxime ethers are also good radical acceptors for heterocyclic carbon-centered secondary radicals, giving novel alpha-amino acid derivatives.

Synthesis of Hydroxylamines

“…Similar results were achieved in a free-radical chain addition reaction with free radicals generated from an Et 3 B-air 239,240 or Et 3 B-air/alkyl iodide system (equation 76) 241 . …”

Control of Asymmetry in the Radical Addition Approach to Chiral Amine Synthesis

“…Although difunctional alkyl iodides afforded lower yields, subsequent work has successfully employed more complex radicals. [14]…”

Synthetically useful carbon–carbon and carbon–sulphur bond construction mediated by carbon- and sulphur-centred radicals in water and aqueous media

“…Scheme 3 depicts the scope of glyoxylic oxime ethers as excellent radical acceptors in water/methanol mixtures. 17 When glyoxylic oxime ether 21 reacts in a methanol/water mixture with dihydro-3-iodofuran-2(3H)-one 22, in the presence of Et 3 B, product 23 is obtained in 82% yield, with a diastereomeric ratio equal to 2 : 1 (Scheme 3). Iodoethylacetate, under the same reaction conditions affords product 24 in 76% yield, while benzyl iodide, affords product 25 in 62% yield.…”

“…Iodoethylacetate, under the same reaction conditions affords product 24 in 76% yield, while benzyl iodide, affords product 25 in 62% yield. 17 Ketimines have also been used as alkyl radical acceptors in water to construct new carbon-carbon bonds. 18 In particular, ketimines having N-heteroatom substituents stabilizing the intermediate aminyl radical or the N-alkyl group, have been used in the intermolecular radical reaction.…”