The invention of new radical chain reactions. Part VIII. Radical chemistry of thiohydroxamic esters; A new method for the generation of carbon radicals from carboxylic acids

Preparation of Novel Selenopenams by Intramolecular Homolytic Substitution

“…Selective hydrolysis of the t-butyl ester in a 1:1 mixture of trifluoroacetic acid and dichloromethane afforded the monoacid 10 in quantitative yield. Further reaction of 10 with N-hydroxypyridine-2-thione in the presence of dicyclohexylcarbodiimide (DCC) afforded the pyridinethioneoxycarbonyl (PTOC, Barton) [11] ester free radical precursor 11 (Scheme 1). The Barton ester proved to be quite labile and was not purified.…”

The first total synthesis of natural grenadamide

“…With the desired cyclopropane in hand the tert-butyl ester was hydrolyzed cleanly in the presence of 99% formic acid to give acid 16, 6 in 89% yield, which was subsequently decarboxylated using the Barton protocol in 86% yield. 7 Baeyer-Villiger oxidation of the resultant ketone 4 using MCPBA proceeded with excellent selectivity to give phenol ester 3 in 91% yield, Scheme 6. 4b Due to purification difficulties phenol ester 3 was transesterified to furnish methyl ester 17 in 93% yield, which was subsequently hydrolyzed to give cyclopropyl fatty acid 2 in 93% yield.…”

Toward Pyridine-Fused Selenium-Containing Antioxidants

“…Kim recently described a new method for generating carbon-centred radicals from thiohydroximate esters of carboxylic acids and we have generally found this precursor to be superior to those described by Barton and coworkers [14] for reasons including stability, especially in tertiary systems [15]. Therefore, reaction of N-methyl-hydroxydithiocarbamate and dicyclohexylcarbodiimide (DCC) with 20 afforded precursor 21 which was isolated as a yellow oil after column chromatography.…”