Lithium malonate enolates 4 or 13 are oxidized to the corresponding radicals by ferrocenium hexafluorophosphate (1) or CuCl2 (2). Trapping by TEMPO (5) to produce 6, dimerization to 7, or radical 5‐exo cyclizations are possible subsequent reaction steps following radical generation. The structure of the radical cyclization acceptor determines the outcome of the overall reaction sequence. Tertiary benzylic, alkyl, and α‐alkoxy radicals are oxidized by 1. The carbenium ions are stabilized by nucleophilic trapping or deprotonation to give compounds 14 and 18. Secondary alkyl and vinyl radicals are not oxidized and, in the absence of trapping reagents, form radical‐derived products. Radical 5‐exo cyclization of 13 induced by CuCl2 (2) was also efficient. At least for alkyl radicals, however, ligand transfer is the exclusive stabilization pathway, giving access to chloroalkylcyclopentane derivatives 21. Radical scavenging studies revealed that malonyl radical trapping is slow, so that 5‐exo cyclizations occurred. The cyclized radicals couple with TEMPO (5) to afford oxygenated cyclopentane derivatives 31, depending on the rate of radical SET oxidation. The reaction behavior of compounds 14, 22, 23, and 31 was investigated. Mechanistic issues are discussed and implications for synthetic planning are given.

A generally applicable method for the synthesis of protected α‐oxygenated carbonyl compounds is reported. It is based on the single‐electron‐transfer oxidation of easily generated enolates to the corresponding α‐carbonyl radicals. Coupling with the stable free radical TEMPO provides α‐(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate‐to‐excellent yields. Enolate aggregates influence the outcome of the oxygenation reactions significantly. Competitive reactions have been analyzed and conditions for their minimization are presented. Chemoselective reduction of the products led to either N–O bond cleavage to α‐hydroxy carbonyl compounds or reduction of the carbonyl functionality tomonoprotected 1,2‐diols or O‐protected amino alcohols.

[reaction: see text] An efficient oxidative radical cyclization approach for the synthesis of 2-alkenyl cyclopentane or cyclohexane carboxylates from omega-silylallyl ester enolates induced by recyclable SET oxidant ferrocenium hexafluorophosphate has been developed. A new tandem alkoxycarbonylation/oxidative radical cyclization/cationic termination process forms the basis for a five-step synthesis of the cyclopentanoid monoterpene dihydronepetalactone and analogues.

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Keywords: Enolates / Hydroxy esters / Oxidation / Prostaglandins / Radical reactions 6,8-Nonadienoate enolates, which undergo radical 5-exo cyclization on SET oxidation with ferrocenium hexafluorophosphate, were studied as radical cyclization precursors. The trapping of the cyclized allylic radicals occurred with good regioselectivity through dimerization, TEMPO trapping, or SET oxidation/deprotonation reactions. 3-Alkoxido