William E. Fristad

Mechanisms for Manganese(III) Oxidations with Alkenes

Abstract In the reaction of manganese(III) acetate with carboxylic acids and alkenes, three distinct processes have been identified which involve the alkene and two processes which are independent of alkene. A combination of product studies, rearrangements, dilution experiments and literature kinetic data allow the proposal of a unified mechanistic picture to describe these processes. Specifically, the role of α-H acidity of the carboxylic acid component, electron deficient radical additions, metal complexed organic radicals, and the importance of an oxo-centered manganese(III) triangle are discussed as they relate to the lactone annulation reaction. Single electron transfer oxidation of alkenes is described as a route toward 1,2-diacetates of alkenes within the 8.1-7.5 eV I.P. range. Three less common modes of Mn(III) reaction are discussed and compared with the two primary processes of lactone annulation and 1,2-diacetate formation.

Vinylsilane mediated regiospecific cyclopentenone annulation of ketones

Abstract The development of a new cyclopentenone annulation sequence of general scope which involves Friedel-Crafts acylation of a vinylsilane with an α,β-unsaturated acid chloride followed by Nazarov cyclization is reported.

Oxidation Chemistry of cis-2-(3-Furylidene)ethanol

Submission of the tri-n-butylstannylmethyl ether (9) of furylcarbinol (8) to Still rearrangement leads stereoselectively to 10 as the exclusive product. The cis-oriented nature of the hydroxyethyl and 3-furyl functional groups in 10 is cause for ready ring closure either to benzofuran (10) or lactone (13) depending upon conditions