Authors: Ayhan S. Demir,; Mustafa Emrullahoglu,

Source: Current Organic Synthesis, Volume 4, Number 3, August 2007 , pp. 321-350(30)

Publisher: Bentham Science Publishers

Abstract:

Free radical reactions have become increasingly important, as well as a very attractive tool, in organic synthesis within the last two decades, due to their powerful, selective, specific, and mild reaction abilities. Mn(OAc)3 mediated oxidative free radical reactions have been extensively developed in the last twenty years. Numerous regio-, chemo-, and stereoselective synthetic methods have been developed in both inter- and intramolecular reactions, and have detailed the progress of Mn(OAc)3 mediated oxidative free radical reactions since the end of the 19th century. The new literature about the new synthetic methods on Mn(OAc)3 mediated carbon-carbon bond formation and carbon-oxygen bond formation reactions has not been extensively reviewed. The present paper summarizes the recent developments in oxidative free radical reactions mediated by Mn(OAc)3. Mn(OAc)3 mediated reactions of conjugated systems (e.g., alkenes, alkynes, 1,3-alkadienes, l,3-alkadiynes, 1-alken-3-ynes) with β-dicarbonyl compounds, Mn(OAc)3 mediated alkylation, such as the oxidative addition of an aldehyde or ketone to alkenes, Mn(OAc)3 mediated free-radical cyclization of alkenes with active methylene compounds in the presence of oxygen to afford the cyclic peroxides; lactone synthesis by the Mn(OAc)3 mediated oxidative addition of carboxylic acids to alkenes, Mn(OAc)3 mediated cyclization of α- (methylthio)acetamides, enamides, and β-keto carboxamides to afford cyclic products.

Mn(OAc)3 oxidative free-radical cyclizations of allylic β-dicarbonyl compounds, for example, the cyclization of allylic β-ketoesters to afford the corresponding γ-lactone. The reaction of alkenes with sodium azide in the presence of acetic acid was investigated to afford 1.2-diazides. The selective oxidation of enones led to α'-acetoxy-enones by Mn(OAc)3 oxidation. In general, Mn(OAc)3 oxidations are characterized by higher α'-regioselectivity and chemical yields, and milder reaction conditions, in turn tolerating many sensitive functional groups. The use of Mn(OAc)3 in combination with other carboxylic acids or manganese(II) carboxylates extends this methodology to the preparation of a variety of α'-acyloxyenones that are otherwise inaccessible in a one-step procedure.

Keywords: Free radical reactions; Lactone synthesis; Cycloperoxidation; Oxidative Cyclization; Carbon-Oxygen Bond Formation

Document Type: Research article

DOI: http://dx.doi.org/10.2174/157017907781369289

Publication date: 2007-08-01

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• Current Organic Synthesis publishes in-depth reviews on all areas of synthetic organic chemistry i.e. asymmetric synthesis, organometallic chemistry, novel synthetic approaches to complex organic molecules, carbohydrates, polymers, protein chemistry, DNA chemistry, supramolecular chemistry, molecular recognition and new synthetic methods in organic chemistry. The frontier reviews provide the current state of knowledge in these fields and are written by experts who are internationally known for their eminent research contributions. The journal is essential reading to all synthetic organic chemists. Current Organic Synthesis should prove to be of great interest to synthetic chemists in academia and industry who wish to keep abreast with recent developments in key fields of organic synthesis.

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