Xiangwei Du, Haoyi Chen, Yuanhong Liu
Oct 29, 2008
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Influential Citations
34
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Journal
Chemistry
Abstract
Hypervalent iodine compounds have been proved to be mild and selective oxidizing agents in an impressive array of synthetic methodologies and have received much attention in recent years. 2-Iodoxybenzoic acid (IBX, 1-hydroxy-1,2benziodoxol-3ACHTUNGTRENNUNG(1H)-one 1-oxide) was first synthesized in 1893; however, it was rarely used in organic synthesis until 1983 when Dess and Martin transformed IBX into the highly soluble Dess–Martin periodinane (DMP). In 1994, Frigero and Santagostino reported that IBX could be readily dissolved in dimethyl sulfoxide (DMSO) and served as valuable oxidant toward a variety of alcohols. Since then, a great deal of work has been done in IBX-mediated transformations with regards to mechanistic and synthetic aspects. Generally, IBX is used as an efficient and mild oxidizing reagent, for example, for the mild oxidative cleavage of oximes and tosyl hydrazones, oxidation of amines to imines, oxidative rearrangement of tertiary allylic alcohols, oxidation of silyl enol ethers to enones, a-hydroxylation of carbonyl compounds, oxidative multicomponent reactions, and so forth. IBX also operates as a singleelectron-transfer oxidant, such as in benzylic oxidation. However, IBX-induced annulation strategies are quite limited. A remarkable work has been reported by Nicolaou et al. ; they have shown that IBX can promote the cyclization of unsaturated anilides, carbamates, and ureas via amide-centered radicals to form novel and biologically important N-heterocyclic compounds. Nevertheless, there is no report for IBX-assisted cyclization of alkynes, to the best of our knowledge. In this paper, we report for the first time of IBX-promoted cascade oxidation/cyclization of cis2-en-4-yn-1-ols, which represents an efficient and diversity oriented protocol for the convergent construction of substituted 2-acyl furans. 2-Acyl furans and furfurals are of significant synthetic interest, since they can be applied as flavouring agents, perfume components, or as useful and versatile synthetic intermediates for access to the condensed furanic ring systems that shows widespread biological activity, such as Dantrolene analogues, anti-malarial agents, Phosphoinositide 3-Kinase g inhibitors, HIV-1 integrase binding inhibitors, and so forth. However, the synthetic route for multisubstituted 2-acyl furans in a regioselective manner is rare (Scheme 1).