Mercury(II) acetate

Abstract

Examples of stereoselective oxymercuration have been found in cases of neighboring group participation (hydroxyl4a or carboxy groups4b in appropriate positions). These reactions are reported to offer very good yields with excellent stereoselectivity (only one product is isolated from the reaction mixture).4 Work of Høebabecki et al.5a is a nice example of using a different nucleophile (azide) to open the olefin-HgOAc complex. Azidomercuratio5 followed by reduction serves as a convenient way of introducing an amino group into the molecule. In the chemistry of thiosugars, the anomeric benzyl-protected thio group is often the result of a sulfur atom introduction into the furanose molecule. It may be conveniently acetolysed using mercury(II) acetate in glacial acetic acid with good to near quantitative yields.6 This reaction is widely used in the preparation of thionucleoside analogues. Mercury(II) salts have a strong affinity towards sulfur, which can be exploited in a number of desulfurization procedures.7 Very interesting procedures for the preparation of variously substituted furans were reported recently.8 Reacting mercury(II) acetate with homopropargyl or allenyl thiolate leads to the formation of tetrasubstituted furans. This procedure is facilitated by the thiophilicity of the mercuric species, which allows an easy elimination of the sulfur moiety. Various cyclization protocols including multiple9a and sequential9b cyclizations yielding structures based on tetrahydrofuran have been reported employing mercury(II) acetate. The depicted bis-tetrahydrofurane system represents a core part in several biologically active natural products (e.g., asimitrin, salzmanolin). Mercury(II) acetate-catalyzed vinylation of allylic alcohols followed by Claisen rearrangement was used in the syntheses of various natural products. Arbour and coworkers used it in the synthesis of (+)-euphococcinine and (-)-adaline, two alkaloids with opposite configuration.10 © Georg Thieme Verlag Stuttgart • New York.