Bis(arylsulfonyl) Peroxide-Mediated Difunctionalization of Cyclic Enol Ethers

A bis(arylsulfonyl) peroxide-mediated 1,2-difunctionalization of cyclic enol ethers is reported. Bis(nosyl) peroxide selectively sulfonylates the 3-position of enol ethers, generating an oxocarbenium ion that is trapped by a carboxylic acid nucleophile at the 2-position. The reaction proceeds in a good yield and tolerates a variety of cyclic enol ethers, including glycals as well as various carboxylic acids, which act as the oxocarbeium ion trapping reagents.

A Sequential Acyl Thiol-Ene and Thiolactonization Approach for the Synthesis of δ-Thiolactones

A novel strategy for the synthesis of δ-thiolactones from inexpensive and readily available γ-unsaturated esters has been developed. This strategy incorporates a radical acyl thiol-ene reaction as the key C-S bond forming step. Cyclization is achieved via a Steglich-type thiolactonization of 5-mercaptopentanoic acids. We report the facile and scalable synthesis of δ-thiolactones in moderate to good yield under mild reaction conditions with tolerance for a range of functional groups.

Radical-Mediated Reactions of α-Bromo Aluminium Thioacetals, α-Bromothioesters, and Xanthates for Thiolactone Synthesis

Thiolactones have attracted considerable attention in recent years as bioactive natural products, lead compounds for drug discovery, molecular probes, and reagents for polymerisation. We have investigated radical-mediated C-C bond forming reactions as a strategy for thiolactone synthesis. Cyclisation of an α-bromo aluminium thioacetal was investigated under radical conditions. It was found that at low temperature, a radical fragmentation and rearrangement process occurs. A putative reaction mechanism involving a previously unreported aluminium templated thiol-ene step for the rearrangement process is presented. Cyclisation reactions of α-bromo thioesters and α-xanthate thioesters under radical mediated conditions furnished the desired thiolactones in moderate yields.