Regiocontrol and Stereocontrol In the Intramolecular Nitrile Oxide Cycloaddition To 2-furylthiol and 2-furylmethanethiol Derivatives

A series of 2-furyl and 2-furylmethyl substituted nitrosulphides with a proper chain length were prepared and showed to undergo a totally regiocontrolled intramolecular furan-nitrile oxide cycloaddition to give cis-fused products in high yield. Insertion of a stereocenter on the cycloaddends did not allow satisfactory control of the absolute stereochemistry of the reaction. Enantiomerically enriched products (e.e. less-than-or-equal-to 95%) were obtained by a kinetic resolution process involving oxidation of the sulphide cycloadducts to the corresponding sulphoxides