Insertion into Donor–Acceptor Cyclopropanes with Carbon–Sulfur Moieties Derived from Sulfoxonium Ylides and Elemental Sulfur

The (3 + 2) cycloaddition of donor–acceptor cyclopropanes (DACs) with carbon–sulfur 2π components has become an emerging method to rapidly assemble tetrahydrothiophenes. Starting materials donating the carbon–sulfur unit are often isolated from thionation of carbonyls or carboxylic acid derivatives. Herein we report a method for the cycloaddition of DACs with carbon–sulfur moieties presumably formed in situ via β-sulfuration of α-carbonyl sulfoxonium ylides with elemental sulfur. The insertion occurred without the assistance of Lewis acid, perhaps due to the strongly polarized carbon–sulfur-containing intermediate. The hitherto challenging α-monosubstituted tetrahydrothiophenes were obtained with a wide range of tolerated functionalities.