Copper(I) Iodide Catalyzed [3+3] Annulation of Iodonium Ylides with Pyridinium 1,4-Zwitterionic Thiolates for the Synthesis of 1,4-Oxathiin Scaffolds

The selective assemblyof the 1,4-oxathiin nucleus has been treatedas a powerful strategy to access this scaffold present in moleculeswith very interesting properties. In this study, the chameleon-likereactivity of pyridinium 1,4-zwitterionic thiolates is exploited toassemble the 1,4-oxathiin core through a [3 + 3] annulation. The optimalannulation partner has been found to be the iodonium ylide of thecyclic 1,3-diketones. The developed protocol allows the synthesisof a variety of bicyclic 1,4-oxathiin derivatives under very mildconditions under copper(I) iodide catalysis. Access to benzoannulated1,4-oxathiins has been achieved through iodine-mediated aromatizationof the initially obtained bicyclic compounds.

Automated summary

The chameleon-like reactivity of pyridinium 1,4-zwitterionic thiolates has been utilized to selectively assemble the 1,4-oxathiin core through a [3 + 3] annulation. The iodonium ylide of cyclic 1,3-diketones was found to be the optimal partner for the annulation reaction. Under copper(I) iodide catalysis, the protocol enables the synthesis of various bicyclic 1,4-oxathiin derivatives under mild conditions. Benzoannulated 1,4-oxathiins have also been successfully accessed through iodine-mediated aromatization of the initially obtained bicyclic compounds.