Synthesis of 1,4-oxathiins via [3+3] annulation of pyridinium 1,4-zwitterionic thiolates with iodonium ylides

A straightforward and valuable approach for the synthesis of 1,4-oxathiins has been developed via [3 ​+ ​3] annulation of pyridinium 1,4-zwitterionic thiolates with iodonium ylides. C–S and C–O bonds were formed in one pot manner in this transformation, which features with readily available substrates, excellent tolerance of functional groups and mild reaction conditions. It would be of great value for the construction of 1,4-oxathiins with biological and pharmacological activity.