Annulation of α-carbonyl vinyl sulfoxonium ylides with hypervalent iodine diazo compounds.

A metal-free [3 + 3] annulation of α-carbonyl vinyl sulfoxonium ylides with α-diazo-λ3-iodanes has been found to allow for straightforward access to trisubstituted pyridazine derivatives. The hypervalent iodine diazo substrates serve as N-terminal electrophiles with sulfoxonium ylide nucleophiles in completely regioselective transformations, offering a broad substrate scope and high product yields under mild open-air reaction conditions.