K(2)CO(3)-Catalyzed Rapid Conversion of N-Sulfonylhydrazones to Sulfinates

[Image: see text] N-Sulfonylhydrazones derived from alkyl, aryl, and heteroaryl aldehydes and ketones undergo rapid conversion into the corresponding sulfinates when heated with 10 mol % K(2)CO(3) in N,N′-dimethylethylene urea (DMEU) at elevated temperature. The reaction conditions are amenable to several functional groups and suitable for gram-scale synthesis. Under these base-catalyzed conditions, N-tosylhydrazones derived from O-allylated and O-propargylated 2-hydroxyarylaldehydes do not undergo the well-established intramolecular [3 + 2]-cycloaddition reactions and generate corresponding sulfinates in good yields. The base-catalyzed transformation proceeds via crucial rapid intermolecular protonation of the diazo intermediate 11 to generate diazonium ion 12, which upon nucleophilic displacement by the sulfonyl ion 10 provides the desired sulfinate selectively.