K2CO3-Catalyzed Rapid Conversion of N-Sulfonylhydrazones to Sulfinates

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.