3 + 2 Cycloaddition of (Diazomethyl)dialkylphosphine Oxide and Aryldiazonium Salts

A convenient approach to 2,5‐disubstituted tetrazoles bearing a dialkylphosphine oxide substituent at the C‐5 position is developed. The method involves silver‐catalyzed 3 + 2 cycloaddition of (diazomethyl)dialkylphosphine oxide and aryl diazonium salts. The proposed reaction is compatible with various substituents at the aryl ring and has low susceptibility to their electronic and steric effects. Several heterocyclic diazonium salts were also involved into the transformation successfully. The proposed reaction pathway may include synchronous 3 + 2 cycloaddition or two‐step formation of the tetrazole ring starting with electrophilic attack of aryl diazonium salt at the diazoalkane carbon atom.