The reactions of 4-hydroxymethylsydnones with alcohols and benzene

Abstract

In the presence of a Lewis acid, 4-hydroxymethylsydnones undergo reaction with alcohols and benzene to form 4-alkoxysydnones 1a, bis(4-sydnonylmethyl) ethers 1b, or 4-benzylsydnones 1d depending upon the reaction conditions. At 0 °C, compounds 1a and 1b are formed from compound 1 in benzene and alkyl alcohol, respectively. Compound 1b is converted to compound 1d at 40 °C. When the reactions are carried out in a cosolvent of benzene and methyl alcohol at 40 °C, compound 1a is obtained preferentially and followed by conversion to compound 1d. The α-sydnonyl-methylene cation derived from either compound 1 or 1a is responsible for the formation of compound 1d.