Unexpected alkoxyl migration in the reaction of silyl ketene acetals with p-toluenesulfonyl azide

The reaction of p-toluenesulfonyl azides with several silyl ketene acetals has been investigated. 1-Trimethylsilyloxy-ethylene reacted with TsN3 to give a good yield of N-p-toluenesulfonyl substituted glycinates exclusively. However, during the reaction of 1-trimethylsilyloxy-propene with TsN3, an unexpected alkoxyl migration occurred to give N-acylsulfonyl amides; other products, N-p-toluenesulfonyl substituted aziridines were also obtained. In the case of dialkyl substituted silyl ketene acetals, three products were formed, i.e. aziridines, α-amino esters, and N-acylsulfonyl amides. The mechanism for the alkoxyl migration was discussed.