Silicon and tin substituents surprisingly have only a moderate directing effect on the TiffeneauâDemjanov reaction. The low selectivity is rationalised as being due to the reactive nature of the diazonium ion leaving group, the weaker oxydiazene leaving group was found to give better yields of the silicon-directed ring expanded product.
令人惊讶的是,
硅和
锡取代基对 TiffeneauâDemjanov 反应只有适度的指导作用。选择性低的原因是重氮离子离去基团的反应性,而较弱的氧
二氮烯离去基团则能产生较好的
硅定向扩环产物。