Synthesis and Thermal Reactivity of 2-Azido-5-trimethylsilylthiophene and 2-Azido-5-methylthiophene. The para-Like Substituent Effect on Fragmentation of the Azido Group.

2-Azido-5-trimethylsilylthiophene 1 and 2-azido-5-methylthiophene 2, prepared by azido group transfer of the corresponding heteroaryllithium derivative with toluene-p-sulfonyl azide, show differing chemical reactivity and kinetic behaviour upon 1,3-cycloaddition with the dipolarophile (trimethylsilyl)acetylene and thermal decomposition.