Pd (OAc) 2-catalyzed decomposition of ethyl 2-diazo-4-(4-indolyl)-3-oxobutanoate leads to a tricyclic tetrahydrobenzindole compound formed by a formal C–H insertion reaction. This tricyclic indole rearranges to a novel and thermodynamically more stable naphthalene derivative. Treatment of N-tosyl-protected ethyl 2-diazo-4-(4-indolyl)-3-oxobutanoate with a base induces facile pyrazole formation.