Abstract
Palladium-catalyzed domino reactions are advanced tools in achieving various nitrogen-containing
heterocycles in an efficient and economical manner due to the reduced number of steps
in the process. This review highlights recent advances in domino processes aimed at
the synthesis of indole derivatives and polycyclic systems containing the indole nucleus
in intra/intra- or intra/intermolecular reactions. In particular, we consider domino
processes that involve a double bond in a step of the sequence, which allow the issue
of regioselectivity in the cyclization to be faced and overcome. The different sections
in this review focus on the synthesis of the indole nucleus and functionalization
of the scaffold starting from different substrates that have been identified as activated
starting materials, which involve a halogenated moiety or unactivated unsaturated
systems. In the former case, the reaction is under Pd(0) catalysis, and in the second
case a Pd(II) catalytic species is required and then an oxidant is necessary to reconvert
the Pd(0) into the active Pd(II) species. On the other hand, the second method has
the advantage that it uses easy available and inexpensive substrates.
1 Introduction
2 Indole Scaffold Synthesis
2.1 Activated Substrates
2.2 Unactivated Substrates
3 Functionalization of Indole Scaffold
3.1 Activated Substrates
3.2 Unactivated Substrates
4 Conclusions
Key words
palladium - indole - domino reactions - C–H activation - cyclization - cascade reactions
- catalysis
