New pyrimido[4,5-b]carbazolone derivatives have been synthesized through cascade Ullmann N-arylation and aerobic oxidative C-H amidation reactions catalyzed by CuBr under air and ligand-free conditions.
Optimized conditions are developed which render possible the synthesis of a new class of heterocyclic systems, structural motifs of natural substances.
A simple and efficient protocol for the synthesis of highly substituted cyclopentacarbazolones (50-82%) was developed by employing internal alkynes with 2-bromo-3-formylcarbazoles in the presence of palladium catalyst under ligand-free condition. High regioselectivity was observed for unsymmetrical (alkyl-, arylsubstituted) internal alkynes.
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