Manganese Complex Catalyzed Sequential Multi-component Reaction: Enroute to a Quinoline-Derived Azafluorenes

Area of Science:

• Organic Chemistry
• Catalysis
• Heterocyclic Chemistry

Background:

• Novel synthetic strategies are crucial for creating complex molecular structures and new structural motifs.
• N-heterocycles are vital in life and material sciences, driving research in heterocyclic compound synthesis.
• Sustainable and eco-friendly catalytic processes using first-row transition metals are highly desirable.

Purpose of the Study:

• To develop a novel, sustainable synthetic route for quinoline-based azafluorenes.
• To utilize a sequential dehydrogenative multicomponent reaction (MCR) for efficient heterocycle synthesis.
• To investigate the catalytic activity of newly developed manganese (Mn) complexes.

Main Methods:

• Sequential dehydrogenative multicomponent reaction (MCR) followed by C(sp3)-H hydroxylation and annulation.
• Synthesis of novel quinoline-based azafluorenes.
• Utilized newly developed Mn-complexes as catalysts.
• Conducted control experiments, hydride trapping, reaction kinetics, catalytic intermediate, and DFT studies.

Main Results:

• Successfully synthesized various new quinoline-based azafluorenes.
• Demonstrated the efficacy of Mn-complexes in directing the reaction and minimizing side reactions.
• Achieved high yields of desired functionalized heterocycles.
• Elucidated the reaction mechanism and catalyst function through detailed mechanistic studies.

Conclusions:

• Developed an efficient and sustainable method for synthesizing functionalized quinoline-based azafluorenes.
• The novel Mn-catalyst system enables a sequential MCR approach with high selectivity.
• Mechanistic investigations provide a comprehensive understanding of the catalytic process.