Palladium-catalyzed cyclization of propargylic compounds

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Palladium-catalyzed cyclization of propargylic compounds, first reported in 1985, has been a subject of extensive research.
• Initial studies were limited to the synthesis of heterocyclic compounds.
• Control over reaction outcomes can be achieved through strategic positioning of nucleophilic centers and selection of external nucleophiles.

Purpose of the Study:

• To discuss the development of palladium-catalyzed cyclization reactions of functionalized propargylic compounds with various nucleophiles.
• To review similar reactions reported by other research groups.
• To highlight the synthesis of both carbocyclic and heterocyclic compounds using this methodology.

Main Methods:

• Focus on the cyclization of propargylic compounds bearing a proximate carbon nucleophilic center.
• Detailed investigation of cyclizations with carbon, nitrogen, and oxygen nucleophiles, as well as reactions without external nucleophiles.
• Exploration of tandem C-H activation/bis-cyclization reactions and domino cyclizations initiated by external nucleophiles.

Main Results:

• Developed efficient methods for synthesizing indenes, naphthalenes, polycycles, and spirocyclic compounds.
• Achieved high regio- and stereoselectivity under very mild reaction conditions.
• Demonstrated a novel tandem C-H activation/bis-cyclization and a new domino cyclization pathway.

Conclusions:

• Palladium-catalyzed cyclization of propargylic compounds is a versatile and efficient method for constructing diverse cyclic molecules.
• A deep understanding of reaction mechanisms enables exceptional synthetic control.
• Developed efficient procedures and reagents for palladium-catalyzed propargylic cyclizations, yielding valuable cyclic structures like indenes, cyclopentanones, and benzofurans.