Three-component cycloadditions: the first transition metal-catalyzed [5+2+1] cycloaddition reactions

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Transition metal-catalyzed cycloadditions, including [4+4], [4+2], [5+2], and [6+2] reactions, are established synthetic tools.
• The potential for intercepting two-component reactions with a third component was previously unexplored.
• Development of novel cycloaddition strategies is crucial for accessing complex molecular architectures.

Purpose of the Study:

• To introduce a new three-component transition metal-catalyzed [5+2+1] cycloaddition reaction.
• To investigate the synthesis of bicyclo[3.3.0]octenone adducts.
• To explore the utility of this reaction for generating complex synthetic building blocks.

Main Methods:

• Employed transition metal catalysis to facilitate a three-component cycloaddition.
• Utilized carbonyl-substituted alkynes as key reaction substrates.
• Investigated the effects of reaction parameters such as concentration, temperature, pressure, and catalyst loading.

Main Results:

• Achieved good to excellent yields for the novel [5+2+1] cycloaddition.
• Demonstrated high to complete regioselectivity in the formation of bicyclo[3.3.0]octenone adducts.
• Confirmed the formation of products via transannular closure of an intermediate eight-membered-ring cycloadduct.

Conclusions:

• The developed [5+2+1] cycloaddition provides an efficient route to complex bicyclo[3.3.0]octenone structures.
• The reaction utilizes simple and readily available starting materials, enhancing its synthetic applicability.
• This methodology offers a valuable new approach for constructing intricate molecular frameworks.