Cyclohexa-1,4-dienes in transition-metal-free ionic transfer processes

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Hazardous chemicals necessitate the development of safer alternatives for chemical synthesis.
• Cyclohexa-1,4-dienes have emerged as promising surrogates for reactive species.
• Boron-based Lewis acids, such as B(C6F5)3, are effective catalysts for transfer reactions.

Purpose of the Study:

• To review the principles and applications of cyclohexa-1,4-dienes as electrophilic/hydride (El+/H-) equivalents.
• To summarize the use of these surrogates in catalyzed transfer reactions involving various unsaturated and sigma-donors.
• To discuss the scope, limitations, and future challenges of these novel synthetic methodologies.

Main Methods:

• Utilized B(C6F5)3-catalyzed reactions for the transfer of El-H bonds from substituted cyclohexa-1,4-dienes.
• Investigated transfer reactions to various π-donors (alkenes, alkynes) and σ-donors (carbonyls, imines).
• Demonstrated the application of these surrogates for hydrosilylation, hydrogermylation, hydrogenation, and hydro-tert-butylation.

Main Results:

• Successfully employed substituted cyclohexa-1,4-dienes as safe and convenient surrogates for Si-H, Ge-H, H-H, and C-H bonds.
• Achieved efficient transfer reactions, including ionic transfer hydrosilylation/hydrogermylation, hydrogenation, and hydro-tert-butylation.
• Highlighted the versatility of these surrogates across a range of catalytic transformations.

Conclusions:

• Cyclohexa-1,4-dienes represent a significant advancement in developing safe handling protocols for hazardous reagents.
• These surrogates offer a versatile platform for various catalytic bond formations, expanding synthetic capabilities.
• Further research into optimizing reaction conditions and exploring new applications is warranted.