Analyzing site selectivity in Rh2(esp)2-catalyzed intermolecular C-H amination reactions

Area of Science:

• Organic Chemistry
• Catalysis
• Reaction Mechanism

Background:

• Site selectivity in C-H bond oxidation is challenging due to minimal energy differences between bond types.
• Steric and electronic factors subtly influence reactivity in heteroatom transfer reactions.

Purpose of the Study:

• Investigate factors governing selective C-H amination of isoamylbenzene derivatives catalyzed by Rh2(esp)2.
• Develop a predictive model for site selectivity in C-H amination.

Main Methods:

• Utilized Rh2(esp)2 catalyst for C-H amination reactions.
• Modified nitrogen sources (sulfamate esters) and substrates.
• Employed linear regression modeling correlating IR stretching parameters and Hammett σ(+) values.

Main Results:

• Identified modifications to sulfamate esters and substrates that impact isomeric product ratios.
• Established a mathematical model linking molecular parameters to the free energy difference between benzylic and tertiary C-H amination.
• Achieved a record benzylic-to-tertiary site selectivity of 9.5:1 using a newly designed sulfamate ester.

Conclusions:

• The developed model successfully predicts and guides the enhancement of site selectivity in C-H amination.
• Novel sulfamate esters can significantly improve selectivity for targeted C-H functionalization.
• Understanding the interplay of steric and electronic effects is crucial for designing selective catalytic reactions.