A Change in C–H Activation Mechanism: Experimental and Computational Investigations of Rh-Catalyzed Disubstituted Benzene Functionalization
Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide We report the ethenylation of 1,3- and 1,2-disubstituted benzenes using [(η 2 -C 2 H 4 ) 2 Rh(μ-OAc)] 2 as a catalyst precursor and Cu(OPiv) 2 as the oxidant. The regioselectivity of alkenylation for 1,3-disubstituted benzenes produces 3,5-disubstituted styrene products, while the alkenylation of 1,2-disubstituted benzenes produces 3,4-disubstituted styrene products. The rate of alkenylation is influenced by steric and electronic factors based on the substituents of the benzene unit. In all cases, 1,2-disubstituted benzenes react faster than 1,3-disubstituted benzenes, with a rate difference that is from 2 times up to >70 times more rapid for 1,2-disubstituted substrates. This is likely due to the difference in the number of accessible C–H bonds based on the steric protection of C–H bonds adjacent to functionality. Furthermore, the rate of alkenylation is influenced by the arene substituent electronics. The rates of alkenylation for 1,2-disubstituted benzenes follow the trend OMe > Me > CF 3 > Cl, while for 1,3-disubstituted benzenes the trend is CF 3 > Cl > Me > OMe. Using quantum mechanics DFT calculations, we found that the C–H activation step can occur by two different mechanisms. The electronic properties of substituents on the arene ring change the preferred C–H bond-breaking mechanism for 1,2-disubstituted and 1,3-disubstituted benzenes.
Source: Organometallics
Authors: Christopher W. Reid, Chi Zhang, Lauren E. Baptiste, K. N. Houk, William A. Goddard III, T. Brent Gunnoe
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4415658742