J Org Chem. 2026 Apr 28. doi: 10.1021/acs.joc.5c03133. Online ahead of print.
ABSTRACT
A DFT mechanistic study of C-H borylation of 3-fluorobenzotrifluoride catalyzed by Ir complexes ligated by 4,4′-bis(trifluoromethyl)-2,2′-bipyridine (btfbpy), 4,4′-ditert-butyl-2,2′-bipyridine (dtbpy), and 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), respectively, demonstrates that the C-H bonds distal to the steric -CF3 group exhibit comparable, albeit slightly lower, rate and regioselectivity-determining barriers compared to those proximal to -CF3, which corroborates with the experimental observations of statistical regioselectivity among aryl C-H bonds in the absence of significant steric hindrance. Conversely, utilizing a bulky spirobipyridine ligand that imposes substantial steric hindrance at the activation sphere is predicted to effectively promote meta-to-fluorine regioselectivity, which was found to arise from the stronger catalyst-substrate interactions due to the steric-screening effect, leading to the lower C-H activation barrier.
PMID:42048608 | DOI:10.1021/acs.joc.5c03133
