They could only be attributed to the trapped R2, and many other strong peaks could also be attributed to it (see Supporting Information for details). This experiment proved that the existence of R1 and R2. The intensity of the trapped R2 is 100 times greater than the trapped R1, assuming a similar ionization efficiency of the trapped R1 and R2 species, it suggests that the 1,5-HAT process is very fast and the carbon-centered radical R2 is the resting state for this radical chain process. As shown in substrate scope studies, it is noted that the borylation reactivity is in a order of tertiary C-H bond substrates > secondary ones > primary ones. For tertiary C-H bond substrates, the reactivity of the N-tert-butyl substituted ones are better than that of the N -isopropyl ones. To further elucidate these reactivity patterns, we calculated the standard Gibbs free energy and the activation Gibbs free energy in the process of 1,5-HAT of radicals I to IV (Table ). The results show that the tertiary C-H bonds are the most thermodynamically and dynamically favorable for 1,5-HAT process, probably due to the more stability effect of tertiary alkyl radicals. When replacing tertbutyl with isopropyl in tertiary C-H bond substrates, the activation energy raises from 7.7 to 10.8 kcal • mol -1 (IV.