Isobutyronitrile furnished gem-difluoroalkne 3ma in good yield and excellent regioselectivity. It was worth mentioning that cleavage of C-H bond in cyclopentanone regio-selectively happened at the stronger β-C(sp 3 ) -H bond other than the weaker α-C(sp 3 )-H bond. This is attributed to the polar SH2 transition state and that the cleavage of the more labile α-C(sp 3 )-H bond could lead to an unfavorable polar radical transition state and an unstabilized electron-deficient α-carbon, when the electronegative oxygen-centred radicals in the excited TBADT photocatalyst abstract hydrogen from C(sp 3 )-H bonds. Aside from unactivated Csp 3 -H bonds, benzylic and heteroatom-adjacent Csp 3 -H bonds were also compatible with this transformation (3oa-3ta), and the functionalization site-selectively happened at the weaker α-Csp 3 -H bond position instead of the β position (3pa-3ra).