Photocatalyzed Site-Selective C(sp 3 )-H Functionalization of Alkylpyridines at Non-Benzylic Positions.

Tetrabutylammonium decatungstate (TBADT)-photocatalyzed C-H functionalization of alkylpyridines was investigated. Unlike alkylbenzene counterparts, alkylation of α-C-H bonds did not proceed for the reaction of 2- and 4-alkylpyridines and reluctantly proceeded for 3-alkylpyridines, which allow site-selective C(sp3 )-H functionalization at nonbenzylic positions. The observed nonbenzylic site selectivities are rationalized by the polar inductive effects of pyridyl groups in the SH 2 transition states. Consecutive γ-functionalization and α-bromofunctionalization were successfully carried out in selected cases.