Theoretical insight into decatungstate photocatalyzed alkylation of N -tosylimine via hydrogen atom transfer and proton-coupled electron transfer.

Decatungstate as a photocatalyst can activate various C(sp 3 )-H bonds to successfully construct the C(sp 3 )-C(sp 2 ) bond with N -tosylimines. Herein density functional theory (DFT) calculations reveal a unique radical mechanism triggered by the reductive quenching cycle of decatungstate. First of all, photoexcited *[W 10 O 32 ] 4- activates the C(sp 3 )-H bond of ether through the hydrogen atom transfer (HAT) mechanism to generate [HW 10 O 32 ] 4- and a C-centered radical species. Next, the C-centered radical will selectively attack the imine carbon of N -tosylimine to provide the N-centered radical species containing the C(sp 3 )-C(sp 2 ) bond. Finally, the C(sp 3 )-C(sp 2 ) coupling product can be afforded by the stepwise proton-coupled electron transfer (PCET) process between [HW 10 O 32 ] 4- and the N-centered radical. Importantly, the bridging oxygen in the lateral position of [W 10 O 32 ] 4- is the most active. Intrinsic bond orbital (IBO) analysis confirms that *[W 10 O 32 ] 4- activates C(sp 3 )-H through HAT instead of PCET. Furthermore, the origin of the regio-selectivity has been explored in depth. We hope that the reductive quenching cycle mechanism ([W 10 O 32 ] 4- -*[W 10 O 32 ] 4- -[HW 10 O 32 ] 4- -[W 10 O 32 ] 4- ) can provide a clear understanding of the alkylation of N -tosylimine.