Mild Synthesis of 3,4-Dihydroisoquinolin-1(2H)‑ones via Rh(III)-Catalyzed Tandem C–H-Allylation/N-Alkylation Annulation with 2‑Methylidenetrimethylene Carbonate

A tandem rhodium­(III)-catalyzed system was established to access 3,4-dihydroisoquinolin-1­(2H)-one by coupling of N-methoxy-3-methylbenzamide with 2-methylidenetrimethylene carbonate. This one-pot synthesis protocol processed smoothly under mild reaction conditions. Moreover, a total of 28 examples, broad substrate scope, and high functional-group compatibility were observed. Preliminary mechanism studies were also conducted and demonstrated that the rhodium­(III) catalyst played a vital role in the C–H-allylation and N-alkylation cyclization process.