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.

Automated summary

A tandem rhodium(III)-catalyzed system was developed for the synthesis of 3,4-dihydroisoquinolin-1(2H)-one by coupling N-methoxy-3-methylbenzamide with 2-methylidenetrimethylene carbonate. The method showed excellent substrate scope, functional-group compatibility, and smooth reaction under mild conditions. Mechanism studies indicated the vital role of the rhodium(III) catalyst in C-H-allylation and N-alkylation cyclization.