Arylcarboxylation/Cyclization/Hydrogenation Cascade of Arylalkynes with Formate: Synthesis of Ester-Substituted Dioxodihydrodibenzothiazepine Derivatives.

A novel method has been developed for the arylcarboxylation/cyclization/hydrogenation cascade reaction of arylalkynes with cheap and readily available sodium formate (HCO2Na). This approach facilitates the efficient synthesis of ester-substituted dioxodihydrodibenzothiazepine derivatives in the absence of photocatalysts and transition metals. The methodology features a broad substrate scope, operational simplicity, excellent functional group tolerance, mild reaction conditions, and scalability. Mechanistic experiments proved that the reaction involves a pathway that includes the formation of the carbon dioxide radical anion (CO2•-) from formate. Meanwhile, the hydrogen in the product comes from trace amounts of water in the solvent or HCO2Na.