Synthesis of γ-Thiapyrones by Diels-Alder/Retro-Diels-Alder Reaction of α-Pyrones with 5-H-1,2,3-Thiadiazoles

The efficient synthesis of γ-thiapyrones by a base-mediated Diels-Alder/retro-Diels-Alder reaction of α-pyrones with 5-H-1,2,3-thiadiazoles is reported herein. Thioketenes in situ generated from thiadiazoles as electron-poor dienophile and electron-rich 4-hydroxy-2-pyrones as dienes are conjunctively transformed into a series of γ-thiapyrones with broad functional group compatibility in good to excellent yields (35 examples, 67% average yield).

1,2,3-Thiadiazole as a Modifiable and Scalable Directing Group for ortho-C-H Functionalization

In the last few decades, directed C-H bond functionalization has had enormous applicability in academia and industry. The development of a novel, readily accessible, and scalable directing group with modifiable ability is highly desirable in C-H functionalization. Herein, we report the 1,2,3-thiadiazole as a modifiable directing group for C-H amidation and alkynylation with dioxazolones, p-toluenesulfonyl azide, and bromoalkynes in high yield. The densely functionalized 1,2,3-thiadiazole products are modified into thioamide, multisubstituted furan, γ-thiapyrone, thiazole, and various alkynyl sulfides through simple and one-step reactions. The competition experiments reveal that the directing ability of 1,2,3-thiadiazole is slightly weaker than pyridine and bidentate amide but stronger than the widely used carboxylate.

Silver-mediated annulation between 5-H-1,2,3-thiadiazoles and 1,3-dicarbonyl compounds to construct polysubstituted furans

An efficient synthesis of polysubstituted furans by Ag(i)-mediated annulation between 5-H-1,2,3-thiadiazoles and 1,3-dicarbonyl compounds is reported.

Thioamide synthesis via copper-catalyzed C–H activation of 1,2,3-thiadiazoles enabled by slow release and capture of thioketenes

A copper-catalyzed coupling of 1,2,3-thiadiazoles with various amines under base-free conditions was developed as a robust protocol for the synthesis of thioamide derivatives via C–H activation/Cu coordination strategy.

Sulfur-controlled and rhodium-catalyzed formal (3 + 3) transannulation of thioacyl carbenes with alk-2-enals and mechanistic insights

A rhodium-catalyzed denitrogenative formal (3 + 3) transannulation of 1,2,3-thiadiazoles with alk-2-enals is achieved, producing 2,3-dihydrothiopyran-4-ones in moderate to excellent yields. An inverse KIE of 0.49 is obtained, suggesting the reversibility of the oxidative addition of thioacyl Rh(i) carbenes to alk-2-enals. The late-stage structural modifications of steroid compounds are realized. Moreover, our studies show that thioacyl carbenes have different reactivities to those of α-oxo and α-imino carbenes, and highlight the importance of heteroatoms in deciding the reactivities of heterovinyl carbenes.

Stereochemistry and mechanistic insights in the [2t + 2i + 2i] annulations of thioketenes and imines

The mechanism and stereochemistry of [2^t + 2ⁱ + 2ⁱ] annulations between one thioketene molecule and two imine molecules have been studied experimentally and theoretically.