Intramolecular dehydrogenative C-S bond coupling of thioamides to form 1,3-benzothiazines under metal-free conditions.

A novel HTIB-promoted direct intramolecular dehydrogenative C-S bond coupling reaction of thioamides has been developed to provide 1,3-benzothiazine derivatives in good yields. The reaction proceeds smoothly to reach completion at room temperature within 1 min under metal-free conditions. This protocol provides a mild and efficient strategy for the synthesis of six-membered N,S-containing heterocycles. Preliminary mechanistic studies indicate that a spirocyclic intermediate might be involved.

Fast Construction of 1,3-Benzothiazepines by Direct Intramolecular Dehydrogenative C-S Bond Formation of Thioamides under Metal-Free Conditions.

The first general protocol for the synthesis of 1,3-benzothiazepine derivatives was established. With the aid of bench-stable hypervalent iodine promoter fluoro-HTIB, these seven-membered heterocycles can be rapidly synthesized from readily available thioamides under air atmosphere and metal-free conditions. The transformation can be completed within 1 min at room temperature and features a broad substrate scope.

Synthesis of 6-Phosphorylated Phenanthridines by Mn(II)-Promoted Tandem Reactions of 2-Biaryl Isothiocyanates with Phosphine Oxides.

A novel Mn(II)-promoted tandem phosphorylation/cyclization reaction of 2-biaryl isothiocyanates with phosphine oxides is described. This is the first general method to synthesize 6-phosporylated phenanthridines from 2-biaryl isothiocyanates. The approach is featured by oxidant-free, low loading of P-reagent, easy operation, and high functional group tolerance.

Synthesis of 1-Thio-Substituted Isoquinoline Derivatives by Tandem Cyclization of Isothiocyanates.

A copper-catalyzed tandem arylation-cyclization process to access 1-(arylthio)isoquinolines from isothiocyanates and diaryliodonium salts is described. It is the first general method to construct the potentially useful 1-(arylthio)isoquinoline derivatives. Moreover, 1-(methylthio)isoquinoline derivatives were also achieved successfully with MeOTf instead of diaryliodonium salts under metal-free conditions. Mechanistic studies reveal that these two processes proceed in different routes. This method has been successfully applied to the synthesis of quinazolinone alkaloid rutaecarpine.

ß-ketothioamides: efficient reagents in the synthesis of heterocycles.

ß-Ketothioamides (KTAs) are versatile building blocks for the rapid construction of various heterocyclic compounds. In the past decade, a number of successful reactions based on KTAs have been developed for the construction of heterocyclic skeletons under mild conditions. This minireview focuses on the annulation reactions of KTAs with dielectrophilic or dinucleophilic reagents. Multicomponent reactions using KTAs to construct various heterocycles are also the major contents in this review.