Wei-Si Guo

A new approach to pyridines through the reactions of methyl ketones with 1,2,4-triazines

A new route to prepare pyridine derivatives based on inverse electron demand Diels–Alder/retro-Diels–Alder reactions of ketones with 1,2,4-triazines is reported. It is the first time using methyl ketones directly as a dienophile to react with 1,2,4-triazines without enamine intermediates, which is complementary to the classical Boger reaction.

Copper-catalyzed tandem arylation–cyclization of 2-alkynylaryl isothiocyanates with diaryliodonium salts: an efficient synthesis of thiochromeno[2,3-b]indoles

A catalytic tandem arylation–cyclization approach using 2-alkynylphenyl isothiocyanates with diaryliodonium salts is described. The reaction is performed under mild conditions and thiochromeno[2,3-b]indoles are obtained in moderate to good yields. This tandem protocol involves chemoselective S-arylation, regioselective 5-endo-trig cyclization and Friedel–Crafts-type cyclization processes. Two C–C bonds, one C–S bond, and two heterocyclic rings are formed in a single step. Preliminary mechanistic studies indicate that a carbocation mechanism is involved.

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.

Yb(OTf)3 catalyzed [3 + 2] annulations of D–A cyclopropanes with β-oxodithioesters: a regioselective synthesis of tetrahydrothiophenes

A new route to prepare tetrahydrothiophene derivatives from D–A cyclopropanes and β-oxodithioesters catalyzed by Yb(OTf)3 is reported. This is the first example using β-oxodithioesters as dipolarophiles to react with D–A cyclopropanes. The method exhibits good regioselectivity.

A copper-catalyzed arylation/nucleophilic addition/fragmentation/C–S bond formation cascade: synthesis of bis(arylthio)imines

A new tandem arylation/nucleophilic addition/fragmentation/C–S bond formation reaction involving diaryliodonium salts as electrophiles was developed with Cu(OTf)2 as the catalyst. A series of unexpected bis(arylthio)imine derivatives were generated in good yields. The reaction proceeds under mild conditions, and the bis(arylthio)imines are readily transformed to other useful products.

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.

Acid/base-controlled chemodivergent synthesis of two differently functionalized tetrahydroimidazo[1,2-a]pyridines

A new approach for the facile chemodivergent synthesis of tetrahydroimidazo[1,2-a]pyridines from β-ketothioamides, aldehydes and heterocyclic ketene aminals is described. In the presence of a base, an unprecedented ring-opening, tautomerization, recyclization cascade is observed and H2S eliminated tetrahydroimidazo[1,2-a]pyridines were formed in good yields. With catalytic amounts of acid, another type of different substituted tetrahydroimidazo[1,2-a]pyridines were obtained through dehydration.

Catalyst- and solvent-free bisphosphinylation of isothiocyanates: a practical method for the synthesis of bisphosphinoylaminomethanes

A general and convenient double addition of phosphine oxides to isothiocyanates is described. It is a practically useful protocol for the construction of bisphosphinoylaminomethanes. The reaction can be carried out smoothly under metal- and solvent-free conditions. It also features a broad substrate scope, simple operation and purification. A possible mechanism involving a tandem double nucleophilic addition/H2S elimination/in situ imine reduction process is proposed.

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.