I2/CH3ONa-Promoted Ring-Opening Alkylation of Benzothiazoles with Dialkyl Carbonates

Dialkyl carbonates were used as the green alkylating reagents in the I2-promoted ring-opening alkylation of benzothiazoles. A variety of benzo[d]thiazole derivatives underwent the alkylation smoothly to provide the diverse N-alkyl-N-(o-alkylthio)phenylformamides in moderate to excellent yields. The synthetic utility of this protocol was verified by gram-scale reaction and further derivatization of the products. The mechanism of the involvement of two molecules of dialkyl carbonates in the formation of sulfur-alkyl and nitrogen-alkyl groups, respectively, was also demonstrated.

Facile preparation of dihydro-1,4-benzothiazine derivatives via oxidative ring-expansion of 2-aminobenzothiazoles with olefins

A concise and efficient approach to prepare dihydro-1,4-benzothiazine derivatives is described via oxidative ring-expansion of 2-aminobenzothiazoles with olefins under metal-free conditions. This protocol is applicable for a wide range of readily accessible 2-aminobenzothiazoles and olefins with moderate-to-good yields. The [4+2] heteroannulation between the intermediacy of oxidative ring-opening of 2-aminobenzothiazoles and olefins is suggested to rationalize the formation of the product.

A palladium-catalyzed ring-expansion reaction of cyclobutanols with 2-haloanilines leading to benzazepines and quinolines

A general synthesis of 2-aryl benzazepines has been developed through palladium-catalyzed ring-expansion reactions of cyclobutanols with 2-haloanilines; the further oxidative rearrangement reaction of benzazepines provided an efficient synthesis of 2-acyl quinolines. These transformations feature the efficient construction of six- and seven-membered N-containing heterocycles from easily obtained materials with excellent functional group tolerance.

Iodine-promoted ring-opening methylation of benzothiazoles with dimethyl sulfite

A halogen-bond promoted ring-opening methylation of benzothiazoles has been developed using dimethyl sulphite as a methylating reagent in the presence of a base. This approach represents a simple and efficient synthesis of N-methyl-N-(o-methylthio)phenyl amides, and features direct construction of both N-Me and S-Me bonds in a one-pot reaction through the decomposition of easily prepared benzothiazoles.

AIBN-Promoted Synthesis of Bibenzo[ b][1,4]thiazines by the Condensation of 2,2'-Dithiodianiline with Methyl Aryl Ketones

A series of bibenzo[ b][1,4]thiazines with various functional groups has been synthesized by a free-radical condensation reaction. Bibenzo[ b][1,4]thiazines were obtained in moderate to good yield (up to 85%) through a one-step reaction of readily available 2,2'-dithiodianiline and methyl aryl ketones with AIBN as radical initiator in HOAc. Bibenzo[ b][1,4]thiazines exhibit diversiform solid-state packing.