Urea → ethyl (2E)-2H-1,4-benzothiazin-3(4H)-ylideneethanoate

Participants

Reaction Steps

(7-Nitro-1,1-dioxo-1,4-dihydro-1λ6-benzo[1,4]thiazin-3-yl)-acetic acid ethyl ester (12b) was prepared by alkylation and cyclization of 2-amino-5-nitro-thiophenol (11) and ethyl 3-chloroacetoacetate (17) to afford ethyl [4H-benzo[1,4]thiazin-(3E)-ylidene]-acetate (12a). The thiophenol 11 was prepared by unraveling 6-nitro-benzothiazole (10; CAS Reg. No. 2942-06-5). The alkylation of thiols and amines is optionally carried out in a solvent or mixture of solvents such as DCM, DMF, PhH, toluene, chlorobenzene, THF, PhH/THF, dioxane, MeCN or sulfolane with an alkylating agent such as an alkyl 3-chloroacetoacetate, optionally in the presence of a tertiary amine organic base or in the presence of an inorganic base, conveniently at temperatures between 0 and 150° C., preferably at temperatures between 0 and 100° C. Cyclization of the intermediate aminoketone occurs spontaneously under the reaction condition to afford 12a. Oxidation of the sulfide to the corresponding sulfone (12a→12b) and hydrolysis of the ethyl ester (12b→13) were carried out using standard protocols to afford 13.

Provenance & Evidence