CHEMISTRY AND CYCLIZATION REACTIONS OF THIENOQUINOXALINE DERIVATIVES: PART I

Abstract

Abstract Reaction of 2(1H)quinoxalinethione-3-carbonitrile 1 with alkyl or aralkyl halides, chloroacetic acid, ethyl chloroacetate, or N-phenylchloroacetamide in ethanolic sodium acetate solution gives the corresponding 3-thioethers of 1. Treatment of 3 with acetic anhydride gives the dimesoionic thiazolo[3′,4′-c]-2-cyanoquinoxaline, 4. Treatment of 6 or 10 with ethanolic sodium ethoxide solution gives the cyclization products, ethyl-3-aminothieno[2,3-b]quinoxaline-2-carboxylate 7 or 3-phenylcarboxamide 11 substituents respectively. Treatment of 11 with carbon disulfide/ethanolic potassium hydroxide soution gives 3-phenylpyromido[4′,5′:4,5]thieno[2,3-b]quinoxaline-4-one-2-thione 12 which is also produced by treatment of 7 with phenyl isothiocyanate in dry pyridine. Compound 11 cyclizes on treatment with benzoyl chloride, acetic anhydride, phenyl isothiocyanate, ethyl chloroformate and/or nitrous acid, to produce the corresponding pyrimidothienoquinoxalines 14–17 and [1,2,3] triazinothienoquinoxaline 18 derivatives respectively. Compound 7 cyclizes with ethanolic potassium hydroxide solution followed by acetic anhydride to give the oxazino compound 19 which gives (with different amino reagents) the corresponding 3-substituted pyrimidothienoquinoxaline-4-ones 20–25.