Synthesis and chemistry of some quinoline-5,8-diones
The synthesis of several 7-substituted analogs of 2-methylquinoline-5,8-dione and their chemistry are described. In this investigation the following compounds were prepared.5,7-Diformamido-8-hydroxy-2-methylquinoline (207), 7-formamido-2methylquinoline-5,8-dione (199), 7-acetamido-2-methylquinoline-5,8-dione (6), 7-isobutyramido-2-methylquinoline-5,8-dione (200), 7-amino-2-methylquinoline-5,8-dione (210), 7-amino-6-chloro-2-methylquinoline-5,8-dione (213), 7-methoxy-2-methylquinoline5,8-dione (214), 7-ethoxy-2-methylquinoline-5,8-dione (215), 7-isopropyloxy-2methylquinoline-5,8-dione (216), 7-amino-5-ethyl-5-hydroxy-2-methylquinoline-8-one (218), 7-acetamido-5-ethyl-5-hydroxy-2-methylquinoline-8-one (220), and 7-chloro-2methylquinoline-5,8-dione (222).Trimetylacetic formic anhydride (206) was prepared according to McGarvy,s 68 method from treatment of sodium formate (204) and trimethylacetyl chloride (203) in the presence of poly (4-vinylpyridine-N-oxide) (205) as catalyst. 7-Formamido-2methylquinoline-5,8-dione (199) was prepared according to the following general procedure. 8-Hydroxy-2-mehylquinoline (5) was reacted with a 70% mixture of HNO3/H2SO4 to produce 5,7-dinitro-8-hydroxy-2-methylquinoline (18). Compound 18 was reduced by H2/Pd-C in the presence of HCl and then the resulting 5,7-diamino-8-hydroxy-2 methylquinolin-5,8-dione hydrochloride salt (198) reacted with trimethylacetic formic anhydride to produce 5,7-diformamido-8-hydroxy-2-methylquinoline-5,8-dione (207). Compound 207 was treated with a solution of potassium dichromate in acetic acid-water mixture to give product 199.7-Acetamido-2-methylquinoline-5,8-dione (6) was prepared from reaction of a solution of 198 with acetic anhydride in the presence of sodium acetate and sodium sulfite followed by oxidation with potassium dichromate in acetic acid-water solution. 7-Isobutyramido-2methylquinoline-5,8-dione (200) was prepared according to following procedure. Treatment of a solution of 198 with isobutyric anhydride in the presence of sodium acetate and sodium sulfite afforded 5,7-diisobutyramido-8-isobutyroxy-2-methylquinoline (212). Partial hydrolysis of 212 in boiling methanol-water mixture gave 5,7-diisobutyramido-8-hydroxy-2methylquinoline (211). Oxidation of 211 by a solution of potassium dichromate in acetic acid-water mixture afforded product 200.7-amino-2-methylquinoline-5,8-dione (210) was prepared from alcoholysis of 7-acylamino-2-methylquinoline-5,8-diones 6, 199,and 200 with methanol and sulfuric acid. 7-Alkoxy-2-methylquinoline-5,8-diones 214, 215, and 216 were prepared from reaction of 7-acetamido compound 6 with alcohols in the presence of sulfuric acid. Reaction of 7-acylamino compounds 6, 199, and 200 with methanol in the presence of hydrogen chloride gas at 60°C afforded 7-amino-6-chloro-2-methylquinoline-5,8-dione (213).Reaction of compound 210 with diethylaluminum cyanide gave 7-amino-5-ethyl-5hydroxy-2-methylquinoline-8-one (218). The same reaction was carried out on compound 6 to give 7-acetamido-5-ethyl-5-hydroxy-2-methylquinoline-8-one (220).1-[(tert-Butyldimethylsilyl)oxy]-2-methyl-l-aza-1,3-butadiene (4) was prepared from treatment of methyl vinyl ketone (210) and t-butylmethylsilylhydroxylamine (202) in dichloromethane in the presence of molecular sieves. Cycloaddition reaction of a solution of 4 in dichloromethane with 2,6-dichloro-1,4-benzoquinone (221) in sealed tube afforded 7-chloro-2-methylquinoline-5,8-dione (222).