Synthesis of Some New Naphthopyran, Pyrazole, Pyridine, and Thienobenzochromene Derivatives Using 1-(1-Hydroxy-2-naphthyl) Ethanone as a Versatile Starting Material

Treatment of the enaminone 2, prepared from 1-(1-hydroxy-2-naphthyl)ethanone 1 and N,N-dimethylformamide dimethylacetal with acetic acid, thionyl chloride, or bromine, gave the corresponding 4-oxo-4H-naphtho[1,2-b]pyran derivatives 3, 4, and 5. Refluxing of p-toluidine or p-anisidine with 2 afforded compounds 6 and 7, respectively. The naphtho[1,2-b]pyran-3-carbaldehyde 9 was prepared via the acetylation of 2. Condensation of 9 with malononitrile or ethyl cyanoacetate gave the pyridine derivatives 10 and 11. Refluxing of 9 with hydrazine hydrate, phenylhydrazine, semicarbazide hydrochloride, or thiosemicarbazide afforded the pyrazole derivatives 12, 13, 14, and 15 respectively. Reaction of ethanone 1 with malononitrile gave the chromene carbonitrile derivative 16. Treatment of 16 with malononitrile afforded the chromene malononitrile derivative 17. Also, compound 17 was obtained from the reaction of 1 with excess of malononitrile and catalytic piperidine. Treatment of 16 with ethyl cyanoacetate produced compound 18. When 16 was treated with elemental sulfur, theino[3,4-c]benzochromene derivative 19 was produced. Hydrolysis of 16 with hydrochloric acid yielded the benzochromene carbonitrile derivative 20 which on heating with elemental sulfur afforded the theinobenzochromene derivative 21. Treatment of 21 with acetic anhydride, p-chlorobenzaldehyde, phenyl isothiocyanate, or thionylchloride furnished compounds 22, 23, 24, and 25, respectively.