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2-Aminopyridine-3-carbonitrile derivative 1 reacted with each of malononitrile, ethyl cyanacetate, benzylidenemalononitrile, diethyl malonate, and ethyl acetoacetate to give the corresponding [1,8]naphthyridine derivatives 3, 5, 8, 11, and 14, respectively. Further annulations of 3, 5, and 8 gave the corresponding pyrido[2,3-b][1,8]naphthyridine-3-carbonitrile derivative 17, pyrido[2,3-h][1,6]naphthyridine-3-carbonitrile derivatives 18 and 19, respectively. The reaction of 1 with formic acid, formamide, acetic anhydride, urea or thiourea, and 4-isothiocyanatobenzenesulfonamide gave the pyridopyrimidine derivatives 20a,b, 21, 22a,b, and 26, respectively. Treatment of compound 1 with sulfuric acid afforded the amide derivative 27. Compound 27 reacted with 4-chlorobenzaldehyde and 1H-indene-1,3(2H)-dione to give the pyridopyrimidine derivative 28 and spiro derivative 30, respectively. In addition, compound 1 reacted with halo compounds afforded the pyrrolopyridine derivatives 32 and 34. Finally, treatment of 1 with hydrazine hydrate gave the pyrazolopyridine derivative 35. The structures of the newly synthesized compounds were established by elemental and spectral data.

The novel cyanothioformamides 2a-d were prepared by treatment of isothiocyanatosulfonamides 1a-d with potassium cyanide at room temperature. Cyclocondensation of compounds 2b,c with phenyl isocyanate as electrophile furnished the corresponding imidazolidines 3a,b. The reactivity of compound 3a towards some nitrogen nucleophiles was investigated. Thus, the thiosemicarbazone 4 and imidazo[4,5-b]quinoxaline 6 were synthesized by condensation of compound 3a with thiosemicarbazide and o-phenylenediamine, respectively. Treatment of 3a with hydrochloric acid afforded compound 7. Our investigation was extended to include the reactivity of cyanothioformamide 2 towards o-aminophenol, anthranilic acid, and o-phenylenediamine and yielded the corresponding heterocycles 9, 11 and 13 derivatives, respectively. Structures of the synthesized compounds were established by their elemental analysis and spectral data.

2-Aminopyridine-3-carbonitrile derivative 1 reacted with each of malononitrile, ethyl cyanacetate, benzylidenemalononitrile, diethyl malonate, and ethyl acetoacetate to give the corresponding [1,8]naphthyridine derivatives 3, 5, 8, 11, and 14, respectively. Further annulations of 3, 5, and 8 gave the corresponding pyrido[2,3-b][1,8]naphthyridine-3-carbonitrile derivative 17, pyrido[2,3-h][1,6]naphthyridine-3-carbonitrile derivatives 18 and 19, respectively. The reaction of 1 with formic acid, formamide, acetic anhydride, urea or thiourea, and 4-isothiocyanatobenzenesulfonamide gave the pyridopyrimidine derivatives 20a,b, 21, 22a,b, and 26, respectively. Treatment of compound 1 with sulfuric acid afforded the amide derivative 27. Compound 27 reacted with 4-chlorobenzaldehyde and 1H-indene-1,3(2H)-dione to give the pyridopyrimidine derivative 28 and spiro derivative 30, respectively. In addition, compound 1 reacted with halo compounds afforded the pyrrolopyridine derivatives 32 and 34. Finally, treatment of 1 with hydrazine hydrate gave the pyrazolopyridine derivative 35. The structures of the newly synthesized compounds were established by elemental and spectral data.

Cyclocondensation of cyanothioformamides (1) with arylhydrazonomalononitriles (2) afforded the novel imidazole derivatives (4a–e) in good yields. Isothiocyanatoazobenzene (6) was allowed to react with potassium cyanide and gave the new cyanothioformamide (7) which was reacted with 4-chlorophenyl isocyanate to yield imidazolidinethione (8). Compound (8) was subjected to react with hydrochloric acid, o-phenylenediamine, 4-methylaniline, and hydrogen sulfide and furnished compounds (10), (11), (12), and (15), respectively. Also, the reactivity of thiohydantoin (15) toward some electrophilic reagents such as N,N-dimethylformamide-dimethylacetal and arylidene-malononitriles was investigated. The structure of the synthesized compounds was established by analytical and spectral data. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:218–225, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20113