No abstract

2-Aminobenzimidazole (1a) and its 5,6-dimethyl derivative 1b react with phenylpropynenitrile (2) to give 2-amino-4-phenylpyrimido[1,2-a]benzimidazoles 8a,b in excellent yields. Of these compounds, 2-amino-7,8-dimethyl-4-phenylpyrimido[1,2-a]benzimidazole (8b) has been shown to possess diuretic properties. Acetylenic aldehydes 9a,b also react with 1a,b to give pyrimido[1,2-a]benzimidazoles 13a-13d in good yield.

2-Aminobenzimidazole (1a) and its 5,6-dimethyl derivative 1b react with 4-hydroxy-2-alkynenitriles 2a-d in ethanol under reflux to give 2-amino-4-(1'-hydroxyalkyl)pyrimido[1,2-a]-benzimidazoles 5a-e and in dimethylformamide at 155°C to give (2,2-dialkyl-2,3-dihydrooxazolo[3,2-a]benzimidazolylidene)ethanenitriles 7a-e.

Ring closure reactionsRing closure reactions O 0130 Thermolysis of Symmetrical Dithiobiurea and Thioureidoethylthiourea Derivatives. -Microwave heating or pyrolysis of the title thiourea derivatives (I), (VI) and (IX) results in intramolecular heterocyclization processes furnishing various N,S-heterocycles. Application of microwave irradiation provides higher yields in comparison with yields obtained by thermal processes. -(HASSAN*, A. A.; MOURAD, A.-F. E.; EL-SHAIEB, K. M.; ABOU-ZIED, A. H.; DOEPP, D.; Heteroat. Chem. 14 (2003) 6, 535-541; Dep. Chem., Fac. Sci.,

Conjugate addition of the imino nitrogen of 2-aminobenzothiazoles 1 to the alkyne β-carbon atom of acetylenic acids 2 followed by ring closure gives rise to novel 2H-pyrimido[2,1-b]-benzothiazol-2-ones in good yield.