Generation of a structurally diverse library through alkylation and ring closure reactions using...

3-Dimethylamino-1-(thiophen-2-yl)propan-1-one hydrochloride (2), a ketonic Mannich base derived from 2-acetylthiophene, was used as a starting material in different types of alkylation and ring closure reactions with a view to generate a structurally diverse library of compounds. Compound 2 reacts with S-alkylated dithiocarbamic acid salts and aryl mercaptans to produce dithiocarbamates and thioethers, respectively. The dimethylamino moiety in compound 2 was exchanged with various aliphatic secondary and aromatic primary and secondary amines, whereas monocyclic NH-azoles such as pyrazole, imidazole, 1,2,4-triazole, and tetrazole were N-alkylated by compound 2. Ketones, pyrrole and indoles have been the substrates subjected to C-alkylation reactions by compound 2. Ring closure reactions of compound 2 with a suitable bifunctional nucleophile yielded pyrazolines, pyridines, 2,3-dihydro-1,5-1H-benzodiazepines, 2,3-dihydro-1,5-1H-benzothiazepine, pyrimido[1,2-a]benzimidazole and 4-hydroxypiperidine derivatives.