Synthesis, reactions, and antioxidant activity of 3-(pyrrol-1-yl)-4,6-dimethyl selenolo[2,3-<i>b</i>]pyridine derivatives

<p>Ethyl 4,6-dimethyl-3-(pyrrol-1-yl) selenolo[2,3-<i>b</i>]pyridine-2-carboxylate <b>(2)</b> was synthesized by the reaction of previously prepared ethyl 3-amino-4,6-dimethyl selenolo[2,3-<i>b</i>]pyridine-2-carboxylate <b>(1)</b> with 2,5-dimethoxytetrahydrofuran in acetic acid. The pyrrolyl ester <b>(2)</b> was converted into the corresponding carbohydrazide <b>3</b> which reacted with acetyl acetone, aromatic aldehydes, carbon disulfide in pyridine, and sodium nitrite to afford the corresponding dimethyl pyrazolyl <b>4</b>, arylidene carbohydrazides <b>5a–d</b>, oxadiazolyl thiole <b>6,</b> and caboazide compound <b>8,</b> respectively. The carboazide <b>8</b> reacted with different alcohols and amines to give the corresponding carbamates <b>9a–c</b> and the aryl urea derivatives <b>10a–d</b>. Heating of carboazide <b>8</b> in dry xylene afforded the pyridoselenolo-pyrrolopyrazinone <b>11</b>. The latter compound was used as a versatile starting precursor for synthesis of other pyridoselenolo-pyrrolopyrazine compounds. The newly synthesized compounds and their derivatives were characterized by elemental analysis and spectroscopy (IR, <sup>1</sup>H-NMR, and mass spectra). Some of the newly synthesized pyrrolyl selenolopyridine compounds showed remarkable antioxidant activity compared to ascorbic acid.</p>