6-Iodo-2-isopropyl-4<i>H</i>-3,1-benzoxazin-4-one as building block in heterocyclic synthesis

<p>As a part of ongoing studies in the synthesis of a variety of heterocycles of biological importance, we report here an efficient and convenient method for the synthesis of novel compounds from 6-iodo-2-isopropyl-4<i>H</i>-3,1-benzoxazin-4-one <b>1</b> as building block. The reaction of benzoxazinone <b>1</b> with various reagents such as diethylmalonate, sodium azide, and phosphorus pentasulfide yielded the compounds <b>2–5</b>. The behavior of benzothiazin-4-thione <b>5</b> toward formamide and hydrazine hydrate was investigated, forming the compounds <b>6</b> and <b>7</b>. The reaction of quinazolinone derivative <b>8</b> with β-D-glucose pentaacetate, ethyl 2-methyl-5-((1S,2R,3R)-1,2,3,4-tetrahydroxybutyl)furan-3-carboxylate, epichlorohydrin and benzenesulphonyl chloride afforded quinazolinone derivatives <b>9, 10, 12,</b> and <b>13</b> respectively. The reaction of quinazolinone derivative <b>10</b> with acetic anhydride resulted in formation of the acylated compound <b>11</b>. The behavior of quinazolinylacetohydrazide derivative <b>14</b> toward carbon electrophiles<sup>[</sup><a href="#CIT0016" target="_blank"><sup>16</sup></a><sup>]</sup> has been investigated by its reaction with ethyl benzoylacetate, potassium thiocyanate, and phenyl isothiocyanate, affording the quinazolinone derivatives <b>15, 16,</b> and <b>18</b>, respectively. Treatment of compound <b>16</b> with sodium hydroxide followed by hydrochloric acid yielded the mercapto-triazole derivative <b>17</b>. The structures of the newly synthesized compounds were confirmed by elemental analysis, infrared (IR), <sup>1</sup>H NMR, <sup>13</sup>C NMR, and mass spectra. The antimicrobial activities of some of the synthesized compounds were preliminarily evaluated.</p>