Regioselectivity and regiospecificity of benzoxazinone (2-isopropyl-4<i>H</i>-3,1-benzoxazinone) derivatives toward nitrogen nucleophiles and evaluation of antimicrobial activity

<p>A novel group of 6-iodoquinazolin-4(<i>3H</i>)-one derivatives was prepared. The reaction of the benzoxazinone <b>3</b> with various nitrogen nucleophiles such as formamide and hydrazine hydrate and also the reaction of the isopropylquinazolinone <b>4</b> with hydrazonyl chloride have been shown to proceed with a high degree of regioselectivity at C(2). Spiro heterocycles have been found to play fundamental roles in biological processes and have exhibited diversified biological activity and pharmacological and therapeutical properties; thus reaction of acetohydrazides <b>10a–c</b> afforded the spiro compounds <b>11a–c</b>. The acetohydrazide derivative <b>7</b> reacted with carbon electrophiles such as acetylacetone, ethyl acetoacetate, acid chlorides, and benzaldehyde to give some interesting heterocyclic compounds <b>12–16</b>, respectively. The structures of all the synthesized compounds were inferred by infrared, ¹H NMR, and mass spectra as well as elemental analyses. The antimicrobial activities of some of the synthesized products were preliminarily evaluated.</p

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^[<a href="#CIT0016" target="_blank">¹⁶</a>^] 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), ¹H NMR, ¹³C NMR, and mass spectra. The antimicrobial activities of some of the synthesized compounds were preliminarily evaluated.</p