Comparison of Substituting Ability of Nitronate versus Enolate for Direct Substitution of a Nitro Group.
α-Nitrocinnamate underwent the conjugate addition of an active methylene compound such as nitroacetate, 1,3-dicarbonyl compound, or α-nitroketone, and the following ring closure afforded functionalized heterocyclic frameworks. The reaction of cinnamate with nitroacetate occurs via nucleophilic substitution of a nitro group by the O-attack of the nitronate, which results in isoxazoline N-oxide. This protocol was applicable to 1,3-dicarbonyl compounds to afford dihydrofuran derivatives, including those derived from direct substitution of a nitro group caused by O-attack of enolate. It was found the reactivity was lowered by an electron-withdrawing group on the carbonyl moiety. When α-nitroketone was employed as a substrate, three kinds of products were possibly formed; of these, only isoxazoline N-oxide was identified. This result indicates that the substituting ability of nitronate is higher than that of enolate for the direct SN2 substitution of a nitro group.
['Mukaijo|Yusuke|Y|', 'Yokoyama|Soichi|S|', 'Nishiwaki|Nagatoshi|N|0000-0002-6052-8697']
D002244:Carbon D002264:Carboxylic Acids D004583:Electrons D004952:Esters D005663:Furans D007477:Ions D007555:Isoxazoles D007659:Ketones D009682:Magnetic Resonance Spectroscopy D009574:Nitro Compounds D009589:Nitrogen Oxides D010087:Oxides D011437:Propylamines D013237:Stereoisomerism
nitronate enolate nitro group conjugate addition 1,3-dicarbonyl compound nucleophilic substitution isoxazoline N-oxide dihydrofuran nitroketone