Aryliminodimagnesium Reagents. XIV. Reactions with Nitrobenzenes Having Electronegative<i>ortho</i>-Substituents. Effects of Reaction Conditions on Condensation, Replacement, and Substitution
In reactions of ArN(MgBr)2 with o-MeO- and o-halo-substituted nitrobenzenes, types and yields of products were different from those in its reactions with m- and p-substituted substrates. Condensation (leading to unsymmetrical azoxy- and azobenzenes), o-substituent replacement, and nuclear substitution took place. Relative yields of products were greatly affected by substituents and reaction conditions
ArN(MgBr)2与o-MeO-和o-卤代硝基苯的反应中,产物的类型和产率与其与m-和p-取代底物的反应不同。发生缩合(导致不对称的偶氮苯和偶氮苯)、邻位取代基和核取代。产物的相对产率受取代基和反应条件的影响很大。o-MeO 和 oF 有利于置换,而 o-Cl、o-Br 和 oI 有利于置换。当使用小摩尔过量的试剂和低浓度时,置换和/或取代占主导地位,而当使用大摩尔过量的试剂和高浓度时,缩合占主导地位,从机理上讨论了这种现象。
Aryliminodimagnesium Reagents. IV. The Independent Preparation of Unsymmetrically Substituted Azoxyarene Isomers and Their Deoxygenation
作者:Masao Okubo、K\={o}ji Koga
DOI:10.1246/bcsj.56.203
日期:1983.1
By use of the condensation reaction of aryliminodimagnesium reagents (ArN(MgBr)2) with nitroarenes, six symmetrical and eight unsymmetrical azoxyarenes including four pairs of isomers were prepared in 40–80% yields. The deoxygenation reaction of the azoxyarenes by treating with five molar equivalents of p-MeOC6H4N(MgBr)2 at 55 °C in tetrahydrofuran was also studied, and the reactivity of deoxygenation
A treatment of 3-chloro-NNO-4′-methylazoxybenzene (1β) with CrO3 in acetic acid gave 3-chloro-ONN-4′-methylazoxybenzene (1α) in good yield, whereas 4-methoxy-ONN-4′-methylazoxybenzene (2α) isomerized partially to 4-methoxy-NNO-4′-methylazoxybenzene (2β) under the same conditions. The structures of 1α and 2α have been determined by X-ray analysis.