Nachweis und Darstellung metallierter Nitroaromaten

Abstract

Nitrobenzol wird durch Lithiumorganyle nicht metalliert. Dagegen oxydiert es Phenyllithium in Tetrahydrofuran (THF) schon bei tiefer Temperatur quantitativ zu Phenol. Der Brom-Lithium-Austausch an 2-Brom-I-nitro-benzol und seinen Methylhomologen fiihrt in hohen Ausbeuten zu den unterhalb von ~ 100' stabilen, tieffarbigen Titelverbindungen, die man durch Carboxylierung nachweist. Die mit dem Halogen-Metall-Austausch konkurrierende Reduktion der Nitrogruppe tritt bei hiiherer Temperatur und in weniger polaren Losungsmitteln starker hervor; sie uberwiegt bei 3-und 4-Brom-I-nitro-benzol auch unter optimalen Bedingungen.

A General Amination Method Based on the Addition of Polyfunctional Arylmagnesium Reagents to Functionalized Arylazo Tosylates

“…They react with arylmagnesium halides 9 and provide after reductive workup diarylamines of type 1 in excellent overall yields 5. A drawback of this method is requirement of two equivalents of the Grignard reagent 9 , since one equivalent of Ar 2 MgX is consumed in the reduction of the nitroarene to an intermediate arylnitroso species 10 5d. We have examined the direct use of the arylnitroso derivatives 10 as starting materials for the amination procedure6 since this would preclude the use of an excess of the arylmagnesium reagent.…”

Nitro‐Substituted Aryl Lithium Compounds in Microreactor Synthesis: Switch between Kinetic and Thermodynamic Control

“…[3] Therefore, the generation of aryl lithium and aryl magnesium compounds with a nitro group in the ortho position is possible only at very low temperatures. [4,5] Moreover, the generation of m-or p-nitrosubstituted aryl lithium and aryl magnesium compounds in a conventional manner has been reported to be very difficult. [6] We envisioned that the concept of flash chemistry could provide a solution to this problem.…”

In Search of Simplicity and Flexibility: A Rational Access to Twelve Fluoroindolecarboxylic Acids

“…How-ever, if the reaction mechanism is really single electrontransfer triggered, as the Italian authors plausibly surmise, [39] the vinyl radical has anyway no other choice than to combine with an oxygen rather than the nitrogen atom. Moreover, as G. Köbrich et al have shown, [41] even nitrobenzene itself reacts with two equiv. of phenyllithium to produce quantitatively (two equiv.!)…”