Lehmstedt–Tanasescu reaction

The Lehmstedt - Tănăsescu reaction also known as Lehmstedt - Tănăsescu method or the Lehmstedt - Tănăsescu - acridone synthesis is a name reaction in organic chemistry. The reaction was stopped after the Romanian Ioan Tănăsescu chemist (1892-1959) who discovered it in 1928, and named the German chemist Kurt Lehmstedt. Using this reaction acridones and derivatives thereof may be synthesized from 2 -nitrobenzaldehyde and aromatic components.

Overview reaction

In the presence of sulfuric acid and catalytic amounts of sodium nitrite 2 -nitrobenzaldehyde and chlorobenzene react to 3 - Chloracridon.

Instead of chlorobenzene, other benzene derivatives with 2- nitrobenzaldehyde can respond to acridone or the corresponding derivatives.

Mechanism

Since there is limited information on the mechanism, the following representation is only a suggested course of the reaction. Under the acidic reaction conditions of sodium nitrite nitrous acid, which reduces the nitro group, and itself be oxidized into nitric acid. This oxidized later, the alcohol group and is thus reduced again to nitrous acid.

First, the carbonyl group of 2- nitrobenzaldehyde 1 is protonated. It is followed by a nucleophilic attack of chlorobenzene on the partially positively charged carbon atom of the carbonyl group 2 with elimination of an H ion rearomatized is six-membered ring of chlorobenzene 3 In addition, a molecule nitrous acid in the vicinity of the nitro group positioned 4 Nitrous acid reduces the nitro group via the intermediate stage of a five-membered ring to a 5 nitrosyl 6 and leaves the molecule as a nitric acid oxidized molecule. The nitrosyl group is protonated and then in turn attacked by the nucleophilic aromatic compounds chlorobenzene 7 Due to the elimination of a proton 8 then again finds a place rearomatization 9 Finally, the alcohol group is oxidized by nitric acid to the keto group 10, the nitrous acid is present again as a catalyst ago and 11 as a product creates a Acridonderivat.