Oxidation of 1,2-Dihydroquinolines Under Mild and Heterogeneous Conditions

An Investigation of the Reaction of 2-Aminobenzaldehyde Derivatives with Conjugated Nitro-olefins: An Easy and Efficient Synthesis of 3-Nitro-1,2-dihydroquinolines and 3-Nitroquinolines

“…1,2-Dihydroquinolines can be oxidized to quinolines by using several oxidants . However, DDQ has not been reported as one of these.…”

“…During the purification of product 3 by flash column chromatography, it was found that small amounts of product 3 were converted to product 4 in the presence of silica gel. On the basis of this fact and the oxidation of 1,2-dihydroquinolines by oxygen, 7d,e silica gel was added to the reaction solution after the complete formation of 3 , and the solution was then heated at 110 °C for 1 h. When the solution was heated at 110 °C, the benzene evaporated. The silica gel was then washed with CH 2 Cl 2 , and upon evaporation of the solvent, product 4 was obtained (eq 3 and Table ).…”

Applications of Some Metal Hydrogen Sulfates in Organic Transformations

“…A combination of NaHSO 4 .H 2 O and Na 2 Cr 2 O 7 .2H 2 O in the presence of wet SiO 2 was used for the oxidation of 1,2dihydroquinolines in dichloromethane (Scheme 32) [46]. The authors correlated the progress of the reaction to the in situ generation of H 2 CrO 4 at the surface of SiO 2 in low concentration by the reaction of NaHSO 4 [47,48].…”

Molybdatophosphoric Acid/NaNO2/Wet SiO2 as an Efficient System for the Aromatization of 1,2‐Dihydroquinolines under Mild and Heterogeneous Conditions

“…Classic reagents of this type are manganese dioxide (MnO 2 ), potassium permanganate (KMnO 4 ), chromium trioxide (CrO 3 ), potassium chromate (K 2 CrO 4 ), potassium dichromate (K 2 Cr 2 O 7 ), [13] and a combination of sodium hydrogen sulfate and sodium dichromate. [14] These are all frequently used reagents, whether in the laboratory or in industry, and yet they are be set with multiple liabilities. For satisfactory and reproducible results, these oxidants demand rigorous control of the experimental conditions.…”