Substituted Quinolinones. Part 19. New and Unexpected Results from Oxidation of 3-Acetyl-1-Alkyl- 4-Hydroxyquinolin-2(1H)-Ones Using Selenium Dioxide

Abstract

Oxidation of 3-acetyl-1-alkyl-4-hydroxyquinolin-2(1H)-ones using selenium dioxide under Riley conditions was described. The oxidation reaction produced a mixture of 2 unexpected α-keto acid and its dehydrated dimer derivatives. The oxidation reaction was studied under different reaction conditions in order to maximize the yields and optimize reaction conditions.

Synthesis of New Quinolinones from 3-Nitropyranoquinolinones

“…So, the mixture was crystallised using ethanol and the minor products that dissolved in hot ethanol were characterised as the α-ketoacids 2-(1-alkyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetic acids 4a,b (R = CH 3 , CH 2 CH 3 ). 16 The major products that were insoluble in hot ethanol were identified as 3-nitroacetyl derivatives 3a,b (Scheme 2).…”

“…The more adsorbed product was characterised as α-keto acid 4a or 4b. 16 The product that was insoluble in ethanol was identified as 3-nitroacetyl derivative 3a or 3b (Scheme 2). It was observed that by increasing the time of hydrolysis of the nitropyrone 1, the β-ketoacid 2 which was formed first was converted to nitroacetyl 3 and then converted to α-ketoacid 4, 14,15 which was further converted to 3-carboxylic acid 5.…”

“…The precipitate was filtered, dried and crystallised from ethanol to give the α-ketoacid; 4a: Yield 1.3 g (90%); m.p, 188-190 °C (lit. 16 191 °C); or 4b: Yield 82%; m.p. 200-202 °C (lit.…”