88844-14-8

Upstream product

• 116465-86-2 N-(2-ureido-benzoylamino)-benzoic acid 
• 19670-04-3 [2-(4-oxo-4H-benzo[d][1,3]oxazin-2-yl)-phenyl]-urea 
• 24042-37-3 isamic acid 
• 91-56-5 indole-2,3-dione 
• 28144-70-9 anthranilic acid amide 
• 36567-87-0 2-(2'-nitrophenyl)-4(3H)-quinazolinone 
• 19589-44-7 5H-quinazolino[4,3-b]quinazoline-6,8-dione 
• 62-53-3 aniline 
• 118-92-3 anthranilic acid 
• 27259-73-0 2-(2'-aminophenyl)-4(3H)-quinazolinone 
• 15900-43-3 13H-quinazoline[3,4-a]quinazolin-5,13-dione 

Relevant academic research and scientific papers

Oxidative ring expansion of spirocyclic oxindole derivatives

Oxidation of the spirocyclic oxindole derivative, isamic acid 1, led to decarboxylation and ring expansion to quinazolino[4,5-b]quinazoline-6,8-dione 7 rather than, as previously believed, its isomer 6. The structure of 7 was confirmed by X-ray crystallography. Condensation of isatin (indole-2,3-dione) and 2-aminobenzamide led to the spirocyclic molecule, spiro[3H-indole-3,2′(1H)quinazoline]-2,4′(1H,3H)dione 8, which was also identified as an intermediate in the oxidation of isamic acid. Mild hydrolysis of 7 gave the 10-membered molecule 22. Isamic acid could easily be converted to N-nitrosoisamic acid, which when heated in ethanol underwent a ring expansion to a hydroximino derivative, 38, of compound 6. The structure of 38 was confirmed by X-ray crystallography.