2.4- Dioxo-l ,2,3,4-tetrahydroquinazolines

Falbe and co-workers have studied carbonylation of unsaturated amides to give imides (34), unsaturated amines to give lactams (37), and unsaturated alcohols to give lactones (38). Rosenthal and co-workers studied carbonylation of aromatic ketoximes, (127), phenylhydrazones (131), semicarbazones (129), azines (129), and nitriles (128) to produce phthalimidines. Horiie (65) has described the carbonylation of azobenzenes to give indazolones or 2,4-dioxo-l,2,3,4-tetrahydroquinazolines. Pritchard (121) and Murahashi et al. (103) have described the carbonylation of Schiff s bases to yield substituted phthalimidines. 

Uses of bases of this type, such as DBU and DBN have been reviewed [15] and more recently they have been used as stoichiometric bases in the synthesis of 2H-isoindoles [ 16],biaryl thioethers [17],phthalocyanines [18] and the related macrocyclic compounds [18], 2,4-dioxo-l,2,3,4-tetrahydroquinazolines [19], dihydro alanine-containing peptides [20] and [[pyrazolylmethyl)amino]-propyl azepinones and -pyrrolidinones [21]. Chiral DBU/DBN-related molecules have also been synthesized which were fovmd to be useful as catalysts in an asymmetric Michael reaction [22]. 

In the reaction at 230 °C, on the other hand, 2-phenyl-3-indazolinone is further carbonylated to give 3-phenyl-2,4-dioxo-l,2,3,4-tetrahydroquinazoline 7.51. Anthranilic acid is easily prepared with a high yield by hydrolysis of a quinazoline derivative 7.51. Hence, double carbonylation of diazobenzene at 230 °C is a good method for the preparation of anthranilic acid, as shown in Scheme 7.8 in the previous section [64, 65, 67]. 

Aromatic azo compounds react with carbon monoxide to form indazolones. At higher temperatures, further reaction of the indazolones leads to insertion of CO to form 2,4-dioxo-l,2,3,4-tetrahydroquinazolines [678,696]. 

Thus the reaction of azobenzenes between 170 and 190 °C yields 2-phenylindazolone which reacts with further CO at 220 to 230 °C to form 2,4-dioxo-3-phenyl-l, 2,3,4-tetrahydroquinazoline. 

With potassium permanganate under basic or neutral conditions, the pyrido[2,l- )]quinazolinone 286 and its 8-nitro derivative 364 yielded the quinazolin(3//)-4-one, while in acidic medium the product was the 2,4-dioxo-1,2,3,4-tetrahydroquinazoline. 

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