4-Quinazolone ring, opening

Reductive 4-quinazolone ring opening with and without oxazolidine ring closure... 

Without additional reagents 4-Quinazolone ring opening... 

Photolysis of the 1,2,3,5-oxathiadiazine (132) in the presence of ethanol leads to the quinazolone (133). The product is not formed in the absence of ethanol, and the proposed mechanism involves electrocyclic ring opening, addition of ethanol, photochemical diradical formation and closure on to the C-6 phenyl ring followed by aromatization as shown in Scheme 8 (79JOC4435). 

Isatin-l-ethylcarbamate and urea yield a ring-opened product, which after treatment with ammonia yields a spiro hydantoinquinazolone301 (Scheme 70). Similarly, 1-carboxamidoisatins furnish quinazolones upon treatment with thiourea derivatives302 (Scheme 71). 

Lactim ethers and thioethers (300) furnish condensed quinazolones 301 when interacted with IA.303 Ring opening of IA s to the corresponding anthranilic acids and reaction of its potassium salts with chloroacetone yields 2-indolyl ketones 302.304 Potassium cyanide with (V-substituted IA s produces iminoindolinones 303, which were readily hydrolyzed to the corresponding isatins.305 Reaction of 303 to the spiroindoloquinazoline... 

H)-QuiBazolinethiones, 2-amino- 29,814 4-Qninazolone ring, opening, reductive 29, 40 2-Quinazolones... 

In the catalytic hydrogenolysis of an oxadiazole (129) bearing an o-nitrophenyl (or amino) group at C-5 the ring was opened and then closed again to give a quinazolone (130) (76CPB1197, 77H(6)107). However, the appropriately substituted quinazolone (131) in acid solution hydrolyzed back to the oxadiazole (132) (79H(12)239). 

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