Quinazolin-4-ones, 3-amino-, oxidation

Synthesis of pyrido[ 1,2-bJquinazolines through formation of the azole ring from properly substituted quinazoline precursors is also known (61AP556). Thus, the cyclodehydrobromination of the 2-(4-bromo-butyl)quinazolin-4-one (445) with alkali was claimed to give only the linearly annulated 1,2,3,4-tetrahydropyrido[ 1,2-6]quinazolin-4-ones (446) (61AP556). Oxidation of the 3-amino-2-(butyn-l-yl)quinazolin-4-ones (447) with lead tetraacetate led to intramolecular addition of the produced /V-nitrene intermediate to the triple bond to give 449 [86JC S(P 1) 1215]. 

Oxidation of 3-amino-2-(2,5-dihydroxybenzyl)quinazolin-(3i/)-one (494) with acidic ferric chloride or aqueous sodium hydroxide gave a quinone that spontaneously cyclized to the quinazolino[3,2-fc]cinnoline-2,7(13//)-dione (495) [66JCS(C)2190]. 

Amino- (459) and 3-amino-quinazolin-2-ones (460) (75JCS(Pl)3l), as well as 1-amino- and 2-amino-indazoles (92AHC(53)85) can be oxidized to 1,2,3-benzotriazines. C-Amino compounds can also give triazines oxidation of 3-aminoindazole (461) with hydrogen peroxide forms 1,2,3-benzo-triazin-4-one (462) <1899LA(305)289). 

The preparation of /in-benzoinosine-4,9-quinone (168) was carried out by regioselective ribo-sylation of 4-nitroimidazo[4,5- ]quinazolin-8(3//,7//)-one followed by nitro group reduction, Fremy oxidation, and deacetylation <9lJOC776>. 4-Amino-//n-benzohypoxanthine (169 R = H) was prepared (80%) by sodium dithionite reduction of 5-nitroimidazo[4,5-.9]quinazolin-8(3//,7//)-one, but... 

Quinazoline is deuterated preferentially in positions 2 and 4 on heating with deuterium oxide and platinized short-fibre asbestos (Caution carcinogenic) in a sealed tube or pressure vessel at 130 250 C. ° Deuteration of 7-amino-6-nitroquinazolin-4(3/y)-one (1) in [ Hjmethanol under reflux yields product 2 deuterated in position 8, whereas in 6,7-diaminoquinazolin-4(377)-one (3), on treatment with deuterium oxide in dimethylformamide, 5H and 8H are exchanged for deuterium to give the deuterated derivative 4. ° ... 

The pyrrolo[l,2-fl]quinazoline 4-oxides 149 and 150 were deoxygenated by hydrogen over Raney nickel. Upon reduction in methanol over palladium on carbon, the 5-chloropyrrolo[l,2-a]quinazoline 166 was transformed into the tetrahydropyrrolo[l,2-a]quinazolin-5-one 167. If magnesium oxide was also present, 166 was converted to the pyrrolo[l,2-a]-quinazoline 168. The 7-nitro group in compounds of type 78 was hydrogenated to an amino group over palladium on carbon. ... 

Compounds in which other heterocyclic rings (pyrazoles, isoxazoles, imidazoles ) are fused to thiopyrans have been described. The interesting thiazolium salts (56) were prepared by allowing the betaines (55) to react with 4-thioxothiazolidin-2-ones. Application of the Fischer indole synthesis and the Friedlander reaction to tetrahydrothiopyran-3-one led to the exported indolo-and quinolino-derivatives. Ring closure of (57) under acidic conditions afforded the rearranged product (58). Syntheses of benzothiopyrano[4,3,2-flfe]-quinazolines (59) from 1-amino-thioxanthones and of their S- and 7V-oxides have been described. ... 

Same reaction has also been carried out with methyl iodide in place of amine and in the presence of sodium hydride to yield N-methyl-3,4-dihydropyrazino[2,l-b] quinazolin-6-ones. The novel pyrimido[4,5-d]pyrimidine derivatives of biological significance from electron rich 6-[(dimethylamino)methylene]amino uracil undergoes [4+2] cycloaddition reactions with various in situ generated glyoxylate imine and imine oxides, after elimination of dimethylamine from the (1 1) cycloadducts and oxidative aromatization. This method provides a suitable method for the direct synthesis of pyrimido[4,5-d]pyrimidines in excellent yields, when reaction was carried out in the solid state and under microwave irradiations (Prajapati et al., 2006). 

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