Quinazoline-2,4-diones, 1,3-dimethyl

Dibenzofuran, I- and 2-hydroxy-chlorination, 59, 251 chloro-dehydroxylation, 59, 251 Dibenzofuran, methoxy-, dimethoxy-, bromination, 59, 252 Dibenzo[/, /i]quinazoline-2,4-dione, 1,3-dimethyl-, 55, 226... 

Furthermore, 6-chloro-l,3-dimethyl-5-vinyluracils are readily transformed into the 6-azido derivatives. UV irradiation in acetone leads, under denitrogenation, to nitrenes, which insert into the sidechain to give pyr-rolo[2,3-acetone solvent to afford, under 6ir-electron cyclization, benzo[/z]quinazoline-diones (85UP1). 

The highly viscous solution of poly(quinazoline dione) in N-methyl pyrroli-done or dimethyl acetamide can be directly wet or dry spun. The hygroscopic, thermally stable, and poorly burnable fiber is considered for use as protective clothing or as filter mats for hot gas filtration. 

Ethyl 7-amino-2,3-dimethyl-6-quinoxalinecarboxylate (196) and urea gave 7,8-dimetb ipyrazino[2,3-g]quinazoline-2,4(l //, 3//)-dione (197) (neat reactants, 198°C, 20 min 92%) analogs likewise.247... 

Mesoionic pyrido[2,l- >][1,3]oxazines (54) afforded 4-oxo-4//-pyrido[l,2-a]pyrimidin-l-iumolates (55) and 4//-quinolizin-4-one (56) with phenyl iso(thio)cyanates [78LA1655 79CB1585 82ZN(B)222] and dimethyl acetylenedicarboxylate (79CB1585), respectively. Reaction of 2-cyano-3-methyl-lH,6//-pyridol[l,2-a][3,l]benzoxazine-l,6-dione with ammonium acetate and hydroxylamine, hydrazines, primary aliphatic or aromatic amines, and (thio)ureas gave 5-unsubstituted and 5-substituted 2-cyano-3-methyl-l//,6H-pyrido[l,2-a]quinazoline-l,6-diones (93CCC1953). 

The synthesis of 3,7-dimethylimidazo[4,5- ]quinazoline-6,8(5//,7//)-dione and imidazo[4,5- ]qui-nazoline-6,8(5/7,7/7)-dione, the 1-methyl and 1,9-dimethylated versions (155) of //n-benzoxanthine, respectively, has been achieved using an approach (Equation (75)) based upon an imidazole ring assembly on 7-chloro-3-methyl-6-nitroquinazoline-2,4(l//,3//)-dione, effected by treatment with NH3 or MeNH2 followed by reductive cyclization in HC02H <84JHC79l>. In this same investigation, the 9-(formylamino)-/m-benzoxanthine derivatives (156) were obtained from 7-hydrazino-6-nitro-quinazoline-2,4(l//,3//)-dione precursors. 

Benzo[f]quinazoline-l,3-diones, 55, 207 Benzo(/]quinazoline-1,3-dione, 2,4-dimethyl-6-phenyl-, 55, 226 Benzo[/i]quinazoline-2,4-diones, 55, 200 Benzo[g]quinoline-5,10-dione, 3-methyl-, 57, 14... 

Ethyl 2-(trichloroacetamido)bcnzoate and 2-(trichloroacetamido)benzonitrile 10 on treatment with ammonium acetate in dimethyl sulfoxide at 90-95 C undergo cyclization to quinazoline-2,4(1//,3-ff)-dione and 4-aminoquinazolin-2(l/7)-one 11, respectively. ... 

Heating of a-cyano-)3-(dimethylamino)crotonamide (15a) or A -aminocarbonyl-iV. A -dimethyl-formimidamide (15b) with ethyl anthranilate in glacial acetic acid yields quinazoline-2,4(1/f,3/f)-dione. The enaminoamide 15a or formimidamide 15b is decomposed in situ on heating in glacial acetic acid into isocyanic acid which subsequently reacts with ethyl anthrani-... 

Reactions of piperazine-2,5-diones with phosphorus pentachloride and phosphorus pentabromide have been described in Sections V.ID and V.IF, respectively. Aromatic aldehydes condense with 3-methylpiperazine-2,5-dione in the presence of acetic anhydride to form mainly mono-A -acetyl derivatives of trans-3-arylidene-6-methylpiperazine-2,5-diones (e.g., 96, R = Ac) (1066). In these products the acetyl group was shown to be attached to position 1 and the 4,5-amide group was found to be sterically hindered. Photolysis formed the cis isomers. Both isomers were deacetylated with methanolic potassium hydroxide (1066). Condensation of 1,4-diacetylpiperazine-2,5-diones with aldehydes has been applied to the synthesis of unsymmetrical 3,6-diarylidenepiperazine-2,5-diones and the reaction has been extended to l,4-diacetyl-3,6-dimethylpiperazine-2,5-diones (1624). Treatment of (96, R = H) with triethyloxonium tetrafluoroborate in dichloromethane gave the monoimino ether, 5-benzylidene-6-ethoxy-3-hydroxy-2-methyl-2,5-dihydropyrazine (97) (1066). l-Methylpiperazine-2,5-dione similarly treated gave 5-ethoxy-l-methyl-2-oxo-l,2,3,6-tetrahydropyrazine (which was condensed with anthranilic acid at 150° to 2-methyl-l,2-dihydropyrazino[2,l-fi]quinazoline-3(4/0.6-dione (98) (1625), and l,4-dimethylpiperazine-2,5-dione gave 5-ethoxy-l,4-dimethyl-2-oxo-1,2,3,4-tetrahydropyrazine and 5,5-diethoxy-l,4-dimethylpiperazin-2-one (1626). 

Various biological activities were found in the following derivatives 2,4-bis(dialkylaminoalkyl)quinazolines (curare mimetics), l-((o-dimethyl-aminoalkyl)-3-substituted quinazoline-2,4-diones (inhibition of gastric secretions), 4-alkoxycarbonylmethylthioquinazolines (radioactivity protecting agents), and 2-amino-6-hydroxymethyl(or formyl)quinazolin-4-ones (xanthine oxidase inhibitors). ... 

A series of 4-aryl-7,7-dimethyl and 1,7,7-trimethyl-octahydro-quinazolin-2,5-diones 511 (R2 = H or Me, X = O) were synthesized by condensation of urea or N-methylurea with 1 and aromatic aldehydes... 

An elegant route to quinazoline-2,4-diones (251) starts, unusually, from substituted uracils (249) other dienophiles e.g. methyl vinyl ketone and dimethyl fumarate) also cyclo-add to the dienolate anions (250) (Scheme 100)." ... 

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