Reduction quinazoline-3,6-diones

Reduction of 2,3,6,7-tetrahydro-177,5i/-pyrido[3,2,l-//]quinazoline-l,3,7-trione and 7-chloro-6-formyl-2,3-dihydro-177,5i/-pyrido[3,2,1 -(/]quinazo-line-l,3-dione with NaBH4 in THF in the presence of 60% aqueous solution of NaOH gave 7-hydroxy and 7-chloro-6-hydroxymethyl derivatives, respectively (01MI28). 

Lee, C.-H. Skibo, E. B. Active site directed reductive alkylation of xanthine oxidase by imidazo[4,5-g]quinazoline-4,9-diones functionalized with a leaving group. Biochemistry 1987, 26, 7355-7362. 

Reduction of the N(ll)=C(lltf) double bond of l,4-dihydro-2//-pyrazino[2,l-A quinazoline-3,6-diones 30 (R1 = indol-3-ylmethyl R2 = Me) and 31 (R1 = CH2-C6H4-C1- z Rz = Me) was effected with NaBH4. While the m-diastereomer, 30, retained its configuration, the /razw-diastereomer, 31, epimerized during the reaction. <1999JOC7233>. 

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. 

An elimination of ammonia from LXXXIV to purine followed by reduction of the latter may also be possible [468] such a reduction route is analogous to that of 4-amino-quinazoline in acid solution [409], in which quinazoline can be detected as an intermediate during the reduction. A similar reaction, a reduction followed by elimination of an amine and further reduction is found for the herbizide hexazinone (3-cyclohexyl-6-(dimethyla-mino)-1 -methyl-1.3.5-triazine-2,4( 1 H,3H)-dione [469]. 

The base-induced rearrangement of the 1,3-dipolar cycloadducts of 2,5-di-f-butyl-/ -benzoquinone with 2,6-dichlorobenzonitrile oxide has been shown to afford isoxazole-fused / -quinol derivatives (250) by way of the pathway outlined in Scheme 64. Reduction of 2,4-dihydro-l//-pyrazino[2,l-fc]quinazoline-3,6-diones (251) with sodium borohydride has been reported to yield 11,1 la-dihydro derivatives... 

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