5,5-Dimethylbarbituric acid

A related pyranopyrimidine 63 has been prepared by the irradiation of 1,3-dimethylbarbituric acid 61, a methylene active nitrile 47a and N,N-di-methylformamide dimethylacetal 45 [77]. After initial formation of the enam-... 

As aldehydes, commercially available rac-citronellal and a synthesized aromatic aldehyde and also two commercially available 1,3-diketones, 1,3-dimethylbarbituric acid and Meldrum s acid, were selected [18]. By 2 x 2 combinations of these reactants, four different cycloadducts were generated ([OS 57]). 

P 39] Protocol for single-run processing reservoirs of the 110 Caliper chip were filled with the following solutions [18] 0.10 M solutions of rac-citronellal and a synthesized aromatic aldehyde in methanol/water (80 20) and 0.12 M solutions of 1,3-dimethylbarbituric acid and Mel drum s acid in methanol/water (80 20) with 10% molar catalyst efhylenediamine diacetate (EDDA). 

DIEA—diisopropylethylamine DMAP—4-dimethylaminopyridine DMBA—1,3-dimethylbarbituric acid DMDO—2,2-dimethyldioxirane E-CADI—epithelial Cadherin 1... 

The anodic oxidation of catechol in the presence of 1,3-dimethylbarbituric acid was carried out in aqueous solution containing sodium acetate in an undivided cell at graphite and nickel hydroxide electrodes [114]. The results did not fit with the expected structure (Scheme 47, path A) but a dis-piropyrimidine was isolated in 35% yield (Scheme 47, path B). It seems that the initial attack of 1,3-dimethylbarbituric acid on the anodically formed o-quinone does not occur through the carbon-oxygen bond formation but rather through the carbon-carbon bond formation, giving rise to the final product via several consecutive reaction steps. 

A variety of other carbon nucleophiles have been alkylated with alcohols including malonate esters, nitroaUcanes, ketonitriles [119, 120], barbituric acid [121], cyanoesters [122], arylacetonitriles [123], 4-hydroxycoumarins [124], oxi-ndoles [125], methylpyrimidines [126], indoles [127], and esters [128]. Selected examples are given in Scheme 35. Thus, benzyl alcohol 15 could be alkylated with nitroethane 147, 1,3-dimethylbarbituric acid 148, phenylacetonitrile 149, methyl-pyrimidine 150, and even f-butyl acetate 151 to give the corresponding alkylated products 152-156. 

By using the same catalytic system, alkylations of 1,3-dimethylbarbituric acid with alcohols were also accomplished (Scheme 5.31) [68]. The Cp lr-catalyzed alkylation using 2-iodobenzyl alcohol, followed by palladium-catalyzed carbon-carbon bond formation with allene, gave spirocyclic barbituric acid derivatives in a one-pot process. 

Michael addition of 1,3-dimethylbarbituric acid to etacrynic acid 384 gave the addition product 385, which upon fusion with ammonium acetate yielded the annulated pyridopyrimidinedione 386 (Scheme 14) <1997PHA97>. 

Dimethylbarbituric acid [769-42-6] M 156.1, m 123 . Crystd from water and sublimed in a vacuum. Also purified by dissolving lOg in lOOml of boiling CCI4/CHCI3 (8 2) (Ig charcoal), filtered and cooled to 25°. Dried in vacuo [Kohn et al. AC 58 3184 7956]. 

With triethylamine in methanol, 1,3-dimethylbarbituric acid (217) adds DMAD in Michael fashion to give 218, which, after heating to 170° or treatment with boron trifluoride etherate at 120° to 130° gave pyrano[2,3-[Pg.384]

Cyclocondensation routes also provide access to pyrimidines. 2,3-Disubstituted pyrido[2,3-/i]-quinazolin-4(3//)-ones are obtained via cyclocondensation of 5-aminoquinoline-6-caiboxylic acid with acid chlorides <02SC235>. 5,6,8-Trialkyl-7-methoxy-2-aminoquinazolines are obtained from 1,3-dimethoxybenzenes via cyclocondensation of intermediate dihydrobenzenes with guanidine carbonate <02TL3295>. Diastereoselective intramolecular hetero Diels-Alder cyclization of a pyrazole carboxaldehyde condensed onto 1,3-dimethylbarbituric acid (101) gave polycyclic heterocycle 102 <02T531>. An efficient one-step synthesis of cyclobutene-annelated pyrimidinones 103 from methyl 2-chloro-2-cyclopropylideneacetate and amidines has been... 

Chloro-5-formyl-l,3-dimethyluracil is a starting material that is easily accessible by Vilsmeier formylation of the commercially available 1,3-dimethylbarbituric acid (71YZ1372). 

The reaction of 1,3-dimethylbarbituric acid with 7-methyl-6-octenal affords a Knoevenagel adduct that undergoes an intramolecular hetero Diels-Alder reaction to two diastereomeric tricyclic cycloadducts [90AG675, 90AG(E)665] (Scheme 131). 

Physical Properties. - Polarographic reduction of some 5-(2-benzo-thiazolylhydrazono)-1,3-dimethylbarbituric acids has been reported2 0. Complexes of 2-mercaptobenzothiazole with [CdI (S0CNEt )-J... 

Pyrimidines 73 with dinucleophiles, such as 2-amino-pyridine, 1,3-dimethylbarbituric acid, 5,5-dimethylcyclohexa-l,3-dione and 4-hydroxy-6-methyl-pyran-2(lH)-one, were carried out in boiling acetic acid formed 4H-pyrido[l,2-fl]pyrimidin-4-one (76), lH-pyrano[2,3-d]pyrimidine-2,4,7(3H)-trione (77), 6H-chromene-2,5-dione (78) and pyrano[4,5-b]pyran-2,5-dione (79) in 30%, 67%, 56% and 73% yields, respectively (Scheme 26). 

Sulfur monochlonde added dropwise at 70° to 1,3-dimethylbarbituric acid in glacial acetic ac, and heated 5 min at 100° bis-(l,3-dimethyl-5-barbituryl)... 

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