5- Hydroxy-5- -barbituric acid

A number of other heterocycHc diazo components such as thiazole, iadazole, thiophenes, and thiadiazole types (see Fig. 1), as well as heterocycHc couplers, ie, 6-hydroxy-2-pyridinone [626-06-2] barbituric acid [67-52-7] and tetrahydroquiaoline [25448-04-8] h.2L e been cited ia the Hterature (90,91). Reviews on disperse dyes have been pubUshed (92,93). 

As expected, heterocyclic enols and potential enols (i.e, compounds existing mainly in the CH form) behave toward diazomethane similarly to the open chain and isocyclic enols, i.e. they form enol methyl ethers by reactions of the SnI type (cf. footnote 29). Examples of this behavior are barbituric acid, picrolonic acid, dchydroacetic acid (64), 3-methyl-l-phenylpyrazolin-5-one, 1-phenylpyrazoli-dine-3,5-dione, 1,2-diphenylpyrazolidine-3,5-dionc, 3-hydroxy-... 

JOU2236). In the case of TCE 33 the cyclization proceeds without a catalyst on short heating (73CB914). However, continuous heating leads to bis(6-hydroxy-2,4-dioxo-l,2,3,4-tetrahydropyrimidin-5-yl)malononi-trile. Modern modification involves a three-component reaction of aromatic aldehyde, malononitrile, and barbituric acid with solvent-free conditions under microwave irradiation (4-8 min, 70-95%) (03TL8307). 

An amino or hydroxy group facilitates 5-bromination even in aqueous solution. A -bromosuccinimide (NBS) and molecular bromine are the commonest reagents used. In uracils, cytosines, and barbituric acids, products of both addition and substitution can be identified in aqueous solution, and 5,5-dibromo products are common. In the bromination of uracils, addition products, including covalent hydrates, form rapidly, and the acid-catalyzed dehydration step to 5-bromouracils is much slower. Cytosine and related compounds behave similarly <1994HC(52)1, 1996CHEC-II(6)93>. 

Condensation of formyl-pyrroles and -indoles with a wide range of other activated methylene compounds has been reported. These include, for example, hydantoin, which provides a useful synthetic route to tryptophane and j8- (pyrrolyl)alanines, thiohydantoin, rhodanine and AT-substituted barbituric acids (B-77MI30505, 79HC(25-3)357). Flash pyrolysis of the condensation product derived from 3-formyl-2,5-dimethylpyrrole with Meldrum s acid produces 6-hydroxy-2-methylindole, (440) — (441) (74AJC2605), whilst the analogous... 

Benzo[6]thiophene aldehydes have been condensed with a variety of active methylene compounds, including cyclic511, 644 and open-chain645-647 ketones, aliphatic aldehydes,90 benzyl cyanides,93-436 malononitrile,487 rhodanine,144,648 hippuric acid,477 barbituric acid,487 diethyl malonate,487 and malonic acid (Section VI,M). Aliphatic nitro compounds condense smoothly with most benzo[6]-thiophene aldehydes03,141,337,343, 556,640,650 (except 5-hydroxy- and... 

The applications of re-acidic chiral stationary phases include the resolution of a-blockers and /1-blockers, amines, arylacetamine, alkylcarbinols, hydantoins, barbiturates, naphthols, benzodiazapines, carboxylic acids, lactams, lactones, phthaldehydes selenoids, and phosphorus compounds. Hyun et al. [16] achieved a chiral resolution of a homologous series of iV-acyl-x-(l-naphthyl )cthylaminc on AA(3,5-dinitrobenzoyl-(i )-phenylglycine and N-(3,5 - dini tr o ben zoy I)-(,S ) -1 c u c ine CSPs. The authors used hexane-2-propanol (80 20, v/v) as the mobile phase. Similarly, the scope of re-basic CSPs comprises the chiral resolution of / -blockers, amino acids, amines, diamines, amino phosphonates, naphthols, benza-diazapines, carboxylic acids, hydroxy acids, dipeptides, tripeptides, diols,... 

The introduction of a third activating substituent facilitates nitration even more. Temperatures below 50°C with mixed acids are frequently successful with various combinations of alkyl, amino, and hydroxy substituents (OICB3362 57JCS2146 61JOC455 65JOC3153), and barbituric acids react very readily indeed, even to the extent of /pso-substitution at C-5 [01LA(315)259 05LA(339)37],... 

Disposition in the Body. Readily absorbed after oral administration. Metabolites which have been identified in urine are 3 -hydroxyvinylbitone and the corresponding desvinyl derivative, 5-(3-hydroxy-l-methylbutyl)barbituric acid. Less than 5% of a dose is excreted in the urine unchanged in 72 hours. 

The following German patents have also been taken out for alipliatic acid mercurials Ibid, 246207, behenolic acid esters, stearolio acid ester. Ibid, 264267, aryl hydroxy fatty acids. Ibid, 279199, aminometiiane disulphonic acid. Ibid., 228877, oleic acid ethyl ester, triolein. Ibid., 387850 American Patent, 1457675 diethyl diallylmalonate, diallyb barbituric acid, ethyl dialiylacetate, diethjri o-phenylenediacrylate, diplienio acid and ethyl diphenylamine-2-ca.rboxylate. 

Phenobarbltal, USP. Phenobarbital. S-cthyl-S-phcnyf barbituric acid (Luminal), is a long-acting. sedative and hypnotic. It is also a valuable anticonvulsant, especially in generalized tonic-clonic and partial seizures (see the discus.sion on anticonvulsants). Metabolism to the p-hydroxy compound followed by gluctironidaiion accounts for about 90% of a dose. 

Barbiturate Parent Hydroxy Derivatives N-Glucosyl Derivatives Carboxylic Acids... 

Cochin and Daly30 isolated 5-ally1-5(1-hydroxy-1-methylbutyl) barbituric acid from... 

In aqueous solution the hydroxy forms of barbituric acids are in equilibrium with their mono- and dianionic conjugate bases (Scheme 1). The acid-base equilibria are strongly dependent on the site of substitution and the nature of the substituents37-45 (Table I). 

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