5-Methylbarbituric acid

Pyrimido[5,4-e][l,2,4]triazinediones in aqueous acidic media were hydrated at the N4-C4a bond to give covalent hydrates the structures of which were confirmed by X-ray analysis. The products of hydrate decomposition in acidic media were formic acid, 5-diazo-3-methylbarbituric acid, and methylparabanic acid (88KGS1654). 

Metharbital Metharbital, 5,5-diethyl-l-methylbarbituric acid (4.1.9), is synthesized by condensation of diethyhnalonic ester with methylurea [6,7]. 

A green approach for the synthesis of polyfimctionalized pyrazolo[4, 3 5,6]pyrido [2,3-rfl-pyrimidines 60 was elaborated by Tu and co workers [104] via a MCR of an aromatic aldehyde, a 3-methyl-1-phenyl-l//-pyrazol-5-amine and 1-methylbarbituric acid in water under microwave irradiation without catalyst. The yield of this reaction was affected by the volume of water. This protocol could be applied to aromatic aldehydes with either electron-withdrawing or electron-donating groups and also to heterocychc aldehydes giving excellent yields (Scheme 44). 

ETHYL PHENYL KETONE see EOL500 5-ETHYL-5-PHENYL-N-METHYLBARBITURIC ACID see ENB500... 

CL1157 81JHC1329 82JHC301). The 5-deaza-lO-oxaflavin is also obtained by condensation of 1-methylbarbituric acid and o-halobenzalde-hydes (90CPB307) (Scheme 119). 

Due to the relative rapidity of the reactions and to the protonation of the free amine by the excess scavenger during the deprotection of allyl carbamates, the risk of formation of allylamine seems very limited and has not been reported. In the reactions with dimedone, a possible complication is the formation of substantial amounts of hydrolytically stable oxo-enamine by condensation with the liberated amine. For this reason, the use of N,N-di-methylbarbituric acid is probably a safer solution. 

The formation of some 5-alkyl or 5-arylmethylbarbituric acids has been studied by Sekiya et a/.236-238 The barbituric acid derivatives 65 (o-, m-, p-substituted phenyl, benzyl, styrenyl R1, R2 = H and/or methyl) containing a methylidene bond at the 5-position can be reduced by triethylammonium formate (TEAF) in high yield [Eq. (3)]. Similarly, 5-arylaminomethylene- and 5-alkylaminomethylene-substituted barbituric acids can be converted to 5-methylbarbituric acids.238... 

Malonomonoamides can be condensed with aldehydes to give acrylamides or cinnanamides, but condensation with malonodiamides is of only minor importance.3 In contrast to Meldrum s acid (58), Knoevenagel reactions of barbituric acid (56) and NJV-d methylbarbituric acid have been less explored. However, several aliphatic, aromatic and heteroaromatic aldehydes are known to react easily and with high yields in most cases.37-87-88 Reactions of l,2-dimethyl-3,5-pyrazolidinedione (93) with several aliphatic and aromatic aldehydes using standard conditions yield Knoevenagel products in good yield.141 A similar reactivity is observed with 2-phenyl-3,5-dioxoisoxazolidine (94)142 and oxazepanediones (45 see Section I.11.2.5).34-82 Recently, the oxidations of alcohols to carbonyl compounds and thiols to disulfides with 5-arylidene-l,3-dimethylbarbituric acids (95) have been described. Mechanistically (95) mimics enzymic oxidation by flavin adenine dinucletide (FAD).143... 

Certain bacteria can oxidize uracU to barbituric acid (4-oxouracil) and thymine to the corresponding 5-methylbarbituric acid (see Fig. 13-2). An enzyme called barbiturase cleaves the pyrimidine ring to form malonic acid and urea, probably through a ureidomalonic acid intermediate, although this has not been identified. 

The availability of the exceptionally successful method for the purification of flavins developed by Pasternack and Brown makes this method the one of choice for the synthesis of several flavins. In addition to riboflavin, [2- C]riboflavin 2 6,7-dimethyl-9-(i -L-lyxityl)isoalloxazine , b-ethyl-y-methyl-9-, 6-methyl-7-ethyl-9-, 6,7-diethyl-9-, and 3,6,7-trimethyl-9-(i -D-ribityl)isoalloxazine ° (using 2-methylbarbituric acid) have been prepared by this method. AT-(i -D-Ribityl)-2-/)-tolylazo-4-ethylaniline , -2-/)-nitrophenylazo-4-chloro-5-methylaniline2 and -2-/>-nitrophenylazo-4-methyl-5-chloroaniline react poorly or not at all with barbituric acid under a variety of conditions. 

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