4- Methoxy-6-aminopyrimidines

There is a scattered body of data in the literature on ordinary photochemical reactions in the pyrimidine and quinazoline series in most cases the mechanisms are unclear. For example, UV irradiation of 4-aminopyrimidine-5-carbonitrile (109 R=H) in methanolic hydrogen chloride gives the 2,6-dimethyl derivative (109 R = Me) in good yield the 5-aminomethyl analogue is made similarly (68T5861). Another random example is the irradiation of 4,6-diphenylpyrimidine 1-oxide in methanol to give 2-methoxy-4,6-diphenyl-pyrimidine, probably by addition of methanol to an intermediate oxaziridine (110) followed by dehydration (76JCS(P1)1202). 

In extension of this work, the amino-debromination reaction of 4-methoxy-, 4-phenyl-, 4-t-butyl-, and 4-(A-methylanilino)-5-bromopyrimi-dine was investigated. It was found that in all these reactions, good yields of the corresponding 6-aminopyrimidines are obtained no indication for the formation of a 4-substituted 5-aminopyrimidine was observed (Scheme II.3) (64TL2093 65TL555 68TL9). 

The photochemical behavior of aqueous solutions of O-methyl cytosine (14, 2-methoxy-4-aminopyrimidine) was apparently different... 

Amino-3-methyl-l,2,4-thiadiazole has a relatively high melting point and low solubility in water, compared with that of the 3-ethyl homolog and the parent compound the isosteric 4-aminopyrimidines show a parallel behavior (see Table VT).6 5-Amino-3-methoxy-l,2,4-thiadiazole melts at a higher temperature than does the ethoxy homolog.83... 

A later study using a more homologous series of 5-(substituted benzyl)-2, 4-di-aminopyrimidines led to a surprising result [39, 56]. All derivatives had a methoxy group in the 3-position of the benzyl ring. Their lipophilicity varied only with the... 

Many amides have been prepared from pyrazinecarboxylic acid chlorides some are listed below with the relevant amines and references 2-chlorocarbonyl [MeNHj/ EtOAc (138) Me NH/EtOAc (138) BujNH etc/EtOAc (138) aniline/EtOAc (138, 1335) other aromatic and heterocyclic amines/EtOAc (138) sulfanilamide/ pyridine (1336) p-(2 -aminoethyl)benzenesulfonamide (1385) p-anisidine/benzene (1334) 4-hydroxypiperidine/benzene chloroform (1386) morpholine/DMF/20° (1387) 2-aminopyrimidine/benzene (1388) glycine/NaOH/ether (1201, cf. 1333, 1360)] 2-chlorocarbonyl-5-methyl [MeNHj/benzene (1337) MejNH/benzene (1337) 4-phenylpiperazine or diethanolamine/benzene-chloroform (1386) 2-chlorocarbonyl-3-phenyl (6-aminopenicillanic acid) (1024) 2-chloro-3-chloro-carbonyl (morpholine/benzene) (838) 2-chloro-5-chlorocarbonyl (NH4OH) (839) 2-chloro-6-chlorocarbonyl (Et2NH/benzene) (870, 1389) 2-chlorocarbonyl-5-hydroxy (aniline/benzene) (1055) 2-chlorocarbonyl-3-methoxy (morpholine/ benzene) (867) 2-chlorocarbonyl-5-methoxy (morpholine/benzene-chloroform) (1386) and 2-(l -chlorocarbonylethyI) (morpholine/benzene) (364). 

But-2-enal condenses with 5-aminouracil and its 1,3-dimethyl derivative,443 or with 2,5-di-aminopyrimidin-4(3//)-one (8)444 in the presence of hydrochloric acid to give the corresponding 6-methy lpyrido[3,2-rf]pyrirnidine-2,4(1/7,3/7)-diones 7 and 9, respectively. Because of the hydrolysis of the methoxy groups, the same procedure with 2,4-dimethoxypyrimidin-5-amine also yields 6-methylpyrido[3,2-c/]pyrimidine-2,4(1/7,3//)-dione, whereas with acetic acid as catalyst the methoxy groups are retained.443... 

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