Pyrimidine amino-, reactions

Table 20 Ring closures to [1,2,4]triazolo[1,5-a]pyrimidines by reaction of 3-amino[1,2,4]triazoles with /3-oxo ketones, esters, nitriles, or malonic acid derivatives...

A further example of the formation of a fused pyrimidine by reaction of ortho amino/cyano groups is illustrated by condensation of 2-amino-4-(4-nitrophenyl)-3-thiophenecarbonitrile with formamide in the presence of PhsP at elevated temperature <2006T11311>. 

Treatment of the symmetrical triaminopyrimidine (50-1) with sulfuryl chloride ties up the two adjacent amines in a thiadiazole ring, protecting those groups from attacks in subsequent reactions. Reaction of the product (50-2) with ortho difluorinated benzylamine (50-3) results in the replacement of the pyrimidine amino group by that in the reagent most hkely by an addition-elimination sequence to afford (50-4). That amino group is then converted to the formamide (50-5) with formic acid. Exposure of the product to Raney nickel leads to a loss of sulfur and the formation of the transient intermediate (50-6). This cyclizes to a purine... 

Most derivatives of this ring system are prepared from 2-aminopyrimidines. Ethoxy-methylenemalonic ester (220) is a versatile synthon which can be reacted with 2-aminopyrimidines to give pyrimido[l,2-a]pyrimidine precursors. Reaction of 2-aminopyrimidine (219) with this ester gives the aminomethylenemalonic ester (221), which can be thermally cyclized to the heterocyclic ester (222). The enamine analogous to (221) which is derived from 2-amino-4,6-dimethylpyrimidine cannot be cyclized under these conditions. Presumably this cyclization fails due to steric hindrance of the methyl groups (72JMC1203). 

Tetrazolof l,5-c]pyrimidine, 8-amino-7-chloro-purine synthesis from, 5, 591 Tetrazolopyrimidines purine synthesis from, 5, 591 Tetrazolof 1,5-a]pyrimidines cycloaddition reactions, 5, 881 reactions, 5, 880 ring opening, 5, 880 structure, 5, 859, 860 synthesis, 5, 902 thermolysis, 5, 881 Tetrazolof 1,5-c]pyrimidines hydrogenation, 5, 881 reactions, 5, 881 structure, 5, 859, 860 synthesis, 5, 902 thermolysis, 5, 881... 

Flowers et al.164 reacted perfluoro-2-methyl-2-pentene with 2-aminopyri-dine or 2-amino-4-methylpyridine in tetrahydrofuran at room temperature to obtain the pyrido[1.2-u]pyrimidines (95). Reaction with 2-amino-6-methylpyridine yielded the 1,8-naphthyridine (96). 

Acyl(or cyano)pyrimidines substituted at the 4-position with chlorine, methoxy or methylsulf-anyl have also been used as intermediates in the preparation of pyrimido[4,5-rf]pyrimidines by reaction with guanidine, urea, or amidines.110114 139,140 Thus, 5-phenylpyrimido[4,5-<7]-pyrimidine-2,4,7-triamine (35) is obtained by reaction of 2-amino-4-methoxy-6-phenylpyrimi-dine-5-carbonitrile (34) with guanidine.114... 

Solvated Electron Reaction Rates. Purines and Pyrimidines. The reaction rates of e aq with purines and pyrimidines at neutral pH are shown in Table II. All are very reactive, the reaction rates being close to diffusion controlled. However, the pyrimidine cytosine, which has an amino group at the C-4 position, is somewhat less reactive than thymine and uracil which have carbonyl groups at this position. Adenine, which also has an amino group in this position, has a very high reactivity, but this is probably because of the presence of the positively charged imidazole ring. 

Structures comprising One Five-Membered and One Six—Membered Ring (5,6). - Thiazolon.2-al-. r3,4-al-, and 5,4-dlpyrimidines tC NS-C N ]. The reaction of 2-amino-2-thiazoline or thiazolidine with EtOOCCHRCOOEt/Na or R1R2NCH(C00Et)2[R1,R2=various] affords (252 R=alkyl,NR1R2 R3, R = H,bond)285 288. Other methods utilised include the preparation of thiazolo[3,2-a]pyrimidines by reaction of tetrahydropyrimidine-2-thione with broraoketones and... 

It is clear that further reaction of the hydrocarbons produced in reaction (3) will produce a more complicated series of aldehydes and nitriles via reactions (1) and (2). In the presence of liquid water, a still more complicated reaction sequence becomes possible. Because of the limitations of space, I shall confine the discussion to the possible production of the components of proteins and nucleic acids. The principle pathways of interest here are the synthesis of carbohydrates from formaldehyde and the formation of amino acids, purines and pyrimidines by reactions involving aqueous solutions of HCN. [Although there have been suggestions that HCN can undergo direct polymerization in the gas phase (Matthews and Moser, 1966 Matthews et al., 1977), this reaction has never been directly observed.]... 

The protected 2-formyl-L-arabinal reacted with thiourea and cyanamide in the presence of sodium hydride to afford, via ring transformations, the 5- [ lR,2S-l,2-bis(benzyloxy)-3-hydroxypropyl]- 1,2-dihydropyrimidines. Similarly, treatment with 3-amino-2H-1,2,4-triazole yielded 6-[lR,2S-l,2-bis(benzyloxy)-3-hydroxypropyl][l,2,4]-triazolo[l,5-a]pyrimidine [151]. Reaction of 27 with 2-aminoimidazole and 2-aminobenzimidazole gave 96 and its bezo-analogues [64]. 

From the young pea seedlings of Pisum sativum L. var. Rondo there was isolated another pyrimidine amino acid, the structure of which was initially proposed [429] as L- -(5-uracilyl)alanine (LXXVIIIa). However, its physical constants by no means agree with those of the authentic -(5-uracilyl)alanine unequivocally synthesised earlier [430, 431]. The structure has since been revised to L- -(3-uracilyl)alanine (LXXIX, isowillardiine) by examination of its ultraviolet absorption characteristics and chemical reactions [422] and substantiation by infrared, NMR, and mass spectrometry [432]. Its biological role has not yet been determined. 

Hydrogen cyanide can also be converted to cyanoacetylene and hydrogen cyanate, both precursors of pyrimidines. These reactions were reproduced in the laboratory. In fact, in 1828, F. Wohler made urea from hydrogen cyanate and ammonia, the first synthesis of an animal substance from inorganic materials. Very likely, all these processes occurred primarily in an aqueous environment where and OH" ions acted as specific-acid or specific-base catalysts. It is particularly impressive that the three major classes of nitrogen containing biomolecules, purines, pyrimidines, and amino acids are formed by the hydrolysis of the oligomers formed directly from... 

Pyrimidine, see also azines amino-, reactions of, 234 4-amino-2-methyl-, 137 anilino-dechlorination of, 274 benzo-fusion, effect of, 350 6-bromo-, reaction with piperidine, 143... 

Isothiazolo[5,4-t/]pyrimidines.—Successive reaction of 5-amino-3-methylisothia-zole-4-carbonitrile (86 X = CN) with orthoesters and primary amines produces 4-amino-3-methylisothiazolo[5,4-f/]pyrimidines, apparently by rearrangement of the primarily produced isomers, which were not isolated. Condensation of (86 X = CN) with amidines gave the same products in one stage, albeit in very low yields. The 4-carboxamide (86 X = NH2CO) may in turn be cyclized with orthoesters to 5/f-isothiazolo[5,4-[Pg.354]

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