5-Aminopyrimidine

C10H10N4O2S. White powder, which darkens on exposure to light m.p. 255-256 C. Prepared by condensing p-acet-amidobenzenesulphonyl chloride with 2-aminopyrimidine and subsequent hydrolysis. Soluble sulphadiazine is the sodium salt. Sulphadiazine is the least toxic of the more potent sulphonamides. ... 

Thiophenealdehyde has been used in the reductive alkylation of 2-aminopyridine and 2-aminopyrimidine. 2-Arylamino-4- (2-thienyl )thiazoles have been prepared by the reaction of 2-acetylthio-phene with A-arylthioureas in the presence of iodine, ... 

Aromatic rings containing more than one hetero atom also yield active antihistamines. Alkylation of 2-aminopyrimidine (6S) with p-methoxybenzyl chloride gives the corresponding secondary amine (66). Alkylation with the usual chloroamine affords thonzylamine (67), Application of the same sequence to 2-aminothiazole (68) affords zolamine (70). ... 

Finally, Katritzky et al.sii have measured first-order rate coefficients for deuteration of pyrimidines by deuterated sulphuric acid (Table 152), and all pD and —D0 values given in the Table refer, as in the earlier work, to a temperature of 20 °C. For 2-aminopyrimidine, reaction clearly occurs on the free base and comparison of the data with the earlier work on anilines and by making a number of assumptions, conjugate acid at higher acidities is apparent and this follows the previously established pattern. This work yielded a value of 0.55 for [Pg.236]

Figure 5.2 Polyimide syntheses by imide exchange with 2-aminopyrimidine as leaving group.

The resin-bound reagents thus obtained were reacted with a variety of nucleophiles to give different heterocycles (Scheme 13). So, reaction with hydrazine or hydroxylamine gave respectively pyrazoles and isoxazoles in excellent yields (94-99%, 34 examples) and excellent purities (> 95%). Reaction with guanidines afforded 2-aminopyrimidines. 

As for the solid support, several polymer-supported amines were tested (Fig. 2). For either the pyrazole and isoxazole synthesis, the best results were given by aniline-functionalized cellulose, which has also the advantage of a relatively low cost. For the 2-aminopyrimidine library, polystyrene-based piperazine and piperidine gave products with a much higher purity compared with other secondary non-cyclic or primary amines, hi both cases, the resins could be reused for up to four times before degradation in their behavior was observed. This reusability could be further enhanced (up to 10 cycles for cellulose-based aniline) when the microwave-assisted protocols were used. 

Fig. 2 Various polymer-supported bases used in the catch-and-release synthesis of pyra-zoles, isoxazoles and 2-aminopyrimidines...

Completion of the total synthesis afforded only six further steps, including the installation of the second 2-aminopyrimidine ring via a second domino sequence. This process presumably involves a conjugate addition of guanidine (2-293) to the enone system of2-292, followed by a cyclizing condensation and subsequent aromatization. Under the basic conditions, the ethyl ester moiety is also cleaved and 2-294 is isolated in form of the free acid, in 89 % yield. Finally, decarboxylation and deprotection of the amino functionality yielded the desired natural product 2-295. 

Reaction of 3-formyM/7-pyrido[ 1,2- ]pyrimidin-l-ones with hydroxylamine O-sulfonic acid at 5 °C, then 50 °C yielded 3-nitriles <2003T4113>. Treatment of 2-hydroxy-3-(dimethylamono)methyF4//-pyrido[l,2- ]pyrimidin-4-one with Mel, then with KCN gave the 3-cyanomethyl derivative <2004MI215>. A condensation product was obtained from 5-amino-l-ethyl-6-hydroxy-l,3-dihydrobenzimidazol-2-one and 3-lbrmyl-2-hydroxyA//-pyndo[ 1,2- ]pynmidin-l-one <2002W002/38549>. l-(2-Aminopyrimidin-4-yl)-8-phenyl-l,2,3,4-tetrahydro-6//-pyrido[l,2- ]pyrimidin-6-ones were prepared from l-(2-methylthiopyrimidin l-yl)-8-phenyl-l,2,3,4-tetrahydro-6//-pyrido[l,2- ]pyrimidin-6-one by treatment with MCPBA, and then with aralkylamines <2005W005/070932>. 

Diaryl-2-aminopyrimidines react with acrylonitrile in pyridine under reflux to give, after work-up, the 6,8-diaryl-2,3-dihydro-4-oxo-47/-pyrimido[l,2- ]pyrimidines in low yield <1996IJB915>. 

Libraries of 3,4-dihydropyrimido[l,2- ]pyrimidines were formed by reacting 2-aminopyrimidines with an aldehyde and an olefin in a one-pot reaction in the presence of acid, for example, TFA <2002W0030934>. 

A microwave-assisted, one-pot, two-step protocol was developed for the construction of polysubstituted 2-aminoimidazoles 101 via the sequential formation of imidazo[l,2-a]pyrimidinium salts from readily available 2-aminopyrimidines 99 and a-bromocarbonyl compounds 100, followed by opening of the pyrimidine ring with hydrazine <06OL5781>. A... 

Aldehydes and the corresponding 2-aminopyridine, pyrazine, or pyrimidine are admixed in presence of a catalytic amount of clay (50 mg) to generate iminium intermediate. Isocyanides are subsequently added to the same container and the reactants are further exposed to MW to afford the corresponding imidazo[l,2-a]pyridines, imi-dazo[l,2-a]pyrazines and imidazo[l,2-a]pyrimidines (Scheme 6.48). The process is general for all the three components, e. g. aldehydes (aliphatic, aromatic and vinylic), isocyanides (aliphatic, aromatic and cyclic) and amines (2-aminopyridine, 2-amino-pyrazine and 2-aminopyrimidine). A library of imidazo[l,2-a]pyridines, imidazo[l,2-ajpyrazines and imidazo[l,2-a]pyrimidines can be readily obtained by varying the three components [151]. 

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