Compounds with alkoxycarbonylmethyl groups in adjacent positions in a pyrimidine ring can be used as synthons in the preparation of polycyclic heterosystems. Our previous attempt [1] to synthesize pyrimidine derivatives having S-and N-alkoxycarbonylmethyl groups respectively in positions 2 and 3 of the ring by alkylation of the corresponding 4-hydroxy-2-mercaptopyrimidine or methyl 4-hydroxy-2-methoxycarbonylmethylsulfanylacetate with methyl bromoacetate were unsuccessful since only the S-or N-dialkylation product was formed. Continuing our work in this area we have found that compounds 2a,b can be prepared by treating the corresponding 2-methylsulfanyl derivatives 1a,b with methyl or ethyl mercaptoacetate in the presence of base: N N O Me SMe N N O Me CH 2 COOR 2 R 1 HSCH 2 COOR 2 R 1 CH 2 COOR 2 SCH 2 COOR 2 1a,b 2a,b 1,2 a R 1 = Br, R 2 = Me; b R 1 = NO 2 , R 2 = EtIt should be noted that compound 2a was obtained by refluxing compound 1a in tert-butanol with methyl mercaptoacetate in the presence of potassium tert-butylate whereas treatment of compound 1b with ethyl mercaptoacetate under the same conditions gave a complex mixture of products, from which pure compounds could not be separated. Compound 2b was prepared with the use of triethylamine as base.IR spectra were obtained on a Perkin-Elmer BX FT-IR spectrometer for KBr tablets. 1 H NMR and 13 C NMR spectra were taken on a Varian Unity Inova instrument (300 and 75 MHz respectively) using CDCl 3 relative to TMS.Compound 1a was prepared as described before [2].
The reaction of methyl esters q ['2-subslituted 5-pyrimidinecarbo.~. lic acids with hydrazine hydrate at 0-5't2 results in the nucleophilic substitution oJ'readiO~ elhninating groups (CI, CHjS) Hydrazides of pyrimidinecarboxylic acids and their derivatives, possessing interesting biological properties [1][2][3][4][5][6], are utilized in organic synthesis [7][8][9][10][11]. The most common method for the synthesis of hydrazides is the acylation of hydrazine by esters [12]. The majority of known hydrazides of 5-pyrimidinecarboxylic acids were synthesized by this method [1, 8,[13][14][15][16]. According to the data of the works [8, 17, 18], readily removable groups at the electrophilic carbon atom at the position 2 of the pyrimidine ring can cause competitive nucleophilic attack by hydrazine molecule and the very formation of hydrazinopyrimidines or the mixture of hydrazinopyrimidines and the corresponding 5-pyrimidinecarboxylic acid hydrazides. No more detailed investigations in this regard were found in the literature.With the object of a qualitative evaluation of the relative reactivity of the ester group and groups situated at the position 2 of the pyrimidine ring, we studied the reaction of the methyl esters of 2-substituted N~,,%,/CONHNI I_, ~ /COOMe
I I,NI-IN/]~N ~ VIIUnder mild conditions (0-5~ the esters I-llI only undergo nucleophilic attack by hydrazine molecule at the position 2 of the pyrimidine ring, whereby the eliminating groups are ranged in the following order according to mobility: CI > CH3S > CH30. The ester group does not react with hydrazine hydrate under these conditions. Methyl 2-hydrazino-5-pyrimidinecarboxylate (V) is formed as a result of the reactions. The compound IV is unchanged under these conditions. The ester groups of the compounds IV and V enter into the reaction with hydrazine hydrate with difficulty. The formation of hydrazides was not even noted during the prolonged boiling of the reaction mixture in solutions of methanol or ethanol. The corresponding hydrazides VI and VII were only
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Reaction of Esters of 2-Substituted 5-Pyrimidinecarboxylic Acids with Hydrazine Hydrate -[qualitative evaluation of the relative reactivity of the ester group and substituents located at the 2-position of the pyrimidine ring in hydrazinolysis reactions].-(TUMKEVICIUS, S.; YAKUBKENE, V.; VAINILAVICIUS, P.; Chem. Heterocycl.
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