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Abstract
A new series of pyrimidine and fused pyrimidine derivatives were prepared. These derivatives includes differently substituted benzylidenes, heterocycles such as pyrazole ring and fused ring systems such as triazolo[4,3-a]pyrimidine, pyrido[2,3-d]pyrimidine and pyrimido[4,5-d]pyrimidine systems. The synthetic routes were adopted via formation of substituted amino pyrimidine core structure in simple and efficient procedures. In order to obtain the target compounds, the following routes were adopted: SCHEME 1 (Synthesis of intermediates I-VI, VII): Alkylation of thiourea with dimethyl sulfate to give methyl isothiourea sulfate (I). Condensation of malononitrile with triethyl orthoformate in acetic anhydride to afford 2-(ethoxymethylene) malononitrile (II). Kneovenagel condensation of malononitrile or ethyl cyanoacetate with benzaldehyde derivatives to afford IIIa-e. Synthesis of 4-amino-2-(methylthio) pyrimidine-5-carbonitrile (V) by the reaction of methyl isothiourea sulfate (I) with 2-(ethoxymethylene) malononitrile (II). Hydrolysis of 4-amino-2-(methylthio)pyrimidine-5-carbonitrile (IV) to afford 4-amino-2-(methylthio)pyrimidine-5- carboxamide (V). Nucleophilic substitution of methylthio group with hydrazine hydrate to afford 4-amino-2-hydrazinylpyrimidine-5-carbonitrile (carboxamide) VI, VII. . SCHEME 2: (Synthesis of hydrazoneyl pyrimidine derivatives). Condensation of 4-amino-2-hydrazinylpyrimidine-5-carbonitrile (VI) and 4-amino-2-hydrazinylpyrimidine-5-carboxamide (VII) with different benzaldehyde and acetophenone derivatives to give compounds VIIIa-j and IXa-h