## 2 Results and Discussion  
### Chemistry  
Ethyl 3-acetyl-1,5-diphenyl-1\(H\)-pyrazole-4-carboxylate (**1**) [53] was used as the starting compound for the preparation of a number of novel pyrazolyl-pyridine derivatives via one-pot multicomponent reactions. For example, a series of novel 2-amino-3-cyano-6-(pyrazol-3-yl)-pyridines **4a-f** was prepared by a one-pot reaction of 3-acetylpyrazole derivative **1** with the appropriate aldehyde **2**, malononitrile **3**, and ammonium acetate under reflux in acetic acid (Scheme 1). Both elemental analyses and spectral data were used to elucidate the structures of the products **4a-f**. The IR spectra of compounds **4a-f** revealed in each case three absorption bands in the regions \(\upsilon\) 3431-3211, 2218-2210, 1715-1709 cm\({}^{-1}\) attributed to the NH\({}_{2}\), CN and C=O groups. The \({}^{1}\)HNMR spectrum of compound **4a** taken as a typical example of the products **4**, revealed two signals at \(\delta\) = 6.93 (brs, 2H, NH\({}_{2}\)) and 8.11 (s, 1H, pyridine-H5), in addition to the expected signals for the aryl and ester protons. Moreover, the mass spectra of product **4** showed in each case the respective molecular ion peak which is consistent with the assigned structure. In a similar manner, another series of pyrazolylpyridines **6a-f** was synthesized using ethyl acetoacetate in lieu of malononitrile. Thus, the reaction of 3-acetylpyrazole derivative **1** with the appropriate aldehyde **2**, ethyl acetoacetate **5**, and ammonium acetate in refluxing acetic acid afforded the corresponding products **6a-f** (Scheme 2). The structure **6** assigned for the obtained products was established by elemental analyses and spectral (IR, \({}^{1}\)HNMR, and MS) data. For example, the IR spectra of products **6a-f** revealed, in each case, four absorption bands assigned for the three carbonyl groups and the -NH group of the pyridinone ring (see Section 3). The \({}^{1}\)HNMR spectra displayed three singlet signals near \(\delta\) 2.58, 9.80 and 7.79 ppm attributed to the acetyl, NH and pyridinyl-5H protons, in addition to the expected signals due to the ester and aryl protons (see Section 3). To account for the formation of products **4** and **6**, it was suggested that the reaction proceeds by condensation of the acetyl group of Compound **1** with the aldehyde to give the corresponding chalcone which reacts with ammonium acetate to give the imino derivative, followed by tandem Michael addition of the active methylene group of **3** (or **5**) to afford the non-isolable tetrahydropropyline intermediates **A** (or **B**). The latter undergo in situ auto-oxidation (followed by tautomerization in case of **A**) and formation of the final products **4** (or **6**) (Scheme 3). Our study was extended to prepare another new bipyridine derivatives including the pyrazole moiety via multi-component reaction. Thus, the reaction of 3-acetyllypyrazole derivative **1** with terephthalaldehyde **7**, malonomitrile **3**, and ammonium acetate in acetic acid under reflux furnished the bipyridine derivative **8** (Scheme 4). Similarly, the reaction of compound **1** with terephthalaldehyde, ethyl acetoacetate **5**, and ammonium acetate in acetic acid under reflux gave the respective bipyridinone **9** (Scheme 4). The structure of products **8** and **9** were confirmed by elemental analyses and spectral data (IR, \({}^{1}\)HNMR, and MS) (see Section 3). On the other hand, chalcone **10**, prepared by the reaction of **1** with benzaldehyde in ethanol containing catalytic amounts of NaOH [54], was used for preparation of 6-(pyrazol-3-yl) pyrimidine-2-thione derivative **11** via its reaction with thiourea in ethanol containing a catalytic amount of sodium hydroxide [54]. Reaction of the latter compound **11** with a number of hydrazonoyl chlorides **12a-h**[55] in dioxane in the presence of triethylamine afforded the respective products **15a-h** through the non-isolated intermediates **13** and **14** (Scheme 5).