Regioselective synthesis of some functionalized 3,4’-bis-(pyrazolyl)ketones and chemoselectivity in their reaction with hydrazine hydrate

A new enamino ester, (E)-ethyl 3-(dipropylamino)acrylate, was prepared and used for synthesis of various pyrazole derivatives, 4a-k and 5a-d. Other new enaminone, (E)-ethyl 3-(3-(dimethylamino)acryloyl)-1-(4-nitrophenyl)-1H-pyrazole-4-carboxylate (8), was also prepared from compound 4a and utilized as precursor for synthesis of different functionalized 3,4'-bis-pyrazolyl ketones 9a-c, 10a-c. The site selectivity in hydrazinolysis of the latter was studied. The structures of the products namely pyrazolo[3,4-d]pyridazine derivatives 11(13) were confirmed by spectral and elemental analyses and by alternate unambiguous synthesis

Synthesis of novel 3,4-dihydroquinoxalin-2(1H)-one derivatives

New derivatives of 3,4-dihydroquinoxaline-2(1H)-one were synthesized and characterized. Representative examples were evaluated for their antimicrobial and antifungal activities using Tetracycline and Nystatin as reference compound. One of the tested compounds 10a was found to exhibit slight activity against Staphylococcus aureus. Compounds 10b, 11b and 14b showed slight activity against Escherichia coli. Moreover, nineteen compounds were screened for their inhibition effect on CDK5, CK1, and GSK-3β. None of the tested compounds showed an inhibition activity below 10 µM concentration

Site-selectivite Synthesis and Tautomerism of Arylazo Derivatives of Pyrazolo[3,4-d]pyrimido-[1,6-b][1,2,4]triazine

A simple synthetic strategy is described for synthesis of the hitherto unreported 5-arylazo-1,3-diphenyl-6-substituted-1H-pyrazolo[3,4-d]pyrimido[1,6-b][1,2,4]triazines 5a-n. The spectral data indicated that the studied compounds exist predominantly in the hydrazone tautomeric form 5A. The site-selectivity and mechanism of the studied reactions are discussed

Ethyl (Z)-2-chloro-2-(2-phenyl­hydrazin-1-yl­idene)acetate

The title compound, C10H11ClN2O2, features an almost planar Car—N(H)—N=C(Cl) unit [torsion angle = 0.8 (1)° whose phenyl substituent is almost coplanar with it [dihedral angle = 2.8 (2)°]; this unit is slightly twisted with respect to the carboxyl –CO2 fragment [dihedral angle = 10.3 (2)°]. In the crystal, the amino group acts as a hydrogen-bond donor to the carbonyl O atom of an adjacent mol­ecule; the hydrogen bond generates a helical chain that runs along the b axis of the monoclinic unit cell

Ethyl 2-chloro-[2-(4-chloro­phen­yl)hydrazin-1-yl­idene]acetate

The title compound, C10H10Cl2N2O2, features a planar Car—N(H)—N=C(Cl) unit [torsion angle = 5.5 (4)°] whose benzene substituent is coplanar with it [dihedral angle = 4.7 (4)°]; this unit is slightly twisted with respect to the carboxyl –CO2 fragment [dihedral angle = 2.2 (52)°]. The amino group acts as a hydrogen-bond donor to the carbonyl O atom of an adjacent mol­ecule; the hydrogen bond generates a helical polymer that runs along the b axis of the monoclinic unit cell

4-Bromo­benzoic acid–6-(4-bromo­phen­yl)-3-methyl-1,2,4-triazolo[3,4-b][1,3,4]thia­diazole (1/1)

In the title 1:1 co-crystal, C10H7BrN4S·C7H5BrO2, the triazolothia­diazole system is approximately planar [with a maximum deviation of 0.030 (4) Å] and forms a dihedral angle of 8.6 (1)° with the bromo­phenyl ring. In the carb­oxy­lic acid mol­ecule, the carboxyl group is rotated by 6.4 (3)° out of the benzene ring plane. The crystal structure features O—H⋯N and C—H⋯O hydrogen bonds, π–π stacking inter­actions [centroid–centroid distances = 3.713 (2), 3.670 (2) and 3.859 (3) Å] and short S⋯N [2.883 (4) Å] contacts

A convenient synthesis of 5-amino-4-(2-benzothiazolyl)pyrazoles

1175-117

3-[1-(4-Isobutyl­phen­yl)eth­yl]-6-(4-methyl­phen­yl)-1,2,4-triazolo[3,4-b][1,3,4]thia­diazole

In the title compound, C22H24N4S, the methylphenyl and isobutylphenyl rings are inclined at an angle of 79.98 (1)° and they form dihedral angles of 4.59 (1) and 75.47 (1)°, respectively, with the triazolothia­diazole unit. An intra­molecular C—H⋯S hydrogen bond generates an S(5) ring motif. The crystal structure is stabilized by inter­molecular C—H⋯N hydrogen bonds and weak C—H⋯π and π–π inter­actions [centroid–centroid distances between the thia­diazole ring and a symmetry-related phenyl ring and between the triazole ring and the phenyl ring range from 3.5680 (8) to 3.7313 (8) Å]

Carbenic nitrile imines: Properties and reactivity

Structures and properties of nitrile imines were investigated computationally at B3LYP and CCSD(T) levels. Whereas NBO analysis at the B3LYP DFT level invariably predicts a propargylic electronic structure, CCSD(T) calculations permit a clear distinction between propargylic, allenic, and carbenic structures. Nitrile imines with strong IR absorptions above ca. 2150 cm-1 have propargylic structures with a CN triple bond (RCNNSiMe 3 and R2BCNNBR2), and those with IR absorptions below ca. 2150 cm-1 are allenic (HCNNH, PhCNNH, and HCNNPh). Nitrile imines lacking significant cumulenic IR absorptions at 1900-2200 cm -1 are carbenic (R-(C:)-N=N-R′). Electronegative but lone pair-donating groups NR2, OR, and F stabilize the carbenic form of nitrile imines in the same way they stabilize "normal" singlet carbenes, including N-heterocyclic carbenes. NBO analyses at the CCSD(T) level confirm the classification into propargylic, allenic, and carbenic reactivity types. Carbenic nitrile imines are predicted to form azoketenes 21 with CO, to form [2+2] and [2+4] cycloadducts and borane adducts, and to cyclize to 1H-diazirenes of the type 24 in mildly exothermic reactions with activation energies in the range 29-38 kcal/mol. Such reactions will be readily accessible photochemically and thermally, e.g., under the conditions of matrix photolysis and flash vacuum thermolysis