Ethyl 4-oxo-1,4-dihydropyridine-3-carboxylate

The title compound, C8H9NO3, likely generated through hydrolysis and esterification of 3′-carboxy-3-methyl-(1,4′-bipyridin)-1-ium chloride by ethanol, which contained water, has a nearly planar conformation. The crystal structure is sustained by one-dimensional chains along the a-axis direction based on bifurcated N—H...(O,O) hydrogen bonds between the NH group of the 4-oxo-1,4-dihydropyridine ring and the two carbonyl O atoms.

Crystal structure and Hirshfeld surface analysis of 6-amino-8-(2,6-dichlorophenyl)-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrimidine-7,9-dicarbonitrile

In the molecular structure of the title compound, C16H13Cl2N5, the 1,4-dihydropyridine ring of the 1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrimidine ring system adopts a screw-boat conformation, while the 1,3-diazinane ring is puckered. In the crystal, intermolecular N—H...N and C—H...N hydrogen bonds form molecular sheets parallel to the (110) and (\overline{1}10) planes, crossing each other. Adjacent molecules are further linked by C—H...π interactions, which form zigzag chains propagating parallel to [100]. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from N...H/H...N (28.4%), H...H (24.5%), C...H/H...C (21.4%) and Cl...H/H...Cl (16.1%) contacts.

Crystal structure and Hirshfeld surface analysis of 6-amino-8-phenyl-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrimidine-7,9-dicarbonitrile

In the title compound, C16H15N5, the 1,4-dihydropyridine ring has a shallow boat conformation, while the 1,3-diazinane ring adopts an envelope conformation. In the crystal, pairwise N—H...N hydrogen bonds generate centrosymmetric dimers featuring R 2 2(12) motifs and C—H...N contacts connect these dimers to form double layers lying parallel to (001). Weak C—H...π and N—H...π interactions help to consolidate the double layers and van der Waals interactions occur between layers. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H...H (38.5%), N...H/H...N (33.3%) and C...H/H...C (27.3%) contacts.

Crystal structure and Hirshfeld surface analysis of ethyl 2-[9-(2-hydroxyphenyl)-3,3,6,6-tetramethyl-1,8-dioxo-2,3,4,4a,5,6,7,8a,9,9a,10,10a-dodecahydroacridin-10-yl]acetate

In the title compound, C27H33NO5, a 3,3,6,6-tetramethyltetrahydroacridine-1,8-dione ring system carries an ethyl acetate substituent on the acridine N atom and an o-hydroxyphenyl ring on the central methine C atom of the dihydropyridine ring. The benzene ring is inclined to the acridine ring system at an angle of 80.45 (7)° and this conformation is stabilized by an intramolecular O—H...O hydrogen bond between the hydroxy substituent on the benzene ring and one of the carbonyl groups of the acridinedione unit. The ester C=O oxygen atom is disordered over major and minor orientations in a 0.777 (9):0.223 (9) ratio and the terminal –CH3 unit of the ethyl side chain is disordered over two sets of sites in a 0.725 (5): 0.275 (5) ratio. In the crystal, C—H...O hydrogen bonds combine to link the molecules into a three-dimensional network. van der Waals H...H contacts contribute the most to the Hirshfeld surface (66.9%) followed by O...H/H...O (22.1%) contacts associated with weak hydrogen bonds.

Crystal structure, Hirshfeld surface and frontier molecular orbital analysis of 10-benzyl-9-(3-ethoxy-4-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione

In the fused ring system of the title compound, C32H37NO4, the central dihydropyridine ring adopts a flattened boat conformation, the mean and maximum deviations of the dihydropyridine ring being 0.1429 (2) and 0.2621 (2) Å, respectively. The two cyclohexenone rings adopt envelope conformations with the tetrasubstituted C atoms as flap atoms. The benzene and phenyl rings form dihedral angles of 85.81 (2) and 88.90 (2)°, respectively, with the mean plane of the dihydropyridine ring. In the crystal, molecules are linked via an O—H...O hydrogen bond, forming a helical chain along the b-axis direction. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (65.2%), O...H/H...O (18.8%) and C...H/H...C (13.9%) contacts. Quantum chemical calculations for the frontier molecular orbitals were undertake to determine the chemical reactivity of the title compound.

Advanced Catalyst-Free Pseudo-Six-Component Synthesis of Tetrahydrodipyrazolopyridines in Water by Using Ammonium Carbonate as an Ecofriendly Source of Nitrogen

This work describes an improved environmentally friendly method for the synthesis of tetrahydrodipyrazolopyridines (THDPPs) in water through a catalyst-free pseudo-six-component reaction of alkyl acetoacetates, hydrazine hydrate, and ammonium carbonate with an aldehyde in a mole ratio of 2:2:1:1 at room temperature. The ammonium carbonate serves as a green source of nitrogen for the central 1,4-dihydropyridine ring in the THDPPs. Methyl acetoacetate reacts faster than either ethyl or propyl acetoacetate in this method. The product precipitates during the reaction and is simply collected by filtration. Advantages of this environmentally benign method include no use of an organic solvent, no hazardous waste, rapid clean reactions, and excellent yields of products.

Diethyl 4-(1H-imidazol-2-yl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C16H21N3O4, the 1,4-dihydropyridine ring adopts a flattened boat conformation, with the imidazole substituent in an axial orientation [dihedral angle between ring planes = 82.9 (6)°]. In the crystal structure, pairs of N—H...O and N—H...N hydrogen bonds with graph-set notation R 2 2(14) connect the molecules into chains running along the c-axis direction.

Diethyl 4-(3-chlorophenyl)-2,6-diphenyl-1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C29H26ClNO4, the dihydropyridine ring adopts a shallow boat conformation. The mean plane of the dihydropyridine ring (all atoms) subtends dihedral angles of 66.54 (1), 73.71 (1) and 79.47 (1)° with the two phenyl rings and the chlorophenyl ring, respectively. In the crystal, N—H...O hydrogen bonds link the molecules into [001] chains.

Synthesis, crystal structure and Hirshfeld surface analysis of diethyl 2,6-dimethyl-4-(thiophen-3-yl)-1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C17H21NO4S, the 1,4-dihydropyridine ring has an envelope conformation with the Csp 3 atom at the flap. The thiophene ring is nearly perpendicular to the best plane through the 1,4-dihydropyridine ring, the dihedral angle being 82.19 (13)°. In the crystal, chains running along the b-axis direction are formed through N—H...O interactions between the 1,4-dihydropyridine N atom and one of the O atoms of the ester groups. Neighbouring chains are linked by C—H...O and C—H...π interactions. A Hirshfeld surface analysis shows that the most prominent contributuion to the surface contacts are H...H contacts (55.1%).