Efficient synthesis of new tricyclic pyrano[3,2-c]pyridine derivatives

Arylidenemalononitriles as Versatile Synthons in Heterocyclic Synthesis

BACKGROUND

Arylidenemalononitriles are valuable synthons for the construction of a variety of novel complex heterocyclic motifs, fused heterocycle derivatives and spirocyclic compounds. They are versatile chemical intermediates and have increasing applications in industry, agriculture, medicine, biological science.

OBJECTIVE

The aim of this review is to highlight the preparation methods and reactions of arylidenemalononitriles in the synthesis of various heterocyclic compounds.

CONCLUSION

In this review, we have presented the application of arylidenemalononitriles to construct a variety of heterocycles. Various catalysts for the preparation of arylidnemalononitriles have been described.

Crystal structure and Hirshfeld surface analysis of ethyl 6'-amino-2'-(chloro-meth-yl)-5'-cyano-2-oxo-1,2-di-hydro-spiro-[indoline-3,4'-pyran]-3'-carboxyl-ate

The mol-ecular conformation of the title compound, C17H14ClN3O4, is stabilized by an intra-molecular C-H⋯O contact, forming an S(6) ring motif. In the crystal, the mol-ecules are connected by N-H⋯O hydrogen-bond pairs along the b-axis direction as dimers with R 2 2(8) and R 2 2(14) ring motifs and as ribbons formed by inter-molecular C-H⋯N hydrogen bonds. There are weak van der Waals inter-actions between the ribbons. The most important contributions to the surface contacts are from H⋯H (34.9%), O⋯H/H⋯O (19.2%), C⋯H/H⋯C (11.9%), Cl⋯H/H⋯Cl (10.7%) and N⋯H/H⋯N (10.4%) inter-actions, as concluded from a Hirshfeld surface analysis.

Crystal structure and Hirshfeld surface analysis of 5,7-diphenyl-1,2,3,5,6,7-hexa-hydro-imidazo[1,2-a]pyridine-6,6,8-tricarbo-nitrile methanol mono-solvate

In the title compound, C22H17N5·CH4O, the imidazolidine ring of the 1,2,3,5,6,7-hexa-hydro-imidazo[1,2-a]pyridine ring system is a twisted envelope, while the 1,2,3,4-tetra-hydro-pyridine ring adopts a twisted boat conformation. In the crystal, pairs of mol-ecules are linked by O-H⋯N and N-H⋯O hydrogen bonds via two methanol mol-ecules, forming a centrosymmetric R 4 4(16) ring motif. These motifs are connected to each other by C-H⋯N hydrogen bonds and form columns along the a axis. The columns form a stable mol-ecular packing, being connected to each other by van der Waals inter-actions. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H⋯H (43.8%), N⋯H/H⋯N (31.7%) and C⋯H/H⋯C (18.4%) contacts.

Crystal structure and Hirshfeld surface analysis of 3-cyano-4-hy-droxy-2-(4-methyl-phen-yl)-6-oxo-N-phenyl-4-(thio-phen-2-yl)cyclo-hexane-1-carbox-amide 0.04-hydrate

In the title compound, C25H22N2O3S·0.04H2O, the central cyclo-hexane ring adopts a chair conformation. In the crystal, mol-ecules are linked by N-H⋯O, C-H⋯O, and C-H⋯N hydrogen bonds, forming the mol-ecular layers parallel to the bc plane, which inter-act by the van der Waals forces between them. A Hirshfeld surface analysis indicates that the contributions from the most prevalent inter-actions are H⋯H (41.2%), C⋯H/H⋯C (20.3%), O⋯H/H⋯O (17.8%) and N⋯H/H⋯N (10.6%).

Crystal structure and Hirshfeld surface analysis of 3-amino-1-oxo-2,6,8-triphenyl-1,2,7,8-tetra-hydro-iso-quinoline-4-carbo-nitrile

In the title compound, C28H21N3O, the 1,2-di-hydro-pyridine ring of the 1,2,7,8-tetra-hydro-iso-quinoline ring system is planar as expected, while the cyclo-hexa-1,3-diene ring has a twist-boat conformation, with Cremer-Pople parameters Q T = 0.367 (2) A, θ = 117.3 (3)° and φ = 327.3 (4)°. The dihedral angles between the best planes through the iso-quinoline ring system and the three phenyl rings are 81.69 (12), 82.45 (11) and 47.36 (10)°. In the crystal, mol-ecules are linked via N-H⋯O and C-H⋯N hydrogen bonds, forming a three-dimensional network. Furthermore, the crystal packing is dominated by C-H⋯π bonds with a strong inter-action involving the phenyl H atoms. The role of the inter-molecular inter-actions in the crystal packing was clarified using Hirshfeld surface analysis, and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (46.0%), C⋯H/H⋯C (35.1%) and N⋯H/H⋯N (10.5%) contacts.

Crystal Structure and Hirshfeld Surface Analysis of Acetoacetanilide Based Reaction Products

We report an unprecedented multicomponent reaction of acetoacetanilide with malononitrile leading to a structurally novel bicyclic product (9) in a high yield. The structure has been confirmed by X-ray crystallography and comparative Hirshfeld surface analysis of 5-cyano-2-hydroxy-2-methyl-N-phenyl-4-(yridine-4-yl)-6-(thiophen-2-yl)-3,4-dihydro-2H-pyran-3-carboxamide 2, 5-cyano-2-hydroxy-2-methyl-6-oxo-N-phenyl-4-(thiophen-2-yl)piperidine-3-carboxamide 4 and 2-(8-amino-7,8a-dicyano-1-imino-4a-methyl-3-oxo-2-phenyl-1,3,4,4a,5,8a-hexahydroisoquinolin-6(2H)-ylidene)-N-phenylacetamide 9.