Weak attractive interactions between methylthio groups and electron-deficient alkenes in peri-naphthalenes: a competition with conjugative effects

O(−)⋯C interactions and bond formation in 1-naphtholate anions with peri-located electrophilic carbon centres

n–π* interactions between naphtholate O anions and carbonyl groups are determined to be shorter than in corresponding naphthols by X-ray crystallography, and lead to cyclisations with long O–C bonds when the carbonyl group is replaced by a strongly electron deficient alkene.

Aromaticity of peri- and para-Substituted Naphthalene-1-carbaldehyde. Comparison with 1-Nitronaphthalene

Aromaticity of the naphthalene ring substituted by formyl or nitro and secondary amine groups in peri and para positions has been investigated. HOMA (harmonic oscillator model of aromaticity) index of the naphthalene rings has been used to characterize the aromaticity of the investigated molecules. Ellipticity of C2-C3 (C6-C7) bonds, obtained by means of topological analysis of the electron density, has been used as a measure of the through-resonance effect between the para substituents. Dependence of the HOMA values on the rotation angle of formyl and nitro groups to the aromatic plane for naphthalene-1-carbaldehyde and their derivatives with dimethylamino group in para position has been analyzed. It has been shown that the nitro group has a stronger resonance effect and causes greater decrease of aromaticity than the formyl group only for planar or close to planar conformation. The attractive and repulsive peri interactions have been analyzed by using the QTAIM and NCI methods. Interrelation between the peri and para interactions has been discussed.

Crystal structure of 5-[4-(diethylamino)benzylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione

The title compound, C17H21NO4, consists of substituted Meldrum's acid with a [4-(diethylamino)phenyl]methylidene fragment attached to the fifth position. The heterocycle assumes a distorted boat conformation. The planar part of heterocycle is almost coplanar with the benzene ring due to the presence of a long conjugated system in the molecule. This leads to the formation of C—H...O-type intramolecular contacts. As a result of the absence of hydrogen-bond donors in the structure, the crystal packing is controlled by van der Waals forces and weak C—H...O interactions, which associate the molecules into inversion dimers.