Structure and Properties of 9,14,15,16,17,18,19,20-Octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene

Michelle E Masnovi,Steven M Schildcrout,John Masnovi

doi:10.1155/2016/8129210

Michelle E Masnovi, Steven M Schildcrout + Show 1 more

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https://doi.org/10.1155/2016/8129210

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Abstract

The compound 9,14,15,16,17,18,19,20-octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene, C28H24, was prepared by hydrogenation of the 4πs+4πs photocycloadduct of dibenz[a,c]anthracene and 1,3-cyclohexadiene with Pt/C in ethyl acetate. The X-ray diffraction analysis shows that the compound crystallizes in the monoclinic space group P21/c with the geometric parameters of a = 11.0090(17) Å, b = 13.733(2) Å, c = 13.091(2) Å, and β = 109.583(13)°. In addition to several close intramolecular contacts involving hydrogens derived from the dibenzanthracene moiety, long interannular C–C single bonds of about 1.593 Å are present. These bonds are shorter by about 0.18 Å than the corresponding bonds in the unsaturated precursor, which can be attributed to reduced strain in the more saturated polycyclic ring system. Anisotropic shielding of the four endo-methylene hydrogens in the 1H NMR spectrum is larger for the two hydrogens lying above the phenanthrene unit, which resonate at 1.03 ppm, than those above the benzenoid ring, which resonate at 1.24 ppm. Theoretical calculations reproduce the geometry with good agreement.

Highlights

The photochemical cycloadditions of conjugated dienes to benzenoid aromatic hydrocarbons provide a test of the validity of Woodward-Hoffmann orbital symmetry theory [1]
Employment of naphthalene, benzanthracenes, and dibenzanthracenes has revealed the preferential formation of 4πs + 4πs adducts which follow the Alder rule for maximization of secondary orbital overlap, diagnostic of processes involving concerted bond formation (Scheme 1) [2]. Such adducts have been found to contain unusually long interannular carboncarbon single bonds [3,4,5], and the endo-hydrogens which lie above aromatic moieties in these structures resonate at relatively high field in the 1H NMR spectra [6] due to anisotropic shielding by the subjacent aromatic rings [7,8,9]
The solid state structure of 9,14,15,16,17,18,19,20-octahydro9,14[1󸀠,4󸀠]-benzenobenzo[b]triphenylene 2 was determined by single crystal X-ray diffraction to have no disorder and revealed several close intramolecular nonbonded contacts involving hydrogens derived from the dibenzanthracene moiety

Summary

Introduction

The photochemical cycloadditions of conjugated dienes to benzenoid aromatic hydrocarbons provide a test of the validity of Woodward-Hoffmann orbital symmetry theory [1]. Employment of naphthalene, benzanthracenes, and dibenzanthracenes has revealed the preferential formation of 4πs + 4πs adducts which follow the Alder rule for maximization of secondary orbital overlap, diagnostic of processes involving concerted bond formation (Scheme 1) [2]. Such adducts have been found to contain unusually long interannular carboncarbon single bonds [3,4,5], and the endo-hydrogens which lie above aromatic moieties in these structures resonate at relatively high field in the 1H NMR spectra [6] due to anisotropic shielding by the subjacent aromatic rings [7,8,9]. We prepared compound 2, 9,14,15,16,17,18,19,20-octahydro9,14[1󸀠,4󸀠]-benzenobenzo[b]triphenylene (Scheme 2), which is free of the disorder associated with other analogues [3, 4], and performed theoretical calculations in order to establish the specific relationships involved

Methods

Results

Conclusion