A Synthetic, X‐ray, NMR Spectroscopy and DFT Study of β‐Naphthil Dihydrazone, Di(β‐naphthyl)acetylene, Tetra(β‐naphthyl)cyclopentadienone, and Hexa(β‐naphthyl)‐benzene: C6(C10H7)6 Is a Disordered Molecular Propeller
Journal Articles
Overview
Research
Identity
Additional Document Info
View All
Overview
abstract
AbstractTreatment of β‐naphthil dihydrazone, 1, with silver oxide yields di(β‐naphthyl)acetylene, 2, which undergoes Diels–Alder cycloaddition with tetra(β‐naphthyl)cyclopentadienone, 4, to give hexa(β‐naphthyl)benzene, 5, upon decarbonylation. Molecules 1, 2 and 4 have been characterised by X‐ray crystallography, but hexa(β‐naphthyl)benzene exhibits rotational disorder of the peripheral substituents. Nevertheless, calculations at the density functional level reveal the favoured structure of 5 to be a molecular propeller, in which the eight possible rotamers are essentially iso‐energetic. Variable‐temperature NMR spectroscopy studies yield a naphthyl rotational barrier of approximately 17 kcal mol−1, similar to that previously found for meta‐substituted phenyl groups. Enantiomerisation of hexa(β‐naphthyl)benzene engendered by rotation of a single naphthyl ring has been studied by DFT calculations, and the process has been represented pictorially.
