[2.2.2.2](2,7)‐1‐Bromonaphthalenophane from a Desymmetrized Building Block Bearing Electrophilic and Masked Nucleophilic Functionalities

Abstract

In search of 2,7‐ethylene‐bridged naphthalenophanes with desymmetrized naphthalene cores as inherently chiral cyclophanes, nucleophilic substitution of 1‐bromo‐7‐(bromomethyl)‐2‐[(trimethylsilyl)methyl]naphthalene, a desymmetrized building block bearing an electrophilic group (CH2Br) and a masked nucleophilic functionality (CH2TMS) which can be activated by fluoride anion, was examined. As a result, in contrast to the case of parent naphthalenophanes wherein the smallest [2.2]naphthalenophane was obtained as the major product, only [2.2.2.2](2,7)‐1‐bromonaphthalenophane was obtained albeit in low yields, whereas the corresponding [2.2]‐ or [2.2.2]naphthalenophanes were not obtained. Though the [2.2.2.2]‐1‐bromonaphthalenophane can adopt four idealized geometries of different symmetry, among which three are inherently chiral, theoretical calculations predict that three conformers have almost equal energy and may equilibrate in solution. The X‐ray crystallographic study shows that it adopts a C2 conformation with anti,anti,anti orientation of the C−Br bonds at least as a major component in crystal.

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

“…There is also one report of methyltrimethylsilylation of naphthalene-2,7-diyl bis(diethylcarbamate) 242 ( Scheme 58 ). 308 This was carried out using [(trimethylsilyl)methyl]magnesium chloride in the presence of Ni(acac) 2 to form 243 , which was subsequently transformed into the unsymmetrical dibromide 244 , found to undergo cyclo-oligocondensation to form tetrameric [2.2.2.2]naphthalenophane 245 , potentially useful as a chiral host molecule (through modification of the bromine atoms by larger groups, suppressing ring inversion) or as a precursor to curved aromatic compounds via intramolecular C–C coupling reactions. Interestingly, there are no reports of CC between nonfused ArOAms and silylmagnesium reagents in the literature.…”