Synthesis of a Double-Spanned Resorc[4]arene via Ring-Closing Metathesis and Calculation of Aggregation Propensity

Ring-closing metathesis (RCM) catalyzed
by a second-generation
Grubbs catalyst has been used to synthesize resorc[4]­arenes 2b–5b starting from undecenyl resorc[4]­arene 1b fixed in the cone conformation. X-ray diffraction analysis
of the major metathesis product, 3b (50% yield), revealed
a cavity-shaped architecture resembling a basket, endowed with a large
intramolecular space (∼10 Å) and a strong propensity to
self-assemble as a supramolecular trio of heterochiral dimers. This
prompted us to investigate the aggregation propensity of basket 3b in THF/water solution by UV–visible spectroscopy.
The cavitation Gibbs free-energy change (ΔΔGcav = 4.78 kcal mol–1) associated with
the self-assembly of macrocycle 3b was calculated as
a measure of the solvophobic interactions involved in the process.