✍ Scribed by Schätz, Rolf ;Weber, Christian ;Schilling, Gerhard ;Oeser, Thomas ;Huber-Patz, Ursula ;Irngartinger, Hermann ;von der Lieth, Claus-W. ;Pipkorn, Rüdiger
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A series of ten inverse calix[n]arenes (2–11) bearing four to thirteen benzene units were prepared by starting from 3,4,5‐trimethoxybenzaldehyde followed by LC separation on silica gel. In 2–11 the substitution pattern is interchanged compared with the usual calixarenes. The conformational analysis was undertaken by variable temperature ^1^H‐NMR spectroscopy and by MM2 calculations. Calix[4]arene 2 is a rigid molecule and shows the 1,3‐alternate conformation which in addition was proven by X‐ray analysis. At low temperatures the calix[5]arene 3 adopts the uudod conformation, where a methyl group of one benzene unit residues in the cavity of the macrocycle. At low temperature calix[6]arene 4 forms an 1:2 equilibrium between the 1,3,5‐alternate (ududud; 4E) and the uududu (4B) conformation. Conformation 4B can be regarded as an intramolecular combination of a cone and an alternate arrangement of the benzene units. The calix[8]‐arene shows the highest Δ__G__* value of the series and adopts an uuududdd conformation at low temperature. The inverse calixarenes 5 and 7–11 bearing seven and nine to thirteen aromatic units, respectively, are conformationally highly flexible systems even at low temperatures.
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## Abstract Hydroxy[3.1.1]metacyclophane 4c, which is regarded as an unsymmetric or uncomplete “homocalixarene” bearing a propane bridge, has been synthesized using Nafion‐H catalyzed cyclobenzylation. A novel “pendulum” type motion steered by intramolecular hydrogen bonding has been observed Demet