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A rhodium(II)‐catalyzed asymmetric cyclooligomerization of bifunctional monomers possessing triazolyl and vinyl groups at 2,3‐ and 3,4‐positions on the thiophene ring is studied. Structurally interesting cyclic dimers in which thienylene and cyclopropylene units are alternately connected are obtained as the major components. The eight‐membered rings in the center are non‐planar and adopt a tub‐shaped conformation. We also observe the phenomenon of racemization caused by a tub‐to‐tub ring‐flipping, the activation energy of which is determined as 108 kJ mol−1 by electronic circular dichroism spectra measurement. [ABSTRACT FROM AUTHOR]

An chiral RhII‐catalyzed cyclooligomerization reaction of thiophenes having triazolyl and vinyl substituents at the 2‐ and 4‐positions was studied. Structurally interesting cyclic trimers, having chirality that is ascribed only to the orientation of the 2,4‐disubstituted thiophene rings, are obtained. The 2,4‐disubstitution of the starting thiophene monomer allows production of each of the enantiomers. The observed electronic circular‐dichroism spectra are in accord with those simulated by density‐functional theory calculations. [ABSTRACT FROM AUTHOR]