Synthesis, Structure, and Dynamics of Chiral Eight‐Membered Cyclic Molecules with Thienylene and Cyclopropylene Units Alternately Connected.

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]