Electrophilic Spirocyclization of a 2‐Biphenylacetylene via Conformational Fixing within a Hollow‐Cage Host

摘要

Abstract A 2‐biphenylacetylene was fixed into a specific conformation within the confined cavity of a hollow cage, where it underwent a regioselective spirocyclization in the presence of an electrophile. A 5‐endo‐dig cyclization proceeded selectively in the cage, which stands in sharp contrast to the 6‐endo‐dig cyclization that normally occurs in common organic media. The folded conformation adopted by the substrate within the cage was examined by 1H NMR spectroscopy and X‐ray crystallographic analysis.