Strategy for the Synthesis of Tube‐Shaped Molecules

The conformationally flexible “molecular tube” 1 a was prepared by cyclization of the corresponding [3.3]phane according to the dilution principle. The formation of isomer 1b with a crossed arrangement of the phane units can be ruled out on the basis of NMR results and mechanistic considerations. The cavity in 1a has enough space to accommodate molecules the size of benzene.