Novel Concepts in Directed Biaryl Synthesis, XVI. Synthesis and Structure of Benzonaphthopyrans; Helically Distorted, Bridged Biaryls with Different Steric Hindrance at the Axis

Abstract

Abstract A simple two‐step synthesis of a series of ether‐type bridged biaryls 3 , as favorable models for studies of helimerization processes, is described. Starting from the known corresponding lactones 1 , a variety of differently substituted representatives 3 is prepared, greatly varying by the degree of steric hindrance and thus molecular distortion. NMR spectroscopy and especially X‐ray diffraction reveal the ethers 3 to be helically distorted, depending on the size of the ortho substituents R.