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

✍ Scribed by Bringmann, Gerhard ;Hartung, Thomas ;Göbel, Lothar ;Schupp, Olaf ;Peters, Karl ;von Schnering, Hans Georg

Publisher: John Wiley and Sons
Year: 1992
Tongue: English
Weight: 659 KB
Volume: 1992
Category: Article
ISSN: 0947-3440
DOI: 10.1002/jlac.1992199201127

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✦ Synopsis

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.

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## Abstract The preparation and crystal structure of the __O__‐methyl‐protected analog 5 of a lactolate‐type intermediate 3 in the atropisomer‐selective ring opening of configuratively unstable lactone‐bridged biaryls 1 is described. Thus, 5a could be prepared by oxidation of the cyclic ether 7a to