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Novel Concepts in Directed Biaryl Synthesis, XXXVIII. Synthesis and Structure of a Protected Lactolate‐Bridged Biaryl with Relevance to the Atropisomer‐Selective Ring Opening of Biaryl Lactones
Author(s) -
Bringmann Gerhard,
Schöner Bernd,
Peters Karl,
Peters EvaMaria,
von Schnering Hans Georg
Publication year - 1994
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199419940418
Subject(s) - chemistry , atropisomer , steric effects , ring (chemistry) , stereochemistry , ether , lactone , crystallography , organic chemistry
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 give the substituted pyrylium salt 6a and subsequent reaction with methanolate. Attempts to similarly prepare the more strained higher homologous 5 , i.e. with a higher steric hindrance next to the biaryl axis, failed. Structural information on 5a could be obtained through X‐ray crystallography, but no decoalescence was observed in the low‐temperature NMR spectrum.