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Novel concepts in directed biaryl synthesis, XXXVII. Synthesis and enantiomerization of a nonracemic 2‐hydroxy‐2′‐biarylcarbaldehyde, a probable intermediate in the atropo‐enantioselective ring opening of biaryl lactones
Author(s) -
Bringmann Gerhard,
Hartung Thomas
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.199419940314
Subject(s) - chemistry , enantioselective synthesis , isomerization , ring (chemistry) , stereochemistry , lactol , optically active , lactone , organic chemistry , catalysis
Abstract The directed preparation of a “free”, i.e. nonprotected biaryl with a phenolic OH function and a formyl group in opposite ortho positions, in a nonracemic form, is described. The free activation barrier ΔG ≠ for the atropisomerization, which was determined to be 99.2 kJ mol −1 , is far lower than expected for an exclusively physical rotation process and is more likely in agreement with an isomerization via lactol‐type cyclic intermediates previously postulated.