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Die Protonierung von 1‐Formyl‐ und 1‐Acetyl‐azulenen
Author(s) -
Meuche Doris,
Dreyer D.,
Hafner K.,
Heilbronner E.
Publication year - 1967
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19670500425
Subject(s) - chemistry , protonation , azulene , conjugate , steric effects , stereochemistry , group (periodic table) , planar , methyl group , medicinal chemistry , photochemistry , organic chemistry , ion , mathematical analysis , computer graphics (images) , mathematics , computer science
Abstract NMR. data show that protonation of 1‐formyl‐azulene yields essentially a one‐to‐one mixture of conjugate acids in which the hydroxyl group assumes the syn ‐planar or anti ‐planar configuration relative to the tropylium nucleus. The presence of a minute amount of protonation in position 3 is demonstrated by the rapid hydrogendeuterium exchange in this position. Steric interference in 1‐formyl‐azulenes with a methyl group in the peri position 8 favours the anti ‐planar configuration. As shown by one example, the conjugate acids of 1‐acetyl‐azulenes without substituents in positions 2 or 8 assume the anti ‐planar configuration. In 1‐acetyl‐azulenes carrying a methyl group in position 8, addition of a proton to the carbon centre 1 is the preferred route of protonation, as a consequence of the accompanying strain release.