Premium
Bimolecular Formation of Radicals by Hydrogen Transfer, 13. Uncatalyzed Transfer Hydrogenation of Azulene and the Initiation of the Azulene‐Naphthalene Rearrangement
Author(s) -
Keller Friedrich,
Beckhaus HansDieter,
Rüchardt Christoph
Publication year - 1997
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199719971008
Subject(s) - azulene , chemistry , tetralin , anthracene , naphthalene , photochemistry , radical , reaction mechanism , hydrogen atom , diphenyl ether , hydrogen , organic chemistry , catalysis , alkyl
From the uncatalyzed transfer‐hydrogenation of azulene 1 with the hydrogen donors 9,10‐dihydroanthracene ( 4 ), 7 H ‐benz[ de ]anthracene ( 5 ) and 9,9‐diphenyl‐10,10‐dideuteroanthracene ( 6 ) at 340–375°C in diphenyl ether, two isomeric octahydroazulenes and, in addition, naphthalene and tetralin are obtained. From product studies, kinetics, isotopic labelling experiments and semiempirical MO calculations, a nonchain stepwise radical mechanism is proposed, which is initiated by H‐atom transfer from the donor to azulene. The proposed mechanism for the formation of naphthalene and tetralin via azulene‐naphthalene rearrangement under these conditions is a combination of the Scott mechanism and the Alder “walk” mechanism, which are initiated by the hydrogen‐transfer step.