Azulenylcarbene and naphthylcarbene isomerizations. Falling solid flash vacuum pyrolysis.
1-Azulenylcarbene 18 has been generated from 5-(1-azulenyl)tetrazole and the sodium salt of azulene-1-carbaldehyde tosylhydrazone using the falling solid flash vacuum pyrolysis (FS-FVP) method. The principal products, which are also formed from both 1- and 2-naphthylcarbenes, cyclobuta[de]naphthalene 6, cyclopenta[cd]indene 16, and benzofulvenallene 17, are explained in terms of two reaction paths, (a) a rearrangement to benzofulvenyl-7-carbene 13 and (b) a rearrangement to 1-naphthylcarbene 1. Moreover, 16 is also formed from 2-azulenylcarbene 30, thereby indicating the occurrence of a 2-azulenylcarbene-1-azulenylcarbene rearrangement. The reaction mechanisms are supported by density functional theory calculations at the B3LYP/6-31G** level, which indicate that all the rearrangements have activation barriers of <35 kcal/mol, thus making them readily achievable under FVP conditions.
†School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
David
D
Kvaskoff
‡Fachbereich Chemie der Philipps-Universität Marburg, D-35037 Marburg, Germany.
Jürgen
J
Becker
†School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.|‡Fachbereich Chemie der Philipps-Universität Marburg, D-35037 Marburg, Germany.
Curt
C
Wentrup