Issue 13, 2010
From the journal:

Organic & Biomolecular Chemistry

Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions†

Michael Black,a   J. I. G. Cadogan*b  and  Hamish McNab*a  

* Corresponding authors

a School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, UK
E-mail: H.McNab@ed.ac.uk
Fax: +44 131 650 4743
Tel: +44 131 650 4718

b Department of Chemistry, University of Wales Swansea, Swansea, UK

Abstract

Flash vacuum pyrolysis (FVP) of aryl 2-(allyloxy)benzoates 5 and of the corresponding aryl 2-(allylthio)benzoates 6 at 650 °C, gives dibenzofurans 19 and dibenzothiophenes 20, respectively. The mechanism involves generation of phenoxyl (or thiophenoxyl) radicals by homolysis of the O-allyl (or S-allyl) bond, followed by ipso attack at the ester group, loss of CO2 and cyclisation of the resulting aryl radical. Synthetically, the procedure works well for p-substituted substrates, which lead to 2-substituted dibenzofurans 19b–f (73–90%) and dibenzothiophenes 20b–c (90–94%). Little selectivity is shown in the cyclisation of m-substituted substrates and competing interactions of the radical with the substituent—and ipso-attack—complicate the pyrolyses of o-substituted substrates. FVP of related radical precursors including 2-(allyloxy)phenyl benzoates 43 gave no dibenzofurans, whereas 2-(allyloxy-5-methyl)azobenzene 44 gave a much reduced yield. No carbazoles were obtained by FVP of 4-methylphenyl 2-(allylamino)benzoate 42.

Graphical abstract: Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions

About
Cited by
Related
Download options Please wait...

Supplementary files

Article information

DOI
https://doi.org/10.1039/C002480E
Article type
Paper
Submitted
10 Feb 2010
Accepted
06 Apr 2010
First published
11 May 2010

Org. Biomol. Chem., 2010,8, 2961-2967

Permissions

Request permissions

Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions

M. Black, J. I. G. Cadogan and H. McNab, Org. Biomol. Chem., 2010, 8, 2961 DOI: 10.1039/C002480E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements