Synthesis 2005(9): 1445-1454  
DOI: 10.1055/s-2005-865316
PAPER
© Georg Thieme Verlag Stuttgart · New York

The Photo-Dehydro-Diels-Alder Reaction: An Efficient Route to Naphthalenes

Pablo Wessig*, Gunnar Müller, Andreas Kühn, Robert Herre, Haiko Blumenthal, Stefanie Troelenberg
Institut für Organische und Bioorganische Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin
Fax: +49(30)20937450; e-Mail: pablo.wessig@chemie.hu-berlin.de;
Further Information

Publication History

Received 10 March 2005
Publication Date:
18 April 2005 (online)

Abstract

The photo-dehydro-Diels-Alder reaction (PDDA), a new photochemical route to naphthalenes is presented. The [4+2] cycloaddition takes place between 3-arylynones and arylacetylenes, in which these moieties may be located in two molecules (intermolecular PDDA, 1) or in the same molecule (intramolecular PDDA, 5 and 9). Especially the latter approach is attractive from a preparative point of view and permits a straightforward access to highly functionalized naphthalenes. The irradiation of unsymmetrical reactants 9 provides, in contrast to symmetrical reactants 5, two isomeric naphthalenes. We found that the regioselectivity can be easily influenced by suitably located substituents in the aromatic rings and by blocking undesired positions. Notably, the PDDA may be used for the preparation of binaphthyls, as shown by the formation of 14 and 16. The mechanism of the PDDA was elucidated by spectroscopic analyses and theoretical (DFT) calculations.

4

The introduction of electron-donating groups, which facilitate oxidative degradation of aromatic rings, reduce the Norrish-Yang reactivity of corresponding ketones dramatically.1c,d

16

We thank Dr. B. Ziemer for performing the X-ray structure analysis of 16. Details of the structure investigation are available on request from the Cambridge Crystallographic Data Centre, on quoting the depository number CCDC 266349.