Synthesis 2007(9): 1426-1433  
DOI: 10.1055/s-2007-965998
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Photocycloaddition of 2,3-Dihydro-2,2-dimethyl-4H-thiopyran-4-one (a 4-Thiacyclohex-2-enone) to bona fide Triplet Quenchers. A Contradiction?

Paul Margaretha*, Kerstin Schmidt, Jürgen Kopf, Volker Sinnwell
Fachbereich Chemie, Universität Hamburg, M. L. King Platz 6, 20146 Hamburg, Germany
Fax: +49(40)428385592; e-Mail: Paul.Margaretha@chemie.uni-hamburg.de;
Further Information

Publication History

Received 11 January 2007
Publication Date:
23 March 2007 (online)

Abstract

2,3-Dihydro-2,2-dimethyl-4H-thiopyran-4-one undergoes regiospecific photocycloaddition to 2-chloroacrylonitrile as well as regio- and stereospecific photocycloaddition to ethylidenemalononitrile. On irradiation in the presence of either 2,3-di­methylbuta-1,3-diene or isoprene, the same enone affords mainly [2+2]-cycloadducts and only minor amounts of (stepwise) [2+4]-cycloadducts, whereas quantitative quenching is observed in the presence of 2,5-dimethylhexa-2,4-diene. In contrast, the corresponding pyran is almost quantitatively quenched in the presence of any of the enenitriles or dienes mentioned.

28

CCDC-633282 contains the supplementary crystallographic data for 5. This data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request.cif.

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CCDC-632623 contains the supplementary crystallographic data for 10. This data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request.cif.