Ring contraction during the 6π-electrocyclisation of naphthopyran valence tautomers

CD Gabbutt, BM Heron, SB Kolla, C Kilner…

Index: Gabbutt, Christopher D.; Heron, B. Mark; Kolla, Suresh B.; Kilner, Colin; Coles, Simon J.; Horton, Peter N.; Hursthouse, Michael B. Organic and Biomolecular Chemistry, 2008 , vol. 6, # 17 p. 3096 - 3104

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Citation Number: 16

Abstract

The thermal and photochemical ring-opening of spiro (3H-naphtho [2, 1-b] pyran-3, 9′- thioxanthene-10, 10-dioxide) 3 results in the facile ring-contraction to 9-(naphtho [2, 1-b] furan-2-yl)-9H-thioxanthene-10, 10-dioxide 6. Similar behaviour is displayed by the isomeric spiro (2H-naphtho [1, 2-b] pyran-2, 9′-thioxanthene-10, 10-dioxide) 9 affording 9-(naphtho [1, 2-b] furan-2-yl)-9H-thioxanthene-10, 10-dioxide 12, though more severe reaction ...