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Photochemical and Thermal Rearrangement of Acyl‐Substituted Quinone Methides, Accessible by Dimethyldioxirane Oxidation of Benzofurans and Subsequent Valence Isomerization of the Resulting Epoxides
Author(s) -
Adam Waldemar,
Sauter Markus
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931261220
Subject(s) - chemistry , isomerization , dimethyldioxirane , photochemistry , valence (chemistry) , quinone , benzofuran , tautomer , photoisomerization , thermal decomposition , organic chemistry , catalysis
The photoisomerization of quinone methides 3 to benzocycloheptafuran 4 and the thermolysis of the latter to xanthenes 5 are reported. The quinone methides 3 are accessible by dimethyldioxirane oxidation and subsequent valence isomerization of the resulting benzofuran epoxides 2 . On irradiation (λ > 400 nm), the quinone methides 3 rearrange by cyclization to the corresponding norcaradiene, and ring enlargement affords the benzocycloheptafurans 4 . Thermolysis of the cycloheptatrienes 4 leads to the xanthenes 5 , first by cycloreversion to the norcaradienes, followed by electrocyclization to the chromenes and tautomerization of the latter. The new cycloheptatrienes 4 and xanthenes 5 were fully characterized.