Triaryl Substituted Divinyl Ketones Cyclization: Nazarov Reaction versus Friedel Crafts Electrophilic Substitution.
The acid catalyzed cyclization of a wide range of triaryl substituted divinyl ketones has been studied. It was found that the reaction pathway strongly depends on the nature of the aryl substituent at the a position to the carbonyl group. An electron rich aromatic substituent promotes the reaction to proceed through the intramolecular Friedel Crafts electrophilic substitution giving dihydronaphthalene derivatives. In contrast, the presence of an electron deficient substituent is favorable for the Nazarov 4p conrotatory cyclization yielding triaryl substituted cyclopentenones. The electrophilic substitution reaction was applied to thiophene and thiazole derivatives.
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