Facile syntheses of 2,4,6-cycloheptatrienyl ketones

Abstract

The synthesis of the 2,4,6-cycloheptatrienyl ketones 1a – 1e by two alternative routes is reported: Route 1): The adducts 3a–c from the phenyl(trimethylsiloxy)-acetonitriles 2a–c , known as “umpolung” reagents, and tropylium tetrafluoroborate are cleaved by triethylammonium fluoride to form the aromatic cycloheptatrienyl ketones 1a – 1c . Route 2): the phenyl, methyl, and cyclopropyl ketone ( 1a , 1d , 1e ) are prepared by treatment of the acid chloride 7 with the corresponding organomanganese iodides RMnI ( 8a , 8d , 8e ). The Fe-catalyzed coupling reaction of the acid chloride 7 with a Grignard reagent was also used for the preparation of ketone 1b .