ORGN 31 |
Benzocycloheptynes by intramolecular Nicholas reactions
| James R. Green and Yu Ding. Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Ave., Windsor, ON N9B 3P4, Canada |
| A reliable method for the synthesis of hexacarbonyldicobalt complexes of benzocycloheptynes has been investigated. Preparation of the precursor aryl and heteroaryl enyne propargyl acetate complexes 1 may be accomplished by the stereoselective palladium catalyzed reduction of a variety of arylaldehyde dibromoalkene derivatives 2, with subsequent Sonogashira coupling and complexation reactions. Formation of the benzocycloheptyne complexes 3 then occurs upon Lewis acid mediated Nicholas reactions of 1. Dibenzocycloheptyne complexes 4 also may be prepared by an analogous intramolecular Nicholas reaction. The effect of susbtituents on the aromatic ring on the facility of the cyclization process will be discussed, along with attempts at reductive removal of the dicobalt hexacarbonyl unit. 
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