New Syntheses of Benzobarrelenes
New syntheses of both substituted and unsubstituted benzobarrelenes are described. Treatment of 3,5-cyclohexadiene-cis-1,2-diol with benzaldehyde dimethylacetal in the presence of a catalytic amount of p-toluenesulfonic acid gave 1,2-(benzylidenedioxy)-3,5-cyclohexadiene(2). Addition of benzynes to 2 provided 3 and 4. Treatment of 3 and 4 with excess LDA and potassium tert-butoxide afforded benzobarrelenes 1 and 5 in good yields.
© 1994 American Chemical Society. Received October 18, 1993. This work was supported by the Air Force Office of Scientific Research (AFOSR-88-0094). We thank Dr. Andy Muir of ICI Specialties and ICI Chemicals and Polymers, Runcorn, UK, for providing 3,5-cyclohexadiene-cis-1,2-diol.