New Syntheses of Benzobarrelenes

Article abstract of DOI:10.1021/jo00085a024

New syntheses of both substituted and unsubstituted benzobarrelenes are described.Treatment of 3,5-cyclohexadiene-cis-1,2-diol with benzaldehyde dimethyl acetal 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.