Benzocyclobutenes Benzocyclobutenols

The diazotization of anthranilic acid, a classic route to benzyne, when carried out in the presence of vinyl acetate, vinyl ethers or 1,1-dichloroethylene gives the expected benzocyclobutenes in about 40% yield. Despite the rather moderate yields this method represents a convenient route to multigram quantities of the parent compounds, benzocyclobutenol and benzocyclobutenone. The latter is easily converted to benzocyclobutene-1,2-dione. The diazotization sequence applied to 2-amino-3,6-dimeth-oxybenzoic acid and 1,1-dichloroethylene results in a 80% yield of 3, imethoxycyclobuten-l-one. Trapping of benzynes with other ethylene derivatives, and especially more substituted alkenes, has given generally poorer, variable results. ... 

Intramolecular cyclizations via aryl anions have been used to prepare benzocyclobutenes (138) from o-bromo-3-phenethyl bromides and benzocyclobutenols (139) from o-bromostyrene oxides. ... 

Whereas trmajor product (33 %), caryophyllene and cis-cyclononenes give only ene reactions. Benzocyclobutenols are among the products of addition of benzyne to cyclic enolates, as shown in Scheme 25. ... 

---