Reinvestigation relative to the regioselectivity of the aryne cycloaddition. Synthesis of the tricyclo[6.2.0.02,5]-1,5,7-triene-3,10-dione

A rapid and total synthesis of a tricyclo[6.2.0.0]deca-1,5,7-triene-3,10-dione 7b is described. Its synthesis involves the [2+2] cycloaddition of a benzyne to 2-methylene-1,3-dioxepane followed by hydrolysis to the corresponding ketone. This reaction is totally regioselective and the real structure of the molecule is given thanks notably to the X-ray crystal structure of the intermediate benzo-bis-cyclobutene.