A brief and mild method for the generation of Benzofuran-2,3-xylylene in solution

Benzofuran-2,3-xylylene 3b (2,3-dimethylene-2,3-dihydrobenzofuran) can be generated at -4-degrees-C in acetonitrile by treatment of 2-acetoxymethyl-3-triisopropylsilymethylbenzofuran (7b), available from 3-methylbenzofuran-2-carboxylic acid dianion (5) in two steps, with tetrabutylammonium fluoride. Trapping the xylylene 3b in situ using reactive Diels-Alder dienophiles gives high yields of the adducts 8 (2-substituted or 2,3-disubstituted 1,2,3,4-tetrahydrodibenzofurans).