Generation and cycloaddition of o-quinodimethane in aqueous medium

Abstract

o-Quinodimethane can be generated from α,α′-dihalo-o- xylenes using zinc in aqueous solution. In the presence of activated dienophiles cycloadducts can be obtained directly. Catalysis with tris-triphenylphosphine ruthenium(II) dichloride reduces side reactions such as reduction and polymerisation and improves the yield. This is the first example of an organometallic cyclisation in aqueous medium using dihalo compounds.