Preparation of isobenzofurandiones by flash vacuum pyrolysis involving retro-Diels–Alder expulsion of ethylene and concomitant C–O cleavage of methoxy or ethylenedioxy groups

Flash vacuum pyrolysis (fvp) of a number of substrates, prepared by hydrogenating adducts derived from dimethoxy- or ethylenedioxy-substituted benzynes and furan, affords isobenzofurandiones through retro-Diels–Alder expulsion of ethylene and C–O bond cleavage of the methoxy or ethylenedioxy groups. The parent isobenzofuran-4,5-dione is reactive and undergoes two-fold conjugate addition of water to afford 3,4-dihydroxybenzene-1,2-dicarboxaldehyde.