In 1968, we reported that l-and 3-arylpropanes were readily oxidized by DDQ to give reactive intermediates which could be directly converted to a variety of products.
1 Shortly thereafter, Sadler and Stewart2 described the conversion of several arylpropenes to aldehydes by excess DDQ. In this report, we wish to define the structure of the unstable intermediate formed from arylpropenes and DDQ, and the mechanism by which they are converted to aldehydes. Addition of 0.025 mole of 1-R-methoxyphenylpropene (anethole) to 0.025 mole of DDQ in 250 ml of benzene produces an intensely colored molecular complex which fades to a yellow solution within one minute, with concomitant precipitation of 0.0125 mole (50%) of 2,3dichloro-5,6-dicyanohydroquinone (DDRQ), identified by ir, uv, nmr, and mass spectra and by conversion to the diacetate, m.p. 182-1830. 3 Removal of even part of the solvent at this point gives only polymer; however the product can be stabilized by addition of dioxane (50 ml) and washing with water (5 x 50 ml), after which the solvent may be safely removed & vacua. Brief trituration of the solid residue with ice-cold methanol4 gives a 55% yield of crude material which on repeated recrystallieation from dioxane-hexane (1:3) gives material of constant melting point (124O), identified as 2,3-dichloro-5,6-dicyanohydroquinone bis-(3-P-methoxyphenyl-trans-2-propenyl) ether (I) from the following evidence: CN CN CH30 @ CU=CR-CH2-0 -@ 0-CR2CB=C"+R3 4851