Radical addition to 1,4-benzoquinones: addition at O- versus C-atom.

Addition of alkyl radicals generated from B-alkylcatecholboranes onto 1,4-benzoquinones leads to substituted hydroquinones in good overall yields. Formation of aryl ethers via a unique radical addition to the oxygen atom of the enone system is the main reaction when bulky secondary and tertiary alkyl radicals are used. Less hindered secondary and primary radicals give the expected 1,4-conjugate addition products. [reaction: see text]