DDQ as an oxidant

One of the limitations of the copper- and indium-catalyzed oxidative alkylation protocol is the use of a relatively reactive malonate. Li found that simple ketones 16 can undergo oxidative alkylation reactions with benzyl ethers 36 by using DDQ as an oxidant at high temperatures (Scheme 23) [40]. 

A nice feature of reductive as well as oxidative coupling reactions has been presented recently in the synthesis of quateranthene 132 (Scheme 32) [82]. After addition of the lithiated species of 128 into the bianthrone and dehydrogenation, base induced cyclization gave the intermediate 130. Grignard addition to the ketone and subsequent reduction delivers 131, which was then fully aromatized by a Scholl-reaction involving DDQ as an oxidant in the presence of Sc(OTf)3. 

Musgrave and Buchan developed a procedure for the preparation of triphenylene-l,4-quinones from 2,3-diaryl-l,4-benzoquinones using an acid-catalyzed intramolecular Scholl reaction. Using the 2,3-diaryl-1,4-benzoquinone 17, the AlCls-mediated cyclization occurred to afford a quinol intermediate that was then oxidized in the presence of FeCb to afford the triphenylenequinone 18 in moderate yield under mild reaction conditions. Inclusion of 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) as an oxidant has also been shown to increase the yield of the reaction up to 50%. 

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