3,3',5,5'-tetra-tert-butyldiphenoquinone, DPQ
The organic oxidant 3,3',5,5'-tetra-tert-butyldiphenoquinone (DPQ) is commercially available and can also be readily prepared by oxidation of the inexpensive o,o'-di-tert-butylphenol. DPQ is a two electron acceptor that forms o,o'-di-tert-p-bisphenol as product, which can easily be separated. Reoxidation using oxygen in the presence of base is possible in near quantitative yields, which means, that O2 can formally be considered as the terminal oxidant in these reactions. (M. S. Kharasch, B. S. Joshi, J. Org. Chem. 1957, 22, 1439. DOI)
Compared with benzoquinone, one of the advantages is the non-nucleophilic character of the reaction product. Thus, DPQ can be used in reactions with electrophiles without any interference.
Recent Literature
Cooperative carbene catalysis allows selective oxidative acylations of
alcohols with aldehydes even in the presence of amino groups by using a readily
available cheap organic oxidant. Quantum chemical calculations support the
suggested mechanism.
S. De Sarkar, S. Grimme, A. Studer, J. Am. Chem. Soc., 2010,
132, 1190-1191.
A N-heterocyclic carbene catalyzes the oxidative esterification of various
aldehydes in the presence of 3,3',5'5-tetra-tert-butyldiphenoquinone to
yield hexafluoroisopropylesters, which are useful active esters for in situ
amide bond formation. This transition metal-free organocatalytic system also
enabled a mild oxidative azidation of aldehydes.
S. De Sarkar, A. Studer, Org. Lett., 2010,
12, 1992-1995.
S. De Sarkar, A. Studer, Org. Lett., 2010,
12, 1992-1995.
A broad range of functionalized Grignard compounds were coupled by using
diphenoquinone as an electron acceptor. The oxidative dimerization of
alkenylmagnesium reagents proceeds with complete retention of the
stereochemistry.
A. Krasovskiy, A. Tishkov, V. del Amo, H. Mayr, P. Knochel, Angew. Chem. Int. Ed., 2006,
45, 5010-5014.
