3, 5-di-tert-butyl-o-benzoquinone

The development of catalysts for the efficient oxidation of catechol and its derivatives in water is topic of ongoing work in this laboratory. Towards this end, polyethylene glycol side-chains were incorporated in a pentadentate salen ligand to enhance the water solubility of the complexes derived thereof. A dinuclear copper(II) complex is found to catalyze the oxidation of 3,5-di-tert.-butylcatechol into 3,5-di-tert-butyl-o-benzoquinone more than twice as fast in aqueous organic solution as in purely organic solvents (ly,at/knon= 140,000). Preliminary data are discussed. 

Oxidation of 3,5-di-tert-butyl catechol to 3,5-di-tert-butyl-o-benzoquinone by 02 is catalyzed by the Ir111 catecholate complex (124).212 The authors suggest that formation of the dioxygen adduct, as in reaction Scheme 16, is an important step in the process. 

In the reaction of Mes2Ge = NS02PhMe 137 with 3,5-di-tert-butyl-o-benzoquinone, a single electron transfer process was evidenced by an ESR study, as well as by the characterization of isobutene. The initially formed o-semiquinonic species could afford the dimesitylgermadioxolane 148 according to two different pathways590 (Scheme 27). 

Scheme 10. The proposed catalytic cycle for the selective oxidation of 3,5-di-ier<-butylcatechol to 3,5-di-tert-butyl-o-benzoquinone.

C14H17N04 DL-5-benzoylamino-5-isopropyl-4-oxo-1,3-diox 51127-25-4 25.00 1 1790 2 27599 C14H20O2 3,5-di-tert-butyl-o-benzoquinone 3383-21-9 25.00 0.9953 2... 

The uv-vislble absorption spectra for the anion radical products were compared with those for the products from controlled potential electrolytic reduction of 3,5-di-tert-butyl-o-benzoquinone (Xmaxz 340 and 380 nm), dehydroascorblc acid (Xmax/ 360 nm), phenazine, lumiflavin (Xmax, 420 nm), and azobenzene (Xmax 410 nm). 

Di-tert-butyl-o-benzoquinone [3383-21-9] M 220.3, m 112-114, 113-114. It can be recrystallised fiom MeOH or petroleum ether, and forms fine red plates or rhombs. [Flaig et al. Justus Liebigs Ann Chem 597 196 1955, IR Ley Muller Chem Ber 89 1402 1956, Beilstein 7 IV 2113 ]... 

The redox potentials for several quionones (Q 3,5-di-tert-butyl-o-quinone, o-benzoquinone, p-benzoquinone, and tetrafluoro-o-benzoquinone), their semi-quinone anion radicals (SQ- -) and their fully reduced forms [catechols (H2Cat) and catechol anions (HCat-)] in four aprotic solvents [acetronitrile (AN), di-methylformamide (DMF), dimethylacetaminde (DMA), and dimethyl sulfoxide (Me O)] are summarized in Table 12.2.12... 

To our knowledge, the first examples of asymmetrically substituted monocyclic phosphoranes are 60 and 61, described by Moriarty et al.135 and involving the reaction of a substituted o-benzoquinone136,137 (Scheme 6) on an aminophosphine (59), itself obtained by alcoholysis of 58 with l-( — )-menthol. In contrast to the amino phosphine 53 (Scheme 5), 59 is a mixture of the diastereoisomers 59a and b, and its reaction with 3,5-di-tert-butyl-l,2-benzoquinone yields two diastereoisomeric phosphoranes, 60a and b. Finally, alcoholysis of the P(V)—NR2 bond138 in 60a and b leads to 61a and b or 62. 

Complex 218 could oxidize rapidly and almost quantitatively (>95%) 2,4-di(tert-butyl)phenol (216) and 3,5-di(ferf-butyl)catechol (219) at —80°C to the corresponding biphenyl and o-benzoquinone (217 and 220), respectively. 

Yamamura comprebensively reviewed stoicbiometric oxidations of phenols with both metal (VjOg, VOClj, MnOj, CrOj, MoOCl, Tl O, Ag O) and nonmetal compounds (hypervalent iodobenzenes, 2,3-dichloro-5,6-dicyano-/)-benzoquinone, dioxirane, di-tert-butyl peroxide, di-ferf-butyl peroxyoxalate) [57]. Some of these reagents, for example, metal-free PhI(OAc)j and PhI(OCOCF3)j, seem to be rather safe and are especially useful in the low-scale synthesis of complex molecules of natural products. However, one should remember that none of the stoichiometric oxidations is compatible with the concept of green chemistry because such processes produce vast amounts of effluents, which are difficult to dispose of. For example, the active oxygen content in bis(trifluoroacetoxy)iodobenzene is only 3.8%, and a typical E-factor for oxidations with this oxidant lies in the range of 15-25. 

In contrast to o-phenylenediamines, l,8,naphthylenediamine and most of its derivatives react with 2,6-di-tert-buty 1-1,4-benzoquinone to give perimidinespirocy-clohexadienone 11 (Scheme 5).4,6-8 The reaction occurs readily under noncatalytic conditions when refluxing propanol or toluene solutions of the components. By contrast, catalysis of the reaction with strong proton acids (e.g., /Hoi ucncsul Ionic acid) is necessary for the preparation of 2,3-dihydro-2-spiro[4(4//)-2-fert-butyl-l-naphthalenone pcrimidine 4 when 2,6-di- fcrt-buty 1-1,4-benzoquinonc is replaced in this reaction by 2-fert-butyl- 1,4-naphthoquinone. 9... 

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