Alkyl‐1,4‐Benzoquinones – From Synthesis to Application

Abstract

Alkyl-1,4-benzoquinones (ABQs) such as 2,3-, 2,5-and 2,6-dimethyl-and 2,6-di-tert-butyl-1,4-benzoquinones are versatile building blocks and also have many others applications known for this type of compounds. Nowadays the requirements of environmental safety necessitate revising preparation processes of such compounds and searching for alternative synthesis ways. Until recently, there have been many efforts to develop sustainable green processes. However, the efficiency of proposed methods differs significantly. For this reason, in this review we would like to outline a variety of chemical properties of ABQs in order to show their great potential as chemical precursors, to describe some interesting applications of ABQs and then to give description of existing ABQ synthesis procedures developed in the last few decades. The review summarizes advances in liquid-phase selective oxidation of alkylphenols with molecular oxygen, hydrogen peroxide, and t-butyl hydroperoxide by using both homogeneous and heterogeneous catalysts. Consideration of old methods for ABQ synthesis is of interest for understanding the evolution of preferences in the field and for comparing the efficiency of methods.Benzoquinones are a versatile class of compounds possessing several sites of potential reactivity, viz. C = C and C = O. Owing to this feature, they may enter into various reactions such as amination, acylation, alkylation and arylation as well as cycloaddition, changing and modifying their structures. [3] Let us give some examples below.Nair et al. demonstrated that zwitterionic species generated by adding cyclohexyl isocyanide [4] or isoquinoline [5] to dimethyl acetylenedicarboxylate can react with C = O bond of quinones, giving iminolactones [Reaction (1)] and derivatives of isoquinoline [Reaction (2)].

Oxidative cleavage of lignin model substrates with Co(salen) catalyst: an experimental study on the effect of different reaction parameters in batch and continuous flow

“…[11][12][13][14] Latter benzoquinones can be used for the synthesis of anthraquinones through diels-alder reaction (H 2 O 2 production), 15 precursor for hydroquinones (polyether ether ketone synthesis), 16 polyaminoquinones (coatings, adhesion agent) 17 or as high value intermediate for other applications. 18 The proposed mechanism of the oxidation starts with the activation of the Co(salen) complex with triplet oxygen, forming a Co(III) superoxo complex, which will initiate the reaction (Scheme 1, a). Initial coordination of O 2 typically requires the presence of a coordinating base as an axial ligand, for example, pyridine, to form the superoxo complex.…”

Selective oxidation of substituted phenols with Co–N–C catalysts fabricated via low temperature heat treatment

“…Alkyl-1,4-benzoquinones are employed in many key processes as synthetic intermediates. 9 Among the industrially relevant quinones is 2,3,5-trimethyl-1,4-benzoquinone (TMBQ), one of the key intermediates for the synthesis of vitamin E. 10 More than 80% of vitamin E compounds in the market are artificially synthesized, and are known as important lipid-soluble antioxidants in biological systems. 11 Efficient selective oxidation of 2,3,6-trimethylphenol (TMP) into TMBQ is of continuing economic interest, because of the ready availability of inexpensive TMP.…”

Electrochemical oxidation of phenols in flow: a versatile and scalable access topara-benzoquinones

“…Benzoquinones represent a versatile class of compounds with manifold fields of applications. [1][2][3] They are ubiquitous in nature and play crucial roles in biological redox processes, making them pivotal for life. 4,5 Moreover, their unique redox properties often equip them with remarkable biochemical activity (Scheme 1).…”