Secondary quinone

M.L. Paddock, S.H. Rongey, G. Feher, and M.Y. Okamura, Pathway of proton transfer in bacterial reaction centers replacement of glutamic acid 212 in the L subunit by glutamine inhibits quinone (secondary acceptor) turnover, Proc. Natl. Acad. Sci. USA 86 6602 (1989). 

Oxidation H ir Colorant. Color-forming reactions are accompHshed by primary intermediates, secondary intermediates, and oxidants. Primary intermediates include the so-called para dyes, -phenylenediamine, -toluenediamine, -aminodiphenylamine, and p- am in oph en o1, which form a quinone monoimine or diimine upon oxidation. The secondary intermediates, also known as couplers or modifiers, couple with the quinone imines to produce dyes. Secondary intermediates include y -diamines, y -aminophenols, polyhydroxyphenols, and naphthols. Some of the more important oxidation dye colors are given in Figure 1. An extensive listing is available (24,28). 

Rifamycin S also undergoes conjugate addition reactions to the quinone ring by a variety of nucleophiles including ammonia, primary and secondary amines, mercaptans, carbanions, and enamines giving the C-3 substituted derivatives (38) of rifamycin SV (117,120,121). Many of the derivatives show excellent antibacterial properties (109,118,122,123). The 3-cycHc amino derivatives of rifamycin SV also inhibit the polymerase of RNA tumor vimses (123,124). 

E) coumarins, (F) quinones, (G) flavonoids, (H) tannins, (I) alkaloids, (J) terpenoids and steroids and (K) miscellaneous and unknowns. Although many of these compounds are secondary products of plant metabolism, several are also degradation products which occur in the presence of microbial enzymes. 

Arcmatic compounds phenols, phenolic acids, cinnamic acid derivatives, coumarins, flavonoids, quinones, and tannins, all of which are aromatic compounds, comprise the largest group of secondary plant products. They are often referred to as "phenolics" and have been identified as allelopathic agents in more instances than all of the other classes of compounds combined 5). 

The origin of many of the components of black tea aroma has been studied. Aldehydes are produced by catechin quinone oxidation of amino acids. Enzymic oxidation of carotenoids during manufacture generates ionones and their secondary oxidation products such as theaspirone and dihydroactinidolide. Oxidation of linoleic acid is responsible for the formation of trans-2-hexenal.82... 

J.R. Bolton If the electron reaches the quinone via the linkage, then the transfer must involve the molecular orbitals of the linking structure and thus the solvent will have only a secondary effect. If the electron transfer occurs through the solvent, then the solvent should have a first-order effect on the rate. 

OxidationThe rate of oxidation of alcohols with 1 can be markedly increased by addition of pyridine. In fact 1 in combination with pyridine is an excellent reagent for oxidation of 1,4-hydroquinones to the quinones. When used in the absence of pyridine, 1 can effect selective oxidation of benzylic alcohols in the presence of a secondary alcohol. 

The addition of B-alkylcatecholboranes to quinones has recently been investigated [85]. Good yield of the expected conjugate addition product are obtained with primary and most secondary radicals (Scheme 34, Eq. 34a). However, hindered secondary radicals and tertiary alkyl radicals afford an unexpected product resulting from a radical addition to the oxygen atom of the quinone (Eq. 34b). 

For the cracking of catechol and 3-methylcatechol in the presence of iron oxide, reaction pathways for the secondary products appeared to follow the same trend based on the assumption that the possible identities of the products we proposed above were correct. As presented in Scheme 12.1, catechol and 3-methylcatechol were oxidized to their corresponding quinones, 1,2-benzoquinone, and methylbenzoquinone, respectively. This was followed by an expulsion of CO to form cyclopentadienones and further followed by one more CO expulsion to form possibly vinyl acetylene from catechol and pentenyne from 3-methylcatechol. These products were eventually converted to the tertiary products. The formation of quinones was also observed in other studies where the oxidation of catechols was carried out. The formation of secondary products I in our study is in agreement with the previous studies (e.g., Wornet et Therefore, it is reasonable to propose the reaction pathways de-... 

A very remote secondary H/D isotope effect has been measured for the 2 + 2-cycloaddition of TCNE to 2,7-dimethylocta-2,fran -4,6-triene. The reaction of nitric oxide with iV-benzylidene-4-methoxyaniline to produce 4-methoxybenzenediazonium nitrate and benzaldehyde is thought to proceed via a 2 + 2-cycloaddition between nitric oxide and the imine double bond. A novel mechanism for the stepwise dimerization of the parent silaethylene to 1,3-disilacyclobutane involves a low-barrier [1,2]-sigmatropic shift. Density functional, correlated ab initio calculations, and frontier MO analysis support a concerted 2 + 2-pathway for the addition of SO3 to alkenes. " The enone cycloaddition reactions of dienones and quinones have been reviewed. The 2 + 2-photocycloadditions of homochiral 2(5H)-furanones to vinylene carbonate are highly diastereoisomeric. ... 

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