Cross oxidative

Addition Reactions. The addition of nucleophiles to quinones is often an acid-catalyzed, Michael-type reductive process (7,43,44). The addition of benzenethiol to 1,4-benzoquinone (2) was studied by A. Michael for a better understanding of valence in organic chemistry (45). The presence of the reduced product thiophenyUiydroquinone (52), the cross-oxidation product 2-thiophenyl-1,4-benzoquinone [18232-03-6] (53), and multiple-addition products such as 2,5-(bis(thiophenyl)-l,4-benzoquinone [17058-53-6] (54) and 2,6-bis(thiophenyl)-l,4-benzoquinone [121194-11-4] (55), is typical ofmany such transformations. 

Recognition of the thio group s key role in biochemistry has led to studies of l,4-ben2oquinone with glutathione, a tripeptide 7-Glu-Cys-Gly (GSH). The cross-oxidation of the initial addition product by excess quinone leads, under physiological conditions, to all three isomeric products (46), ie, the 2,3-and 2,6-isomers as well as the 2,5-disubstituted l,4-ben2oquinone shown. 

The importance of both electronic and steric effects is clear in cycloadditions as in cross-oxidations. One example is a heterocycHc modification leading to the thermodynamically less stable natural form of juglone derivatives such as ventiloquinones JT [124917-64-2] (84) and I [124917-65-3] (85) (83). The yields are 97% (84) from 6-chloro-2,3-dimethoxy-l,4-ben2oquinone [30839-34-0] and 100% (85) upon hydrolysis. 

Ruby, C. Fusy J. Genin, J-M.R. (1999) Preparation and characterization of cross oxide films deposited on MgO (100). Thin solid films. 352 22-28... 

Fig. 62. Plots of the estimated and observed (crosses) oxidation potentials for the M3+ -> M4+ process against the L-values of the trivalent actinides showing the generic form of Inclined W .

CH2 CH CH0. a colourless, volatile liquid, with characteristic odour. The vapour is poisonous, and intensely irritating to eyes and nose b.p. 53"C. It is prepared by the distillation of a mixture of glycerin, potassium sulphate and potassium hydrogen sulphate. It is manufactured by direct oxidation of propene or cross-condensation of ethanal with meth-anal. 

Figure C2.16.9. Schematic cross-section and biasing of a metai-oxide-semiconductor transistor. A unifonn conducting channei is induced between source (S) and drain (D) for > V. Voitage is appiied between the gate (G) and the source. Part (A) shows the channei for - V the transistor acts as a triode. The source-...

The oxidative coupling of thiophene, furan[338] and pyrrole[339,340] is also possible. The following order of reactivity was observed in the coupling of substituted furans[338] R = H > Me > CHO > CO Me > CH(OAc)i > CO2H. The cross-coupling of furans and thiophenes with arene is possible, and 4-phenylfurfural (397) is the main product of the cross-coupling of furfural and benzene[341]. 

The most interesting and difficult cross-coupling is alkyl-alkyl coupling, because oxidative addition of alkyl halides having /i-hydrogen is slow. In addition, easy elimination of /d-hydrogen is expected after the oxidative addition. 

There are also palladium-catalysed procedures for allylation. Ethyl 3-bromo-l-(4-methylphenylsulfonyl)indole-2-carboxylate is allylated at C3 upon reaction with allyl acetate and hexabutylditin[27], Ihe reaction presumably Involves a ir-allyl-Pd intermediate formed from the allyl acetate, oxidative addition, transmetallation and cross coupling. 

Figure 4.12 Spherulites of poly( 1-propylene oxide) observed through crossed Polaroid filters by optical microscopy. See text for significance of Maltese cross and banding in these images. [From J. H. MaGill, Treatise on Materials Science and Technology, Vol. lOA, J. M. Schultz (Ed.), Academic, New York, 1977, with permission.]...

The presence of the unsaturated substituent along this polyester backbone gives this polymer crosslinking possibilities through a secondary reaction of the double bond. These polymers are used in paints, varnishes, and lacquers, where the ultimate cross-linked product results from the oxidation of the double bond as the coating cures. A cross-linked polyester could also result from reaction (5.J) without the unsaturated carboxylic acid, but the latter would produce a gel in which the entire reaction mass solidified and is not as well suited to coatings applications as the polymer that crosslinks upon drying. ... 

Furfural reacts with ketones to form strong, crosslinked resins of technical interest in the former Soviet Union the U.S. Air Force has also shown some interest (42,43). The so-called furfurylidene acetone monomer, a mixture of 2-furfurylidene methyl ketone [623-15-4] (1 )> bis-(2-furfurylidene) ketone [886-77-1] (14), mesityl oxide, and other oligomers, is obtained by condensation of furfural and acetone under basic conditions (44,45). Treatment of the "monomer" with an acidic catalyst leads initially to polymer of low molecular weight and ultimately to cross-linked, black, insoluble, heat-resistant resin (46). 

Fig. 37. Resist images obtained with a cross-linking monocomponent TSI resist (PHOST polymer), cross-linked by photo-oxidation using light at 193-nm wavelength. After exposure, the film was treated with a vapor of dimethyl silyl dimethyl amine and then plasma developed using O2—RIE (122).

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