Arylethanals

Thus the Meerwein reaction is a homologation of the Sandmeyer reaction. The arylethane radical 10.17 is a homologue of the aryl radical in the Sandmeyer reaction. 

The low yields of vinyl polymers (Ganushchak et al., 1972) are probably due to the arylethane radical 10.17 reacting more rapidly with CuCl2 than with the vinyl monomer. The formation of 10.17 is also the initiation of the polymerization chain reaction. 

Patent applications from Astellas Pharma [77,78] and Fujisawa [79] have disclosed series of guanine, imidates and aminoimidazoles built on a bis arylethane core structure. Some of these are very potent. Compound 36 inhibits the human and rat enzymes with IC50 = 150 nM and 12nM, respectively compounds 37, 38 and 39 inhibit human SSAO/VAP-1 with IC50 = 5.7 nM, 5.3 nM and 2.4 nM, respectively. 

Oxidative C-H amination has been an area of intensive research since the publication of CHEC-II(1996). This methodology has been applied to the synthesis of a variety of 1,2-thiazine 1,1-dioxides. In the simple cases, substrates containing an aromatic C-H can be cyclized in the presence of hypervalent iodine. For instance, the reaction of A-methoxy(2-arylethane)sulfonamide 202 with [hydroxyl(tosyloxy)iodo]benzene rapidly affords benzenesulfon-amide 203 in excellent yield (Equation 30) <20030BC1342> see also <2000JOC926> and <2000JOC8391>. 

The cobalt carbonyl complex is also an effective catalyst for the siloxy-methylation of aromatic aldehydes.110 Arylethane-l,2-diol disilylethers are obtained in good yields, resulting from incorporation of one molecule of CO and two molecules of HSiR3. Good selectivity for the siloxymethylation product is observed at 0°C in hexane. At 15°C, faster reaction rates are observed, but the selectivity for the CO-incorporated product is lower. In contrast, aliphatic aldehydes react under these conditions (1 atm CO, 0°C) to give only a small amount of CO-incorporated product, with a major product resulting from hydrosilylation. 

Styrene oxides can be reduced selectively to either 2-arylethanols or 1-arylethan-ols. Attack of hydride at the non-benzylic carbon atom can sometimes be achieved with LiAlH4, but most reducing agents, in particular under acidic reaction conditions, will lead to cleavage of the benzylic C-O bond (Scheme 4.62). 

Chiral amino alcohols and diamines. The chiral vtc-diols available by catalytic asymmetric dihydroxylation of alkenes (14, 237-239) can be converted via a derived cyclic sulfite into chiral 1,2-amino alcohols and diamines as shown in equation I. The same transformations are useful in conversion of 1-alkyl- or arylethane-1,2-diols into the corresponding amino alcohols and diamines. 

The reaction of sodium azide with l-bromo-l-nitro-2-arylethenes takes place by a formal 1,3-cycloaddition Scheme leading to 4(5)-aryl-5(4)-nitro-l,2,3-triazoles [487-489], During the synthesis of nitrotriazoles the bromonitroarylethenes can be replaced successfully by the more readily obtainable l,2-dibromo-l-nitro-2-arylethanes [489], The intermediate product in the synthesis of 3-nitropyrazoles from 2,2-dinitroethanol and diazo ketones or diazoacetic ester is 1,1-dinitroethene [490,491] (Scheme 68). 

Now, what is this dimer For nearly 70 years it was believed to be hexaphcnyl-ethane. It—and dozens of analogs—were studied exhaustively, and the equilibria between them and triarylmethyl radicals were interpreted on the basis of the hexa-arylethane structure. Then, in 1968, the dimer was shown to have the structure I. 

Pleurke et al. (1965) have used e.s.r. to measure the degree of dissociation of some tetra-arylethanes (19) into diarylmethyl radicals (20) over a range of temperatures and have computed the enthalpy and entropy changes for dissociation e.g. for R = CH8, AH = 22 kcal per mole, and for R = CjHs, AH = 12 kcal per mole. 

With styrenes, the typical reaction conditions provide the a-amino P-hydroxy a-arylethanes as the major product. This regioselectivity can be changed by the use of a pH-controlled method when a carbamate is the nitrogen nucleophile [361],... 

Decarbonylation and carbonylation. 1,1 -Di arylethanes (of particular interest are the chiral members) are obtained from decarbonylation of 3,3-diarylpropanals. Such compounds are accessible from cinnamaldehydes in two steps, involving two different Rh-catalyzed reactions. ... 

Acid treatment of arylethanals may lead to 2-phenylnaphthalenes or l,2,9,10-tetrahydro-l,9-epoxydibenzo[a,e]cyclooctenes (Kagan s ether). 2-Phenylnaphthalenes were obtained by a C-condensation of the enolated form on the keto form. The resulting aldol condensation product underwent an intramolecular reaction to give, after rearomatisation, the 2-phenylnaphthalenes, Fig. (1). 

More curiously, N-tosylated phenylalanine derivatives [10] and phenyllactic acid [11] can also be converted into 2-phenylnaphthalene in moderate yields whereas 3,4-dimethoxyphenyllactic acid treated with boron tribromide gives Kagan s ether in almost the same yield as 3,4-dimethoxyphenylethanal does [11]. In these cases, the decomposition of aryllactic acid or alanine derivatives may give arylethanal with the formation of water and carbon monoxide, Fig. (4). 

Preferred gauche conformations of 1-alkyl-2-arylethanes and 1,2-diaryl-ethanes have been interpreted in terms of attractive steric interactions between the hydrocarbon moieties (Hirola et al., 1985), and, by having opposite polarity in the aryl groups, electrostatic or charge-transfer interactions may stabilize the gauche form of 1,2-diarylethanes (El-Torki and Jacobus, 1985). 

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