Arenes Tetralins

Labelling experiments provided the evidence that the Fe1- and Co1-mediated losses of H2 and 2H2 from tetralin are extremely specific. Both reactions follow a clear syn- 1,2-elimination involving C(i)/C(2) and C(3)/C(4), respectively. In the course of the multistep reaction the metal ions do not move from one side of the rr-surface to the other. The kinetic isotope effect associated with the loss of the first H2 molecule, k( 2)/k(Y)2) = 3.4 0.2, is larger than the KIE, WFLj/ATHD) = 1.5 0.2, for the elimination of the second H2 molecule. A mechanism of interaction of the metal ion with the hydrocarbon n-surface, ending with arene-M+ complex 246 formation in the final step of the reaction, outlined in equation 100, has been proposed241 to rationalize the tandem MS studies of the unimolecular single and double dehydrogenation by Fe+ and Co+ complexes of tetraline and its isotopomers 247-251. 

A similar intramolecular alkylation of arene-ene substrates is catalyzed by RuGl3/AgOTf, providing good to excellent yields of cyclization products (chromanes, tetralins, terpenoids, and dihydrocoumarins).25 This method is applied to the synthesis of tricyclic terpenoids, which are formed in nearly quantitative yields with high stereoselectivities (trans cis various between 99 1 and 99 2), as shown in Equation (24). 

The preference of 2,7-disubstituted oxepins for this tautomeric form at equilibrium may be rationalized in terms of a steric substituent effect. The eclipsing interactions of the 2,7-substituents in the arene oxide form will be diminished by isomerization to the oxepin. When the 2,7-substituents form part of an annelated ring system, e.g. (22)-(24), the tautomeric preference will be determined by the size of the methylene bridge (67AG(E)385). Thus when n = 5 the annelated oxepin (24) was present in approximately equal proportions with the arene oxide form. However with n =4. (23) tetralin 9,10-oxide was dominant. The... 

Reduction of arenes.1 Raney nickel (Mozingo type) in combination with 2-propanol (reflux) effects reduction of aromatic rings in 2-18 hours. Naphthalene is reduced in 18 hours to tetralin (90% yield) and cis- and frans-decalin (10% yield). Anisole is reduced in 110 hours to cyclohexyl methyl ether (90% yield). Nitrobenzene is reduced quickly to aniline and then further to cyclohexylamine and cyclohexylisopropylamine. 

Tetrahydrofurans (see Heterocycles) Tetrahydropyrans (see Heterocycles) Tetralins (see Arenes)... 

The addition-protonation procedure maintains the arene-chromium bond and allows further application of the activating effect of the metal. In an approach to the synthesis of anthraquinone antibiotics, the dihydronaphthalene complex (79) was allowed to react with a cyanohydrin acetal anion and then quenched with acid.129 The resulting tetralin complex (80) could be metallated effectively and carried on to a key intermediate (81) in anthraquinone construction (equation 54)... 

In addition to alkenes, arenes can sometimes be used as radical acceptors in Sml2-mediated carbonyl-alkene couplings. For example, Schmalz reported extensive studies on ketyl additions to arenechromium tricarbonyl complexes 66,67 tetralin-Cr(CO)3 complex 49 underwent reductive carbonyl addition to the aromatic ring upon treatment with Sml2 to furnish the skeleton of the naturally occurring aryl glycoside pseudopterosin G (Scheme 5.37).66,67 Here, the bulky metal tricarbonyl group not only serves to control the... 

The Mills-Nixon hypothesis had, as its foundation, certain differences in the chemical behaviour of indan (3) and tetralin (4) from which a localization of the aromatic 7r-bonds was predicted to occur in the direction depicted by la rather lb. The original experimental evidence upon which the effect was based was shown to be erroneous, but calculations at various levels of theory indicated that aromatic bond localization should exist and become more pronounced as the size of the annelated ring decreases In essence one can recognize that the structure of benzene has a symmetry such that both Kekule structures must contribute equally. With Q tetralin (4) (and the lower homologues) no such symmetry requirement exists and ring annelation could induce bond length alternation within the arene nucleus. As the strain imposed by the fused ring increases, the Mills-Nixon effect should increase. The hypothesis has been the subject of considerable discussion and the controversy is far from settled. 

Naphthalene 1,2-oxide. Yagi and Jerina have reported a new method for synthesis of arene oxides. The starting material for the preparation of naphthalene 1,2-oxide (5) is I-hydroxy-2-bromotetralin, (I), which is acetylated with irifluoroacctic anhydride in chloroform to give (2) in 84 % yield. This is converted into the dibromide (3) by treatment with NBS (note that tetralin 1,2-epoxidc is uiLstable to bromination with NBS). The... 

With nickel(II) 2-ethylhexanoate and triethylaluminum, tetralin (59) is obtained by hydrogenation of naphthalene (55). Polycyclic aromatics, such as anthracene (57 equation 8), 9-methylanthracene and 9-trifluoroacetylanthracene, are partially hydrogenated to 1,2,3,4-tetrahydroanthracene derivatives by use of [Rh(DPPE)(arene)]+ in methanol and by ruthenium hydride complexes having triphenylphosphine ligands... 

Bridging substituent groups also influence the preference for either the arene oxide or the oxepin valence bond tautomer. Thus, when n = 3, indan 8,9-oxide 7 exists exclusively as the oxide form. With n = 4, tetralin 9,10-oxide 8 is dominant over its oxepin form while similar amounts of the arene oxide and oxepin are present when n = 5 (9). 

Several X-ray structures of the parent p-substituted calix[5]arenes have been obtained, including 5 as the acetone complex, the tetralin complex, the ethyl acetate complex, and the self complex 51.1.3,3-tetramethyibutyi... 

The oxidation of hydroarenes to arenes by quinones such as 2,3-dichloro-5,6-dicyano-l,4-quinone (DDQ) is frequently used for the synthesis of aromatic compounds. Brower et al. have already shown that the dehydrogentaion 1,4-cyclo-hexadiene to benzene [128] or tetraline to naphthalene [129] by thymoquinone is accelerated by pressure giving a negative volume of activation ((AV = —33 (75 °C) and —28 (175 °C) cm mol respectively). A similar effect of pressure has been observed for the oxidation of leuco crystal violet with p-chloranil ((AV = -25 cm mol (21 °C) [130]. The pressure-dependent kinetic isotope effect of this reaction (29 °C kn/ D = H-5 (1 bar) and 8.2 (1.5 kbar)) indicates that hydrogen transfer occurs in the rate-determining step. The large kn/ko value at 1 bar and it pressure dependence was attributed to a quantum mechanical tunneling. 

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