Dihydronaphthalenes, formation

Doering, W. von E., and J. W. Rosenthal 9.10-Dihydronaphthalene. Formation from bullvalene and Nenitzescu s hydrocarbon, thermal reorganization, and photorearrangement to bullvalene. J. Amer. chem. Soc. 88, 2078 (1966). 

The formation of an enamine from an a,a-disubstituted cyclopentanone and its reaction with methyl acrylate was used in a synthesis of clovene (JOS). In a synthetic route to aspidospermine, a cyclic enamine reacted with methyl acrylate to form an imonium salt, which regenerated a new cyclic enamine and allowed a subsequent internal enamine acylation reaction (309,310). The required cyclic enamine could not be obtained in this instance by base isomerization of the allylic amine precursor, but was obtained by mercuric acetate oxidation of its reduction product. Condensation of a dihydronaphthalene carboxylic ester with an enamine has also been reported (311). 

A number of basic studies in the area of donor solvent liquefaction have been reported (2 -9). Franz (10J reported on the interaction of a subbituminous coal with deuterium-labelled tetra-lin, Cronauer, et al. (11) examined the interaction of deuterium-labelled Tetralin with coal model compounds and Benjamin, et al. (12) examined the pyrolysis of Tetralin-l-13C and the formation of tetralin from naphthalene with and without vitrinite and hydrogen. Other related studies have been conducted on the thermal stability of Tetralin, 1,2-dihydronaphthalene, cis-oecalin and 2-methylin-dene (13,14). 

Dihydronaphthalene (DHN) is frequently assumed to be an intermediate in hydrogen transfer reactions. While this appears reasonable, efforts to detect and/or measure this intermediate have never been very successful. Assuming that DHN is present, we have briefly explored its role in hydrogen transfer and methyl indan formation. 

Our uncertainty is derived in part from the lack of a measured enthalpy of vaporization, cf Reference 67. However, what triggered our skepticism is the observation that the isomeric 1,2-and 1,4-dihydronaphthalenes have reported enthalpies of formation that differ by ca 13 kJ mol-1 while the corresponding species lacking the benzene ring, the isomeric 1,3- and 1,4-cyclohexadienes, are almost isoenergetic (see Section V.D of this chapter). From J. F. Liebman, in The Cyclophanes (Eds. P. M. Keehn and S. M. Rosenfeld), Academic Press, New York, 1983,... 

Proton landing defines the basicity of anion-radicals. This landing assumes 1 1 stoichiometry with respect to an anion-radical and a proton donor molecule. For example, in the reaction of the naphthalene anion-radical (CjoH ) with methanol, this 1 1 stoichiometry should result in the formation of 50 50% mixture of naphthalene (CjoHj) and dihydronaphthalene (CioHjo). 

The effect of structural variation and the use of different caboxylate salts as cocatalysts was investigated by Pietikainen . The epoxidation reactions were performed with the chiral Mn(III)-salen complexes 173 depicted in Scheme 93 using H2O2 or urea hydrogen peroxide as oxidants and unfunctionalized alkenes as substrates. With several soluble carboxylate salts as additives, like ammonium acetate, ammonium formate, sodium acetate and sodium benzoate, good yields (62-73%) and moderate enantioselectivities (ee 61-69%) were obtained in the asymmetric epoxidation of 1,2-dihydronaphthalene. The results were better than with Ai-heterocycles like Ai-methylimidazole, ferf-butylpyridine. 

Diels-Alder reactions with p-quinones (6. 65 66). The orientation of Diels-Alder reactions of 6-meihoxy-l-vinyl-3,4-dihydronaphthalene (1) with p-quinones is subject to reversal by addition of BF, etherate (1.3 equivalent). Thus the thermal reaction with 2,6-dimethyl-/>-bcnzoquinone (2) results in exclusive formation of 3, whereas the catalyzed reaction leads predominately to the isomer 4. The adduct 3 is stable to base, but the syn, m-isomer 4 on treatment with NaX O, is converted to the more stable anti, frau.s-isomer 5. 

In the dihydronaphthalene series, the selective exo addition of the nucleophile and exo addition of the electrophile (steric approach) results in exclusive formation of the c/r-ot,3-disubstituted tetralin (78 equation 53).128... 

The unsaturated lactones (341) behave in a similar fashion and yield the isomers (342).283 The formation of the oxygen-bridged quadricyclane (343) is a consequence of intramolecular addition in 7-oxa-norbornadiene (344)284 many analogous transformations have been reported in substituted 7-oxanorbornadienes285 and in l,4-epoxy-l,4-dihydronaphthalenes,286 which are further converted to benzoxepins. 

For benzene, it has not been possible to measure directly the rate constant kv for deprotonation of the benzenonium ion in order to complete the determination of Ka (— kp/kg). However, this has been possible for 1-protonated naphthalene,106 9-protonated phenanthrene,25 9-protonated anthracene, and 2-protonated benzofuran.75 In the case of the naphthalene, Thibblin and Pirinccioglu showed that the naphthalene hydrate is sufficiently reactive to form the naphthalenonium ion in aqueous azide buffers (pH 4-5).106 Formation of this ion leads to competition between loss of a proton and trapping by azide ion to form the 2-azido-l,2-dihydronaphthalene. From the trapping ratio kp is determined as 1.6xlOlos 1 by the usual clock method. 

It is interesting to note that the archival enthalpies of formation of 1,2- and 1,4-dihydronaphthalene differ by 12.7 2.3 kJ mol-1 and those of their 1-ring de-benzoated counterparts 1,3- and 1,4-cyclohexadiene have been suggested to be nearly identical (see Reference 8). 

The reaction of a BMI with an acetylenic end-capped oligomer has been undertaken. The mechanism was thought to proceed according to the two pathways indicated in Fig. 21 either by a kind of ene synthesis with formation of an hypothetic cycloallene leading to a dihydronaphthalene derivative (pathway a) or by a condensation concerted with an hydride shift (pathway b). No experimental proof was given for the structure but the condensation of both oligomers gave an expected linear product with a better Glc than the one of BMI alone (324 J m 2 vs. 34 J m 2) [73]. 

An alternative mode of reactivity is observed for [Os]-naphthalene when the nucleophile for the tandem addition is built into the electrophile. The normal mode of reactivity results in the formation of cis-l,4-dihydronaphthalenes (vide supra), but when a solution of the methyl vinyl ketone Michael addition product 24 in methanol (Table 6, entry 1) and a catalytic amount of triflic acid are allowed to react, the complexed hydrophenanthrenone 25 is isolated in 89 % yield [18]. This reactivity results from the pendant ketone undergoing a tauto-merization to form an enol, which can then attack the allyl cation at C2. The stereochemistry of the nucleophilic addition is still anti to the face involved in the metal coordination, but the... 

Formation of Free Radicals by Molecular Disproportionation. A significant conclusion that may be drawn from considerations of rate and equilibrium constants for molecular disproportionation is that this path can provide appreciable concentrations of free radicals in many systems long after most weak chemical bonds have ruptured and bond homolysis has ceased to be a major source of free radicals. In "pure tetralin, for instance, trace concentrations of 1,2-dihydronaphthalene are expected to equilibrate with tetralin and tetralyl radicals,... 

Exhaustive cleavage of the carbon-silicon bond followed by treatment with an acid converted the complex benzo[f]furan 261 to phenol 262, as illustrated in Equation (154) <2003JA12994>. Villeneuve and Tam were able to interrupt this phenol formation by choosing Cp"Ru(COD)Cl as the catalyst. Thus, the reaction of 1,4-epoxy-1,4-dihydronaphthalene 263 with a ruthenium catalyst in 1,2-dichloroethane at 60 °C afforded the 1,2-naphthalene oxide 264 (Equation 155) <2006JA3514>. 

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