1,2-Dihydronaphthalene, with

Asymmetric epoxidation of olefins with ruthenium catalysts based either on chiral porphyrins or on pyridine-2,6-bisoxazoline (pybox) ligands has been reported (Scheme 6.21). Berkessel et al. reported that catalysts 27 and 28 were efficient catalysts for the enantioselective epoxidation of aryl-substituted olefins (Table 6.10) [139]. Enantioselectivities of up to 83% were obtained in the epoxidation of 1,2-dihydronaphthalene with catalyst 28 and 2,6-DCPNO. Simple olefins such as oct-l-ene reacted poorly and gave epoxides with low enantioselectivity. The use of pybox ligands in ruthenium-catalyzed asymmetric epoxidations was first reported by Nishiyama et al., who used catalyst 30 in combination with iodosyl benzene, bisacetoxyiodo benzene [PhI(OAc)2], or TBHP for the oxidation of trons-stilbene [140], In their best result, with PhI(OAc)2 as oxidant, they obtained trons-stilbene oxide in 80% yield and with 63% ee. More recently, Beller and coworkers have reexamined this catalytic system, finding that asymmetric epoxidations could be perfonned with ruthenium catalysts 29 and 30 and 30% aqueous hydrogen peroxide (Table 6.11) [141]. Development of the pybox ligand provided ruthenium complex 31, which turned out to be the most efficient catalyst for asymmetric... 

Compounds lb and 2b were the Urst fluorinated ligands tested in Mn-catalyzed alkene epoxidation [5,6]. The biphasic Uquid system perfluorooc-tane/dichloromethane led to excellent activity and enantioselectivity (90% ee) in the epoxidation of indene with oxygen and pivalaldehyde (Scheme 1, Table 1). In addition, the fluorous solution of the catalyst was reused once and showed the same activity and selectivity. This represents a considerable improvement over the behavior in the homogeneous phase, where the used catalyst was bleached and reuse was impossible. Unfortunately, indene was the only suitable substrate for this system, which failed to epoxidize other alkenes (such as styrene or 1,2-dihydronaphthalene) with high enantioselectivity. The system was also strongly dependent on the oxidant and only 71% ee was obtained in the epoxidation of indene with mCPBA at - 50 °C. 

In spite of these limitations, three examples of (salen)-metal complex adsorption have been described. In the first one, Jacobsen s complex (la-MnCl) was adsorbed on Al-MCM-41 [27] by impregnation with a solution of the complex in dichloromethane, an approach that prevents the possible cationic exchange. The results in the epoxidation of 1,2-dihydronaphthalene with aqueous NaOCl were comparable to those obtained in solution, with only a slight reduction in enantioselectivity (55% ee instead of 60% ee). However, recycling of this catalyst was not described. 

The basic reactions of Tetralin and derivatives have been extended to the use of 1-13C labels and 1,2-dihydronaphthalene, with and without a source of free radicals. The studies with Tetralin were monitored equally well with C-NMR and GLC techniques. The rate constant for the conversion of Tatralin to methyl indan in the presence of dibenzyl at 450°C was 6.4 x 10 min i which is consistent with that previously reported [2]. 

The behavior of the isomeric dihydronaphthalenes emphasizes the importance of the relative stabilities of carbocation intermediates in ionic hydrogenations. Treatment of 1,2-dihydronaphthalene with Et3SiH/TFA at 50-60° gives a 90% yield of tetralin after one hour. Under the same conditions, the 1,4-dihydronaphthalene isomer gives less than 5% of tetralin after 70 hours.224 This difference in reactivity is clearly related to the relatively accessible benzylic cation formed upon protonation of the 1,2-isomer compared to the less stable secondary cation formed from the 1,4-isomer.224... 

Co-ozonolysis of 1,2-dihydronaphthalene with formaldehyde, acetyl cyanide (pyruvonitrile), benzoyl cyanide, or acetaldehyde afforded an ozonide attached to a benzaldehyde group 89 and none of the isomeric ozonide with a propionaldehyde group. This indicates the preference for scission of the molozonide so as to favor conjugation between the aromatic ring and the aldehyde group rather than with the carbonyl oxide group. Subsequent co-ozonolysis of products 89 with vinyl acetate produced diozonides 90, as shown in Scheme 26 and Table 11. 

Dihydronaphthalene, with iodine isocyanate and methanol to give methyl (/r[Pg.72]

In 1994, Jacobsen and co-workers demonstrated that stereoseleetive oxidation of benzylic C—H bonds is possible utilizing readily available chiral Mn(salen) complexes.They studied the kinetic resolution of 1,2-dihy-dronaphthalene oxide via an asymmetric C—H bond hydroxylation reaction (Scheme 1.59). During the course of experiments on the asymmetric epoxidation of 1,2-dihydronaphthalene with C24, it was observed that the... 

TABLE 18.1. Reaction of 1,2-dihydronaphthalenes with HTIB in flnoroalcohoIsC... 

The oxidation of 1,4-dihydronaphthalene with oxygen with irradiation gave l,2-dihydro-2-naphthyl hydroperoxide that decomposed thermally to 3-benzoxepin (3).189... 

Comparable results were achieved in the asymmetric epoxidation of dihydronaphthalene with the Katsuki-type catalyst 53 in [C4Ciim][PF6].[50] Again, higher reaction rates were observed in the presence of the ionic liquid and the overall stability of the catalyst appeared to be superior to that with... 

Complexation of dihydronaphthalene with chromium tricarbonyl facilitates the attack of a nucleophilic amine and stereoselectively directs the protonation "anti" to the metal atom. (+)-(l S,2 R)-, 2-Dihydro-7-methoxy-1,4-dimethyl-1 - 2 -[methyl(trifiuoroacetyl)amino]propyl -naphthalene [(+)-7] was treated with chromium hexacarbonyl to give a mixture of a- and /(-chromium tricarbonyl complexes in a 10 1 ratio ( H NMR). The complexes were separated and the a-isomer cyclized by base treatment and sonication. Dccomplexation gave the ben-zomorphan tricycle 8 in low yield [40%, based on recovered (+)-7]18. The trifluoroacetyl protection of the amino group was necessary to achieve both stereoselective complexation with chromium tricarbonyl and successful cyclization. 

Synthesis of the chiroporphyrins (67) and (68) was achieved by reacting the chiral aldehydes (17 )-(-)-cw-caronaldehyde acid methyl ester and (1/ )-(-)-myrhenal with pyrrole [236]. Chloromanganese(III) derivatives of the Z)2-symmetric a a -atropisomers, which appear to be the most abundant, were applied to the epoxidation of some unfunctionalized aromatic alkenes with PhlO. A high ee value (70%) was obtained in the epoxidation of dihydronaphthalene with this type of catalyst whereas it was significantly lower when functionalized substrates were used (17% for p-chlorostyrene). 

Also in 2000, attachment of the Jacobsen catalyst to polymeric supports such as poly(ethylene glycol) and different polystyrene-based resins through a glutarate spacer was described [28]. Soluble as well as insoluble polymer-bound complexes were employed as catalysts in the epoxidation of styrene, cfs-2-methylstyrene, and dihydronaphthalene with wx-CPBA/NMO. Results were similar to those achieved with the nonsupported catalyst. Catalyst recycling was shown to be possible either by filtration or by precipitation and one catalyst system could be used for three cycles without significant loss of activity and enantioselectivity. 

Ring opening of l,4-oxa-l,4-dihydronaphthalene with R2Zn proceeds in the presence of (MeCN)2PdCl2 to afford cw-2-alkyl-l-hydroxy-1,2- dihydronaphthalenes. ... 

The preferred conformations for the dihydronaphthalenes are 6.80 and 6.81 for the compounds with a substituent in the axial- (i. e., 2-) and pseudoaxial (i. e., 1-) positions, respectively. As shown in (6-33) and (6-34) dihydronaphthalenes with a substituent in either position undergo addition of diazomethane from the less hindered face opposite to that substituent. 

Diels-Alder Reactions. Bp3-OEt2 is used to catalyze and reverse the regiospecificity of some Diels-Alder reactions, e.g. with pen-hydroxylated naphthoquinones, sulfur-containing conpounds, the reaction of 1-substituted trans-1,3-dienes with 2,6-dimethylbenzoquinones, and the reaction of 6-inethoxy-l-vinyl-3,4-dihydronaphthalene with p-quinones. BFs-OEta has a drastic effect on the regioselectivity of the Diels-Alder reaction of quinoline- and isoquinoline-5,8-dione with piperylene, which produces substituted azaanthraquinones. This Lewis acid is the most effective catalyst for the Diels-Alder reaction of furan with methyl acrylate, giving high endo selectivity in the 7-oxabicyclo[2.2.1]heptene product (eq 35). ... 

One of these isomers has a heat of hydrogenation of 101 kJ/mol (24 1 kcal/mol) and the heat of hydrogenation of the other is 113 kJ/mol (27 1 kcal/mol) Match the heat of hydrogenation with the appropriate dihydronaphthalene... 

Neither compound exhibits properties that would suggest aromaticity. The NMR spectra are consistent with polyene structures. Both compounds are thermally unstable and revert back to dihydronaphthalenes ... 

Peroxvaad oxidation of bridged 5,6,7,8-tetrafluoro 1 4-dihydronaphthalene-1,4 imines gives aromatic fluorohydrocarbons by elimination of the imine bridge [91] (equation 84) Almost the same yields are achieved by oxidation with 30% hydrogen peroxide m refluxing methanol [91]... 

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). 

---