2-Methoxy-5,8-dihydronaphthalene

Catalytic systems at very low metal loading 0.1% (w/w) obtained in this way can be conveniently used in the hydrogenation of a,P-unsaturated ketones to the corresponding saturated carbonyl compounds with very high efficiencies and selectivities. In Table 4 we report the results obtained in the selective hydrogenation of 4-(6-methoxy-2-naphthyl)-3-buten-2-one, 1, and 2-acetyl-5,8-dimethoxy-3,4-dihydronaphthalene, 2, to the corresponding saturated carbonyl products (I), which are important intermediates... 

Photoamination of 7-methoxy-l,2-dihydronaphthalene in the presence of p-dicyanobenzene similarly affords the amine 153147 and l-benzamido-9,10-anthraquinone reacts with butylamine under UV irradiation in air to yield 154148. 

The specific acid-catalysed solvolysis of l-methoxy-l,4-dihydronaphthalene or 2-methoxy-l,2-dihydronaphthalene has been subjected to kinetic and product studies. The elimination product, naphthalene, predominates. 

Specific acid-catalysed solvolysis of l-methoxy-l,4-dihydronaphthalene or 2-methoxy-l,2-dihydronaphthalene in 25% acetonitrile in water has been found to yield mainly the elimination product, naphthalene, along with a small amount of 2-hydroxy-1,2-dihydronaphthalene, there being no trace of either the 1-hydroxy-1,4-dihydronaphthalene or the rearranged ether. The nucleophilic selectivity, ns/ hoh = 2.1 X 10", between added azide ion and solvent water has been estimated for the relatively stable = 1 x 10 s ) intermediate benzallylic carbocation for which the barrier to dehydronation is unusually low k = 1.6 x 10 ° s ), as evidenced by the large elimination-to-substitution ratio with solvent water as base/nucleophile. The kinetics of acid-catalysed solvolysis of 1-hydroxy-1,4-dihydronaphthalene and 2-hydroxy-1,2-dihydronaphthalene have also been studied. 

In the case of p-methoxystyrene (p-MeOCgH4CH=CH2), the cation-radical ring closure can lead to 1,2-dianisylcyclobntane or 4-anisyl-6-methoxy-3,4-dihydronaphthalene. Thermodynamic simulations show that the former should be favored in the absence of a solvent, whereas the latter product could be stabilized by a polar solvent (O Neil and Wiest 2006). Of course, such a solvent has to be fairly polar and not nncleophilic. 

PREPARATION OF CYANO COMPOUNDS USING ALKYLALU-MINUM INTERMEDIATES. II. l-CYANO-6-METHOXY-3,4-DIHYDRONAPHTHALENE, 52, 96... 

The present method developed by the submitters is the only practical process for preparation of l-cyano-6-methoxy-3,4-dihydronaphthalene. Birch and Robinson have reported that 6-methoxy-l-tetralone did not react with hydrogen cyanide or sodium acetylide. 

This process presents a typical procedure applicable to preparation of cyanohydrins from ketones and aldehydes of low reactivity. l-Cyano-6-methoxy-3,4-dihydronaphthalene is useful as an intermediate for synthesis of polycyclic compounds. 

Examples of this type include the reactions of 2,6-dimethyl-p-benzoquinone with piperylene (Schmidt, C., Sabnis, S. unpublished results referred to in Liu, T. T. H Schmidt, C. Tetrahedron 27, 5289 (1977)) and 6-methoxy-l-vinyl-2,3-dihydronaphthalene (Dickinson, R. A., Kubela, R McAlpine, G. A., Stojanac, Z Valenta, Z. Can. J. Chem. 50, 2377 (1972)), and the reactions of citraconic anhydride with 1-phenyl-butadiene (Alder, K., Haydn, J.,... 

Inoue and May(21) later modified the preceding synthesis with the presence of an 8-methoxyl substituent (Scheme 4.8). The key intermediate dihydronaphthalene (66) gave on treatment with mercuric acetate 8-methoxy-2,lla-dimethyl- la-hydroxybenzomorphan (67) in 49% yield, 5% of the 11/3-methyl isomer (69) and 13% of the la-acetate (68) corresponding to 67. Transformation to the desired 11-epimeric benzomorphans 70 and 71 was by standard methods. 

When the trifluoromethyl group is the only electron-withdrawing. substituent of the cyclic dienophilc, such as in 4-(trifluoromethyl)-1,2-dihydronaphthalene, high pressure is required for the reaction to occur. The yield is improved when the reaction is performed with the tricarbonyl chromium complex 21 of 4-(trifluoromethyl)-l,2-dihydronaphthalene. In the reaction with l-methoxy-.3-(trimethylsiloxy)buta-l,3-diene (Danishefsky s diene, 4), the cycloadducts are obtained as a 1 1 mixture ofcHr/o/c.vo-addition products. They are easily converted into the (trifluoroniethyl)phenanthrenone 22 by the action of bromotrimethylsilane. 

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. 

Three successive [2+4] cycloadditions were used in the synthesis of the pentacyclic methyl ether of G-2N by Kraus and Zhao [92] and later, by a slightly modified procedure, also of the natural product G-2N (118) [93] (Scheme 31). Thermal reaction of the cyclobutanol 112 with acrylic ester gave the dihydronaphthalene 113 which was demethylated by treatment with boron tribromide and converted into the exocyclic ketene acetal 114. This unstable diene was reacted in a second cycloaddition with 2,6-dichlorobenzoquinone (115) to afford the tetracyclic chloroquinone 116. In a last Diels-Alder reaction, ring E was anella-ted by treatment of 116 with l-methoxy-l,3-bis[(trimethylsilyl)oxy]-l,3-buta-diene (117) to yield the pentacyclic natural product G-2N (118) [93]. 

Diels-Alder Reactions. Reagent 1 is useful as an efficient chiral dienophile in asymmetric Diels-Alder reactions. Reaction of 1 with cyclopentadiene in the presence of a Lewis acid occurs with high stereoselectivity. Reaction with 6-methoxy-l-vinyl-3,4-dihydronaphthalene in the presence of EtAlCh proceeds with... 

Under highly protic conditions, the major products of cathodic reductions of cyclic conjugated hydrocarbons are usually dihydro derivatives [11,13,53,164]. In 2-methoxy-ethanol, for example, naphthalene yields 1,4-dihydronaphthalene [164] and COT provides mainly 1,3,6-cyclooctatriene [53]. 

Diels-Alder reactions with p-quinones (6, 65-66).1 The orientation of Diels-Alder reactions of 6-methoxy-l-vinyl-3,4-dihydronaphthalene (1) with p-quinones is subject to reversal by addition of BF3 etherate (1.3 equivalent). Thus the thermal reaction with 2,6-dimethyl-p-benzoquinone (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 Na2C03 is converted to the more stable anti, fran.v-isomcr 5. 

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