1.2- Dihydronaphthalene-3-carboxylate

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). 

Chiral oxazolines developed by Albert I. Meyers and coworkers have been employed as activating groups and/or chiral auxiliaries in nucleophilic addition and substitution reactions that lead to the asymmetric construction of carbon-carbon bonds. For example, metalation of chiral oxazoline 1 followed by alkylation and hydrolysis affords enantioenriched carboxylic acid 2. Enantioenriched dihydronaphthalenes are produced via addition of alkyllithium reagents to 1-naphthyloxazoline 3 followed by alkylation of the resulting anion with an alkyl halide to give 4, which is subjected to reductive cleavage of the oxazoline moiety to yield aldehyde 5. Chiral oxazolines have also found numerous applications as ligands in asymmetric catalysis these applications have been recently reviewed, and are not discussed in this chapter. ... 

The photooxygenation of chiral l,2-dihydronaphthalene-2-carboxylic acids leads to a mixture of the diendoperoxide (37) and hydroperoxide (38) arising from a double [4+2] cycloaddition and an ene reaction, respectively <96CC2585>. 

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. 

Naphthalene oxides. The Diels-Alder reaction of 1,4-diacetoxybutadiene (1) with benzyne (generated from o-benzenediazonium carboxylate, 1, 46) gives the diacetate of l,4-dihydronaphthalene-cis-l,4-diol (2) in 53% yield. The product is converted into 3 by reaction with hydrogen peroxide and catalytic amounts of osmium tetroxide. The monotosylate of 3 is converted into 4 by treatment with base. This epoxy diol has the stereochemistry found in the carcinogenic epoxy diols formed as metabolites of aromatic hydrocarbons. The dimesylate of 3 is converted into the syft-diepoxide 5. 

The angular 7a-phenyl hicyclic lactam can he prepared hy the cyclocondensation of 3-henzoylpropionic acid and (S)-valinol in 85% yield. Dialkylation of this lactam also affords cleanly the a,a-disubstituted compound. Lactam hydrolysis releases chiral, nonracemic a,a-disuhstimted y-keto carboxylic esters (or acids) (eq 5) and 3,3-disuhstituted dihydronaphthalenes may he obtained via cyclization. ... 

Acyl esters of vicinal diols are obtained by the reaction of alkenes with metal carboxylates [436]. Lead tetraacetate in acetic acid at 70 °C converts 1,2-dihydronaphthalene to rranj-l,2-diacetoxy-l,2,3,4-tetrahy-dronaphthalene in 72% yield [436]. The reaction is not always stereospecific. Cyclohexene treated with thallium triacetate gives a mixture of diastereomers in varying ratios, depending on reaction conditions, and byproducts as a result of rearrangements (equation 89) [411],... 

Reductive coupling, in aprotic solvents, of aromatic hydrocarbons with CO2 has long been known. Reduction of naphthalene in DMF in the presence of COo leads to 1,4-dicarboxy-1,4-dihydronaphthalene ( 50%) [246]. Under similar conditions, phenanthrene gives fra725-9,10-dicarboxy-9,10-dihydrophenanthrene ( 30%) [246]. Carboxylation of aromatic halides can be achieved in aprotic solvents either by using transition metal catalysts or by direct reduction using sacrificial anodes in undivided cells (cf. Chapter 8). 

Bcnzyne does not act as a dienophile with butadiene, presumably because the diene exists in the transoid arrangement. However, benzyne and butadiene generated from 3-sulfolene react to give 1,4-dihydronaphthalene in low yield (9%). The reaction is carried out by decomposing benzenediazonium 2-carboxylate and 3-sulfolene at 100° in pentanone-2.5 The reaction presumably occurs because the butadiene is generated in the cisoid conformation. 

The dominant influence of secondary orbital interactions is apparent in the reaction of methyl cyclopenta[e]-l,2,4-triazine-3-carboxylate with enamines from 3,4-dihydronaphthalen-1 (2//)-or -2(l/f)-ones. In the case of the 3,4-dihydronaphthalen-2-amine the fused pyridine 24 is obtained directly using the 3,4-dihydronaphthalen-l-amine the dihydropyridine is isolated, but can be oxidized to give the aromatic pyridine 25 derivative via a Cope elimination.403... 

MEYERS Asymmetric synthesis Cheat oxazoles in asymmetric synthesis of carboxylic acids, aldehydes, chiral dihydronaphthalenes. 

A stereochemically interesting observation was made by Carrie s group (Vebrel et al., 1987) in their investigations of diazomethane cycloaddition to methyl l,2-dihydronaphthalene-3-carboxylates substituted at the 1- or 2-position by alkyl or phenyl groups. The 4,5-dihydro-3//-pyrazoles were isomerized into the l//-isomers for easier identification by NMR spectroscopy, in part also by X-ray analyses (6-33). 

With in situ generated peroxycarboxylic acids from urea-H202, carboxylic acid anhydrides and N-methylmorpholine N-oxide as an additive, chiral derivatives of Mn-salen complex I were found to oxidize effectively dihydronaphthalene and indene (126). The combination employing maleic anhydride has led to good results, up to 87 % ee and 71 % yield. Generally, lowering the temperature from 2 to —18°C had marginal positive effect on the yield and enantiomeric excess of the epoxides. 

Another example of the use of acycUc dienes has been recently reported by Lautens et al. in the synthesis of dihydronaphthalenes (Equation 12.43) [91]. The cycloadditions of benzyne generated from benzenediazonium-2-carboxylate with the carbonyl-substituted dienes 167 afford cycloadducts 168. Excellent diastereose-lectivity was observed when the diene was attached to Oppolzer s sultam as a chiral auxiUary. The cycloaddition was employed in the multistep synthesis of racemic sertraUne. 

Reductive C-acylation l-Acyl>l,4-dihydronaphthalenes from carboxylic acid esters... 

The cinchonine-based thiourea (606) has been proven to be an efficient catalyst for the asymmetric Michael addition of 2-hydroxy-1,4-naphtho-quinones (603) to (3,y-unsaturated a-acylphosphonates (604) generating the corresponding (3-(3-hydroxy-l,4-dioxo-l,4-dihydronaphthalen-2-yl)-sub-stituted carboxylates (605) in excellent yields and enantioselectivities (up to > 99% ee) upon quenching the generated parent structures with DBU and MeOH, as a second nucleophile (Scheme 149). ... 

With 1,2-dihydronaphthalenes, competition between the ene reaction giving the 4-hydroperoxide and cycloaddition depends on the substituent with a chiral 1-phenyl-l,2-dihydronaphthalene-2-carboxylic acid and some related compounds, the his-endoperoxide is the main product and is formed with high diastereoselectivity. With (alkyl)indenes, the result is strongly dependent on conditions. At -78°C, the [4-(-2]-addition predominates (in this case, leading to rearranged di-epoxyperoxides), while in acetonitrile or methanol the [2-1-2]-mode predominates and cleaved dicarbonyls are obtained the ene reaction is one of the processes occurring at room temperature. " ... 

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