Meso‐ and Dl‐ Diethyl 2,3‐Diphenylsuccinate from the Electrochemical Reduction of Ethyl α‐Bromophenylacetate

1987

The reductive electrochemical dimerization of ethyl a-bromo-p-halogenophenylacetates, (ABr) (1 )-(3), to the corresponding racemic and meso succinates (AA) (7)-( 9) is reported. Monoesters A H (4)-(6) and epoxides (11)-(13) were also isolated. A n excess of racemic isomer for (7)-( 9) is observed, decreasing in the order of the F, CI, and Br substituent in the phenyl group. Voltammetric experiments show only slight differences between the reduction potentials of the isomeric meso and racemic compounds (8), whereas in the case of the isomeric p-bromo-substituted compounds (9) the reduction potentials are almost identical. The meso compounds can be distinguished from the DL isomers by n.m.r. spectroscopy. This feature is also observed in the n.m.r. spectra of epoxides(1 1 )-(I 3).The electrochemical reductive dimerization of ethyl a-bromo-phalogenophenylacetates ABr (1)-(3) to give the corresponding succinates AA (7)-( 9) is reported. In principle, symmetrical succinic acids or esters are obtainable, chemically, by Wiirtztype reactions,, by dimerization of thermally or photochemically

Section: Resultsmentioning

confidence: 99%

Electrochemical synthesis of diethyl 2,3-bis-p-halogenophenylsuccinates; reduction of α-bromo-p-halogenophenylacetates¹

Luca¹,

Inesi²,

1987

“…60 mV (25 "C), as expected for a one-electron transfer; on the other hand, a single larger curve is obtained, as expected, from molecules bearing two identical reducible groups. The peak currents obey equation (1) where &(,-A) is the peak current observed with each diester, i,,(AH) is the peak current for the corresponding monoester when the concentrations of diester and monoester are the same, the i, values being determined on the pure compounds, and DA-A and DA-H are the diffusion coefficients for diesters and corresponding monoesters, respectively. The relative values of the diffusion coefficients can be approximately evaluated by equation ( 2) 7 b…”

Section: Resultsmentioning

confidence: 99%

“…Elution with pure CHCl, gave compound (5), followed by a mixture of (5) and (6) (1 : 2), which was separated by preparative h.p.1.c. It was surprising that no monoester (1) was found in this run. In the third run, no column chromatography was performed on the mixture of products; n.m.r.…”

mentioning

confidence: 91%

“…C.p.e. (controlledpotential electrolysis) at a potential selected between the first, more positive, and the second peak results in the near exclusive formation of monoester(1) [or (2)] and diesters (5) + (6) [or (7) + (8)] from (3) [or (4)], respectively, with napp = 1. Thus, having prepared pure monoester (1) [or (2)] chemically or electrochemically, and diesters (5) and (6) [or (7) and (8)] electrochemically, the voltammetric behaviour of (5>-(8) can…”

mentioning

confidence: 99%

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Cathodic reduction of ethyl α-bromonaphthalene-1- and -2-acetate: electrochemical synthesis and voltammetric behaviour of meso- andDL-diethyl 2,3-di-1- and -2-naphthylsuccinate

Luca¹,

Inesi²,

1985

Diethyl 2,3-dinaphthylsuccinates ( 5)-( 8) can be prepared through electrochemical reduction of ethyl a-bromonaphthalene-1and -2-acetate (3) or (4) (ABr) in DMF-O.1 M-Et,NClO, at a vitreous carbon electrode. These dinaphthylsuccinates (5)-(8) (A-A) are good model systems for the study of electron transfer to molecules containing two identical redox centres. Cyclic voltammetry shows that dimeric species A-A are reduced at more positive potentials than the corresponding AH compound; meso-diethyl 2,3-di-2-naphthylsuccinate ( 7) is reduced at a slightly more positive potential than the corresponding oL-succinate (8). The 1 -naphthyl derivatives are more easily reduced than the corresponding 2naphthyl compounds, the difference being larger between bromoesters (3) and (4). Previous studiesof the electroreduction of a-bromo-aphenylalkanoic esters have led to the corresponding diesters. This contribution seeks to establish the ways in which changing from phenyl to 1-and 2-naphthyl will affect the electrochemistry of aryl a-bromoesters, giving, at the same time, a method for preparing the apparently unknown diethyl 2,3-dinaphthylsuccinates. These last compounds, as well as the nonbrominated esters (1) and (2), were expected to be reduced in the potential range available. The following questions were appropriate. (i) What is the effect of changing the position from 1 to 2 upon the electroreduction of ethyl naphthaleneacetate [compounds (1) and (2)]? (ii) What is the corresponding difference between compounds (3) and (4)? (iii) What is the difference, in terms of electrochemical behaviour, between the monomeric compounds (1) or (2) and the corresponding dimers (5) and (6) or (7) and (8), respectively? (iv) What is the difference, if any, between the reduction potentials of the meso-and the corresponding DL compounds, i.e. between (5) and (6) or (7) and (8)? Experimental was prepared through hydrolysis and esterification of naphthalene-1acetonitrile (Fluka) (50 g, ca. 0.2 mol) by refluxing with concentrated sulphuric acid (45 ml) and 95% ethyl alcohol (140 ml) for ca. 7 h, obtaining ester (1) (42 g, ca. 84%) as an oil. Its purity was checked by reversed-phase h.p.1.c. with CH,CN-H,O (83:17) as solvent, flow rate 35 ml m i d , using U.V. detection at 253.7 nm. The retention time t, was 3 min 24 s,

“…Five fractions were obtained (from ether-acetone), in the following order of decreasing Rp: (2) (90 mg), (3) (75 mg), (4) (85 mg), unknown products (36 mg), and a residue with Constant Potential Electrolysis of Methyl 2-Bromo-2phenylpropanoate (5) .-The procedure for electrolysis of bromo-ester (5) on r.v.c. was analogous to that adopted for bromo-ester (1). The experiment was repeated several times, in order to ascertain if the same kinds of products were formed.…”

Section: -Bromo-2-phenylpropanoicmentioning

confidence: 99%

Electroreduction of methyl 2-bromo-2-phenylpropanoate on a vitreous carbon electrode: meso- and DL-dimethyl 2,3-dimethyl-2,3-diphenylsuccinate

Luca¹,

Inesi²,

1982

The electrochemical reduction of ethyl a-bromophenylacetate (1 ) and methyl 2-bromo-2-phenylpropanoate (5) in dry dimethylformamide on a vitreous carbon electrode has been studied. Dimeric products are formed as a consequence of controlled potential electrolysis of ( 1) and ( 5) on a reticulated vitreous carbon electrode. By this route, meso-and DL-diethyl2,3-diphenylsuccinate and -dimethyl 2,3-dimethyl-2,3-diphenylsuccinate are obtained from ester (1) and (5), respectively. A triester is also obtained among the products. The spectral data (n.m.r., mass spectra) show the structure of this triester to be almost certainly MeO2C-CMePh.C6H4.CMeCO2Me-CMePh-C02Me (9). To explain the results, a mechanism is proposed, involving the formation of dimer (10) as an intermediate.