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

Abstract

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,

Pyrrolobenzothiazepinones and Pyrrolobenzoxazepinones: Novel and Specific Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitors with Antiviral Activity

“…The synthesis of pyrrolo[2,1- d ][1,5]benzothiazepinones 6 has been accomplished according to literature procedures . C-6 alkylation of 6 by exposure of the corresponding potassium enolates to methyl or ethyl iodide afforded ketones 7 .…”

“…The pyrrolo[2,1- d ][1,5]benzoxazepinones 16 were synthesized as shown in Scheme . Accordingly, starting from the 1-(2-hydroxyphenyl)pyrrole 11 , previously described by Artico, and from the pyrrole derivative 12 , obtained starting from 3-amino-2-naphthol 10 by the same procedure described for compound 11 , the esters 13a − d were prepared by O-alkylation with the appropriate ethyl α-bromo ester (see refs a−c). Saponification of the ethyl ester group (NaOH, H 2 O) ( 14a − d ) and subsequent intramolecular cyclization using phosphorus pentachloride gave ketones 15a − d .…”