Achille Inesi

Synthesis of chiral oxazolidin-2-ones by 1,2-amino alcohols, carbon dioxide and electrogenerated acetonitrile anion

An improved electrochemical synthesis of chiral oxazolidin-2-ones from chiral 1,2-amino alcohols is obtained by direct electrolysis of solutions of MeCN–TEAP containing the amino alcohol, with subsequent CO2 bubbling and addition of TsCl. This synthesis avoids any addition of bases or probases and yields oxazolidinones in high yields.

Electrochemical activation of carbon dioxide: Synthesis of organic carbonates

Abstract Electrochemically activated CO2 reacts, under mild conditions, with primary and secondary alcohols bearing a leaving group at the α-position affording the corresponding cyclic carbonates in high yields; unsubstituted alcohols are converted, after addition of EtI, into the corresponding unsymmetrical ethyl carbonates in moderate to good yields. Tertiary alcohols and phenols are stable to the reagent.

The reaction of amines with an electrogenerated base. Improved synthesis of arylcarbamic esters

Abstract The electrogenerated base of 2-pyrrolidone reacts with amines and anilines yielding the corresponding alkyl and aryl carbamates, after addition of carbon dioxide and ethyl iodide. Arylcarbamic esters are obtained in very good yields under mild reaction conditions with respect to the methods so far reported.

The system as mild and safe carboxylating reagent synthesis of organic carbonates

Abstract The system, originating from electrochemical one-electron reduction of dioxygen in dipolar aprotic solvents and in the presence of CO 2 , converts primary and secondary alcohols bearing a leaving group at α orβ position into the corresponding cyclic carbonates in high to excellent yields. Unsubstituted alcohols are also converted, but in unsatisfactory yields, into the corresponding alkyl ethyl carbonates after completion of the reaction by addition of Etl. Tertiary alcohols and phenols are stable to the reagent, thus allowing selective carboxylation of polyhydroxy derivatives. CH-acid containing compounds underfo diferent reactions, if any, with the reagent but in the cases under study the formation of carboxylation products has never been observed.

Electrochemically induced Knoevenagel condensation in solvent- and supporting electrolyte-free conditions

Solvent- and supporting electrolyte-free electrochemically induced Knoevenagel condensation of malononitrile with aldehydes or ketones, at 40 °C, yields ylidenemalononitriles in high yields.

New synthesis of oxazolidin-2-ones

Abstract Electrochemically generated tetraethylammonium peroxydicarbonate (TEAPC) and tetraethylammonium carbonate (TEAC) react under very mild conditions, with 1,2-amino alcohols affording, after addition of tosyl chloride, the corresponding oxazolidin-2-ones in fair to good yields.

Stereoselective reduction of meso- and dl-1,2-dibromo-1,2-diphenylethane at the mercury electrode

Summary Meso- and dl-1,2-dibromo-1,2-diphenylethane are both reduced to ∼100% trans-stilbene at the mercury electrode in DMF containing 0.1 M Et4NClO4. Polarographic, coulometric and controlled-potential experiments as well as u.v. spectra substantiate a two-electron process giving the trans-olefin and Br− ions. Reduction performed in the presence of weak or strong proton donors gave the same results as in the absence of acids. Arguments in favour of a “synchronous concerted” mechanism are discussed.

Electrochemically-initiated Michael addition of chiral acetoacetic derivatives to methyl vinyl ketone: stereocontrolled construction of quaternary carbon centers

Abstract Stereoselective conjugate addition of chiral β-dicarbonyl derivatives to methyl vinyl ketone was promoted by electrolysis, using a catalytic amount of electricity. With respect to the metal-catalyzed methods, the electrochemical, metal-free conditions resulted in enhanced reactivity of the electrogenerated enolates, so that the Michael addition was found to occur under mild conditions and short reaction times, affording products with significant diastereoisomeric excesses. When Oppolzers sultam was used as the chiral inductor and prolonged reaction times were employed, a reversal in the stereoselectivity was observed, evidencing kinetic control in the electrochemically-induced addition and subsequent thermodynamic equilibration. The electrochemically-based method was also exploited for the elaboration of quaternary stereogenic carbon centers.

Electrochemical reduction of halogen containing compounds at a mercury cathode: Fluoroacetic, difluoroacetic, trifluoroacetic acids and corresponding ethyl esters in dimethylformamide

Summary The electrochemical behaviour of fluoroacetic ethyl ester (I), fluoroacetic acid (II), difluoroacetic ethyl ester (III), difluoroacetic acid (IV), trifluoroacetic ethyl ester (V) and trifluoroacetic acid (VI) in DMF-Et4NClO4 solutions on a mercury cathode has been studied. All compounds except I are reducible. The esters show a one-electron, diffusion controlled, polarographic wave, with E1/2=−2.56 V (III) and E1/2=−2.36 V (V), with cleavage of the C-F bond. The reduction mechanism is discussed: electron transfer via the carbonyl function is suggested. In fluoroacetic acid (I) the hydrogen of the nearly undissociated molecule is reduced, E1/2=−2.29 V. In the case of difluoroacetic acid, two waves are observed, E1/2=−1.74 V and E1/2=−2.16 V respectively, the first one being kinetic in nature. Controlled potential experiments demonstrate that the first wave corresponds to the reduction of solvated proton, whereas the second wave is caused by the hydrogen reduction from the undissociated acid. Trifluoroacetic acid behaves as a moderately ‘strong’ acid in DMF and only the reduction wave of solvated proton is observed, E1/2=−1.48 V.

Electrochemical generation of chiral oxazolidin-2-ones anions: a new procedure for the highly diastereoselective conjugate addition to nitroalkenes

Abstract A mild and efficient electrochemical alternative to classical base-catalyzed conjugate addition of nitrogen nucleophiles is reported here. The cleavage of the carbamic NH bond of Evans’ chiral auxiliaries can be very efficiently performed by electrolysis under galvanostatic control and the resulting naked anions used for highly diastereoselective conjugate addition to nitroalkenes. The degree of stereoselectivity was shown to depend on the steric hindrance of the group at the ring C(4) of the starting oxazolidin-2-one.