Ferruccio D'Angeli

Electrochemical reduction of tetra-O-acetyl-α-D-Glucopyranosyl bromide. A mild and quantitative synthesis of a glycal

The electroreduction of tetra-O-acetyl-α-D-glucopyranosyl bromide (1) has been studied in dipolar aprotic solvents at mercury electrodes. The overall electrode process is a two electron C-Br bond cleavage coupled to a very fast elimination of acetate ion. Macroreduction afforded tri-O-acetyl-D-glucal (2) as the major product, two co-products arising from father-son reactions. In the presence of acetic acid, however, (2) was quantitatively formed.

Electro-carboxylation of 2-bromoisobutyramides. a useful synthetic way to ester-amides of 2,2-dimethylmalonic acid

Abstract The etectroreduction of protic 2-bromoisobutyramides was studied in acetonitrile in the presence of carbon dioxide by means of cyclic voltammetry and controlled-potential electrolysis. The electrogeneration of the α-carbanion is followed by a fast and quantitative carboxylation at the tertiary carbon, despite the N-H acidity of the starting compounds. The carboxylate anion was trapped both after and during the electrolysis procedure by alkylating reagents. High yields of ester-amides of 2,2-dimethylmalonic acid were obtained at both mercury and platinum cathodes.

Cyclocondensations of DMF with α-haloamides, an aziridinone, or a Δ2-1,2,3-triazolin-5-one

The formation of oxazolidin-4-one derivatives from DMf and 2-bromo-isobutyramides (3a,b), the aziridinone 4a, or the 1,2,3-triazolin-5-one 5a, is reported. The possibility that a common dipolar intermediate cycloadds onto the carbonyl group of DMF, is considered.

Enantioselective reactions of 2-bromopropanamides with primary, secondary, or tertiary amines. Synthesis of some alaninamides

Abstract Enantiomeric 2-bromopropanamides react with primary, secondary, or tertiary aliphatic amines in toluene at room temperature, yielding the corresponding secondary or tertiary amino, or quaternary ammonium amide. If the reacting amines are good nucleophiles, either product is obtainable in high yield and e.e., by running the reaction either in the presence or absence of Ag 2 O. With a less nucleophilic amine, Ag 2 O or Ag + promotes the formation either of an optically active amine derivative, or a high diastereomeric excess of a dimeric derivative, whose structure was ascertained by X-ray analysis.

Self-protonation of electrogenerated carbanions. Competition between electrode reduction and chemical decay of the conjugate base of the substrate

Abstract The problem of the electrochemical detection of the conjugate base of the parent compound arising in the self-protonation of electrogenerated carbanions has been addressed. In particular, the case in which the conjugate base decays according to a first- order reaction in competition with its electrode reduction has been theoretically analyzed for the voltammetric method. The outcome of the calculations has been successfully compared with experimental data obtained for a representative case such as the reduction of self-protonating 2-bromo-2,N-dimethylpropanamide in N,N′-dimethylformamide.

Stereoselective synthesis of neutral and cationic 2-heterocyclically substituted propanamides

Abstract Neutral (2 R )-2-(1′-imidazolyl)-N-[(1′ R )-phenylethyl]propanamide 5 and the related methylimidazolium and pyridinium salts 6–9 were easily prepared from 2-bromoamide 1a and imidazole, N-methylimidazole and pyridine at room temperature in toluene. The stereoselectivity was lower than with other nucleophiles, Ag + and Ag 2 O proving less selective promoters, and Ag 2 O allowing racemization of starting material and side reactions to be observed.

2-Bromoamides. Stereocontrolled substitution and application to the synthesis of compounds of biological interest

Summary 2-Bromoamides are interesting and versatile intermediates for substitution of bromine by a variety of nucleophiles and for other synthetic approaches. Whereas emphasis is given to chiral 2-bromoamides, congeners carrying a tertiary or primary C-Br function have also been investigated. Among the peculiar features of 2-bromoamides there are the following: i) possibility of substitution at the tertiary C-Br (RCO 2 H, RRNH, or a saccharide, as the nucleophiles); ii) chiral stability and stereochemical control at the secondary C-Br atom (RRNH, ROH or a saccharide as the nucleophiles); iii) the presence of bromine allows cyclic voltammetry and electroreduction at controlled potential both of starting compounds and relevant intermediates; iv) the Cα polarity can be reversed upon electroreduction, and the resulting Cα enolate forms a C-C bond (CO 2 as the electrophile). Application of the bromine substitution reaction allows the synthesis of aminoamides, alkoxyamides of simple alcohols and sugars, depsipeptides and ψ (NH) pseudopeptides, C 2 symmetric compounds.