Enrico Marcantoni

Oxidation of secondary amines to nitrones using urea-hydrogen peroxide complex (UHP) and metal catalysts

Abstract Secondary amines can be readily oxidized to the corresponding nitrones using urea-hydrogen peroxide complex (UHP) and metal catalysts in methanol at room temperature. Sodium tungstate is the most effective catalyst in several runs and common protecting groups are tolerated in these conditions.

Amberlyst 15: A Practical, Mild and Selective Catalyst for Methyl Esterification of Carboxylic Acids.1

Abstract Mild and selective methyl esterification of carboxylic acids are realized using Amberlyst 15 as acid catalyst in methanol. No race mization, epimerization or ketalization products have been observed with this method. Excellent results are obtained in the esterifications of bile acids.

Synthesis of functionalized nitroalkanes by oxidation of oximes with urea-hydrogen peroxide complex and trifluoroacetic anhydride

Abstract Reaction of urea-hydrogen peroxide complex with trifluoroacetic anhydride in acetonitrile at 0°C affords in a safe and easy fashion anhydrous solutions of peroxytrifluoroacetic acid. These can be used to oxidize aldoximes to nitroalkanes in good yields. Ketoximes fail to react in these conditions and are cleaved to the parent carbonyl compounds.

Enantioselective α-Benzoyloxylation of Ketones Promoted by Primary Amine Catalyst

A mixture of 9-amino-(9-deoxy)epi-dihydroquinidine and salicylic acid was able to promote the direct reaction of various cyclohexanones with dibenzoyl peroxide, thus affording the corresponding protected α-hydroxy carbonyl compounds in high yield and enantioselectivity. Interestingly the same catalytic salt was found to be active when 1-indanones derivatives were directly employed in the reaction with dibenzoyl peroxide furnishing chiral 1-oxo-2,3-dihydro-1H-inden-2-yl benzoates in high yields and enantioselectivity. Furthermore their treatment with NaBH(4) gives easy access to the corresponding enantioenriched 1,2-diols in high yields and without any loss of stereoselectivity.

Cerium(III) Chloride Catalyzed Michael Reaction of 1,3-Dicarbonyl Compounds and Enones in the Presence of Sodium Iodide Under Solvent-Free Conditions

Cerium(III) chloride heptahydrate in the presence of sodium iodide catalyses the Michael addition of 1,3-dicarbonyl compounds to α,β-unsaturated ketones and α,β-unsaturated aldehydes with extraordinary efficiency. The very mild conditions allow high chemoselectivity as shown by the absence of the typical side reactions, which can be observed in the conventional base-catalyzed processes. More interestingly, when at least one of the starting materials is liquid at room temperature, the reaction can also be performed without solvents. The CeCl3· 7 H2O/NaI catalyst system can be easily separated from the reaction mixture and it can be reused without an appreciable loss of activity. Advantages of the present procedure, which utilizes cheap and “friendly” reagents, over the previously reported ones, are discussed.

LiClO4-acyl anhydrides complexes as powerful acylating reagents of aromatic compounds in solvent free conditions

Abstract The Friedel–Crafts acylation of various activated benzenes is smoothly carried out with acyl anhydrides in the presence of 2 equiv. of LiClO 4 , as reaction promoter, under solventless conditions.

A new general synthesis of sulfones from alkyl or aryl halides and p-toluenesulfonhydrazide

Abstract Here we report the utilization of commercially available p-toluenesulfonhydrazide as a new nucleophilic reagent in displacement reactions with suitable halides for an improved, general synthesis of sulfones. Good results are obtained with primary, secondary, allylic, benzylic, and aromatic halides activated by withdrawing groups.

Unexpected reactivity of allyl magnesium chloride with nitroarenes. A general method of synthesis of N-allyl-N-arylhydroxylamines and N-allylanilines

Abstract In contrast to alkyl Grignard reagents, the allyl reagent reacts with nitroarenes via 1,2 addition to the nitro group. The “in situ” treatment of the unstable intermediate adduct with LiAlH 4 in the presence of catalytic Pd/C provides a general synthesis of N-allyl-N-arylhydroxylamines or N-allylanilines.

A convergent approach to (R)-Tiagabine by a regio- and stereocontrolled hydroiodination of alkynes.

The occurrence of unsaturated systems in natural products combined with the mildness and the wide range of applicability of CeCl(3) promoted methodologies suggest several potential future synthetic applications within the field of total synthesis of biologically active molecules. On this concept, the use of CeCl(3).7H(2)O-NaI system as an efficient heterogeneous promoter has been highlighted in the iodofunctionalization of carbon-carbon triple bonds. The study has shown that this method would be particularly interesting for the stereoselective formation of trisubstituted (Z)- or (E)-iodoalkenes by simply changing the nature of the solvent. The methodology has been successfully applied to the synthesis of (R)-1-[4,4-bis-(3-methyl-2-thienyl)-3-butenyl]-3-piperidinecarboxylic acid , named (R)-Tiagabine, which is a potent and selective gamma-aminobutyric acid (GABA) uptake inhibitor with proven anticonvulsant efficacy in humans.

Cerium(III) chloride mediated Michael addition of RMgX to nitroenes: a very efficient access to complex nitroalkanes.

Abstract Reactions of RMgXCeCl3 complexes with nitroenes lead to functionalized nitroalkanes in very good yields.