Marino Petrini

Proline-Catalyzed Asymmetric Formal α-Alkylation of Aldehydes via Vinylogous Iminium Ion Intermediates Generated from Arylsulfonyl Indoles

Catalysis with chiral secondary amines (asymmetric aminocatalysis) has become a well-established and powerful synthetic tool for modern synthetic chemistry. The impressive level of scientific competition and high quality research generated in this area have opened up new synthetic opportunities that were considered inaccessible only a few years ago. Even reactions that had been considered impossible became a reality through aminocatalysis. One of the best validations of this approach is the development of the catalytic, asymmetric direct a-alkylation of aldehydes. This highly challenging and valuable C C bond-forming strategy was completely unknown before the advent of asymmetric aminocatalysis. In 2004, Vignola and List presented the first catalytic asymmetric intramolecular a-alkylation of haloaldehydes under enamine catalysis. They demonstrated the ability of proline-derived catalysts to overcome the classical drawbacks associated with the stoichiometric alkylation of preformed aldehyde enolates, such as the tendency toward aldol condensation and the Canizzaro or Tischenko reactions. However, extension of their aminocatalytic strategy to an intermolecular version failed because of deactivation of the amine catalyst by N-alkylation with the alkyl halide. Thus, chemists started to search for different aminocatalytic strategies to accomplish the challenging goal of an intermolecular formal aldehyde a-alkylation. In 2006, Ibrahem and C2rdova reported a non-asymmetric catalytic intermolecular a-allylic alkylation of aldehydes by combination of transition-metal and enamine catalysis. More recently, MacMillan and co-workers exploited a new aminocatalytic activation concept, based on radical intermediates, to solve the synthetic problems of the catalytic asymmetric aallylation, arylation, enolation, and vinylation of unmodified aldehydes. Herein, we report a new challenging strategy for the asymmetric intermolecular enamine-catalyzed formal a-alkylation of aldehydes. The novel approach is founded upon the use of a reagent 1 (Scheme 1), which, because of the presence

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.

Conjugate addition of nitroalkanes to N-substituted maleimides. Synthesis of 3-alkylsuccinimides and pyrrolidines

Abstract 3-Alkylidenesuccinimides obtained by conjugate addition of nitroalkanes to N -substituted maleimides can be reduced to the corresponding 3-alkyl derivatives by catalytic hydrogenation. 3-Alkylsuccinimides can be further reduced using BH 3 ·Me 2 S complex to afford 3-alkylpyrrolidines in good yield.

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.

New and efficient synthesis of ω-nitroalcohols and spiroketals by chemio- and regioselective reductive cleavage of 2-nitrocycloalkanones

Abstract ω-Nitroalcohols have been prepared by a new and efficient chemio- and regioselective reductive cleavage performed on 2-nitrocycloketones with sodium borohydride in acetonitrile / water. This reaction opens a more practical and convenient route to the synthesis of spiroketals.

Unprecedented, Selective Nef Reaction of Secondary Nitroalkanes Promoted by DBU Under Basic Homogeneous Conditions

Secondary nitrocompounds can be converted into the corresponding ketones under basic conditions using DBU in acetonitrile. Primary nitroalkanes are unaffected by these conditions.

Base assisted substitution of α-amidoalkyl sulfones by nitromethane anion. A new entry to functionalized α-amino acids

Abstract The nitromethane anion reacts with α-amidoalkyl sulfones in THF affording the corresponding nitro derivatives that upon oxidation with alkaline potassium permanganate give the corresponding N-protected α-amino acids

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.

2-(2-Nitroethyl)-1,3-dioxolane as reagent for 3-oxopropyl anion synthon : a new route to jasmonoid and prostaglandin intermediates

Abstract 2-(2-Nitroethyl)-l,3-dioxolane 18 a versatile reagent for 3-oxopropyl anion synthon. New methodology, based on nitro- aldol condensation, oxidation and direct or indirect denitration sequence is developed for the conversion of 2-(2-nitroethyl)-l,3 dioxolane into (Z)-l,4-dioxodec-7-ene, (Z)-2-(2-pentenyl)-2-cy clopenten-l-one, methyl 9,12-dioxododecanoate and methyl 7-(5- oxocyclopentenyl)heptanoate, which are popular Intermediates for syntheses of (Z)-jasmonolds and prostaglandins.