Papers by Maurizio Benaglia
Green Chemistry, 2014
Radical copolymerisation of divinylbenzene and a properly modified enantiomerically pure imidazol... more Radical copolymerisation of divinylbenzene and a properly modified enantiomerically pure imidazolidinone inside a stainless steel column in the presence of dodecanol and toluene as porogens afforded the first example of a chiral organocatalyst immobilized onto a monolithic reactor. Organocatalyzed cycloadditions between cyclopentadiene and cinnamic aldehyde were performed under continuous-flow conditions; by optimizing the experimental set up, excellent enantioselectivities (90% ee at 25°C) and high productivities (higher than 330) were obtained, thus showing that a catalytic reactor may work efficiently to continuously produce enantiomerically enriched compounds. The same catalytic reactor was also employed to carry out three different stereoselective transformations in continuo, sequentially, inside the chiral column (Diels-Alder, 1,3-dipolar nitrone-olefin cycloaddition, and Friedel-Crafts alkylation); excellent results were obtained in the case of the former two reactions (up to 99% yield, 93% ee and 71% yield, 90% ee, at 25°C, respectively). In addition to simplify the product recovery, the monolithic reactor performed better than the same supported organocatalyst in a stirred flask and could be kept working continuously for more than 8 days. † Electronic supplementary information (ESI) available: Synthetic procedures and 1 H NMR, 13 C NMR, and IR spectra of new compounds. Preparation, analysis and characterization of polymer-supported chiral catalysts. NMR and HPLC traces of the stereoselective reaction products. See
European Journal of Organic Chemistry, 2008
Tetrahedron Letters, 1998
The first synthesis of β-lactams bound to a soluble/insoluble polyethylene glycol monomethylether... more The first synthesis of β-lactams bound to a soluble/insoluble polyethylene glycol monomethylether polymeric matrix has been realized by standard reactions carried out on immobilized imines. β-Lactams removal from the polymer has been accomplished under acidic and basic conditions.
Optically Active Aminoalcohol Promoted Addition of 2-Pyridylthioester Boron Enolates to Imines: Enantioselective One-pot Synthesis of β-Lactams
Tetrahedron, 1995
The enolates derived from 2-pyridylthioesters by treatment with BCl3·Me2S and enantiomerically pu... more The enolates derived from 2-pyridylthioesters by treatment with BCl3·Me2S and enantiomerically pure aminoalcohols react with aromatic and heteroaromatic imines to afford β-lactams in a convenient one-pot procedure and in up to 78% e.e. The aminoalcohol can be employed both as the metal ligand and as the base to generate the enolate. Among several aminoalcohols tested, N-methylephedrine turned out to be
Soluble-Polymer-Supported Synthesis ofβ-Lactams on a Modified Poly(ethylene glycol)
Chemistry-a European Journal - CHEM-EUR J, 2000
Abstract A modified poly (ethylene glycol)(PEG) has been developed for the soluble-polymer-suppor... more Abstract A modified poly (ethylene glycol)(PEG) has been developed for the soluble-polymer-supported synthesis of β-lactams. The monomethylether of PEG (MeOPEG) with an average MW of 5000 was used as the support, a 4-(3-propyl) phenyl residue as the spacer, and a 4 ...
Triclorosilane-mediated stereoselective synthesis of β-amino esters and their conversion to highly enantiomerically enriched β-lactams
Organic & Biomolecular Chemistry, 2011
A highly stereoselective trichlorosilane-mediated reduction of N-benzyl enamines was developed; t... more A highly stereoselective trichlorosilane-mediated reduction of N-benzyl enamines was developed; the combination of a low cost, easy to make metal-free catalyst and an inexpensive chiral auxiliary allowed to perform the reaction on substrates with different structural features often with total control of the stereoselectivity. By easy deprotection through hydrogenolysis followed by conversion of β-aminoester to 2-azetidinones, the synthesis of enantiomerically pure β-lactams (>98% e.e.) was successfully accomplished.
The Journal of Organic Chemistry, 2006
Structurally Simple Pyridine N-Oxides as Efficient Organocatalysts for the Enantioselective Allyl... more Structurally Simple Pyridine N-Oxides as Efficient Organocatalysts for the Enantioselective Allylation of Aromatic Aldehydes. -A number of pyridine N-oxides such as (I) is prepared. Some of them are suitable catalysts for the asymmetric allylation of aromatic aldehydes. They allow the synthesis of homoallylic alcohols with moderate to good enantioselectivity. -(PIGNATARO, L.; BENAGLIA*, M.; ANNUNZIATA, R.; CINQUINI, M.; COZZI, F.; J.
2-Aminoimidazolyl and 2-Aminopyridyl ( S )-Prolinamides as Versatile Multifunctional Organic Catalysts for Aldol, Michael, and Diels-Alder Reactions
European Journal of Organic Chemistry, 2013
ABSTRACT The synthesis of multifunctional organocatalysts, easily obtained by the condensation of... more ABSTRACT The synthesis of multifunctional organocatalysts, easily obtained by the condensation of (S)-proline with 2-aminopyridine, 2,6-diaminopyridine, or 2-aminoimidazole, is reported. These chiral prolinamides promoted the aldol condensation between cyclohexanone and different aromatic aldehydes with moderate to very high enantioselectivities (up to 98 % ee), depending on the nature of the substituents on the aryl ring. Computational studies were performed to clarify the stereochemical behaviour of the two different types of catalysts and to understand the role of the different structural components of the chiral prolinamides in the recognition processes between the catalysts and the reactants. In preliminary experiments, trifluoroacetate salts of the chiral prolinamides have been used for the first time as catalysts in Diels–Alder reactions between cyclopentadiene and cinnamaldehyde and in Michael reactions.
The Importance of Electrostatic Interactions in the Stereoselective 1,3-Dipolar Cycloadditions of Nitrones to Chiral Allyl Ethers: An Experimental and Force Field Approach
European Journal of Organic Chemistry, 1998
ABSTRACT
Beilstein Journal of Organic Chemistry, 2013
The behavior of readily synthesized and even commercially available (S)-proline derivatives, was ... more The behavior of readily synthesized and even commercially available (S)-proline derivatives, was studied in the trichlorosilanemediated reduction of ketoimines. A small library of structurally and electronically modified chiral Lewis bases was considered; such compounds were shown to promote the enantioselective reduction of different substrates in good chemical yields. In the HSiCl 3 addition to the model substrate N-phenylacetophenone imine, the organocatalyst of choice led to the formation of the corresponding amine with good stereoselectivity, up to 75% ee. Theoretical studies were also performed in order to elucidate the origin of the stereoselection.
Journal of Fluorine Chemistry
A simple derivatisation of commercially available poly(ethylene-glycols) of different molecular w... more A simple derivatisation of commercially available poly(ethylene-glycols) of different molecular weight followed by the reaction with the selected fluorinated organic molecule, perfluoro-tertbutanol, allowed an easy synthesis of several novel polymers of different fluorine content. The properties of the new materials as MRI agents were preliminarily investigated. In all cases a single 19F signal at NMR in deuterated chloroform and D2O was registered; for a few fluorinated polymeric candidates a good solubility in water was observed and MR imaging of the fluorinated polymer successfully provided images. Most interesting results were obtained with the sample of 1436 MW (24% fluorine content) that not only gave a spectrum with a single resonance line, but, most importantly, was tolerated in low doses when in vivo experiments on animals (mice) were conducted.
Coordination Chemistry Reviews, 2008
ChemInform Abstract: New, Readily Available Organocatalysts for the Enantioselective Reduction of α-Imino- and β-Imino Esters
ChemInform, 2011
Tetrahedron, 2005
Oxidation O 0212 Aerobic Oxidation of Alcohols to Carbonyl Compounds Mediated by Poly(ethylene gl... more Oxidation O 0212 Aerobic Oxidation of Alcohols to Carbonyl Compounds Mediated by Poly(ethylene glycol)-Supported TEMPO Radicals. -The MeO-PEG supported TEMPO reagent PST which possesses a spacer between the PEG resin and the TEMPO moiety is an efficient and readily recoverable reagent for oxidation of alcohols under Minisci's conditions. -(BENAGLIA, M.; PUGLISI, A.; HOLCZKNECHT, O.; QUICI, S.; POZZI*, G.; Tetrahedron 61 (2005) 51, 12058-12064; Ist. Sci. Tecnol. Mol., I-20133 Milano, Italy; Eng.) -Nuesgen 14-049
ChemInform Abstract: Chiral Pyridine N-Oxides Derived from Monoterpenes as Organocatalysts for Stereoselective Reactions with Allyltrichlorosilane and Tetrachlorosilane
ChemInform, 2008
ABSTRACT
ChemInform Abstract: Chiral Lewis Base Promoted Trichlorosilane Reduction of Ketimines. An Enantioselective Organocatalytic Synthesis of Chiral Amines
ChemInform, 2009
Starting from the commercially available enantiopure (1S,2S)-2-amino-1-phenyl-1,3-propanediol nov... more Starting from the commercially available enantiopure (1S,2S)-2-amino-1-phenyl-1,3-propanediol novel enantiomerically pure benzimidazoles were prepared; N-alkylation gave chiral benzimidazolium salts, which were tested in asymmetric benzoin condensations. The synthesis of conceptually new, enantiomerically pure, C 2 symmetric bis-thiazolium and bis-benzimidazolium salts was also developed. These new chiral heterocycles were employed as catalysts in the asymmetric dimerisation of benzaldehyde to give benzoin with moderate enantioselectivity.
Novel C 1 -symmetric bis(oxazoline) ligands with a secondary binding sidearm were prepared in ena... more Novel C 1 -symmetric bis(oxazoline) ligands with a secondary binding sidearm were prepared in enantiomerically pure form in good yields, in only four steps starting from commercially available reagents. These new chiral ligands were tested in the enantioselective Mukaiyama aldol condensation between the trimethylsilyl keteneacetal of methyl isobutyrate and a non-chelating substrate such as benzaldehyde to afford the product in up to 55% ee.
Tetrahedron Letters, 1998
The first synthesis of [~-lactams bound to a soluble/insoluble polyethylene glycol monomethylethe... more The first synthesis of [~-lactams bound to a soluble/insoluble polyethylene glycol monomethylether polymeric mallix has been realized by standard reactions carried out on immobilized imines. 13-Lactams removal from the polymer has been accomplished under acidic and basic conditions.
Stereoselective Addition of 1,3-Diketones to β-Nitroacrylates Catalyzed by Chiral Metal-Free Bifunctional Catalysts
Asian Journal of Organic Chemistry, 2014
ABSTRACT Organocatalytic stereoselective additions of different nucleophiles to β-nitroacrylates ... more ABSTRACT Organocatalytic stereoselective additions of different nucleophiles to β-nitroacrylates have been investigated. A thiourea-based cinchona-derived bifunctional catalyst promotes the addition of 1,3-diketones to differently substituted nitroacrylates in modest to fair yields and up to 93 % enantioselectivity. The 1,3 dicarbonyl functionality of the addition products was then used to synthesize enantiomerically enriched 3,4,5-trialkyl substituted pyrazoles via reaction with hydrazine. The stereoselective addition of N-methylindole to nitroacrylate was also preliminarily studied; the Friedel–Crafts alkylation was successfully organocatalyzed in the presence of an acid additive in very good yields and up to 53 % enantioselectivity.
Uploads
Papers by Maurizio Benaglia