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Publications (79)
Alice points out the preference of one conformational enantiomer by “crossing the mirror” thanks to the catalyst formed from the phosphoric acid and bromine “delivered” by N‐bromosuccinimide (NBS). Both the selected conformer and the new catalyst formed in situ merge their respective roads to converge on the product. More information can be found i...
We have studied the enantioselective transannular aminohalogenation reaction using unsaturated medium‐sized cyclic benzosulfonamides using both chiral Bronsted acid or phase‐transfer catalysis. Under the optimized reaction conditions a variety of bicyclic adducts can be obtained with good yields and high enantioselectivities. The mechanism of the r...
The Prins reaction is a very convenient synthetic platform for the preparation of oxygen-containing heterocyclic compounds, especially tetrahydropyrans and tetrahydrofurans. While this reaction has been extensively used by synthetic chemists since its discovery, the last years have witnessed impressive improvements in its performance and scope and...
A transannular approach has been developed for the construction of pyrrolo[1,2-b]isoquinolinones starting from benzo-fused nine-membered enelactams. This process takes place in the presence of a halogenating agent and under Brønsted acid catalysis and proceeds via a transannular amidohalogenation, followed by elimination. The reaction has been foun...
Transannular reactions have shown a remarkable performance for the construction of polycyclic scaffolds from medium- or large-sized cyclic molecules in an unconventional manner. Recent examples of transannular reactions reported from 2011 have been reviewed, emphasizing the excellent performance of this approach when accessing the target compounds....
Prozesu biokimikoen behaketa eta ulertzeak ikertzaileak inspiratu du entzimen jarrera antzeratzen duten molekula organiko bakunak aurkitzeko. 2021eko Kimikako Nobel Saria nabarmendu du biomimetikan oinarritutako organokatalisiak jasandako garapena, halaber organokatalizatzaileek jatorrizko aitzindari entzimatikoekin alderatuta abantailak dituzte, h...
An approximation to the synthesis of several sesquiterpenes from the Guaiane family is described in which the core structure was obtained through a transannular Morita-Baylis-Hillman reaction performed under kinetic resolution. Several manipulations of the obtained MBH adduct have been carried out directed towards the total synthesis of γ-Gurjunene...
The catalyzed desymmetrizative ring expansion of alkenylcyclobutanols promoted by halofunctionalization of the alkene moiety with N-bromosuccinimide has been experimentally and computationally studied. The reaction yields highly enantioenriched cyclopentanones bearing two all-carbon quaternary stereocenters, one of them being generated in the rearr...
An efficient and easy protocol for performing 1,3-dipolar cycloaddition using azomethine ylides and acrolein is presented. The reaction catalyzed by d-proline allows the synthesis of C-3 unsubstituted pyrrolidines. The application of this methodology to the synthesis of an advanced intermediate in the preparation of a Hepatitis C virus inhibitor is...
The 8-azabicyclo[3.2.1]octane scaffold is the central core of the family of tropane alkaloids, which display a wide array of interesting biological activities. As a consequence, research directed towards the preparation of this basic structure in a stereoselective manner has attracted attention from many research groups worldwide across the years....
We have optimized a synthetic approach to (±)‐Ferrugine in 8 steps starting from 5‐aminocyclohept‐1‐ene and using the Brønsted acid‐catalyzed pseudotransannular ring opening of the epoxide derived from this cycloheptene as the key step for the construction of the 8‐azabicyclo[3.2.1]octane central core. While attempting the enantioselective synthesi...
Acylcyclopropanes are employed as useful donor-acceptor cyclopropanes that undergo formal (4 + 2) cyclocondensation with N-unprotected 3-substituted indoles in the presence of a Brønsted acid catalyst. The reaction involves the simultaneous alkylation of both the N and C-2 positions of the indole and provides access to the 8,9-dihydropyrido[1,2-a]i...
Chiral bifunctional tertiary amine/squaramides catalyze the enantioselective Michael/transannular aldol reaction on medium-sized cyclic ketoenones leading to bicycle[5.4.0]undecanes.
Racemic γ-substituted allenes undergo enantioselective higher order [8 + 2]-cycloaddition with azaheptafulvenes using a chiral amino acid derived amidophosphine as catalyst, providing the corresponding azaazulenoid cycloadducts with excellent levels of regio-, diastereo-, and enantioselectivities. In this reaction, the activated allylic phosphonium...
Die chirale Phosphorsäure VAPOL (grün) katalysiert die pseudotransannulare Epoxidringöffnung an von Meso-Cycloalkenylamin abgeleiteten Epoxiden, um hoch enantioangereicherte Tropanolderivate in einem einzigen Schritt durch sehr effiziente Desymmetrierung zu liefern. Diese Strategie wurde auf die Totalsynthese der beiden natürlich vorkommenden Alkal...
The enantioselective synthesis of tropanols has been accomplished through chiral phosphoric acid‐catalyzed pseudotransannular ring‐opening of 1‐aminocyclohept‐4‐ene‐derived epoxides. The reaction proceeds together with the desymmetrization of the starting material and leads to the direct formation of the 8‐azabicyclo[3.2.1]octane scaffold with exce...
Catalytic and enantioselective approaches to transannular reactions are very limited and mostly are based on chiral Lewis acid-catalyzed pericyclic reactions. In this report we present an efficient and straightforward methodology to access bicyclic carbo- and heterocyclic scaffolds combining different ring sizes through transannular Morita-Baylis-H...
Highly enantioenriched, chromatographically-stable secondary allyl boronates featuring a 1,1,2,2-tetraethyl-1,2-ethanediol fragment (Epin) were obtained by kinetic resolution of their racemic mixtures. The Epin group at boron considerably improved stability of allyl boronates allowing them to be readily isolated by chromatography on silica. The res...
We have demonstrated that dihydropyrrole-based enamide derivatives can act as efficient precursors of chiral quaternary N-acyliminium salts under Brønsted acid catalysis that undergo reaction with hydrazones, the latter participating as...
Racemic cyclopropyl ketones undergo enantioselective rearrangement to deliver the corresponding dihydrofurans in the presence of a chiral phosphoric acid as catalyst. The reaction involves activation of the donor‐acceptor cyclopropane substrate by the chiral Brønsted acid catalyst that promotes the ring‐opening event driven by the release of ring s...
Racemic cyclopropyl ketones undergo enantioselective rearrangement to deliver the corresponding dihydrofurans in the presence of a chiral phosphoric acid as catalyst. The reaction involves activation of the donor‐acceptor cyclopropane substrate by the chiral Brønsted acid catalyst that promotes the ring‐opening event driven by the release of ring s...
A diastereodivergent approach to highly substituted bicyclo[3.1.0]hexanes has been developed through a transannular alkylation reaction that builds up the bicyclic core employing asymmetric organocatalysis as the tool for the installation of all stereocenters. On one hand, a Michael/Michael cascade process between enals and 4-alkenyl sulfamidate im...
In this work, carboxylic acids, which are typically regarded as poor nucleophiles, are demonstrated to be competent reagents to promote the ring-opening of formylcyclopropanes after activation of the latter through iminium ion formation. Under optimized reaction conditions, a variety of γ-acyloxy-substituted aldehydes can be obtained in high yields...
An efficient and easy protocol for promoting CN acyl transfer reaction in diverse enantiopure densely substituted pyrrolidine 2,2-dicarboxylates was performed, yielding the corresponding proline ester derivatives with yields in the range of 68-99% and total diastereoselection (d.r. >95:5 in all cases). The substitution pattern both at C-3 and C-5...
BINOL-based N-trifluoromethanesulfonyl phosphoramides have been used to catalyze the enantioselective (4+3) cycloaddition between furans and oxyallyl cations, the latter being generated in situ by oxidation of allenamides. In this methodology, the chiral organic phosphoramide counteranion is proposed to engage in the activation of the oxyallyl cati...
BINOL-based N-trifluoromethanesulfonyl phosphoramides have been used to catalyze the enantioselective (4+3) cycloaddition between furans and oxyallyl cations, the latter being generated in situ by oxidation of allenamides. In this methodology, the chiral organic phosphoramide counteranion is proposed to engage in the activation of the oxyallyl cati...
2-Hydroxydihydropyran-5-ones behave as excellent polyfunctional reagents able to react with enals through oxa-Michael/Michael process cascade under the combination of iminium and enamine catalysis. These racemic hemiacetalic compounds are used as unconventional O-pronucleophiles in the initial oxa-Michael reaction, also leading to the formation of...
Formylcyclopropanes undergo activation in the presence of an N-heterocyclic carbene catalyst generating a donor-acceptor cyclopropane intermediate with the ability to undergo ring-opening followed by formal [4+2] cycloaddition with alkylideneoxindoles. This enables the direct enantio- and diastereoselective synthesis of tetrahydropyrano[2,3-b]indol...
The reaction of nitrones with enals under iminium activation can be modulated by using cooperative H-bonding catalysis to induce the participation of a nitrone ylide (C-N-C) instead of the classical C-N-O dipole. As a consequence, N-hydroxypyrrolidines, rather than the expected isoxazolidines, are obtained. The reaction proceeds smoothly and high e...
The use of chiral N-heterocyclic carbenes (NHCs) as catalysts in asymmetric synthesis has opened a wide range of applications due to their unique ability to generate reaction intermediates with unusual reactivity patterns that very often involve the reversal of the typical polarity associated with the functional groups present in the starting mater...
Pyranone rings have shown a great applicability in diverse organic reactions due to their multiple functionalities and also because the compounds that are obtained from such reactions are present in the framework of several natural products. In this work, we chose 2H-pyran-3(6H)-one as substrate to continue the program directed toward the developme...
The catalytic enantioselective Michael reaction is the conjugate addition of a resonance-stabilized carbanion to an electron-poor olefin (an αβ-unsaturated carbonyl compound or a related derivative) mediated by substoichiometric amounts of a chiral catalyst that enables stereocontrol in the newly generated stereocenter(s). This reaction allows the...
Aminobenzaldehydes react with cyclopropaneacetaldehydes under conditions A) in a one-pot domino process to produce dihydroquinolines with good to excellent e.e.
The possibility for primary or secondary amines to activate enolizable aldehydes or ketones towards a variety of reactions opened the way for their α-functionalization in a catalytic and enantioselective fashion. In the same line, the β-functionalization of enones and enals is possible through the catalytic formation of an α,β-unsaturated iminium i...
An easy and straightforward procedure has been developed for the synthesis of highly enantioenriched pyrrolo[1,2-a]quinolines through a one-pot process that comprises a domino cyclopropane ring opening/aza-Michael/aldol reaction followed by acid-promoted lactamization. The key feature of the synthetic approach relies on the ability of conveniently...
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and...
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and...
The asymmetric and catalytic Michael reaction between α-nitroesters and nitroalkenes has been studied in the presence of two bifunctional catalysts both containing the same absolute chirality at the carbon backbone. The reaction performed in similar conditions allows us to control the syn or anti selectivity of the Michael adduct obtaining good yie...
Nitromethylacrylates have proved to be suitable 1,3-dinucleophiles reacting with α,β- unsaturated aldehydes in the presence of a secondary-amine catalyst to furnish Michael/Henry cascade products in moderate yields and with high enantioselectivities although with moderate diastereoselectivities. The reaction proceeds by iminium ion activation of th...
The modes of catalytic action of three squaramide-derived bifunctional organocatalysts have been investigated using DFT methods. The [5+2] cycloaddition between oxidopyrylium ylides and enals has been used as model reaction. Two primary modes are possible for the different catalysts studied. The preference for one mode over the other is due to the...
A straightforward procedure to carry out the enantioselective benzoin reaction between aldehydes and ynones by employing a chiral N-heterocyclic carbene (NHC) as catalyst was developed. Under the optimized reaction conditions, these ynones undergo a clean and selective 1,2-addition with the catalytically generated Breslow intermediate, not observin...
We have employed 4-alkenyl-5H-1,2,3-oxathiazole 2,2-dioxides as useful reagents able to generate in situ an electron-rich diene intermediate that has the potential to undergo [4+2] cycloaddition with a,b-unsaturated aldehydes through the iminium/enamine activation manifold. Under the optimized reaction conditions, that comprise the use of O-TMS dip...
![Scheme 1: The catalytic enantioselective [3+2] cycloaddition reaction...](publication/275229126/figure/fig1/AS:565832700502016@1511916436165/Scheme-1-The-catalytic-enantioselective-3-2-cycloaddition-reaction-between-azomethine_Q320.jpg)
The [3+2]-cycloaddition reaction between acrolein and in situ generated acyclic azomethine ylides promoted by a chiral secondary amine to generate C-3 unsubstituted pyrrolidines has been studied in detail. Optimum conditions involve the use of the cheap and readily available l-Proline as catalyst to afford the pyrrolidine cycloadduct with complete...
Benzopyrylium ylides generated in situ from 1-acetoxyisochroman-4-ones reacted with α,β-unsaturated aldehydes in the presence of a bifunctional secondary-amine/squaramide catalyst to furnish [5+2] cycloaddition products in good yield with high diastereo- and enantioselectivity. The reaction proceeds by dienamine activation and involves β,γ-function...
The asymmetric synthesis of substituted pyrrolidines has been accomplished using a novel organocatalytic cyclization reaction promoted by a Cinchona alkaloid based primary amine. The reaction proceeds smoothly yielding pyrrolidine-2,2-dicarboxylates after in situ diastereoselective reduction with high levels of enantioselection. Furthermore, these...
We have developed a procedure for the stereoselective and diastereodivergent synthesis of densely functionalised cyclohexanes containing four stereocentres through an asymmetric Michael‐initiated ring closure (MIRC) cascade reaction employing hydrogen‐bond catalysis, which is able to prepare adducts with different absolute configurations starting f...
The enantioselective synthesis of α- and γ-tocopherol (the most biologically active members of vitamin E family) and analogues has been accomplished employing a new enantioselective gold catalyzed intramolecular allylic alkylation reaction followed by an olefin cross-metathesis as key steps. The methodology proved to be applicable to different olef...
We have discovered that N-alkyl aminomalonates undergo a fast and selective intramolecular CN acyl rearrangement reaction in the presence of a strong base, leading to N-protected glycinates in excellent yield. Moreover, the fact that the reaction proceeds through a nucleophilic enolate intermediate has been used for implementing a tandem rearrangem...
Efraim Reyes was born in Galdakao (Bizkaia) in 1978. He graduated from the University of the Basque Country in 2001 and received his PhD in 2006, under the direction of Prof. Dr. D. Badia and Prof. Jose L. Vicario. After postdoctoral studies in 2007 at the Center for Catalysis of the University of Aarhus (Denmark), under the supervision of Prof. Dr...
The Michael reaction of bis(phenylsulfonyl)methane with α,β-unsaturated aldehydes in the presence of catalytic amounts of a chiral secondary amine is presented. This transformation proceeds in good to excellent yields furnishing the corresponding Michael adducts in excellent enantioselectivities. Furthermore, other chiral building blocks are access...
The synthesis of densely functionalized pyrrolo[2,1-a]isoquinolines was accomplished using the organocatalytic [3+2] cycloaddition between enals and azomethine ylides under iminium catalysis developed in our group some years ago as the key step. The cycloaddition proceeds smoothly yielding the corresponding pyrrolidine as a single endo diastereoiso...
A simple one-pot procedure was developed for [3+2]-cycloaddition reactions of ,-unsaturated aldehydes, diethyl aminomalonate, and aromatic aldehydes in the presence of diphenyl[(2S)-pyrrolidin-2-yl]methanol as catalyst. This reaction converts simple, commercially available, starting materials into densely functionalized polysubstituted pyrrolidines...
Unconjugated 2,5-dienals are more reactive substrates than the corresponding fully conjugated α,β,γ,δ-unsaturated aldehydes towards organocatalytic activation through trienamine intermediates. This difference in reactivity has been demonstrated in the Diels-Alder reaction with nitroalkenes, a reaction that proceeds with clean β,ε-selectivity to aff...
The catalytic enantioselective conjugate addition reaction is an important transformation in organic chemistry, which has been used for the synthesis of a significant amount of new products used in many research areas in chemistry. In this chapter, we summarize the literature dealing with catalytic enantioselective versions of this transformation,...
Two efficient and alternative protocols for the preparation of highly enantioenriched piperidine structures are reported. We have also developed a simple route to access to fully diastereo- and enantioenriched substituted piperidinones. The key step of all this synthesis relies on a diastereoselective Mannich reaction, employing the readily availab...
Ethyl glyoxylate N-tosylhydrazone has been identified as an excellent sulfonyl anion surrogate in the DBU-catalyzed conjugate addition reaction with enones and enals for the synthesis of functionalized sulfones. The reaction proceeds under base-catalyzed conditions and provides a direct access to gamma-keto- and gamma-hydroxy-sulfones in a simple a...
The behaviour of aminoacetophenones as Michael donors in catalytic enantioselective Michael reactions with α,β‐unsaturated aldehydes under iminium activation has been studied. These compounds react with each other in the presence of catalytic amounts of a chiral secondary amine through a Michael/hemiaminal formation cascade process which proceeds w...
We optimized the structure of a new family of chiral diarylprolinol‐type organocatalysts with improved performances in conjugate addition reactions performed in water and proceeding under the iminium activation manifold. The principles behind the catalyst design were, firstly, the incorporation of a tertiary amino group at the 4‐position of the pyr...
We have developed an efficient protocol for carrying out the stereocontrolled formal conjugate addition of the hydroxycarbonyl anion equivalents to alpha,beta-unsaturated carboxylic acid derivatives using (S,S)-(+)-pseudoephedrine as chiral auxiliary making use of the synthetic equivalence between the heteroaryl moieties and the carboxylate group....
Donor-acceptor monosubstituted hydrazones participate as suitable reagents able to undergo an enantioselective formal diaza-ene reaction with α,β-unsaturated aldehydes under chiral secondary amine catalysis. This constitutes a new approach for the enantioselective conjugate addition of hydrazones to enals under metal-free conditions and leads to th...
Racemic 5-acyloxydihydropyranones react with enolizable α,β-unsaturated aldehydes in the presence of a chiral secondary amine catalyst furnishing a wide range of differently substituted tetrahydro-1H-isochromanes with excellent results. The reaction relies on the activation of the enal by the catalyst through the formation of a dienamine intermedia...
A broad spectrum of allylic alcohols can be successfully transformed to the azides.
Highlighted in Synfacts 2012, 8(4), 0429
Highlighted in ChemInform 2012, 43, DOI: 10.1002/chin.201224035
Highlighted in organic chemistry portal; http://www.organic-chemistry.org/abstracts/lit3/521.shtm
A direct catalytic azidation of primary, secondary, and tertiary allylic alcohols has been developed. This new azidation reaction affords the corr...
The catalytic enantioselective aza-Michael reaction is an important transformation in organic chemistry, which has been used for the synthesis of a significant amount of nitrogen-containing products for many research areas in chemistry. In this review, we summarize the literature dealing with catalytic enantioselective versions of this transformati...
5-Mercaptotetrazoles have been identified as useful and versatile Michael donors in enantioselective amine-catalyzed aza-Michael reactions with α,β-unsaturated aldehydes, showing excellent behavior as N-nucleophiles instead of their usual trend to react as S-nucleophiles. In addition several unprecedented chemical modifications on the tetrazolothio...
Chiral contact ion-pair catalysis with particular focus on metal-free processes is gaining in interest. As a result, new perspectives are opened, and highly stereoselective transformations, traditionally performed under metal catalysis, can be realized. Herein, we report the development of an unprecedented asymmetric Brønsted acid-catalyzed allylic...
A catalytic enantioselective synthesis of dihydrofurans has been developed. 1,3-Dicarbonyl derivatives react with (E)-β,β-bromonitrostyrenes in the presence of a chiral bifunctional thiourea catalyst providing mild and efficient access to diverse polysubstituted dihydrofurans in good yields and enantioselectivities.
We have developed a very efficient procedure for carrying out the cyclopropanation reaction of alpha,beta-unsaturated aldehydes with diethyl bromomalonate using an O-TMS-diarylprolinol as a catalyst. We have found that the use of water as reaction medium results in a remarkable beneficial effect on the reaction, allowing it to be performed without...
The organocatalytic conjugate addition of different aldehydes to beta-nitroacrolein dimethyl acetal, generating the corresponding highly functionalized nitroaldehydes in high yields and with high stereoselectivities, has been studied in detail. These transformations have been achieved by using both readily available starting materials in a 1:1 rati...
The asymmetric organocatalytic aza-Michael reaction of several nitrogen heterocycles and α,β-unsaturated aldehydes has been studied in detail; under the optimised conditions, the conjugate addition products have been obtained in high to excellent enantioselectivities.
The asymmetric organocatalytic aza-Michael reaction of several nitrogen heterocycles and alpha,beta-unsaturated aldehydes has been studied in detail; under the optimised conditions, the conjugate addition products have been obtained in high to excellent enantioselectivities.
Organolithium reagents undergo highly regio- and diastereoselective 1,4-addition to (S,S)-(+)-pseudoephedrine enamides furnishing the corresponding beta-alkyl-substituted adducts in excellent yields and diastereoselectivities. In addition, the intermediate lithium enolates generated after the conjugate addition step undergo a highly diastereoselect...
Alpha,beta-unsaturated amides derived from the chiral amino alcohol (S,S)-(+)-pseudoephedrine undergo a very clean and diastereoselective tandem conjugate addition/alpha-alkylation reaction. Excellent results have been achieved using a wide range of differently substituted conjugate acceptors, organolithium reagents, and alkyl halides. The chiral a...
