Search

International audience; Recently, porous organic crystals (POC) based on macrocycles have shown exceptional sorption and separation properties. Yet, the impact of guest presence inside a macrocycle prior to adsorption has not been studied. Here we show that the inclusion of trimethoxybenzyl-azaphosphatrane in the macrocycle cucurbit-[8]uril (CB[8]) affords molecular porous host-guest crystals (PHGC-1) with radically new properties. Unactivated hydrated PHGC-1 adsorbed iodine spontaneously and selectively at room temperature and atmospheric pressure. The absence of (i) heat for material synthesis, (ii) moisture sensitivity, and (iii) energy-intensive steps for pore activation are attractive attributes for decreasing the energy costs. 1 H NMR and DOSY were instrumental for monitoring the H 2 O/I 2 exchange. PHGC-1 crystals are non-centrosymmetric and I 2-doped crystals showed markedly different second harmonic generation (SHG), which suggests that iodine doping could be used to modulate the non-linear optical properties of porous organic crystals.

International audience; The synthetic equivalents of the enantiopure binaphthyl bis(aryne) atropisomers derived from BINOL (1,1'bi-2,2'-naphtol) featuring a stereogenic axis vicinal to the two reactive triple bonds can be generated for the first time in solution in an enantiospecific manner. Using a two-step sequence based on the bidirectional [4+2] cycloaddition of furan derivatives followed by an aromatizative deoxygenation reaction, several 9,9'-bianthracenyl-based atropisomers could be prepared enantiospecifically in high enantiomeric purity. Alternatively, bidirectional reactions with anthracene, 2bromostyrene, and perylene as the arynophiles afforded very congested bis(benzotriptycene), bis(tetraphene) and bis(anthra[1,2,3,4-ghi]perylene) nanocarbon atropisomers in equally high enantiomeric purity. In complement, cross reactions with two different arynophiles revealed possible. The unusual atropisomer prototypes described in this study open the way to enantiopure nanographene atropisomers designed for functions.

International audience; Chloroazaphosphatranes, the corresponding halogenophosphonium cations of the Verkade superbases, were evaluated as a new motif for halogen bonding (XB). Their modulable synthesis allowed for synthetizing chloroazaphosphatranes with various substituents on the nitrogen atoms. The binding constants determined from NMR titration experiments for Cl − , Br − , I − , AcO − , and CN − anions are comparable to those obtained with conventional iodine-based monodentate XB receptors. Remarkably, the protonated azaphosphatrane counterparts display no affinity for anions under the same conditions. The strength of the XB interaction is, to some extent, related to the basicity of the corresponding Verkade superbase. The halogen bonding abilities of this new class of halogen donor motif were also revealed by the Δδ(31 P) NMR shift observed in CD 2 Cl 2 solution in the presence of triethylphosphine oxide (TEPO). Thus, chloroazaphosphatranes constitute a new class of halogen bond donors, expanding the repertory of XB motifs mainly based on C Ar −I bonds.

Despite tremendous efforts towards the development of organocatalytic enantioselective Michael additions of nitroalkanes to α,β‐unsaturated carbonyl compounds, highly substituted electrophiles remain challenging. β‐Arylidene‐α‐ketolactones and α‐ketolactams are used as highly electrophilic Michael acceptors that afford the corresponding products in moderate to good yields, with high enantioselectivities.

Two new hemicryptophanes combining a cyclotriveratrylene unit with either an aminotrisamide or a tris(2-aminoethyl)amine (tren) moiety have been synthesized. Although a conventional synthesis approach was used, the molecular cages obtained are devoid of the expected

International audience; A reinvestigation of a chiral phosphoric-acidcatalyzedfour-component Hantzsch enantioselective synthesis of polyhydroquinolines reported in 2009 is presented. In our hands, when the reaction was performed with fidelity to the original report using a chiral enantiopure phosphoric acid catalyst, noenantioselectivity was observed. Unlike in the original report,enantioselectivity results are backed by baseline separation of the enantiomers by HPLC analyses on chiral stationary phase with UV and chiroptical detection.

International audience; Azaphosphatranes were found to act as efficient organocatalysts in the presence of water for the cyanation of differently substituted imines. A relatively safer source of cyanide, trimethylsilyl cyanide (TMSCN), was used, and excellent yields could be obtained with only 0.05 mol % of catalyst. The influence of acidity of azaphosphatranes on catalytic activity as well as the role of azaphosphatranes in the mechanism of the reaction were also investigated.

Tetrahydropyridines are important heterocycles present in many molecules of natural and non‐natural origins that exhibit a wide array of biological activities. With several sp3‐hybridized carbon atoms in their structure, they often include one or several stereogenic centers, whose control represents a great synthetic challenge. For the past two decades, enantioselective organocatalysis has developed as a very powerful strategy to perform the synthesis of enantioenriched compounds, including heterocycles. In this Microreview, we wish to provide the readers with a general overview about the organocatalytic strategies that have been used to achieve the preparation of diversified families of tetrahydropyridines, thereby providing elements of reflection for further developments.

β-Dicarbonyl compounds have established themselves as substrates of choice in enantioselective organocatalysis because of their easy activation. Among them, β-diketones, β-diesters, and β-ketoesters lead the dance and there has been only limited work with other β-dicarbonyl compounds as pronucleophiles. In this Synpacts article, we wish to discuss our recent contributions to the introduction of Weinreb β-ketoamides in organocatalyzed transformations, where they can provide an interesting balance between reactivity and selectivity, with also interesting potentialities in terms of postfunctionalization.1 Introduction2 Preparation of Weinreb β-Ketoamides3 Michael Addition to Nitroolefins4 Multicomponent Synthesis of Tetrahydropyridines5 Outlook

International audience; The organocatalytic enantioselective conjugate addition of secondary β-ketoamides to α,β-unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto’s thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 % ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.

International audience; α,β-Unsaturated acyl cyanides are key bis-electrophile substrates for successful domino enantioselective organocatalyzed Michael-intramolecular acylation domino sequences. This new reactivity has been applied to the synthesis of enantioenriched azaspiro[4,5]decanone ring systems by a formal [3+3]spiroannulation, constituting a rare example of synthesis of glutarimides in an optically active form.

Polysubstituted chiral cyclohexanes and cyclohexenes are important building blocks in organic synthesis. From historical and pioneering reports to the most recent accounts, this review focuses on domino enantioselective organocatalytic methodologies that have allowed the control of the relative and absolute configurations of up to six stereogenic centers in the construction of these versatile molecular architectures. 1 Introduction 2 Two-Component Transformations 2.1 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 2.2 Michael-Initiated Domino Reactions with Nitroolefins 2.3 Non Michael-Initiated Domino Reactions 3 Multicomponent and Related Transformations 3.1 Pseudo-Three-Component Reactions 3.1.1 Michael-Initiated Domino Reactions with Nitroolefins 3.1.2 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 3.2 Consecutive Reactions 3.2.1 Michael-Initiated Domino Reactions with Nitroolefins 3.2.2 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 3.3 Multicomponent Reactions 3.3.1 Michael-Initiated Domino Reactions with Nitroolefins 3.3.2 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 4 Conclusion

International audience; For the first time, enantiomerically enriched atropoisomeric furans have been accessed using a central- to-axial chirality conversion strategy. Hence, oxidation of the enantioenriched dihydrofuran precursors gave rise to axially chiral furans with high enantiopurities accounting from excellent conversion percentages (cp) in most cases.

In this feature article, a general perspective of the research program aimed towards the preparation of polycyclic heterocycles by the means of enantioselective organocatalytic multicomponent reactions is presented. Guidelines for reaction design, including the selection of substrates and organocatalysts are discussed. For all transformations, scope and limitations are presented, along with post-functionalization to afford diversified heterocyclic scaffolds. 1 Introduction 2 Type I Products: 1,4,5,6-Tetrahydropyridines 3 Type II Products: 1,2,3,4-Tetrahydropyridines 4 Type III Products: Bridged Perhydropyridines 5 Conclusion and Perspective

International audience; The reaction between cyclic 1,3-ketoamides and Michael acceptors in the presence of a catalytic amount of a polymer-supported organobase PS-BEMP has been developed for a direct access to spirocyclic 1,3-ketolactams through a domino Michael addition/hemiacetalization sequence. The products could be isolated in high chemical yields and purities after simple filtration, and the catalyst could be re-used without any re-activation. These spirolactams, containing a hemiaminal moiety, may be viewed as precursors of N-acyliminium intermediates upon Lewis acid activation, which allowed various subsequent functionalizations leading to original polycyclic lactams.

A general evaluation of silylated nucleophiles to intercept transient α-oxoketenes generated by microwave-assisted Wolff rearrangement of 2-diazo-1,3-dicarbonyl compounds is presented. Original scaffolds and synthetic intermediates are accessed in a rapid, efficient and easy-to-handle way. Mechanistic studies by DFT calculations and some post-functionalizations are discussed.

Suitably substituted enantioenriched 4-aryl-1,4-dihydro-pyridines prepared by an organocatalytic enantioselective Michael addition were oxidized with MnO2 into axially chiral 4-arylpyridines with central-to-axial chirality conversion. Moderate to complete percentages (cp) were observed, and a model for the conversion of chirality is discussed.

International audience; Aromatics in 3D. Organocatalysis is now reaching beyond the control of stereogenic centers and opens new possibilities for the construction of complex polyaromatic structures with either helical or axial chirality.

International audience; A general evaluation of silylated nucleophiles to intercept transient α-oxoketenes generated by microwave-assisted Wolff rearrangement of 2-diazo-1,3-dicarbonyl compounds is presented. Original scaffolds and synthetic intermediates are accessed in a rapid, efficient and easy-to-handle way. Mechanistic studies by DFT calculations and some post-functionalizations are discussed.

The three-component reaction of β-keto esters, enals, and amines affords two different types of products depending on the presence of a substituent in the α-position of the aldehyde.

International audience; Suitably substituted enantioenriched 4-aryl-1,4-dihydro-pyridines prepared by an organocatalytic enantioselective Michael addition were oxidized with MnO2 into axially chiral 4-arylpyridines with central-to-axial chirality conversion. Moderate to complete conversion percentages (cp) were observed, and a model for the conversion of chirality is discussed.

We have developed the first multicomponent synthesis of enantioenriched polycyclic 1,2,3,4-tetrahydropyridines bearing three contiguous stereogenic centers under iminium activation. The key to the success of this reaction was the use of polyfunctional substrates including 2-aminophenols and scarcely used β-ketoamides triggering a thermodynamically controlled regio- and diastereoselective sequence.

The organocatalytic enantioselective conjugate addition of secondary β-ketoamides to α,β-unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto’s thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 % ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.

International audience; The results on the multicomponent reaction between cyclic β-keto esters, enals, and simple primary aliphatic amines are reported. In thermal conditions in the presence of 4 Å molecular sieves, two different¬ families of heterocyclic products (aminobicyclo[3.3.1]nonanones or cycloalka[b]piperidines) were obtained depending on the presence of a substituent in the α-position of the aldehyde. Moreover, preliminary results on the possibility to obtain these two bicyclic cores from the very same starting materials by introducing organocatalysts with different activation modes in the reaction are presented.

International audience; We have developed the first multicomponent synthesis of enantioenriched polycyclic 1,2,3,4-tetrahydropyridines bearing three contiguous stereogenic centers under iminium activation. The key to the success of this reaction was the use of polyfunctional substrates including 2-aminophenols and scarcely used β-ketoamides triggering a thermodynamically controlled regio- and diastereoselective sequence.

Optimized conditions including a chiral squaramide catalyst render possible the conjugate addition of β-ketoamides to nitroolefins to give the corresponding products with high diastereoselectivities and excellent enantioselectivities.

Aromatics in 3D. Organocatalysis is now reaching beyond the control of stereogenic centers and opens new possibilities for the construction of complex polyaromatic structures with either helical or axial chirality.

International audience; Comprehensive and up-to-date, this book focuses on the latest advances in the field, such as newly developed techniques, more environmentally benign processes, broadened scopes, and completely novel MCRs.

Original and biologically relevant fused tricyclic piperazines are synthesized via this new organocatalytic multicomponent reaction.

International audience; Our findings on the bifunctional squaramide-catalyzed enantioselective conjugate addition of β-ketoamides to nitroolefins are disclosed. It appears that simple acyclic methylene β-ketoamides, unlike the extensively studied β-ketoesters, afford the products in excellent diastereoselectivities, and maintain high yields and enantioselectivities. Moreover, competition and kinetic studies were conducted to rationalize the observed reactivity and selectivity. The high level of diastereocontrol, along with the amenability of the amide group to postfunctionalization, dramatically increase the synthetic usefulness of the transformation.

α,β-Unsaturated acyl cyanides are key bis-electrophile substrates for successful domino enantioselective organocatalyzed Michael-intramolecular acylation domino sequences. This new reactivity has been applied to the synthesis of enantioenriched azaspiro[4,5]decanone ring systems by a formal [3+3]spiroannulation, constituting a rare example of synthesis of glutarimides in an optically active form.

The title reaction of β-ketoamides, acrolein, and aminophenols, catalyzed by a bifunctional thiourea-tertiary amine organocatalyst, enables the preparation of an enantioenriched diazabicyclo[2.2.2]octanone (2,6-DABCO) scaffold. The chemoselective reaction sequence installs five new bonds and three stereocenters, two of which are contiguous tetrasubstituted centers, with excellent yields and high levels of stereocontrol. M.S.=molecular sieves

International audience; The first organocatalytic multicomponent synthesis of enantioenriched pyrrolopiperazines is reported. These biologically relevant fused tricyclic products were obtained under catalytic iminium activation through a reaction sequence involving an enantioselective Michael addition followed by an iminium ion trapping via Pictet-Spengler cyclization (MAPS sequence). Substantial possibilities for variation on the three reaction partners [β-keto ester, enal and N-(2-aminoethyl)pyrrole] along with excellent enantioselectivities are the highlights of the present transformation.

This review aims to highlight the most significant recent developments on synthetic strategies involving consecutive, domino and multicomponent reactions featuring a Michael addition-initiating step for the synthesis of polycyclic heterocycles from 1,3-dicarbonyls. These original sequences constitute more efficient and eco-compatible alternatives to known synthetic approaches to heterocyclic compounds allowing for an even faster and highly desirable generation of molecular diversity and complexity.

Several reactive sites of 1,2- and 1,3-ketoamides were successively exploited in two complementary domino transformations for the synthesis of polysubstituted monocyclic or bridged bicyclic cyclohexanes, with the creation of up to six stereogenic centers. In both cases, a chiral bifunctional thiourea organocatalyst allowed efficient control of chirality in the final carbocycle.

Polysubstituted chiral cyclohexanes and cyclohexenes are important building blocks in organic synthesis. From historical and pioneering reports to the most recent accounts, this review focuses on domino enantioselective organocatalytic methodologies that have allowed the control of the relative and absolute configurations of up to six stereogenic centers in the construction of these versatile molecular architectures. 1 Introduction 2 Two-Component Transformations 2.1 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 2.2 Michael-Initiated Domino Reactions with Nitroolefins 2.3 Non Michael-Initiated Domino Reactions 3 Multicomponent and Related Transformations 3.1 Pseudo-Three-Component Reactions 3.1.1 Michael-Initiated Domino Reactions with Nitroolefins 3.1.2 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 3.2 Consecutive Reactions 3.2.1 Michael-Initiated Domino Reactions with Nitroolefins 3.2.2 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 3.3 Multicomponent Reactions 3.3.1 Michael-Initiated Domino Reactions with Nitroolefins 3.3.2 Michael-Initiated Domino Reactions with α,β-Unsaturated Carbonyl Compounds 4 Conclusion

International audience; The title reaction of β-ketoamides, acrolein, and aminophenols, catalyzed by a bifunctional thiourea-tertiary amine organocatalyst, enables the preparation of an enantioenriched diazabicyclo[2.2.2]octanone (2,6-DABCO) scaffold. The chemoselective reaction sequence installs five new bonds and three stereocenters, two of which are contiguous tetrasubstituted centers, with excellent yields and high levels of stereocontrol. M.S.=molecular sieves

International audience; Several reactive sites of 1,2- and 1,3-ketoamides were successively exploited in two complementary domino transformations for the synthesis of polysubstituted monocyclic or bridged bicyclic cyclohexanes, with the creation of up to six stereogenic centers. In both cases, a chiral bifunctional thiourea organocatalyst allowed efficient control of chirality in the final carbocycle.

The umpolung strategy encompasses all the methods that make organic molecules react in an inverse manner compared to their innate polarity-driven reactivity. This concept entered the field of organocatalysis when it was recognized that N-heterocyclic carbenes (NHCs) can provide catalytic access to acyl anion equivalents. Since then, tremendous efforts have followed to develop a broad variety of NHC-catalyzed reactions. In addition to this, more recent research developments have shown that other families of organocatalysts are also able to mediate transformations in which inversion of polarity is involved. This tutorial review aims at offering a didactic overview of organocatalytic umpolung and should serve as an inspiration for further progress in this field.

The utility of ortho,ortho′-disubstituted triazolium derivatives as NHC-catalysts in the preparation of enantioenriched acyl cyclopropanes is demonstrated.

The umpolung strategy encompasses all the methods that make organic molecules react in an inverse manner compared to their innate polarity-driven reactivity. This concept entered the field of organocatalysis when it was recognized that N-heterocyclic carbenes (NHCs) can provide catalytic access to acyl anion equivalents. Since then, tremendous efforts have followed to develop a broad variety of NHC-catalyzed reactions. In addition to this, more recent research developments have shown that other families of organocatalysts are also able to mediate transformations in which inversion of polarity is involved. This tutorial review aims at offering a didactic overview of organocatalytic umpolung and should serve as an inspiration for further progress in this field.

An innovative access to a β,β-disubstituted Morita–Baylis–Hillman motif, which is a potential intermediate en route to the synthesis of the aglycon of landomycins, is presented. It consists of a finely optimized organocuprate-initiated domino Michael–intramolecular aldol reaction. The use of TMSCl and DMAP as additives proved essential to ensure the success of this reaction sequence.

International audience; Faster, higher, stronger! The N-heterocyclic carbene (NHC) catalyzed diastereo- and enantioselective hydroacylation of cyclopropenes affords structurally valuable acylcyclopropanes. A new family of electron-rich, 2,6-dimethoxyphenyl-substituted NHCs induces excellent reactivity and enantioselectivity. Preliminary kinetic studies unambiguously demonstrated the superiority of this family of catalysts over known NHCs in this challenging transformation.

The organocatalyzed reaction of aromatic aldehydes with cyclopropenes under mild conditions affords valuable acylcyclopropanes in moderate to high yields with high diastereoselectivity.