1,720,993 research outputs found
Functionalization of phospha-thiahelicenes and application of their gold(I) complexes in enantioselective catalysis
No full textHelically chiral structures are known to display peculiar properties and applications in many fields, including asymmetric catalysis. However, both the synthesis of helical phosphorus ligands and their uses in enantioselective organometallic catalysis have been underdeveloped so far [1].
In the course of our studies on helical phosphane derivatives as potential chiral ligands in asymmetric organometallic catalysis [2], we have recently reported the synthesis of a new chiral phospha-thiahelicene based gold (I) complex, which is an excellent and selective pre-catalyst for the enantioselective cycloisomerization of N-tethered enynes [3].
On the basis of these very promising results we have effectively functionalized the phospha-thiahelicene scaffold to obtain new gold (I) complexes, which are then tested as pre-catalysts in other challenging enantioselective cycloisomerization reactions. 1. a) Y. Shen, C.-F. Chen, Chem. Rev. 2012, 112, 1463; b) P. Aillard , A. Voituriez, A. Marinetti, Dalton
Trans. 2014, 43, 15263.
2. a) S. Cauteruccio, A. Loos, A. Bossi, M. C. Blanco Jaimes, D. Dova, F. Rominger, S. Prager, A. Dreuw, E.
Licandro, A. S. K. Hashmi, Inorg. Chem. 2013, 52, 7995; b) K. Yavari, P. Aillard, Y. Zhang, F. Nuter, P.
Retailleau, A. Voituriez, A. Marinetti, Angew. Chem. Int. Ed. 2014, 53, 861.
3. P. Aillard, A. Voituriez, D. Dova, S. Cauteruccio, E. Licandro, and A. Marinetti, Chem. Eur. J. 2014, 20,
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Metal-mediated reactions for the heteroaryl-heteroaryl bond formation: non photochemical synthesis of thiahelicenes
No full textTetrathia[7]helicenes (7-TH), are chiral helical-shaped polyaromatic systems containing four thiophene and three benzene rings. They exhibit peculiar electronic and chiroptical properties suitable for applications in optoelectronics [1], biology [2], and catalysis [3]. For these reasons they are emerging as one of the most popular class of chiral helical-shaped molecules. We are deeply involved in the development of these molecules, with a particular focus on innovative synthesis of the helical scaffold through metal-mediated cross-coupling reactions.
In this presentation, our recent studies on the synthesis of 7-TH derivatives using cross-coupling reactions at different stages of the synthetic sequence will be illustrated. The most recent results are reported in the scheme below
Non-photochemical Synthesis of Functionalized Benzo[1,2-b:4,3-b’]dithiophene Derivatives
No full textThiophene-containing fused, aromatic compounds represent an interesting class of π-conjugated systems in functional organic materials. A role of increasing importance is going to be acquired by benzo[1,2-b:4,3-b’]dithiophene (BDT) which have been studied as units in mono and polydisperse oligomers in field of the materials science, and, more recently, as π-spacers in push-pull organic chromophores for photovoltaic applications1. Moreover, BDT represents a key intermediate in the synthesis of inherently chiral helical systems such as tetrathia[7]helicenes2. Within this context, and in view of potential wider and industrial applications, simple, reliable, reproducible and economic syntheses of BDTs, which avoid the use of photochemical pathway are highly desirable. Herein, we report the first results of our investigations on the FeCl3-mediated cyclization of αα’-disubstituted Z-alkenes 1 as a general and non-photochemical synthesis of BDT derivatives 2.3
The influence of the temperature and the nature of the substituents, in determining the scope and limitations of this methodology have been also explored
METHODOLOGIES FOR THE SYNTHESIS OF THIAHELICENE-BASED PHOSPHORUS DERIVATIVES AND THEIR APPLICATIONS IN ASYMMETRIC CATALYSIS
Full text linkHelicenes are ortho-annulated polycyclic aromatic or heteroaromatic compounds endowed with inherent chirality due to the helical shape of their π-conjugated system, whose unique structural features and physicochemical properties have stimulated countless studies in several fields, including nanosciences, chemosensing, materials science, biomolecular recognition, and asymmetric catalysis. However, whilst axial, central and planar chirality have been largely exploited to build chiral phosphorus ligands and organocatalysts, helical chirality has been rather neglected so far in this field. This Ph.D. thesis aims to provide a meaningful contribution in the development of heterohelicene phosphorus derivatives, especially thiahelicene derivatives, as innovative chiral ligands to use in asymmetric organic and organometallic catalysis. In particular, we set up new classes of tetrathiahelicene(7-TH)-based phosphorus derivatives, including phoshine-borane complexes, phosphine oxides, free phosphanes, phosphathiahelicenes and the corresponding gold (I) complexes. Some of these systems have shown high efficiency as organocatalysts, as well as Au(I) complexes based on chiral phosphathiahelicene ligands were found to be efficient and selective catalysts in some challenging cycloisomerization reactions (ee up to 96%). The promising results obtained in this work will stimulate further developments and applications of these and analogous ligands to new asymmetric processes
Tetrathiahelicenes: eclectic chiral tools in chemistry and biology
No full textHelicenes, as part of the larger family of helical shaped small molecules, are not only original, aesthetically fascinating, intriguing, flexible chiral systems, but have nowadays reached a high degree of appeal within the scientific community thanks to the association of synthetic challenge to manifold applications that they provide, ranging from nanosciences, chemosensing, material science, asymmetric catalysis and molecular recognition. Among helicenes, tetrathiahelicenes are emerging as the most popular systems, thanks to the remarkable improvements reached in their preparation, and thanks to their unique magnetic, conductive, and optical properties. Other recent interesting applications are emerging in catalysis1 and biology. Such a versatility and eclectic behaviour is closely related to the possibility of obtaining a structural variety still maintaining the defining property of the helical structure.
Over the years, our research group has contributed in a significative manner to the development of efficient methods for the synthesis of the helical scaffold of tetrathiahelicenes and its functionalization with the most diverse functional groups. This research has allowed the access to a class of novel variously substituted tetrathiahelicenes. Among them, we have recently developped chiral helicene-based phosphine and phosphine oxide ligands for application in organic and organometallic catalysis, and some interesting results have already been obtained
Chiral thiophene-based biaryl systems : synthesis and characterization
No full textThe biaryl motif occupies an iconic role in chemistry, being a key structural feature of natural products, biologically active molecules, drugs, agrochemicals, and other novel optical and mechanical materials. Furthermore, the stereogenic axes provide rigid molecular frameworks for highly efficient tools in asymmetric synthesis.1 Exploiting the experience acquired in our laboratories on the synthesis of compounds based on alternating thiophene and benzene rings2, we have started the study of a simple and efficient synthetic route to prepare bis(benzoditiophenes) system 2, through Pd-catalysed cross coupling reactions, starting from bromide 1.
This strategy provides a convenient approach to an interesting class of chiral atropisomeric biaryl derivatives with C2-symmetry, which are expected to have broad applications in asymmetric reactions, including the enantioselective synthesis of tetrathiahelicene derivatives
Chiral thiophene-based helicenes: versatile tools in organic chemistry
No full textHelicenes, which consist of ortho-annulated aromatic or heteroaromatic rings having screw-shaped structures, are known as intriguing, intrinsically chiral frameworks, and are intensively studied in wide ranges of areas, including materials sciences, chiroptical devices, and asymmetric synthesis.1 Among helicenes, thiahelicenes are unique thanks to the presence of thiophene rings, which confer special chemical, geometric, and electronic features.2 For several years, we have been interested in the study of the synthesis and functionalization of thiahelicenes, such as tetrathiahelicene (7-TH) derivatives (Figure 1), that are a class of configurationally stable heterohelicenes, potentially very interesting for applications in optoelectronics,3 catalysis,4 and biology.5 Moreover, these systems can be easily functionalized at the 2 and 13 positions of the two terminal thiophene rings, allowing the modulation of the chemical and physical properties. Despite all these potential advantages, most of the synthetic methodologies to prepare 7-TH derivatives involve oxidative photochemical cyclization processes, which require specific equipment, highly diluted solutions, and long reaction times. Recently, we have developed a versatile non-photochemical procedure for the synthesis of functionalized thiahelicenes, thus making available a class of variously substituted compounds
Non-photochemical route to tetrathiahelicenes through Pd-mediated heteroaryl-heteroaryl bond formation
No full textTetrathia[7]helicenes (7-TH), formed by thiophene and benzene rings ortho-fused in an alternating fashion, are emerging as one of the most popular class of chiral helical-shaped molecules [1], thanks to their peculiar electronic and chiroptical properties suitable for applications in optoelectronics [2], biology [3], and catalysis [4]. Despite all these potential advantages, most of the synthetic methodologies to prepare 7-TH systems involve oxidative photochemical cyclization processes, which require specific equipment, highly diluted solutions, limiting the scale-up.
In our ongoing studies on the synthesis and functionalization of 7-TH derivatives, we have set up an innovative and non-photochemical procedure for the synthesis of 7,8-diaryl and dialkyl substituted 7-TH compounds, exploiting a Suzuki-type cross coupling and a Pd-catalyzed annulation with internal alkynes as key steps
Synthesis of benzoditiophene based atropoisomer through Pd-catalyzed cross coupling reactions
No full textThe biaryl motif occupies an iconic role in chemistry, being a key structural feature of natural products, biologically active molecules, drugs, agrochemicals, and other novel optical and mechanical materials. Furthermore, the stereogenic axes provide rigid molecular frameworks for highly efficient tools in asymmetric synthesis.1 Exploiting the experience acquired in our laboratories on the synthesis of compounds based on alternating thiophene and benzene rings2, we have started the study of a simple and efficient synthetic route to prepare bis(benzoditiophenes) system 2, through Pd-catalysed cross coupling reactions, starting from bromide 1.
This strategy provides a convenient approach to an interesting class of chiral atropisomeric biaryl derivatives with C2-symmetry, which are expected to have broad applications in asymmetric reactions, including the enantioselective synthesis of tetrathiahelicene derivatives
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