Alcyne

Résumé

thumb|200px|Exemples d’alcynes. Les alcynes sont des hydrocarbures possédant une insaturation caractérisée par la présence d’une triple liaison carbone-carbone. Les deux carbones sont hybridés sp. La triple liaison est la combinaison de deux liaisons π et d’une liaison σ. La densité électronique de la molécule est répartie de façon cylindrique le long de la liaison C-C. On dit que l’on a affaire à un alcyne vrai ou à un alcyne terminal si R ou R' est un hydrogène. Les alcynes, ou hydrocarbures acétyléniques, ont pour formule générale CnH2n-2, et sont caractérisés par la présence dans leur molécule d’une triple liaison et d’une coexistence possible de doubles liaisons. Nomenclature Les alcynes se nomment comme les alcènes correspondants, en remplaçant la terminaison « -ène » par la terminaison « -yne ». Hors nomenclature IUPAC, le premier terme, C2H2, est également appelé acétylène. Les alcynes linéaires ont pour formule générale CnH2n-2. Exemples :

éthyne (acétylène,

Source officielle

https://fr.wikipedia.org/wiki/Alcyne

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Copper(I) Based Photoredox Chemistry

Murat Alkan

Photoredox catalysis has become a powerful tool for chemists. However, the reliance on expensive Ir and Ru based photoredox catalysts (PC) motivates research for more sustainable options. Copper complexes based on favorable photophysical properties, high abundance and comparatively low prices offer a more sustainable alternative which is outlined in Chapter 1. This dissertation is dedicated to the development of new Cu(I) complexes and their investigation as PCs. Chapter 2 describes the synthesis of a new 2,2'-bipyridine (bpy) based ligand and the heteroleptic [Cu(N^N)(P^P)][PF6] complexes in combination with 4,5-Bis(diphenyl- phosphino)-9,9-dimethylxanthene (Xantphos, 1) and Bis[(2-diphenylphosphino)phenyl] ether (POP, 2). The complexes were thoroughly characterized and employed as PCs for the chlorotrifluoromethylation of activated alkenes with CF3SO2Cl. Complex 1 shows high activity with high yields and wide functional group tolerance in the chlorotrifluoromethylation of styrenes as well as alkenes adjacent to electron-withdrawing groups. The reaction with unactivated alkenes proved to be inefficient. Consequently, the design, synthesis and application of a new Cu(I) based photoredox catalyst is described. Chapter 3 details the use of complex 1 as PC for the chlorosulfonation of alkenes and alkynes with sulfonyl chlorides. The reactions occur under mild conditions and exhibit high functional group tolerance with broad scope in terms of both alkene and sulfonyl chloride. Notably, the reaction occurs with alkynes albeit in moderate to low yields to give exclusively the (E)âproduct. Chapter 4 reports the synthesis of new bpy based ligands and their heteroleptic [Cu(N^N)(xantphos)][PF6] complexes to investigate possible structure-activity relationships. The synthesized Cu(I) complexes are characterized and their activities as photoredox catalysts compared to different Cu(I) based complexes are investigated. Consequently, it is shown that PC 1 is the most active catalyst in the chlorosulfonation of styrenes based on a variety of substrates due its long excited state lifetime in combination with a relatively high photoluminescence quantum yield and photo-stability.

EPFL2020

Chargement

a-Amino ketones and 1,2-amino alcohols are important structural motifs in organic chemistry, that can be observed in natural products, pharmaceutically and bioactive compounds. For these reasons, they constitute privileged targets for the development of new and effective synthetic methods. The dual-functionalisation of unsaturated carbon-carbon bonds is a powerful approach to access these crucial motifs. In this context, Pd catalysis has been comprehensively investigated and has consistently demonstrated its capability. Methods enabling the concomitant formation of a carbonâ heteroatom and a carbonâcarbon bond are highly valuable, but the challenges of intermolecular reactions have led to the development of tether systems that require additional steps for their introduction and removal. In situ tethering strategies have previously been explored within the Waser group to circumvent these limitations. This approach relies on a one-pot, three component, Pd catalysed carboetherification or amination reaction, leading to rapidly increase in complexity of simple substrates. So far, the in situ methodologies developed by the Waser group have focused on the functionalisation of alkenes from allylic amines and alcohols. In this regard, the goal of my PhD was to expand the in situ tethering methodologies established within the Waser group, to the synthesis of a-amino ketones and 1,2-amino alcohols. Specifically, my focus was on the formation a trifluoromethyl hemiaminal with a propargylic amine and using the resulting aminal to direct the oxyalkynylation and oxyarylation of the alkyne substrate via a Pd catalysed transformation. Upon optimisation, the reaction of a protected terminal propargylamine, trifluoroacetaldehyde ethyl hemiacetal and silylbromoacetylene using a Pd0 complex with DPEPhos as the catalytic system and Cs2CO3 as the base gave the desired oxazolidine alkenes in high yields and E:Z selectivity. Substrates with substitution on the terminal position and at the propargylic required a change of ligand and base. The transformation was broadly tolerant towards substitution on the nitrogen and the alkyne. An oxyarylative variant was also developed, using Ruphos as ligand, and worked well with a range of iodoarene partners. The obtained oxazolidines could be conveniently orthogonally deprotected to access the a-amino ketone and terminal alkyne; the hydrogenation of the unsaturated oxazolidines has allowed access to 1,2-amino alcohol scaffolds and the application of gold catalysis converted the enyne-oxazolidine system into trisubstituted silyl furans. The identification of a sideproduct of the oxyalkynylation process led to the development of a carboxy-alkynylation reaction using a "CO2" unit derived from the carbonate base. Optimisation established CsHCO3 to the best base/"CO2" source, using DPEPhos as ligand. This transformation gave convenient access to diverse library of cyclic carbamates. Work is ongoing to achieve an enantioselective oxyarylation using chiral phosphine ligands. The asymmetric synthesis of oxazolidines, followed by the diastereoselective alkene hydrogenation and subsequent tether removal would allow the stereodivergent access to interesting diarylalkyl-1,2- amino alcohols. Most recently, the product was synthesised in 66% yield, with 66%ee using commercially available Trost ligand.

EPFL2020

Chargement

New Synthetic Applications of Water Acetate Pd/TPPTS Catalyst Generated in situ. Evidence for true Pd(0) Valent Species Intermediate

Christian Amatore

Studies on the sp-sp intermolecular coupling reactions with the palladium water-soluble catalyst prepared in situ from palladium(II) acetate and sulfonated triphenylphosphine P(C6H4-m-SO3Na)(3) (TPPTS) in a homogeneous acetonitrile-water system, without Cu(I) promotor, afford diynes with moderate yields (45-65%). Under the same conditions, the sp(2)-sp coupling of 2-iodophenols or 2-iodoanilines and terminal alkynes followed by intramolecular cyclization gives indolic and furanic products in good yields (60-99%). Under these aqueous conditions, an efficient and short synthesis of eutypine illustrated the synthetic potentiality of the coupling. Furthermore, through a series of kinetic and P-31 NMR experiments, we have demonstrated that a mixture of Pd(OAc)(2) and TPPTS affords spontaneously a palladium(0) complex, through formation of bivalent complex Pd(OAc)(2)-(TPPTS)(2). A detailed mechanism of the reaction has been investigated thoroughly and the pertinent rate constants measured. The resulting palladium(0) complex reacts with phenyl iodide via an oxidative addition. This complex is considerably less reactive than the corresponding complex generated from PPh(3), probably due to steric effects.

1995

Chargement

Copper(I) Based Photoredox Chemistry

Murat Alkan

EPFL2020