Hydrocarbure insaturé

Dans la vaste famille des hydrocarbures (molécules formées comme leur nom l'indique d’hydrogène et de carbone), au sein de la classe des hydrocarbures aliphatiques, on distingue les hydrocarbures insaturés. Par opposition aux « hydrocarbures saturés » que sont les alcanes (hydrocarbures dont toutes les liaisons chimiques sont simples, ce qui les rend peu réactifs avec eux-mêmes et assez peu réactifs avec la plupart des autres atomes). Les hydrocarbures insaturés sont beaucoup plus réactifs que les autres hydrocarbures. Deux sous-catégories Les hydrocarbures insaturés constituent une classe regroupant deux types particuliers d'hydrocarbures (tous caractérisés par des liaisons chimiques insaturées) :

les alcènes (de formule chimique : R–CH=CH–R', caractérisés par au moins une double liaison ; si la molécule comprend deux doubles liaisons, on parle de -diène ( 1,3-butadiène) ; les alcènes les plus connus sont l’éthylène (en C), le propylène (C), le

Pd(II)-Catalyzed Aminoacetoxylation of Alkenes Via Tether Formation

Ashis Kumar Das, Stefano Nicolai, Thomas Rossolini, Jérôme Waser

A Pd-catalyzed method based on the use of a molecular tether is described for olefin difunctionalization. Enabled by an easily introduced trifluoroacetaldehyde-derived tether, a simultaneous introduction of oxygen and nitrogen heteroatoms across unsaturated carbon-carbon bonds was achieved under oxidative conditions, most probably via high-valent Pd inter-mediates. Good yields and high diastereoselectivity were obtained with aryl-substituted alkenes, whereas nonterminal alkyl-substituted olefins gave aza-Heck products. Tether cleavage under mild conditions fast access to functionalized alcohols.

2022

Palladium Catalysed Intramolecular Carbo-oxygenation of Propargylic Amines to Access 1,2-Amino Alcohols and alpha-Amino Ketones via in situ Tether Formation

Phillip Gulliver Dominic Greenwood

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

Palladium Catalysed Intramolecular Carbo-oxygenation of Propargylic Amines to Access 1,2-Amino Alcohols and alpha-Amino Ketones via in situ Tether Formation

Phillip Gulliver Dominic Greenwood

EPFL2020

Hydrogénation sélective du but-2-yne-1,4-diol sur catalyseur structuré au palladium

Pd(II)-Catalyzed Aminoacetoxylation of Alkenes Via Tether Formation

Palladium Catalysed Intramolecular Carbo-oxygenation of Propargylic Amines to Access 1,2-Amino Alcohols and alpha-Amino Ketones via in situ Tether Formation

Palladium Catalysed Intramolecular Carbo-oxygenation of Propargylic Amines to Access 1,2-Amino Alcohols and alpha-Amino Ketones via in situ Tether Formation

Hydrogénation sélective du but-2-yne-1,4-diol sur catalyseur structuré au palladium

Pd(II)-Catalyzed Aminoacetoxylation of Alkenes Via Tether Formation