2H-quadrupolar coupling-based analysis of stereochemical and regiochemical memory in the Pd-catalysed allylic alkylation of iso-cinnamyl type substrates employing the chiral monophosphine ligands ‘MOP’ and ‘MAP’

Gouriou, Laure; Lloyd‐Jones, Guy C.; Vyskočil, Štěpán; Kočovský, Pavel

doi:10.1016/j.jorganchem.2003.09.015

Cited by 31 publications

(14 citation statements)

References 47 publications

(20 reference statements)

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“…Experiments using deuterium-labeled allylic substrates have been employed to probe mechanisms of retention or inversion of stereochemistry. 75,76 The cis-alkene deuterium-labeled trichloroacetimidates (S)-18 and (R)-18 were synthesized and submitted to the standard fluorination condition using [IrCl(S,S)-L] 2 catalyst (Scheme 9). For the (S)-18 substrate using [IrCl(S,S)-L] 2 , the (R)-enantioenriched product 19 was obtained with retention of configuration of the olefin geometry (cis).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

The Role of Trichloroacetimidate To Enable Iridium-Catalyzed Regio- and Enantioselective Allylic Fluorination: A Combined Experimental and Computational Study

et al. 2019

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Asymmetric allylic fluorination has proven to be a robust and efficient methodology with potential applications for the development of pharmaceuticals and practical synthesis for 18F-radiolabeling. A combined computational (dispersion-corrected DFT) and experimental approach was taken to interrogate the mechanism of the diene-ligated, iridium-catalyzed regio- and enantioselective allylic fluorination. Our group has shown that, in the presence of an iridium(I) catalyst and nucleophilic fluoride source (Et3N·3HF), allylic trichloroacetimidates undergo rapid fluoride substitution to generate allylic fluoride products with excellent levels of branched-to-linear ratios. Mechanistic studies reveal the crucial role of the trichloroacetimidate as a potent leaving group and ligand to enable conversion of racemic allylic trichloroacetimidates to the corresponding enantioenriched allylic fluorides, via a dynamic kinetic asymmetric transformation (DYKAT), in the presence of the chiral bicyclo[3.3.0]octadiene-ligated iridium catalyst.

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Section: ■ Results and Discussionmentioning

confidence: 99%

The Role of Trichloroacetimidate To Enable Iridium-Catalyzed Regio- and Enantioselective Allylic Fluorination: A Combined Experimental and Computational Study

et al. 2019

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“…Aer observing a switch in regioselectivity upon changing the size of substituent at the 2-position, we employed the larger 2-cyclohexyl group to further explore this trend. Substrate 1j underwent reaction with NaCH(CO 2 Me) 2 and catalyst generated from [Pd(allyl)Cl] 2 or Pd(OAc) 2 to afford predominantly product 2j via benzylic attack with regioselectivities of 84 : 16 and 86 : 14, respectively (entries [11][12][13]. It is noteworthy that benzylic acetate 1j is more reactive with the Pd(OAc) 2 -based catalyst than aliphatic acetate 1h, which did not react with this catalyst (as noted earlier).…”

Section: Factors Controlling Regioselectivity With 2-alkyl Substitute...mentioning

confidence: 99%

“…However, if the isomerization is slow relative to nucleophilic attack, 10 or in the presence of chiral 11 or electronically differentiated 12 ligands, the reaction can show strong memory effects. Under conditions of slow isomerization, nucleophilic attack has a strong preference for reaction at anti -oriented termini.…”

Section: Introductionmentioning

confidence: 99%

Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction

et al. 2014

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η3-Allyl palladium complexes are key intermediates in Tsuji-Trost allylic substitution reactions. It is well known that (η3-1-aryl-3-alkyl substituted allyl)Pd intermediates result in nucleophilic attack at the alkyl substituted terminus. In contrast, the chemistry of (η3-1,2,3-trisubstituted allyl)Pd intermediates is relatively unexplored. Herein we probe the regioselectivity with 1,2,3-trisubstituted allylic substrates in Tsuji-Trost allylic substitution reactions. DFT investigation of cationic (η3-1-Ph-2-B(pin)-3-alkyl-allyl)Pd(PPh3)2 intermediates predict that nucleophilic attack should occur preferentially on anti-allyls rather than the syn-isomers to generate benzylic substitution products under Curtin-Hammett conditions. Experimentally, systematic studies with 1,2,3-trisubstituted allylic substrates revealed that a Linear Free Energy Relationship (LFER) is observed when Charton steric parameters of the C-2 substituents are plotted against the log of the ratio of regioisomers. Bulkier C-2 substituents in 1,2,3-trisubstituted η3-allyl palladium intermediates provide stronger preference for nucleophilic attack at anti-oriented benzylic termini. Additionally, the geometry of 1,4-elimination products supports the presence of anti-allyl palladium intermediates.

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“…In the case of MAP ( L11 ), such outcome is not observed. This behaviour is known as “memory effect” and its origins are still a matter of debate, though many studies suggest that “memory effect” is directly influenced by the modes of stabilisation of cationic species by the monophosphine ligand, which are related to the conditions employed such as concentration and nature of nucleophile, and palladium precursor [ 31 , 32 ].…”

Section: Monophosphine Ligandsmentioning

confidence: 99%

Recent Advances in the Application of Chiral Phosphine Ligands in Pd-Catalysed Asymmetric Allylic Alkylation

2011

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One of the most powerful approaches for the formation of simple and complex chiral molecules is the metal-catalysed asymmetric allylic alkylation. This reaction has been broadly studied with a great variety of substrates and nucleophiles under different reaction conditions and it has promoted the synthesis of new chiral ligands to be evaluated as asymmetric inductors. Although the mechanism as well as the active species equilibria are known, the performance of the catalytic system depends on the fine tuning of factors such as type of substrate, nucleophile nature, reaction medium, catalytic precursor and type of ligand used. Particularly interesting are chiral phosphines which have proved to be effective asymmetric inductors in several such reactions. The present review covers the application of phosphine-donor ligands in Pd-catalysed asymmetric allylic alkylation in the last decade.

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2H-quadrupolar coupling-based analysis of stereochemical and regiochemical memory in the Pd-catalysed allylic alkylation of iso-cinnamyl type substrates employing the chiral monophosphine ligands ‘MOP’ and ‘MAP’

Cited by 31 publications

References 47 publications

The Role of Trichloroacetimidate To Enable Iridium-Catalyzed Regio- and Enantioselective Allylic Fluorination: A Combined Experimental and Computational Study

The Role of Trichloroacetimidate To Enable Iridium-Catalyzed Regio- and Enantioselective Allylic Fluorination: A Combined Experimental and Computational Study

Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction

Recent Advances in the Application of Chiral Phosphine Ligands in Pd-Catalysed Asymmetric Allylic Alkylation

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