Nucleophilic Phosphine Organocatalysis

Methot, Joey L.; Roush, William

doi:10.1002/adsc.200404087

Cited by 931 publications

(205 citation statements)

References 102 publications

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“…From a series of elegant [3+2] cycloaddition reactions affording these mentioned carbocycles the cycloaddition of allenoates and electron-deficient alkenes or imines catalysed by tertiary phosphanes, deserves to be described. 80,81 This so called Lu's [3+2] cycloaddition 82 is normally triggered by the phosphane attack to the b-carbon of the alkyl allenoate (or alkyl propiolates) generating a 1,3-dipole 161, which is an inner salt containing a phosphonium cation (Scheme 37). It was confirmed that the generation of the 1,3-dipole is the rate determining step.…”

Section: Phosphonium-inner Saltsmentioning

confidence: 99%

Metal complexes versus organocatalysts in asymmetric 1,3-dipolar cycloadditions

Nájera¹,

Sansano²,

Yus³

2010

J. Braz. Chem. Soc.

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Neste review apresentamos uma comparação entre reações de cicloadição 1,3-dipolar catalizadas por ácido de Lewis com as organo catalizadas, com ênfase na síntese enantiosseletiva de sistemas hetero ou carbocíclicos de cinco membros. Essas reações exibem características interessantes, mas a mais importante é a formação de até quatro centro estereogênicos em apenas uma etapa de reação.In this review, a comparison between the Lewis acid catalysed and organocatalysed 1,3-dipolar cycloaddition is presented with special focus on the enantioselective synthesis of five-membered hetero-or carbocyclic systems, is described. These reactions exhibit very interesting features, but the most important one is the generation of up to four stereogenic centres in only one reaction step.

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Section: Phosphonium-inner Saltsmentioning

confidence: 99%

Metal complexes versus organocatalysts in asymmetric 1,3-dipolar cycloadditions

Nájera¹,

Sansano²,

Yus³

2010

J. Braz. Chem. Soc.

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“…The reaction has been extended to other carbon acids than 2-nitropropane [362,363]. In 1992, Trost and Kazmaier [364] reported that Ph3P catalyzes the isomerization of conjugated ynones, ynoates and ynecarboxamides (113) The proposed mechanism implies the formation of carbanionic intermediates (e.g., 114 ⇄ 115; 117 ⇄ 118 ↔ 119 ⇄ 120) resulting from protonation and deprotonation of zwitterionic phosphonium intermediates [99]. Methyl but-2-ynoate (122) adds to Ph3P generating zwitterion 123.…”

Section: Umpolung Of Michael Acceptorsmentioning

confidence: 99%

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

et al. 2016

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Catalysis fulfills the promise that high-yielding chemical transformations will require little energy and produce no toxic waste. This message is carried by the study of the evolution of molecular catalysis of some of the most important reactions in organic chemistry. After reviewing the conceptual underpinnings of catalysis, we discuss the applications of different catalysts according to the mechanism of the reactions that they catalyze, including acyl group transfers, nucleophilic additions and substitutions, and C-C bond forming reactions that employ umpolung by nucleophilic additions to C=O and C=C double bonds. We highlight the utility of a broad range of organocatalysts other than compounds based on proline, the cinchona alkaloids and binaphthyls, which have been abundantly reviewed elsewhere. The focus is on organocatalysts, although a few examples employing metal complexes and enzymes are also included due to their significance. Classical Brønsted acids have evolved into electrophilic hands, the fingers of which are hydrogen donors (like enzymes) or other electrophilic moieties. Classical Lewis base catalysts have evolved into tridimensional, chiral nucleophiles that are N-(e.g., tertiary amines), P-(e.g., tertiary phosphines) and C-nucleophiles (e.g., N-heterocyclic carbenes). Many efficient organocatalysts bear electrophilic and nucleophilic moieties that interact simultaneously or not with both the electrophilic and nucleophilic reactants. A detailed understanding of the reaction mechanisms permits the design of better catalysts. Their construction represents a molecular science in itself, suggesting that sooner or later chemists will not only imitate Nature but be able to catalyze a much wider range of reactions with high chemo-, regio-, stereo-and enantioselectivity. Man-made organocatalysts are much smaller, cheaper and more stable than enzymes.

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“…5,6 Indeed, the reducing capabilities of phosphines as well as their ability to serve as initiators/catalysts for Michael conjugate addition reactions is well documented. [55][56][57] The products from the thiol-ene reaction, PNIPAm 50 -S-ALMA and PNIPAm 50 -S-PROPA, were characterized using a combination of 1 H NMR spectroscopy and SEC, Figure 2 and Table 1. b, the resonance associated with the methine group of the isopropyl side chains, indicates a DP of 52.…”

Section: (B)mentioning

confidence: 99%

Sequential thiol‐ene/thiol‐ene and thiol‐ene/thiol‐yne reactions as a route to well‐defined mono and bis end‐functionalized poly(N‐isopropylacrylamide)

Chan

Hoyle

et al. 2009

J. Polym. Sci. A Polym. Chem.

208

191

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Sequential thiol-ene/thiol-ene and thiol-ene/thiol-yne reactions have been used as a facile and quantitative method for modifying end-groups on an N-isopropylacrylamide (NIPAm) homopolymer. A well-defined precursor of polyNIPAm (PNIPAm) was prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization in DMF at 70 C using the 1-cyano-1-methylethyl dithiobenzoate/2,2 0 -azobis(2-methylpropionitrile) chain transfer agent/initiator combination yielding a homopolymer with an absolute molecular weight of 5880 and polydispersity index of 1.18. The dithiobenzoate end-groups were modified in a one-pot process via primary amine cleavage followed by phosphine-mediated nucleophilic thiol-ene click reactions with either allyl methacrylate or propargyl acrylate yielding ene and yne terminal PNIPAm homopolymers quantitatively. The ene and yne groups were then modified, quantitatively as determined by 1 H NMR spectroscopy, via radical thiol-ene and radical thiol-yne reactions with three representative commercially available thiols yielding the mono and bis end functional NIPAm homopolymers. This is the first time such sequential thiol-ene/thiol-ene and thiol-ene/thiol-yne reactions have been used in polymer synthesis/end-group modification. The lower critical solution temperatures (LCST) were then determined for all PNIPAm homopolymers using a combination of optical measurements and dynamic light scattering. It is shown that the LCST varies depending on the chemical nature of the end-groups with measured values lying in the range 26-35 C.

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Nucleophilic Phosphine Organocatalysis

Cited by 931 publications

References 102 publications

Metal complexes versus organocatalysts in asymmetric 1,3-dipolar cycloadditions

Metal complexes versus organocatalysts in asymmetric 1,3-dipolar cycloadditions

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

Sequential thiol‐ene/thiol‐ene and thiol‐ene/thiol‐yne reactions as a route to well‐defined mono and bis end‐functionalized poly(N‐isopropylacrylamide)

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