Multivalency as a Key Factor for High Activity of Selective Supported Organocatalysts for the Baylis–Hillman Reaction

Goren, Kerem; Karabline-Kuks, Jeny; Shiloni, Yael; Barak-Kulbak, Einav; Miller, Scott J.; Portnoy, Moshe

doi:10.1002/chem.201404560

Cited by 11 publications

(8 citation statements)

References 93 publications

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“…As in the previously reported case of multivalent catalysts, [33,34] there is an otable influence of the content of water in the reactionm ixture on the conversion and chemoselectivity parameters of the reaction promoted by the catalyst 15 (Table 3).…”

Section: Resultssupporting

confidence: 70%

Chemoselectivity Improvement via Partial Shielding of an Imidazole Active Site in Branched/Dendritic Homogeneous Catalysts of the Baylis–Hillman Reaction

2016

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While comparing analogousp olystyrenesupported and homogeneous catalysts for the Baylis-Hillmanr eaction, we hypothesized that the hydrophobice nvelopment of the imidazole catalytic sites of the former is responsible for the significantly better chemoselectivity exhibited by the heterogeneous catalysts compared to theirh omogeneousc ounterparts.I no rder to test this hypothesis,w ep repared as eries of branched/dendritic homogeneousc atalysts,w ith an imidazole active site near the focal point andf lexiblet ails of various lengthsa nd polarities,c apable of providing partials hieldingo ft his site.T he design of the catalysts was based on a5 -hydroxyisophthalate scaffold,a nd they were prepared throughanumber of multistep synthetic pathways. Thec omparison of the catalysts under av arietyo f conditions in am odel Baylis-Hillman reactiond emonstrated that long hydrophobic tales enhance the chemoselectivity parameter of the catalysis,w hile reducing the rate of the consumptiono ft he substrates, and that the chemoselectivity is further improvedb y the presence of af ree phenolic moiety in the vicinity of the catalytic imidazole unit. Moreover, in secondgeneration catalysts,t he peripherall ong tails could be either hydrophobic or polar, since the dendritic inner backbone itself presumably partially provides the necessary isolation of the catalytic site.T hus,e xperimental results support our hypothesis.Synthesis of 1,3-bis(methoxymethyl)-5-(methoxymethoxy)benzene: Thec ompound was prepared according to the typical procedure for the benzylic alcohol alkylation, using the followingq uantities:i odomethane (1.68 mL, 28.0 mmol, 4.0 equiv.), [5-(methoxymethoxy)-1,3-phenylene]dimethanol

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Section: Resultssupporting

confidence: 70%

Chemoselectivity Improvement via Partial Shielding of an Imidazole Active Site in Branched/Dendritic Homogeneous Catalysts of the Baylis–Hillman Reaction

2016

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“…In fact, the catalytic activity of 3-FlC2-Pro-Tyr-Asp-Ado-NH 2 was found to be much lower (7% yield in 24 h, see ESI † ) than that of Fl-Pep5-b ( Table 1 , entry 17) in the sulfoxidation of thioanisole under the same conditions, showing the importance of the hydrophobic support resin that would make the flavopeptide conformationally profitable. 21 …”

Section: Resultsmentioning

confidence: 99%

Design of peptide-containing N5-unmodified neutral flavins that catalyze aerobic oxygenations

et al. 2017

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“…Chemical catalysis is another mechanism by which polyvalent recognition events can be magnified in their effect. Although polyvalent catalysts have been intensively investigated for practical reasons in synthetic chemistry—for example, to increase activity by virtue of high local concentration and recyclability by virtue of easier recovery—they have only rarely been tested as a vehicle for information transfer in model systems …”

Section: Figurementioning

confidence: 99%

Polyvalent Catalysts Operating on Polyvalent Substrates: A Model for Surface‐Controlled Reactivity

McKay

Finn

2016

Angewandte Chemie

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Unusually fast rates of nucleophilic catalysis of hydrazone ligation were observed when polyvalent anthranilic acid catalysts operating on polyvalent aldehyde substrates were used with PAMAM dendrimers as the common platform. When presented in this way, the catalyst has a strong accelerating effect at concentrations 40-400 times lower than those required for similar monovalent catalysts and displays unique kinetic parameters. We attribute these properties to polyvalent engagement between the dendrimer surface groups, and a potential "rolling" effect leading to fast interparticle kinetic turnover. The phenomenon is sensitive to the density of functional groups on each dendrimer, and insensitive to factors that promote or inhibit nonspecific particle aggregation. These findings constitute a rare experimental example of an underappreciated phenomenon in biological and chemical systems that are organized on interacting surfaces.

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Multivalency as a Key Factor for High Activity of Selective Supported Organocatalysts for the Baylis–Hillman Reaction

Cited by 11 publications

References 93 publications

Chemoselectivity Improvement via Partial Shielding of an Imidazole Active Site in Branched/Dendritic Homogeneous Catalysts of the Baylis–Hillman Reaction

Chemoselectivity Improvement via Partial Shielding of an Imidazole Active Site in Branched/Dendritic Homogeneous Catalysts of the Baylis–Hillman Reaction

Design of peptide-containing N5-unmodified neutral flavins that catalyze aerobic oxygenations

Polyvalent Catalysts Operating on Polyvalent Substrates: A Model for Surface‐Controlled Reactivity

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