Amidation of [RhI(ethene)]+ via a 2-Rhodaoxetane

Bruin, Bas de; Boerakker, Mark J.; Gelder, R. de; Smits, J.M.; Gal, Anton W.

doi:10.1002/(sici)1521-3773(19990115)38:1/2<219::aid-anie219>3.0.co;2-i

Cited by 30 publications

(33 citation statements)

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“…In this field, 2‐metallaoxetanes5 emerge as valuable candidates to test this possibility, since they can be obtained by oxygenation of olefins with dioxygen 6. Although the reactivity of 2‐metallaoxetanes is currently in its infancy,7 two of them have been reported as suitable for CX (X=N, O) bond formation, as shown by the reactions of 2‐rhoda‐ and 2‐platinaoxetanes with acetonitrile8 and carbon monoxide,9 respectively. Herein, we describe new reactions leading to carboxylic acids and lactones, involving the stoichiometric functionalisation of an allylic CH bond in 1,5‐cyclooctadiene (COD) with carbon monoxide and dioxygen, which proceeds through a discrete 2‐rhodaoxetane intermediate.…”

Section: Methodsmentioning

confidence: 99%

Prostaglandin E₂ is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Kojima

Naraba

Sasaki

et al. 2003

Arthritis & Rheumatism

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Objective. Membrane-associated prostaglandin E synthase (mPGES) is a recently identified terminal enzyme of the arachidonic acid cascade, which converts PGH 2 to PGE 2 in rheumatoid arthritis synovial fibroblasts (RASFs). This study was undertaken to investigate factors regulating the expression of mPGES.Methods. RASFs were treated with interleukin-1␤ (IL-1␤), indomethacin, NS-398, rofecoxib, or meloxicam. The effects of PGE 2 and selective agonists for PGE 2 receptor subtypes (EP1, EP2, EP3, and EP4) were also studied. Expression of mPGES messenger RNA (mRNA) and protein was measured by Northern and Western blot analysis, respectively. EP receptor mRNA expression in RASFs was determined by reverse transcriptase-polymerase chain reaction. Production of PGE 2 and cAMP was measured by enzyme-linked immunosorbent assay.Results. The enhanced expression of mPGES mRNA and protein in IL-1␤-stimulated RASFs was attenuated by the addition of indomethacin, NS-398, rofecoxib, or meloxicam. This reduction of expression was reversed by PGE 2 . IL-1␤-induced PGES activity, measured by conversion of PGH 2 to PGE 2 , was decreased by rofecoxib. EP2 and EP4 receptor mRNA was detected in RASFs. EP2 and EP4 agonists, as well as PGE 2 , restored the inhibitory effect of rofecoxib on mPGES expression. The effect of PGE 2 was mimicked by forskolin, a direct activator of adenylate cyclase. Intracellular cAMP was increased by IL-1␤ and was inhibited by rofecoxib. Conclusion. Enhancement of mPGES expression by PGE 2 via the EP2/EP4 receptors with an increase in cAMP may play an important role in articular inflammation in patients with RA. It also seems that cyclooxygenase 2 (COX-2) inhibitors decrease PGE 2 production not only by direct inhibition of COX-2, but also by reducing mPGES expression in activated RASFs.Prostaglandin E synthase (PGES) catalyzes the final step of PGE 2 production, converting PGH 2 to PGE 2 . PGES exists downstream of cyclooxygenase (COX) (1,2). At least 2 forms of PGES, membraneassociated PGES (mPGES) (3-5) and cytosolic PGES (cPGES) (6), have recently been cloned and characterized. In cotransfection experiments, functional coupling between inducible mPGES and COX-2, as well as between constitutive cPGES and COX-1, has been demonstrated (4,6).Originally called microsomal glutathione S-transferase 1-like 1 (MGST1-L1), mPGES is a glutathione-dependent enzyme that shows coordinated induction with COX-2 in various cells and tissues by inflammatory stimuli (3,4). We recently showed that mPGES and COX-2 were induced by interleukin-1␤ (IL-1␤) on the perinuclear membrane in rheumatoid arthritis synovial fibroblasts (RASFs), causing an increase in PGE 2 production at sites of inflammation (7).

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Section: Methodsmentioning

confidence: 99%

Prostaglandin E₂ is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Kojima

Naraba

Sasaki

et al. 2003

Arthritis & Rheumatism

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“…The reactiono fcis-a nd trans-1,2-dialkyl-substituted epoxide (cis-3 j, trans-3 j)l ed to retention of the configuration in the respectivep roducts (cis-4 j and trans-4 j)a nd to inversion in the case of 1,2-diethylcarboxylate-substituted epoxides (3z). As an epoxide opening that follows an S N 2m echanism would lead to inversion of the configuration in ap ossible intermediate Int-1b,w ec onclude that the activation step B proceeds via oxidative addition under CÀOb ondc leavage to the iridaoxetane [10,11,36] Int-1 a with the substrates cis-3 j and trans-3 j.T his is followed by CO induced migration of the alkoxide from Ir to aC Ol igand [35,37,38] to form 5j.U nder the applied conditions, Int-1 b could also be formed from Int-1 a by Lewis acid ring openingf ollowed by CO coordination and lactone formation by nucleophilic addition of the alkoxide to CO [39,40] to form 5j withoutc hange of the configuration. Attempts to detect 5j from 1,2-dialkylsubstituted epoxides 3j failed, as these substrates do not react without presence of the Lewis acid.…”

Section: Mechanistic Investigationsmentioning

confidence: 99%

Deoxygenation of Epoxides with Carbon Monoxide

Maulbetsch

Jürgens

Kunz

2020

Chemistry A European J

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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer‐iridium(I) complex in combination with a Lewis acid co‐catalyst to achieve a pre‐activation of the epoxide substrate, as well as the elimination of CO2 from a γ‐2‐iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate‐dependent change in the mechanism for the epoxide C−O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.

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“… Activation of 2‐metallaoxetanes by protonation and alkylation of the oxygen atom; Rh=(tpa)Rh 120. 124 …”

Section: Stoichiometric Models For Oxidation Catalysismentioning

confidence: 99%

Functional Models for Rhodium‐Mediated Olefin‐Oxygenation Catalysis

2004

Self Cite

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Oxygenation of C-H and C=C bonds of hydrocarbons with H2O2 and O2 is an important industrial method to convert mineral oil into useful chemicals. Despite their enormous economic impact, these reactions are still not fully understood. In the early 1970s, the potential of Rh and Ir complexes for olefin oxygenation was investigated intensively. Simple inorganic salts of these metals proved to be rather useless for industrial application when compared with the traditional Wacker system. However, the appropriate choice of ligands allows the stepwise oxidation of olefins at Rh and Ir. These systems are therefore useful to study mechanistic details of substrate binding and C-O bond formation at the catalytic metal center. Insight from these model studies helps in understanding the catalytic reactions at these (and possibly other) metal centers. Further insight into the differences between the Rh system and traditional Wacker-type oxidation at Pd may lead to useful applications.

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Amidation of [RhI(ethene)]+ via a 2-Rhodaoxetane

Cited by 30 publications

References 1 publication

Prostaglandin E₂ is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Prostaglandin E₂ is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Deoxygenation of Epoxides with Carbon Monoxide

Functional Models for Rhodium‐Mediated Olefin‐Oxygenation Catalysis

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Amidation of [RhI(ethene)]+ via a 2-Rhodaoxetane

Cited by 30 publications

References 1 publication

Prostaglandin E2 is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Prostaglandin E2 is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Deoxygenation of Epoxides with Carbon Monoxide

Functional Models for Rhodium‐Mediated Olefin‐Oxygenation Catalysis

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Prostaglandin E₂ is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts

Prostaglandin E₂ is an enhancer of interleukin‐1β–induced expression of membrane‐associated prostaglandin E synthase in rheumatoid synovial fibroblasts