Efficient and Recyclable Monomeric and Dendritic Ru-Based Metathesis Catalysts

Garber, Steven B.; Kingsbury, Jason S.; Gray, and Brian L.; Hoveyda, Amir H.

doi:10.1021/ja001179g

Cited by 1,987 publications

(1,130 citation statements)

References 30 publications

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“…In fact, the Hoveyda complex 3 is also a chelated carbene, but it is stable and initiates by dissociation of the chelated ether. [42,43] Alternatively, chelation may result in carbene decomposition. This would be far more problematic, yet decomposition occurring via chelates in the second generation carbene has not been directly observed.…”

Section: Tandem Metathesis-mentioning

confidence: 99%

“…Alkyne insertion is the first step in enyne metathesis, and stopping the reaction at the vinyl carbene stage is a challenge. Successful syntheses have taken a clue from the design of the Hoveyda complex [42,43] which features a chelated carbene fragment. Chelation imposes kinetic stability to the vinyl carbene intermediate.…”

Section: By Alkyne Insertion Into a Metalmentioning

confidence: 99%

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Ruthenium vinyl carbene intermediates in enyne metathesis

Diver

2007

Coordination Chemistry Reviews

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This review provides an overview of ruthenium vinyl carbene reactivity as it relates to enyne metathesis. Methods for the synthesis of metathesis-active and metathesis-inactive complexes are also summarized. Some of the early hypotheses about vinyl carbene intermediates in enyne metatheses were tested in the arena of synthetic chemistry and subsequently led to mechanistic studies. In these two areas, studies from the author's labs are described. There are still many unresolved questions in enyne metathesis that trace back to vinyl carbene reactivity. Hopefully this review will stimulate further investigation into vinyl carbene reactivity which should further refine our understanding of catalytic enyne metathesis.

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Section: Tandem Metathesis-mentioning

confidence: 99%

Section: By Alkyne Insertion Into a Metalmentioning

confidence: 99%

Ruthenium vinyl carbene intermediates in enyne metathesis

Diver

2007

Coordination Chemistry Reviews

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“…Hoveyda and coworkers [55] have described the use of a carbosilane dendrimer for the recovery of Ru-based alkylidine olefin metathesis catalysts. Undoubtedly, olefin metathesis [56], with either ruthenium [57] or molybdenum [58] catalyst systems, is one of the more important reactions in polymer chemistry and natural product synthesis [59] and the ability to recover and reuse the catalysts would greatly impact the cost efficiency of these reactions.…”

Section: Dendrimers Containing Non-ferrocene Organometallic Groups Inmentioning

confidence: 99%

“…As the active catalyst is not bound to the dendrimer, metal species of small dimensions are free in solution and thus catalyst leaching would occur. Also, catalyst self-decay can occur which will also compete with the return step [55]. As such, these species are more suitable for recovery and reuse in batch reactions.…”

Section: Dendrimers Containing Non-ferrocene Organometallic Groups Inmentioning

confidence: 99%

Where Organometallics and Dendrimers Merge: The Incorporation of Organometallic Species into Dendritic Molecules

2005

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This review will describe the ongoing efforts being made to incorporate organometallic fragments into the framework of dendrimers. While purely dendritic organic molecules are well known and well studied, species incorporating organometallic moieties potentially offer many benefits that are not available to only organic containing dendrimers. For example, catalytic or redox active organometallic functions can be included in the dendritic framework and impart these characteristics onto the dendrimer. This report will give an overview of the latest developments in this field by highlighting selected examples that detail novel synthetic strategies or dendrimer construction methodologies, interesting practical applications or address specific problems associated with organometallic dendrimers.

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“…It is noteworthy that numerous attempts (various bases, solvents, additives, and temperatures) to alkylate the Boc carbamate of amine 4 led to low conversion. The addition of propenylmagnesium bromide to Weinreb amide 5 gave vinyl ketone 6, which was then treated with 2 mol % of the second generation Hoveyda−Grubbs catalyst 18 in hot toluene to form the enone ring in good yield. The use of propenylmagnesium bromide led to higher yields in both the vinyl ketone formation and metathesis steps relative to vinylmagnesium bromide.…”

mentioning

confidence: 99%

Enantioselective Synthesis and Profiling of Two Novel Diazabicyclooctanone β-Lactamase Inhibitors

Xiong

Chen

Durand-Réville

et al. 2014

ACS Med. Chem. Lett.

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ABSTRACT:The enantioselective synthesis of two novel cyclopropane-fused diazabicyclooctanones is reported here. Starting from butadiene monoxide, the key enone intermediate 7 was prepared in six steps. Subsequent stereoselective introduction of the cyclopropane group and further transformation led to compounds 1a and 1b as their corresponding sodium salt. The great disparity regarding their hydrolytic stability was rationalized by the steric interaction between the cyclopropyl methylene and urea carbonyl. These two novel β-lactamase inhibitors were active against class A, C, and D enzymes. KEYWORDS: β-lactamase inhibitor, asymmetric synthesis, hydrolytic stability S ince the discovery of penicillin in the 1920s, β-lactam antibiotics have become one of the most important groups of antibiotics. The worldwide usage of these antibiotics has rapidly led to the development of bacterial resistance, mainly by the production and evolution of β-lactamases, which are enzymes responsible for efficiently catalyzing the hydrolysis of the β-lactam warheads. According to the Ambler classification, 1−3 β-lactamases are divided into four subfamilies: class A, C, and D enzymes have a key serine residue in the active site, whereas class B enzymes (also called metallo-β-lactamases) employ either one or two zinc ions.The combination use of several mechanism-based β-lactamase inhibitors (clavulanic acid, sulbactam, and tazobactam) with β-lactam antibiotics is currently one of the most successful strategies in combating such resistance, 4−6 as evident by the wide clinical application of products such as Augmentin, Timentin, Unasyn, Sulperazone, and Zosyn. However, these β-lactamase inhibitors only have activity against class A β-lactamases and weak or no activity against class C and D enzymes. 4 In addition, β-lactamases are rapidly evolving, as evident by the rising number of new β-lactamases reported each year (over 1400 to date). 7 Therefore, this urgent medical need calls for firm commitment to the discovery and development of novel and more efficient inhibitors with broader coverage of β-lactamases.Recently a novel series of β-lactamase inhibitors based on the diazabicyclooctanone (DBO) scaffold was reported. This letter describes our efforts toward the enantioselective synthesis of two new cyclopropane-fused diazabicyclooctanones 1a and 1b aiming to explore whether the introduction of additional ring strain can lead to higher reactivity of the urea carbonyl and broader β-lactamase coverage, while hoping to maintain sufficient hydrolytic stability.

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Efficient and Recyclable Monomeric and Dendritic Ru-Based Metathesis Catalysts

Cited by 1,987 publications

References 30 publications

Ruthenium vinyl carbene intermediates in enyne metathesis

Ruthenium vinyl carbene intermediates in enyne metathesis

Where Organometallics and Dendrimers Merge: The Incorporation of Organometallic Species into Dendritic Molecules

Enantioselective Synthesis and Profiling of Two Novel Diazabicyclooctanone β-Lactamase Inhibitors

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