Silylcarbocyclization reactions catalyzed by rhodium and rhodium-cobalt complexes

Ojima, Iwao; Donovan, Robert J.; Shay, William R.

doi:10.1021/ja00042a061

Cited by 120 publications

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“…It is noteworthy that reductive elimination of the . [99] They studied this silicon-initiated carbocyclization reaction extensively, and have spurred substantial interest in this field. The reaction conditions were compatible with the use of ionic liquids as solvents.…”

Section: Enyne Tandem Reactionsmentioning

confidence: 99%

Cycloisomerization of 1,n‐Enynes: Challenging Metal‐Catalyzed Rearrangements and Mechanistic Insights

Michelet¹,

Toullec²,

Genêt³

2008

Angew Chem Int Ed

950

248

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Metal-catalyzed cycloisomerization reactions of 1,n-enynes have appeared as conceptually and chemically highly attractive processes as they contribute to the highly demanded search for atom economy and allow the discovery of new reactions. Since the pioneering studies with palladium by the research group of Barry Trost in the mid-1980s, several other metals have been identified as excellent catalysts for the rearrangement of enyne skeletons. Moreover, the behavior of 1,n-enynes may be influenced by other functional groups such as alcohols, aldehydes, ethers, alkenes, or alkynes, thus enhancing the molecular complexity of the synthesized products. Apart from the intrinsic rearrangements of 1,n-enynes, several tandem reactions incorporating intramolecular trapping agents or intermolecular partners have been discovered. This Review aims to highlight the main contributions in this field of catalysis and to propose and comment on the mechanistic insights of the recent discoveries.

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Section: Enyne Tandem Reactionsmentioning

confidence: 99%

Cycloisomerization of 1,n‐Enynes: Challenging Metal‐Catalyzed Rearrangements and Mechanistic Insights

Michelet¹,

Toullec²,

Genêt³

2008

Angew Chem Int Ed

950

248

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“…The electronic and steric properties of the catalysts are crucial for the different steps in the catalytic cycle to proceed. However, neither phosphanes such as PPhMe 2 and PPh 3 , nor phosphites [PA C H T U N G T R E N N U N G (OEt) 3 , PA C H T U N G T R E N N U N G (OPh) 3 ] resulted in formation of the desired cyclized product in toluene at 110 8C, although the product from silaboration of the alkyne could be observed.…”

Section: Palladium-catalyzed Silaborationsmentioning

confidence: 99%

“…Of particular interest are methods leading to products containing reactive functional groups for further synthetic elaboration. Silacarbocyclizations, [2] boracarbocyclizations, [3] and stannacarbocyclizations, [4] including a few enantioselective processes, [2d,f,3a] are examples of transformations of this type.…”

Section: Introductionmentioning

confidence: 99%

Regioselective Preparation of Functionalized exo‐Methylene‐ cyclopentanes and exo‐Methylenepyrrolidines via Silaborative Carbocyclization of 1,6‐Enynes

et al. 2010

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Silaborative carbocyclization of 1,6-enynes catalyzed by Pd-PEPPSI-IPr {PEPPSI = pyridine-enhanced precatalyst preparation stabilization and initiation; IPr = N,N-bisA C H T U N G T R E N N U N G [2,6-(diisopropyl)phenyl]imidazolium} employing either (dimethylphenylsilyl)pinacolborane or (chlorodimethylsilyl)pinacolborane provides access to densely functionalized five-membered rings as single diastereomers in excellent yields. The vinylboronate functions were employed in palladium-catalyzed Suzuki cross-coupling reactions with a range of aryl bromides, containing electron-withdrawing as well as electron-donating substituents, furnishing arylated exo-methylenecyclopentanes or exo-methylenepyrrolidines in good yields. Subsequent oxidation of the isopropoxydimethylsilyl function generated via addition of (chlorodimethylsilyl)-pinacolborane provided access to hydroxymethyl derivatives of the arylated compounds. Use of a chiral ester, bismenthyl (2-propenyl)(2-propynyl)malonate, afforded two diastereomeric products which could be separated, thereby giving access to the cyclized compounds as single isomers, with opposite absolute configurations at the newly formed stereocenter.

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“…Following up this discovery, we have investigated the intramolecular version of this reaction using a variety of 1,6-enynes, which led to the discovery of novel silylcarbocyclization (SiCaC) reaction (eq. 1) [1][2][3]. The SiCaC reaction of 1,6-enynes is catalyzed by Rh 4 (CO) 12 (1) which enable the reaction to proceed at ambient temperature and completes mostly within a minute.…”

Section: Silylcarbocyclizations (Sicacs)mentioning

confidence: 99%

“…Other Rh catalysts such as Rh(acac)(CO) 2 are also effective for this reaction, but require 65-70 °C to promote the reaction efficiently. Although CO is not incorporated into the SiCaC products, the cluster catalysts require CO atmosphere to stabilize the active catalyst species [1][2][3].…”

Section: Silylcarbocyclizations (Sicacs)mentioning

confidence: 99%

New cyclization reactions in organic syntheses

Ojima

2002

Pure and Applied Chemistry

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Recent development in the transition metal-catalyzed cyclization reactions for organic syntheses in the author's laboratories is summarized, which includes (i) novel silylcarbocyclizations (SiCaCs) and carbonylative carbotricyclizations, (ii) intramolecular silylformylations and desymmerization of siloxydiynes by sequential double silylformylation, (iii) efficient total synthesis of (+)-prosopinine, (iv) enantioselective desymmetrization of aminodienes, and (iv) new and efficient routes to 1-azabicyclo[x.y.0]alkane amino acids. All these processes are catalyzed by Rh or Rh-Co complexes, and useful for rapid and efficient construction of a variety of heterocyclic and carbocyclic compounds. Mechanisms of these new carbocyclization and cyclohydrocarbonylation reactions are also discussed.It has been the central focus in modern organic synthesis to develop highly efficient catalytic processes for the syntheses of natural and unnatural compounds of medicinal interest or intermediates useful for functional materials. One of the most attractive approaches to such aims is to apply transition metal-catalyzed cyclization reactions for the transformations of simple starting materials into monocyclic, bicyclic, and polycyclic scaffolds that can be further elaborated into specific targets.This account describes new and useful cyclization processes based on silylcarbocyclization (SiCaC), silylformylation, and cyclohydrocarbonylation reactions, which have recently been developed in these laboratories and will find many applications in organic syntheses. SILYLCARBOCYCLIZATIONS (SiCaCs)The first silylcarbocyclization was discovered serendipitously during our detailed product analysis of the silylformylation of 1-hexyne catalyzed by Rh and Rh-Co carbonyl clusters, which gave dibutylcyclopentenone by incorporating two molecules of 1-hexyne, one molecule of hydrosilane, and one molecule of CO. Following up this discovery, we have investigated the intramolecular version of this reaction using a variety of 1,6-enynes, which led to the discovery of novel silylcarbocyclization (SiCaC) reaction (eq. 1) [1][2][3]. The SiCaC reaction of 1,6-enynes is catalyzed by Rh 4 (CO) 12 and Rh 2 Co 2 (CO) 12 , *Lecture presented at the

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Silylcarbocyclization reactions catalyzed by rhodium and rhodium-cobalt complexes

Cited by 120 publications

References 0 publications

Cycloisomerization of 1,n‐Enynes: Challenging Metal‐Catalyzed Rearrangements and Mechanistic Insights

Cycloisomerization of 1,n‐Enynes: Challenging Metal‐Catalyzed Rearrangements and Mechanistic Insights

Regioselective Preparation of Functionalized exo‐Methylene‐ cyclopentanes and exo‐Methylenepyrrolidines via Silaborative Carbocyclization of 1,6‐Enynes

New cyclization reactions in organic syntheses

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