Carbon−Carbon Bond Formations Involving Organochromium(III) Reagents

Fürstner, Alois

doi:10.1021/cr9703360

Cited by 621 publications

(275 citation statements)

References 362 publications

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“…The latter was then employed to alkylate, under basic conditions (LDA, À78! 0 8C), cyclopentanone (17) to afford cyclopentanone derivative 18, which was subjected to intramolecular NozakiHiyama-Kishi coupling [9] (CrCl 2 , cat. NiCl 2 ) to furnish tricyclic tertiary alcohol 19 in 76 % yield.…”

mentioning

confidence: 99%

Synthesis of the Sporolide Ring Framework through a Cascade Sequence Involving an Intramolecular [4+2] Cycloaddition Reaction of an o‐Quinone

Nicolaou¹,

Wang²,

Tang³

2008

Angewandte Chemie

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In a recent publication, Fenical and co-workers [1] reported the structural characterization of the two unique molecular frameworks of sporolides A (1) and B (2; Scheme 1). Isolated from the fermentation broths of a strain of the marine-derived actinomycete Salinispora tropica, these compounds feature molecular architectures that contain 24 carbon atoms (among which only two are not oxygenated or sp 2 hybridized), 10 stereogenic centers, and no less than seven rings. These marine natural products present an intriguing synthetic challenge in view of their unprecedented molecular structures and the opportunity they present for the development of novel synthetic strategies. Herein we report the construction of model system 3, which represents the structural skeleton of sporolide A (1) and B (2) and contains all seven rings of the naturally occurring molecules, through a cascade sequence involving an unprecedented intramolecular [4+2] cycloaddition reaction of an olefinic o-quinone.Scheme 2 shows the retrosynthetic analysis of the sporolide model system 3. Thus, the target molecule was envisioned to arise by selective manipulation of the trioxygenated aromatic nucleus of hexacyclic compound 4 a, whose macrocycle and dioxane moieties were simultaneously dismantled through a retro o-quinone [4+2] cycloaddition reaction to reveal o-quinone ester 5 as a possible intermediate, whose generation from catechol 6 was considered standard. While the origin of precursor 6 was clear (that is, from building blocks 7 and 8), the transformation of o-quinone 5 to macrocycle 4 a through the intended cycloaddition reaction was based on a rather daring hypothesis since we were aware of no precedent for such an intramolecular reaction of an o-quinone. [2,3] Furthermore, should such a scenario be possible, its stereochemical outcome could only be speculated upon at the outset. Encouragingly, both molecular models and molecular mechanics calculations, together with electronic considerations, indicated the desired regio-and diatereoisomer to be favored. Thus, of the four possible isomers of 4 a (4 a-4 d, Scheme 3), the desired isomer 4 a was predicted to be the most favored on the basis of electronic (preferential activation of the C6-carbonyl oxygen atom by the C4'-OBn moiety; conjugated addition of the C6-carbonyl oxygen atom onto C10 of the olefinic bond, Scheme 1. Molecular structures of sporolides A (1) and B (2) as well as sporolide ring framework 3.Scheme 2. Retrosynthetic analysis of sporolide ring framework 3.

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confidence: 99%

Synthesis of the Sporolide Ring Framework through a Cascade Sequence Involving an Intramolecular [4+2] Cycloaddition Reaction of an o‐Quinone

Nicolaou¹,

Wang²,

Tang³

2008

Angewandte Chemie

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“…After being stirred at 25 o C for 15 min, the mixture was quenched by addition of water (20 mL) and extracted with ether. The reaction mixture was filtered, the residues were washed with twice with ether, dried with MgSO 4 and concentrated under vacuum to give the crude product that was purified by column chromatography over silica gel.…”

Section: Addition Of Organochromium Reagents To Heteroaromatic Aldehymentioning

confidence: 99%

“…The Nozaki-Hiyama reaction is mainly applied to aldehydes but ketones can be used in some cases and the reaction can be also extended to other organochromium reagents. This reaction has been widely employed in natural product synthesis, becoming the key step in some synthesis plans and it played a key role, for example, in the highly stereocontrolled synthesis of the aliphatic segment of the antibiotic rifamycin S [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Addition of Organochromium Reagents to Heteroaryl Aldehydes. Synthesis of Heteroaryl Substituted bis-Allyl Ethers and Homoallyl Ethers

Servi

Topaloğlu²

2004

Molecules

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Heteroaryl substituted allyl and homoallyl alcohols were synthesised with two different method. Synthesis of bis-allyl ethers and homoallyl ethers were carried out via reaction of allyl bromide with allyl alcohols and homoallyl alcohols, respectively. [2.3]-Wittig Rearrangement reactions of heteroaryl substituted bis-allyl ethers were investigated using GC/MS techniques. In these reactions two unexpected products were isolated in high yield.

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“…Carbonyl allylations using allylchromium reagents (Nozaki-Hiyama reaction) rank among the foremost methods for natural product syntheses owing to the extreme chemoselectivity and substrate compatibility. [3] Organochromium reagents are easily prepared in situ by the oxidative addition of chromium(II) species to allyl, propargyl, aryl and vinyl halides or triflates (requiring catalytic amounts of Ni(II) salt for sp 2 carbon centers), and can be efficiently added to aldehydes to give the corresponding alcohols in favorable yields. [4] The original Nozaki-Hiyama-Kishi (NHK) reaction relies on the use of stoichiometric quantities of chromium(II) chloride.…”

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confidence: 99%

A Spirocyclic Chiral Borate for Catalytic Enantioselective Nozaki‐Hiyama Allylation of Ketones

Huang¹,

Chen²,

Lee³

et al. 2009

Adv Synth Catal

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A new class of chiral spirocyclic borate ligands 5a-d with a rigid borocycle has been developed. The catalyst formed from chromium(II)-5a promotes the highly efficient enantioselective Nozaki-Hiyama allylation of alkyl and aryl ketones using allyl bromide. The scope of the present method is shown to be wide, and it affords an efficient access to chiral tertiary homoallylic alcohols.Keywords: aminoborates; bipyridyls; chromium catalysts; Nozaki-Hiyama allylation; spirocyclic boratesThe use of organochromium species as reagents began in 1977 when Nozaki and Hiyama et al.[1] as well as Heathcock et al. [2] recognized that these species mediated Barbier-Grignard carbonyl additions, and so participated in carbon-carbon bond-forming reactions in organic solvents. Carbonyl allylations using allylchromium reagents (Nozaki-Hiyama reaction) rank among the foremost methods for natural product syntheses owing to the extreme chemoselectivity and substrate compatibility.[3] Organochromium reagents are easily prepared in situ by the oxidative addition of chromium(II) species to allyl, propargyl, aryl and vinyl halides or triflates (requiring catalytic amounts of Ni(II) salt for sp 2 carbon centers), and can be efficiently added to aldehydes to give the corresponding alcohols in favorable yields.[4] The original Nozaki-Hiyama-Kishi (NHK) reaction relies on the use of stoichiometric quantities of chromium(II) chloride. The catalytic redox system described by Fürstner et al. enabled the quantity of chromium salts to be reduced, making these reactions more valuable and environmentally benign.[5] The catalytic modification of this process has significantly improved the application of and permitted the design of chiral ligands for the enantioselective variations.[6] Chiral homoallyl alcohols with high levels of enantioselectivity have been synthesized by catalytic asymmetric addition of allylchromium reagents to carbonyl compounds. [7,8] Like other enantioselective allyl fragment additions, the asymmetric Nozaki-Hiyama reaction has been successful for aldehyde allylation with a wide range of catalyst systems. [9,10] Recently, ketone allylations have been explored.[11] The development of new, effective chiral ligands for the Nozaki-Hiyama allylation of ketones is extremely intricate and needs a wide screening of chiral ligands. Recently, Sigman et al. elucidated a chromium-catalyzed enantioselective ketone allylation in which allyl bromides were used directly. [12] Herein, we report the synthesis of a chiral spirocyclic borate ligand that is effective in the chromium-catalyzed enantioselective allylation of alkyl and aryl ketones.Chiral bipyridyl ligands derived from enantioenriched pinene allows for a variety of structural variations and affords moderate to high levels of enantiselectivities in different asymmetric transformations. [13] A chiral spirocyclic borate ligand which incorporates a rigid framework in the bipyridyl moiety for NH allylation was synthesized in a three-step process from ketone 1 [14] and amino alcohol...

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Carbon−Carbon Bond Formations Involving Organochromium(III) Reagents

Cited by 621 publications

References 362 publications

Synthesis of the Sporolide Ring Framework through a Cascade Sequence Involving an Intramolecular [4+2] Cycloaddition Reaction of an o‐Quinone

Synthesis of the Sporolide Ring Framework through a Cascade Sequence Involving an Intramolecular [4+2] Cycloaddition Reaction of an o‐Quinone

Addition of Organochromium Reagents to Heteroaryl Aldehydes. Synthesis of Heteroaryl Substituted bis-Allyl Ethers and Homoallyl Ethers

A Spirocyclic Chiral Borate for Catalytic Enantioselective Nozaki‐Hiyama Allylation of Ketones

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