New Strategies in Organic Catalysis:  The First Enantioselective Organocatalytic Friedel−Crafts Alkylation

Paras, Nick A.; MacMillan, David W. C.

doi:10.1021/ja015717g

Cited by 568 publications

(247 citation statements)

References 12 publications

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“…40 A number of conformers of similar energy were located; attack from the bottom, away from the benzyl group is favored as noted by MacMillan. 2,4,6,16 Figures 9 and 10 show the twelve different conformers found in the case of imidazolidinone 1 and 4-hexen-3-one. These correspond to the (E) and (Z) configurations about the N + =C bond, the three staggered conformations involving the bond to the benzyl group, and two conformations of the ethyl group attached to the carbon-nitrogen double bond.…”

Section: Imidazolidinone Catalyzed Diels-alder Cycloadditionsmentioning

confidence: 99%

Origins of Stereoselectivity in Diels−Alder Cycloadditions Catalyzed by Chiral Imidazolidinones

2006

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B3LYP/6-31G(d) density functional theory has been used to study Diels-Alder reactions of cyclopentadiene with α,β-unsaturated aldehydes and ketones organocatalyzed by MacMillan's chiral imidazolidinones. Preferred conformations of transition structures and reaction intermediates have been located. The dramatically different reactivities and enantioselectivities exhibited by two similar chiral imidazolidinones are rationalized.

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Section: Imidazolidinone Catalyzed Diels-alder Cycloadditionsmentioning

confidence: 99%

Origins of Stereoselectivity in Diels−Alder Cycloadditions Catalyzed by Chiral Imidazolidinones

2006

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“…A consideration of the proposed Friedel -Craft s alkylation-ring opening pathway led to the conclusion that the aromatic substrates that participate as Michael donors in the process must be electron rich so that the initial electrophilic aromatic substitution step can occur effi ciently. Although organocatalytic Michael addition reactions of electron-rich aromatic compounds to α , β -unsaturated aldehydes has been intensively studied 40,41 , to our knowledge no precedent exists for bond formation at ipso -positions, which is an essential component of the new α -arylation reaction.…”

Section: Resultsmentioning

confidence: 99%

Direct stereoselective α-arylation of unmodified enals using an organocatalytic cross-coupling-like reaction

Song

Zhang

et al. 2011

Nat Commun

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Cross-coupling reactions typically rely on the use of transition metal catalysis. However, although achieving this process using metal-free organocatalysts is highly challenging, it could offer unique opportunities to discover novel bond-forming strategies in organic synthesis. Here we report a new amine catalysed direct stereoselective C-H α -arylation reaction of unmodifi ed enals with bromoarenes. The power of this process, which involves an unprecedented iminiumMichael-alkylation-enamine-retro-Michael cascade sequence, has been demonstrated in the context of direct α -functionalization reactions of simple, unmodifi ed enals with 4-bromophenols, 1-bromo-2-naphthol and 3-bromoindoles under mild reaction conditions. Notably, the process can be used for highly stereoselective syntheses of non-readily accessible E isomers, which normally require the use of transition metal-promoted cross-couplings and functionalized enals. The results of these studies signifi cantly expand the scope of aminocatalysis.

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“…Here, the outstanding performances of chiral imidazolidinones of first generation were applied in the condensation of pyrroles with enales [27]. This catalytic approach generally requires the use of a strong Brønsted acid as co-catalyst (e.g., TFA, AcOH, HCl, TfOH, MsOH, HClO 4 ) in order to improve the turn-over frequency of the reaction cycle.…”

Section: Privileged Catalystsmentioning

confidence: 99%

General Aspects and Historical Background

Bandini

2009

Catalytic Asymmetric Friedel–Crafts Alkylations

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SummaryThe scope of catalytic enantioselective Friedel-Crafts alkylations is expanding rapidly and since the seminal papers appeared in the mid 1980s, numerous examples featuring enantioselectivities higher than 90% have been published. At present, nearly all the organic compounds displaying electrophilic character have been reacted with aromatic systems in FC-type alkylation reactions. However, the typology of reagents becomes slightly narrower if we limit the survey to approaches that employ chiral catalysts capable of traducing stereochemistry in the final products. Activated as well as unactivated carbon-carbon double bonds and C¼X frameworks characterize the most used classes of electrophilic agents, that are generally combined with privileged chiral organometallic and organic catalysts. It is also worth mentioning the actual distribution of enantioselective FC processes based on the type of aromatic system employed. Interestingly, highly reactive electron-rich arenes (pyrrole and indole) still constitute almost 80% of catalytic enantioselective FC-processes, while asymmetric transformations of benzene-like compounds are quite undeveloped.

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New Strategies in Organic Catalysis: The First Enantioselective Organocatalytic Friedel−Crafts Alkylation

Cited by 568 publications

References 12 publications

Origins of Stereoselectivity in Diels−Alder Cycloadditions Catalyzed by Chiral Imidazolidinones

Origins of Stereoselectivity in Diels−Alder Cycloadditions Catalyzed by Chiral Imidazolidinones

Direct stereoselective α-arylation of unmodified enals using an organocatalytic cross-coupling-like reaction

General Aspects and Historical Background

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