2008
DOI: 10.1002/chem.200701908
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Asymmetric Friedel–Crafts Alkylation of Indoles with Methyl (E)‐2‐Oxo‐4‐aryl‐3‐butenoates Catalyzed by Sc(OTf)3/pybox

Abstract: The asymmetric Friedel-Crafts reaction between a series of substituted indoles 2 a-l and methyl (E)-2-oxo-4-aryl-3-butenoates 3 a-c has been efficiently catalyzed by the scandium(III) triflate complex of (4'S,5'S)-2,6-bis[4'-(triisopropylsilyl)oxymethyl-5'-phenyl-1',3'-oxazolin-2'-yl]pyridine (pybox; 1). Substituted 4-(indol-3-yl)-2-oxo-4-arylbutyric acid methyl esters 4 a-n were usually formed in excellent yields and the enantioselectivity was up to 99 % ee, irrespective of the electronic character of the sub… Show more

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Cited by 65 publications
(24 citation statements)
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“…( 12 a / 13 ),30a Kim and co‐workers ( 12 b / 14 ),30b and Singh and Singh ( 12 c / 15 ),30c whereby variable catalyst loadings (5–20 mol %) provided excellent enantiocontrol (>90 % ee ). Comparable efficiency was also found with chiral scandium(III)–box ( 12 d,e ) catalysts (10 mol %) in combination with α,β‐unsaturated acyl phosphonates 16 ,31a,b α,β‐unsaturated 1‐acylimidazoles 17 ,31c and β,γ‐unsaturated α‐keto esters ( 18 ) 31d…”
Section: Reactions With Cc Multiple Bondsmentioning
confidence: 81%
“…( 12 a / 13 ),30a Kim and co‐workers ( 12 b / 14 ),30b and Singh and Singh ( 12 c / 15 ),30c whereby variable catalyst loadings (5–20 mol %) provided excellent enantiocontrol (>90 % ee ). Comparable efficiency was also found with chiral scandium(III)–box ( 12 d,e ) catalysts (10 mol %) in combination with α,β‐unsaturated acyl phosphonates 16 ,31a,b α,β‐unsaturated 1‐acylimidazoles 17 ,31c and β,γ‐unsaturated α‐keto esters ( 18 ) 31d…”
Section: Reactions With Cc Multiple Bondsmentioning
confidence: 81%
“…Such coordination increases the reactivity of the substrate, and the use of asymmetric catalysts may induce enantioselectivity in the reactions. [9,10] Moreover, the Friedel-Crafts reaction has found many applications in both aromatic and heterocyclic systems (especially with indoles), [11][12][13][14][15][16][17] and all these reactions have been asymmetrically performed by using box [18] and pybox [19] based chiral catalysts. Their absolute configuration was then related to that of 7 by stereospecific isomerization and/or desilylation reactions.…”
Section: Introductionmentioning
confidence: 99%
“…To test the previously prepared transition metal complexes as possible catalysts for asymmetric processes, some organic reactions were performed and the enantiomeric excesses determined by HPLC with chiral columns. The Friedel‐Crafts reaction between the methyl‐( E )‐2‐oxo‐4‐phenyl‐3‐butenoate and indole has been investigated at first (Scheme ) ,…”
Section: Resultsmentioning
confidence: 99%
“…As reported in Table we started using Cu‐9 as a possible catalyst since the structure of ligand 5 c was similar to the well‐known bisoxazoline ligands previously used in Cu catalyzed Friedel‐Crafts reactions . Using the procedure reported by Desimoni, several dry solvents were tested but only dichloromethane gave a moderate 63 % ee.…”
Section: Resultsmentioning
confidence: 99%