Organocatalytic Asymmetric Aza-Friedel−Crafts Alkylation of Furan

Uraguchi, Daisuke; Sorimachi, Keiichi; Terada, Masahiro

doi:10.1021/ja046185h

Cited by 353 publications

(114 citation statements)

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“…The idea of effective aldimine activation by Brønsted acid is important, and should find wide use and application in synthetic organic chemistry. Indeed it has already been utilized in the recent elegant asymmetric catalytic reaction of aldimine promoted by chiral Brønsted acid described independently by Akiyamas [6p] and Teradas [11,29] groups.…”

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confidence: 99%

The Direct, Enantioselective, One‐Pot, Three‐Component, Cross‐Mannich Reaction of Aldehydes: The Reason for the Higher Reactivity of Aldimine versus Aldehyde in Proline‐Mediated Mannich and Aldol Reactions

et al. 2005

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In the proline-mediated Mannich and aldol reactions of propanal as a nucleophile, the aldimine prepared from benzaldehyde and p-anisidine is about 7 times more reactive than the corresponding aldehyde, benzaldehyde, as an electrophile. This higher reactivity of aldimine over aldehyde is attributed to the carboxylic acid of proline protonating the basic nitrogen atom of the aldimine more effectively than the oxygen atom of the aldehyde, an explanation which has been both experimentally and theoretically verified.

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Section: Full Papersmentioning

confidence: 99%

The Direct, Enantioselective, One‐Pot, Three‐Component, Cross‐Mannich Reaction of Aldehydes: The Reason for the Higher Reactivity of Aldimine versus Aldehyde in Proline‐Mediated Mannich and Aldol Reactions

et al. 2005

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“…For example, several additions of indoles to aromatic imines promoted by chiral phosphoric acids [13] as well as thiourea-Cinchona alkaloids [14] have been described. Other examples of Friedel-Crafts alkylations of heteroaromatic compounds include the chiral phosphoric acid-catalyzed addition of furans [15] and pyrroles [16] to electronpoor aromatic aldimines. However, there are relatively few protocols for the enantioselective organocatalytic Friedel-Crafts-type alkylations of simple benzene derivatives.…”

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Enantioselective Organocatalytic Synthesis of Arylglycines via Friedel–Crafts Alkylation of Arenes with a Glyoxylate Imine

2010

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Abstract:The enantioselective organocatalytic synthesis of arylglycines has been developed employing 1 mol% of an enantiopure N-triflyl phosphoramide Brønsted acid as organocatalyst. Various differently substituted phenylglycine derivatives can be synthesized in good to excellent yields and enantiomeric excesses based on a Friedel-Crafts alkylation of electron-rich arenes with a glyoxylate imine. A novel protocol for the deprotection of the N-tert-butylsulfonyl (Bus) group has also been developed.Keywords: amino acids; Brønsted acids; FriedelCrafts reaction; organocatalysis; phosphoric acidsThe enantioselective synthesis of a-amino acids is the focus of intensive current research due to their central role in organic synthesis.[1] a-Amino acids are commonly used as enantiopure substrates for auxiliaries, ligands, catalysts and chiral building blocks in total synthesis.[2] A further important field is in the synthesis of non-natural proteins and peptides.[3] Furthermore, arylglycines are characteristic structural motifs in biologically active compounds like glycopeptide antibiotics [4] and b-lactam antibiotics.[5] Glyoxylate imines are highly electrophilic substrates for the synthesis of non-proteinogenic amino acids and have been used in ene reactions, [6] cycloadditions, [7] radical additions, [8] nucleophilic additions [9] and FriedelCrafts-type reactions.[10]The Friedel-Crafts reaction, discovered in 1877, is an important methodology to form carbon-carbon bonds.[11] In particular, the alkylation of arenes by unsaturated compounds constitutes an atom-economic reaction with a broad range of applications. To date many protocols have been developed offering powerful methods to synthesize various enantiopure aromatic compounds, employing both metal-based catalysts and organocatalysts. [12] Although significant progress has been made in the field of enantioselective organocatalytic Friedel-Crafts-type alkylations there remain limitations in the substrate scope. In most cases heteroaromatic compounds have been used due to their higher reactivity. For example, several additions of indoles to aromatic imines promoted by chiral phosphoric acids [13] as well as thiourea-Cinchona alkaloids [14] have been described. Other examples of Friedel-Crafts alkylations of heteroaromatic compounds include the chiral phosphoric acid-catalyzed addition of furans [15] and pyrroles [16] to electronpoor aromatic aldimines. However, there are relatively few protocols for the enantioselective organocatalytic Friedel-Crafts-type alkylations of simple benzene derivatives. Phenols can be added to trifluoropyruvate [17] and b,g-unsaturated a-keto esters [18] while naphthols are known to undergo an alkylation-cascade reaction with nitroolefins [19] and alkylation/cyclization reactions with a,b-unsaturated aldehydes.[20] A protocol for the enantioselective organocatalytic addition of heteroaromatic compounds to an a-imino ester was developed recently by You and co-workers.[10l] Several indoles can be added to a glyoxylatederived PMP-protected i...

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“…[3,4] Our group has also demonstrated a highly enantioselective 1,2-aza-F-C reaction of N-protected imines with 2-methoxyfuran using the BINOL-derived monophosphoric acid 1a [4a] as the chiral Brønsted acid catalyst. [4][5][6][7] Further applications of the chiral monophosphoric acid-catalyzed 1,2-aza-F-C reaction are desirable as it has the potential for high catalytic efficiency and enantioselectivity and should provide a diverse array of optically active arylmethaneamine derivatives. In particular, the 1,2-aza-F-C reaction of indoles is an attractive transformation towards enantioenriched 3-indolylmethaneamine derivatives.…”

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confidence: 99%

Chiral Phosphoric Acid‐Catalyzed Enantioselective Aza‐Friedel–Crafts Reaction of Indoles

et al. 2007

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A highly enantioselective 1,2-aza-FriedelCrafts reaction of N-tert-butyldimethylsilylindole with N-tert-butoxycarbonyl aromatic imines is demonstrated using a BINOL-derived monophosphoric acid catalyst. The present approach provides efficient access to 3-indolylmethaneamines with aryl substituents in excellent enantioselectivities (up to 98 % ee). An inversion in the sense of enantioselection was found between monophosphoric acid catalysts bearing different substituents introduced at the 3,3'-position of binaphthyl backbone. We also calculated the three-dimensional structure of the monophosphoric acid catalysts to speculate on the inversion of the stereochemical outcome.

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Organocatalytic Asymmetric Aza-Friedel−Crafts Alkylation of Furan

Cited by 353 publications

References 25 publications

The Direct, Enantioselective, One‐Pot, Three‐Component, Cross‐Mannich Reaction of Aldehydes: The Reason for the Higher Reactivity of Aldimine versus Aldehyde in Proline‐Mediated Mannich and Aldol Reactions

The Direct, Enantioselective, One‐Pot, Three‐Component, Cross‐Mannich Reaction of Aldehydes: The Reason for the Higher Reactivity of Aldimine versus Aldehyde in Proline‐Mediated Mannich and Aldol Reactions

Enantioselective Organocatalytic Synthesis of Arylglycines via Friedel–Crafts Alkylation of Arenes with a Glyoxylate Imine

Chiral Phosphoric Acid‐Catalyzed Enantioselective Aza‐Friedel–Crafts Reaction of Indoles

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