1,3-Stereoinduktion bei Radikalreaktionen

Enantioselective proton-transfer reactions (enolate protonations) have been investigated in detail for over a decade and even catalytic variants have been demonstrated. [1] In contrast, enantioselective hydrogen atom transfer reactions have begun to emerge only recently. [2] In principle, these reactions can be carried out in two distinct ways: 1) by H-atom transfer from a chiral reagent to a radical, or alternatively 2) by H-atom transfer from an achiral reagent to a radical complexed to a chiral source. Nanni and Curran, [3a] Metzger and co-workers, [3b,c] Roberts and co-workers, [3d] and Schiesser and co-workers [3e] have reported examples of reactions using chiral H-atom transfer reagents. On the other hand, only a few examples of H-atom transfer to radicals complexed to chiral Lewis acids have been noted in the literature. [4] We have shown that enantioselective conjugate additions proceed with high chemical efficiency and selectivity using a chiral Lewis acid derived from M 2 metal salts in conjunction with a bisoxazoline prepared from aminoindanol. [5] Herein we show that conjugate radical addition to N-acylamido acrylates 1 mediated by a chiral Lewis acid followed by an enantioselective H-atom transfer furnishes a variety of a-amino acid derivatives (2 or 3) with good to excellent efficiency [Eq. (1)].Diastereoselective H-atom transfer reactions to captodative radicals derived from N-acylamido acrylates in both acyclic [6] and cyclic [7] systems proceed with moderate to good selectivity. [8] In contrast, enantioselective variants of these reactions have not been reported and this work constitutes the first example of such a process. We began our experiments [1] For some recent reviews on the Heck reaction, see a) I. P. Beletskaya, [5] For recent references on the synthesis of trisubstituted olefins by the Heck reaction of b-substituted a,b-unsaturated esters, nitriles, aldehydes, or ketones, see a) C. Gürtler, S. L. Buchwald, Chem. Eur.

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Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Sibi

Asano

Sausker

2001

Angew. Chem.

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Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Sibi

Asano

Sausker

2001

Angew. Chem. Int. Ed.

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Enantioselective H‐Atom Transfer Reactions: A New Methodology for the Synthesis of β²‐Amino Acids

Sibi

Patil

2004

Angewandte Chemie

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1,3-Stereoinduktion bei Radikalreaktionen

Cited by 6 publications

References 18 publications

Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Enantioselective H‐Atom Transfer Reactions: A New Methodology for the Synthesis of β²‐Amino Acids

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1,3-Stereoinduktion bei Radikalreaktionen

Cited by 6 publications

References 18 publications

Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Enantioselective Hydrogen Atom Transfer Reactions: Synthesis ofN-Acyl-α-Amino Acid Esters

Enantioselective H‐Atom Transfer Reactions: A New Methodology for the Synthesis of β2‐Amino Acids

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Enantioselective H‐Atom Transfer Reactions: A New Methodology for the Synthesis of β²‐Amino Acids