Enantioselective Free Radical Carbon-Carbon Bond Forming Reactions: Chiral Lewis Acid Promoted Acyclic Additions

Wu, Jason H.; Radinov, Roumen; Porter, Ned A.

doi:10.1021/ja00149a035

Cited by 154 publications

(54 citation statements)

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“…In the following example, a chiral bisoxazoline (BOX) ligand is successfully employed together with zinc triflate as a Lewis acid to achieve an enantiomeric excess as high as 90% (Scheme 6.21) [37]. The following example shown in Scheme 6.22 is remarkable, since both b-and a-stereogenic centers are created with a high degree of enantio-and diastereoselective control [38,39].…”

Section: Multicomponent Coupling Reactions Mediated By Group 14 Radicalsmentioning

confidence: 99%

Free‐Radical‐Mediated Multicomponent Coupling Reactions

Tojino

Ryu

2005

Multicomponent Reactions

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Section: Multicomponent Coupling Reactions Mediated By Group 14 Radicalsmentioning

confidence: 99%

Free‐Radical‐Mediated Multicomponent Coupling Reactions

Tojino

Ryu

2005

Multicomponent Reactions

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“…[1][2][3] Two interesting families of compounds, which have been used for more than 20 years, are oxazolidinones 1 and imidazolidinones 2. [4][5][6][7][8][9][10][11][12] Oxazolidinones or imidazolidinones can be used as chiral auxiliaries in ionic, [10,13,14] radical [15][16][17][18][19] or even in dynamic kinetic resolution (DKR) reactions. [20][21][22][23][24][25][26][27] The majority of these reactions undergo acid catalysis and Evans and coworkers have proposed a mechanism to account for the reaction, as shown in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Study of the Stereoselectivities of the Diels–Alder Addition of Cyclopentadiene to Ethyl‐(S)‐lactyl Acrylate Catalyzed by Aluminium Chloride

Bakalova

Santos

2006

Eur J Org Chem

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We have studied the AlCl 3 -catalyzed cycloaddition of ethyl-(S)-lactyl acrylate (ELA) and cyclopentadiene (CPD) by MP2 and DFT (B3LYP) methods using the 6-31G(d,p) basis set, with or without solvent effects. Four types of dienophileLewis acid (LA) complexes were considered − two types of ELA·AlCl 3 , ELA·2AlCl 3 and ELA·AlCl 2 + . The stereochemical predictions of these models were compared with available experimental data. The participation of lactate-bound ELA·AlCl 3 complexes is insignificant because of their relatively high TS energies. The diastereofacial selectivities exhibited by the chelated ELA·AlCl 2 + complex do not agree

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“…The basis for an explanation of the reaction mechanism is the work of Evans et al about twenty years ago. [11-14, 17, 18] After this, many results were published, both on ionic [16,[20][21][22][23] and radical reactions [24][25][26][27][28][29] (Scheme 2) and even on dynamic kinetic resolutions (DKR) (Scheme 3). [30][31][32][33][34][35][36][37][38][39][40] In spite of the diastereoisomeric excess (de) in different types of reactions being usually higher than 80 up to 95 %, an unexpected stereochemistry is obtained considering the steric hindrance due to the ring substituent (Scheme 2).…”

Section: Introductionmentioning

confidence: 99%

New Chiral Auxiliaries for Dynamic Kinetic Resolution: From Theory to Experiment

Santos¹,

Pereira²,

Afonso³

et al. 2004

Chemistry A European J

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New efficient chiral auxiliaries for dynamic kinetic resolution (DKR) of bromides into amines are proposed, based on a theoretical rationalisation of known literature results. One example was synthesized and tested, affording diastereoselectivities up to 100%. Several results of DKR reactions are known, based on oxazolidinone or imidazolidinone units as chiral auxiliaries. Nevertheless, their behaviour was not fully understood until a recent paper that we published. We now used our proposed mechanism to rationalize the behaviour of other similar chiral auxiliaries and to propose small structure changes in imidazolidinone rings which could largely improve their performance. We could show that the good performance of these molecules as chiral auxiliaries for DKR reactions where bromine is the leaving group and a primary or secondary amine is the nucleophile is due, in a first step, to the formation of a hydrogen bond between the amine and the ring carbonyl oxygen and, in a second step, to the strong electrostatic interaction between the leaving bromide and the carbonyl oxygen in the C-3 substituent. Considering the behaviour of this substituent which rotates to minimize the electrostatic repulsion with the bromide when reaching the transition state, we proposed the introduction of a second substituent in the C-4 position of the imidazolidinone ring, which prevents such rotation, thus increasing the energy difference between the transition states of the two distereoisomers. With such an auxiliary we were able to increase the best de known in literature (88%), when benzylamine is used as nucleophile, to 99, or even 100%, when iodide replaces the bromide in the substrate.

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Enantioselective Free Radical Carbon-Carbon Bond Forming Reactions: Chiral Lewis Acid Promoted Acyclic Additions

Cited by 154 publications

References 0 publications

Free‐Radical‐Mediated Multicomponent Coupling Reactions

Free‐Radical‐Mediated Multicomponent Coupling Reactions

A Theoretical Study of the Stereoselectivities of the Diels–Alder Addition of Cyclopentadiene to Ethyl‐(S)‐lactyl Acrylate Catalyzed by Aluminium Chloride

New Chiral Auxiliaries for Dynamic Kinetic Resolution: From Theory to Experiment

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