General, Highly Selective Synthesis of 1,3‐ and 1,4‐Difunctionalized Building Blocks by Regiodivergent Epoxide Opening

Funken, Nico; Mühlhaus, Felix; Gansäuer, Andreas

doi:10.1002/anie.201606064

Cited by 55 publications

(24 citation statements)

References 83 publications

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“…[6] Ther egioselectivity of epoxide opening leading to indoline formation is generally high (87:13-96:4, Table 3) and is only slightly influenced by the N-substituent (R 2 = aryl, alkyl). [6] Ther egioselectivity of epoxide opening leading to indoline formation is generally high (87:13-96:4, Table 3) and is only slightly influenced by the N-substituent (R 2 = aryl, alkyl).…”

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“…Ther egiodivergent epoxide opening is efficient with R 1 being ap rimary alkyl substituent. [6] Ther egioselectivity of epoxide opening leading to indoline formation is generally high (87:13-96:4, Table 3) and is only slightly influenced by the N-substituent (R 2 = aryl, alkyl). Thereactions of 1c to 2c and 3c display an interesting aspect of the regiodivergent epoxide opening.…”

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“…[5] Owing to their mild conditions and high chemoselectivity,ET-promoted regiodivergent ring openings to radical intermediates are at least as advantageous as classical processes proceeding via an S N 2m echanism. [6] Second, the radical intermediate generated through regiodivergent epoxide opening needs to add to the arene with high diastereoselectivity for the reaction to be useful. [7] R-2' ' may be considered ar adical s-complex after the radical addition of R-2 to the arene (Scheme 2).…”

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Merging Regiodivergent Catalysis with Atom‐Economical Radical Arylation

et al. 2019

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At itanocene-catalyzed regiodivergent radical arylation is described that allows access to either enantiomerically pure tetrahydroquinolines or indolines from ac ommon starting material. The regioselectivity of epoxideo pening that results in the high selectivity of heterocycle formation is controlled by two factors,t he absolute configuration of the enantiopure ligands of the (C 5 H 4 R) 2 TiX 2 catalyst and the inorganic ligand X( X = Cl, OTs). The overall reaction is atom-economical and constitutes ar adical Friedel-Crafts alkylation.The design of catalytic methods to efficiently and highly chemo-and stereoselectively access small molecules with potential biological activity is atopic central to chemistry.T o be attractive for potential applications,such processes have to meet the key requirements of sustainable chemistry.Essential points are that the reaction is atom-economical and, thus, proceeds without the generation of waste,t he use of readily available substrates,and mild reaction conditions.The choice of the catalyst is equally important. Theuse of earth-abundant 3d transition metals [1] that shuttle between neighboring oxidation states is particularly appealing. [2] Herein, we show the validity of these points in at itanocene-catalyzed [3] regiodivergent radical arylation that allows access to enantiomerically pure tetrahydroquinolines or indolines from ac ommon starting material through choice of the appropriate titanocene catalyst. In regiodivergent reactions,o ne constitutional isomer of ap roduct is formed from an enantiomerically pure substrate by the action of one enantiomer of acatalyst and the other isomer by the action of the other enantiomer of the catalyst. In our case,t wo points are critical:F irst, the highly regioselective generation of either R-2 or R-3 from 1 by an electron transfer (ET) from titanium to the epoxide needs to be controlled by the absolute configuration of the titanocene catalyst (Scheme 1).

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Merging Regiodivergent Catalysis with Atom‐Economical Radical Arylation

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“…[11] Catalyst loading can be reduced to 5mol %w ithout significant reduction in the yield of 2.Coll·HCl and Coll·HBr are both suitable acids for mediating catalytic turnover. [12] Scheme 1. Proposed catalytic cycle for the trapping of radicals derived from N-acyl aziridines ([Ti IV ] = (C 5 Me 5 ) 2 TiX, X = Cl or Br).…”

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“…Thefunctional-group tolerance of the reaction is high (entries [11][12][13][14]. Thefunctional-group tolerance of the reaction is high (entries [11][12][13][14].…”

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Titanocene‐Catalyzed Radical Opening of N‐Acylated Aziridines

Zhang

Vogelsang

et al. 2017

Angewandte Chemie

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Ring‐Opening Reactions of Epoxides With Titanium(III) Reagents

RajanBabu¹,

Nugent²,

Halder³

2022

Organic Reactions

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The ring‐opening reactions of epoxides with titanium(III) reagents such as Cp 2 TiCl are critically reviewed, including the scope, limitations, and mechanism of these synthetically useful transformations. The initial reaction proceeds by single‐electron transfer to give a carbon‐centered β‐titanoxy radical. The resulting radical can be terminated by a number of different reaction pathways, including epoxide deoxygenation, reduction to the alcohol, intermolecular addition to activated olefins, and intramolecular addition (cyclization). The literature is surveyed from the first reported examples in 1988 through October, 2021.

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General, Highly Selective Synthesis of 1,3‐ and 1,4‐Difunctionalized Building Blocks by Regiodivergent Epoxide Opening

Cited by 55 publications

References 83 publications

Merging Regiodivergent Catalysis with Atom‐Economical Radical Arylation

Merging Regiodivergent Catalysis with Atom‐Economical Radical Arylation

Titanocene‐Catalyzed Radical Opening of N‐Acylated Aziridines

Ring‐Opening Reactions of Epoxides With Titanium(III) Reagents

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