Organocatalytic Enantioselective Friedel–Crafts Alkylation of Sesamol with Nitro Olefins

Zhang, Hui; Liao, Yu‐Hua; Yuan, Wei‐Cheng; Zhang, Xiaomei

doi:10.1002/ejoc.201000271

Cited by 51 publications

(15 citation statements)

References 43 publications

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“…Following this early study, most catalytic reactions of phenols were designed to prepare pyrans18b, c and chromanes18d through C‐alkylation/O‐cyclization cascade processes. Thus, to broaden the utility of this process in the preparation of chiral phenols, alternative approaches have been explored to repress the inherent cascade pathway 18e…”

Section: Methodsmentioning

confidence: 99%

“…To evaluate the catalytic activities of newly designed C 3 ‐tethered guanidine/bisthiourea catalysts,20 initial studies were conducted using sesamol ( 3 a ) and nitroalkene 4 a (1.0 equiv) as substrates 18e. As the results displayed in Table 1 show, 2 effectively promotes nucleophilic addition at the C6 position of 3 a to selectively afford the corresponding FC product 5 aa .…”

Section: Methodsmentioning

confidence: 99%

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Entropy‐Controlled Catalytic Asymmetric 1,4‐Type Friedel–Crafts Reaction of Phenols Using Conformationally Flexible Guanidine/Bisthiourea Organocatalyst

et al. 2010

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One of the most important aspects of protein function is the motion that occurs in response to substrate binding. [1] In the dynamics of enzyme catalysis, multiple weak hydrogenbonding interactions [2] in the polypeptide that are controlled by interrelated enthalpy and entropy changes play a significant role in governing the conformational changes that take place. [3] In contrast, the development of asymmetric organocatalysts has rarely focused on hydrogen-bond donors [4][5][6][7][8] that have conformationally flexible scaffolds [9][10][11] as a likely consequence of difficulties in controlling the conformation of acyclic skeletons.[12] However, recently our research group has successfully demonstrated the utility of conformationally flexible guanidine/bisthiourea organocatalysts 1 for organocatalytic carbon-carbon bond-forming reactions.[9] Herein, we describe studies that have led to the development of new acyclic C 3 -linked guanidine/bisthiourea organocatalysts 2. Analysis of these processes shows that the catalytic effect resides in a trade off between enthalpies and entropies of activation and reveals the existence of dramatic concentration effects. This investigation has uncovered a unique catalytic stereodiscrimination process controlled only by differences in the activation entropies.The primary aim of this study was to extend our newly developed organocatalytic system to asymmetric 1,4-additions reactions of nitroolefins.[13] A plausible interaction mode for the catalytic reactions of nitroolefins with nucleophilic anions is shown in Scheme 1. In the reactive complex involving an acyclic guanidine/bisthiourea organocatalyst, the thiourea moiety can interact with the nitro group in the acceptor and ionic interactions with the guanidinium cation can orient a nucleophilic anion. [14] We envisaged that a long chiral spacer between the two centers in the catalyst would be required for the promotion of the 1,4-addition reactions that take advantage of these synergistic proximity effects.In the current study, we initially selected catalytic asymmetric Friedel-Crafts (FC) reactions [15,16] of phenol derivatives. [17][18][19] Although a variety of electron-rich aromatic compounds such as indoles, pyrroles, and furans have been successfully utilized as nucleophiles in 1,4-addition processes, [15,16] asymmetric reactions of phenol derivatives have been rarely studied. The difficulty in employing phenol derivatives in these processes could be a result of two intrinsic factors that are related to the fact that phenoxide anions generated in situ 1) often promote ligand exchange with metal catalysts, [17] and 2) can participate in reactions that take place with low levels of chemo-and regioselectivity. In 2007, Chen and co-workers developed the first 1,4-type of FC reaction of naphthols with nitroolefins that utilize cinchona-based thiourea catalysts. These processes give ortho-selective FC products with 85-95 % ee.[18a] However, the undesired dimeric furans that are formed in these reactions cannot be easily separat...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Entropy‐Controlled Catalytic Asymmetric 1,4‐Type Friedel–Crafts Reaction of Phenols Using Conformationally Flexible Guanidine/Bisthiourea Organocatalyst

et al. 2010

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“…Soon after, Chimni presented the same reaction catalyzed by a cinchonidine-derived thiourea (27), obtaining the corresponding 3-aryl-3-hydroxyindoles with modest enantiomeric excesses (Scheme 6). 9…”

Section: Scheme 5 Reactions Of 1-naphthols With Isatins Catalyzed By mentioning

confidence: 99%

Catalytic Enantioselective Friedel–Crafts Reactions of Naphthols and Electron-Rich Phenols

et al. 2016

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The enantioselective Friedel-Crafts reaction is a powerful tool for the construction of benzylic stereocenters in a stereodefined manner. Significant advances have already been achieved with heteroarenes such as indoles and pyrroles; however, the reaction with homoarenes is less developed. This short review covers the most relevant literature on enantioselective Friedel-Crafts reactions with naphthols and phenols. 1 Introduction 2 Friedel-Crafts Reactions Involving 1,2-Nucleophilic Addition to C=X Bonds 3 Friedel-Crafts Reactions Involving Conjugate Nucleophilic Addition to Electrophilic C=C Bonds 4 Friedel-Crafts Reactions Involving π-Allylic Complexes as Electrophiles 5 ipso-Friedel-Crafts Reactions 6 Conclusions

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“…reported the catalytic asymmetric Friedel–Crafts alkylation of sesamol with nitroolefins using a bifunctional acyclic guanidine/bisthiourea organocatalyst with good results. Other organocatalysts were also used for the reaction of active phenol 3b,c,d. Luo3c et al.…”

Section: Optimization Of the Reaction Conditions[a]mentioning

confidence: 99%

Catalytic Asymmetric Friedel–Crafts Reaction of Activated Phenols and 4‐Oxo‐4‐arylbutenoates

Bai¹,

Liu²,

Wang³

et al. 2012

Adv Synth Catal

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A highly enantioselective Friedel-Crafts reaction of activated phenols with (E)-4-oxo-4-arylbutenoates has been developed with the N,N'-dioxide-scandiumA C H T U N G T R E N N U N G (III) complex as the catalyst. A variety of (E)-4-oxo-4-arylbutenoates were found to be suitable substrates for the reaction. The desired products were obtained in moderate to high yields (up to 98%) and excellent enantioselectivities (up to 97% ee). Scheme 2. The transformation of the product 3a. Scheme 1. The asymmetric Friedel-Crafts reaction of 1x with phenol 2a.Figure 2. Proposed catalytic model and the X-ray structure of the product 3s.

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Organocatalytic Enantioselective Friedel–Crafts Alkylation of Sesamol with Nitro Olefins

Cited by 51 publications

References 43 publications

Entropy‐Controlled Catalytic Asymmetric 1,4‐Type Friedel–Crafts Reaction of Phenols Using Conformationally Flexible Guanidine/Bisthiourea Organocatalyst

Entropy‐Controlled Catalytic Asymmetric 1,4‐Type Friedel–Crafts Reaction of Phenols Using Conformationally Flexible Guanidine/Bisthiourea Organocatalyst

Catalytic Enantioselective Friedel–Crafts Reactions of Naphthols and Electron-Rich Phenols

Catalytic Asymmetric Friedel–Crafts Reaction of Activated Phenols and 4‐Oxo‐4‐arylbutenoates

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