Bis‐Terminal Hydroxy Polyethers as All‐Purpose, Multifunctional Organic Promoters: A Mechanistic Investigation and Applications

Lee, Jiwoong; Yan, Hailong; Jang, Hyeong Bin; Kim, Hong Ki; Park, Sung Woo; Lee, Sungyul; Yoon, Dae; Song, Choong Eui

doi:10.1002/anie.200903903

Cited by 104 publications

(92 citation statements)

References 30 publications

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“…[38] They designed crown ether mimics—oligoethylene glycols—such as tetraethylene glycol, which forms an 18-crown-6-like cycle with an opening for the entrance of the metal cation (e.g. K + ), while the two hydroxyl groups on the end of the glycol chain either regulate the nucleophilicity of fluoride or facilitate the leaving group ability (Figure 6).…”

Section: Hydrogen Bonding Controlled Nucleophilic Fluorination By Alkmentioning

confidence: 99%

Hydrogen Bonding: Regulator for Nucleophilic Fluorination

Liang

Hammond

2017

Chemistry A European J

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The recent advances in nucleophilic fluorination, regulated through hydrogen bonding interactions are summarized. Two main categories of fluorine nucleophiles are discussed. Alkali-metal fluorides are widely used in various fluorination transformations because they are inexpensive and safe nucleophilic fluorine sources. But the non-controllable nucleophilicity and strong basicity of some of them cause undesired side reactions, which led to the introduction of hydrogen bonding to fine tune their nucleophilicity and basicity. In contrast, an HF-based fluorine nucleophile, HF/DMPU, is in some aspects superior to the conventional HF/pyridine (Olah's reagent) or HF/Et N because of the higher hydrogen bond basicity of DMPU. It has been used in several nucleophilic fluorinations such as fluorination of alkynes, fluoro-Prins reaction and fluorination of aziridines.

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Section: Hydrogen Bonding Controlled Nucleophilic Fluorination By Alkmentioning

confidence: 99%

Hydrogen Bonding: Regulator for Nucleophilic Fluorination

Liang

Hammond

2017

Chemistry A European J

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“…[23] Unlike the previousreports on desilylative kinetic resolution reaction from the same group, this report describes silylative ki-netic resolution of unprotecteda lcohol substrates with HMDS (hexamethyldisilazane)a sasilylating reagent. [10,12] This provides more practical reactionc onditions for the synthesis of enantioenriched secondary alcohols, because the preparation of the silyl-protected starting alcohol is circumvented. The use of silicon protecting groups enabled homogeneous catalysis, which can dramatically improvet he reaction rate and overall efficiency.…”

Section: Cation-binding Catalysis With Silicon Reagents: Ppm-level Lomentioning

confidence: 99%

Asymmetric Cation‐Binding Catalysis

Oliveira

Lee

2017

ChemCatChem

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The employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts’ solubility in conventional organic solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation‐binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL‐based polyethers. Alkali metal salts, namely KF and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation‐binding catalysis was recently expanded to silicon‐based reagents, enabling highly enantioselective silylation reactions in polyether‐generated chiral environments, and leading to a record‐high turnover in asymmetric organocatalysis. This can lead to further applications by the asymmetric use of other inorganic salts in various organic transformations.

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“…[1] Electrochemical fluorination has generally been carried out in organic solvents containing HF salts such as Et 3 N·nHF and Et 4 NF·nHF as both a supporting electrolyte and fluorine source. [1] Electrochemical fluorination has generally been carried out in organic solvents containing HF salts such as Et 3 N·nHF and Et 4 NF·nHF as both a supporting electrolyte and fluorine source.…”

mentioning

confidence: 99%

“…[4] To improve the nucleophilicity of fluoride ions on anodic fluorination, poly(ethylene glycol) [M n % 200; PEG 200] having the ability to coordinate a cation was introduced as an additive into the reaction system in Et 4 NF·nHF. [3,5] Hence, the electrochemical method is of great significance. Its stability for anodic oxidation was also promising.…”

mentioning

confidence: 99%