Synthesis of 4-Deoxy Pyranosides via Catalyst-Controlled Site-Selective Toluoylation of Abundant Sugars

Yanagi, Masanori; Ueda, Y.; Ninomiya, Ryo; Imayoshi, Ayumi; Furuta, Takumi; Mishiro, Kenji; Kawabata, Takeo

doi:10.1021/acs.orglett.9b01549

Cited by 18 publications

(12 citation statements)

References 41 publications

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“…Additionally, the aforementioned model molecule 2,2′,6,6′-tetrastyryl-4,4′-bipyridine could be efficiently obtained by the reaction of TMBP and benzaldehyde in a mixture of benzoic chloride as an acylation reagent and sodium benzoate as a conjugated base, indicative of the acylationactivated Knoevenagel condensation. Notably, similar to those previous reports, such an intermediate benzoyl pyridinium is quite unstable, 23,24 which is readily recovered to pyridine even in the presence of trace water.…”

Section: ■ Results and Discussionsupporting

confidence: 89%

“…We note that N-acylpyridinium species have been found as highly active intermediates formed in the process of pyridine-catalyzed hydrolysis of acid anhydride or as one type of efficient acylation reagent prepared from pyridine and the acyl donor. 23,24 Therefore, the acylation of methylpyridine derivatives might be able to activate the α-C−H bond. With these reasons in mind, we decided to explore a much lowercost, less toxic, and concise method to construct vinylenelinked COFs based on a methyl-substituted pyridine-based monomer, and we attempted to establish the optimized reaction conditions and understand the corresponding thermodynamically controlled mechanism.…”

Section: ■ Introductionmentioning

confidence: 99%

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Synthesis of Vinylene-Linked Covalent Organic Frameworks by Monomer Self-Catalyzed Activation of Knoevenagel Condensation

Meng

et al. 2022

J. Am. Chem. Soc.

111

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Reticular chemistry based on thermodynamically controlled linking modes and numerous organic building blocks has constituted versatile crystalline frameworks in molecular-level precision. However, vinylene-linked covalent organic frameworks (COFs) are still quite far from flexible tailoring in either their structures or topologies, due to the lack of monomers with sufficient activities. Herein, we establish a strategy to synthesize vinylene-linked COFs via Knoevenagel condensation between a tetratopic monomer 2,2′,6,6′-tetramethyl-4,4′-bipyridine (TMBP) and linear aromatic dialdehydes in a mixed solvent of benzoic anhydride and benzoic acid. Mechanistic investigation suggests that the condensation was promoted by a pyridine self-catalyzed benzoylation upon the cleavage of benzoic anhydride solvent molecules. The layered structures of the resultant COFs are highly crystallized into orthorhombic lattices with vertically aligned AA stacking modes, delivering high surface areas up to 1560 m 2 g −1 . The π-extended conjugated skeletons comprising para-bipyridyl units and vinylene linkages endow these COFs with substantial semiconducting properties, releasing visible-light-stimulated catalytic activity in water-splitting hydrogen evolution with a rate as high as 3230 μmol g −1 h −1 .

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Section: ■ Results and Discussionsupporting

confidence: 89%

Section: ■ Introductionmentioning

confidence: 99%

Synthesis of Vinylene-Linked Covalent Organic Frameworks by Monomer Self-Catalyzed Activation of Knoevenagel Condensation

Meng

et al. 2022

J. Am. Chem. Soc.

111

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“…Inspired by pioneering examples of site-selective deoxygenation of sugar derivatives, [85][86][87][88][89] the improved method was effectively applied to the rapid synthesis of 4-deoxy sugars. 90) Using the acid anhydride method, introducing a p-toluoyl group onto the C(4)-OH group of a glucoside using base (collidine) as cosolvent took 48 h (Fig.…”

Section: Improvement Of Catalytic Performance and Application To Rapid Synthesis Of 4-deoxy Sugarsmentioning

confidence: 99%

Site-Selective Molecular Transformation: Acylation of Hydroxy Groups and C–H Amination

Ueda

2021

Chem. Pharm. Bull.

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Control of site selectivity is an exciting direction for synthetic organic chemistry owing to the possibility of selective modification of multifunctionalized molecules, ultimately including biomacromolecules. In this review, our recent research related to site selectivity in two types of transformation, namely, the acylation of hydroxy groups and C-H amination, is summarized. Regarding the acylation of hydroxy groups, catalystcontrolled site selectivity enables unconventional retrosynthetic analysis, leading to efficient syntheses of sugar-related natural and unnatural products. Regarding C-H amination, the discovery of unprecedented reaction sites in intermolecular amination mediated by dirhodium nitrenes is described. The findings of this research demonstrate the power of site-selective transformation in the synthesis of a particular class of compounds.

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“…In order to achieve a siteselective deoxy product starting from a naturally abundant sugar, multistep protection/deprotection sequences and harsh reduction conditions are usually required (Arita et al, 1972;Rasmussen, 1980;Haque et al, 1986;Lin et al, 1989;Raju et al, 2009;Zou et al, 2012). A method has been developed toward direct synthesis of 4-deoxy pyranosides by two steps, site-selective toluoylation of 4-OH of free pyranosides and subsequent reductive deacyloxylation (Yanagi et al, 2019). However, the catalyst for the toluoylation is not readily available, and the yield for deacyloxylation is low (38-61%).…”

Section: Introductionmentioning

confidence: 99%

Improved Synthesis of Sulfur-Containing Glycosides by Suppressing Thioacetyl Migration

Luo

Zhang

et al. 2020

Front. Chem.

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Complex mixtures were often observed when we attempted to synthesize 4-thio-and 2,4-dithio-glycoside derivatives by double parallel and double serial inversion, thus leading to no or low yields of target products. The reason was later found to be that many unexpected side products were produced when a nucleophile substituted the leaving group on the substrate containing the thioacetate group. We hypothesized that thioacetyl migration is prone to occur due to the labile thioacetate group even under weak basic conditions caused by the nucleophile, leading to this result. Therefore, we managed to inhibit the generation of thiol groups from thioacetate groups by the addition of an appropriate amount of conjugate acid/anhydride, successfully improving the synthesis of 4-thio-and 2,4-dithio-glycoside derivatives. The target products which were previously difficult to synthesize, were herein obtained in relatively high yields. Finally, 4-deoxy-and 2,4-dideoxy-glycoside derivatives were efficiently synthesized through the removal of thioacetate groups under UV light, starting from 4-thio-and 2,4-dithio-glycoside derivatives.

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Synthesis of 4-Deoxy Pyranosides via Catalyst-Controlled Site-Selective Toluoylation of Abundant Sugars

Abstract: A two-step procedure was developed for the synthesis of 4-deoxy pyranosides from the parent pyranosides with four hydroxy groups via organocatalytic site-selective acylation and reductive deacyloxylation.

Cited by 18 publications

References 41 publications

Synthesis of Vinylene-Linked Covalent Organic Frameworks by Monomer Self-Catalyzed Activation of Knoevenagel Condensation

Synthesis of Vinylene-Linked Covalent Organic Frameworks by Monomer Self-Catalyzed Activation of Knoevenagel Condensation

Site-Selective Molecular Transformation: Acylation of Hydroxy Groups and C–H Amination

Improved Synthesis of Sulfur-Containing Glycosides by Suppressing Thioacetyl Migration

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