Pd-complex-bound Amino Acid-based Supramolecular Gel Catalyst for Intramolecular Addition–Cyclization of Alkynoic Acids in Water

Ogata, Kazuhiro; Sasano, Daisuke; Yokoi, Tomoya; Isozaki, Katsuhiro; Seike, Hirofumi; Takaya, Hikaru; Nakamura, Masaharu

doi:10.1246/cl.2012.498

Cited by 31 publications

(9 citation statements)

References 47 publications

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“…Significant changes in and enhancement of the original properties, functions, and performance can be induced by cooperative interactions of arrayed functionalities in well‐ordered nanosized hierarchical architectures. In practice, arrayed functional groups fabricated from functionalized amino acids and peptides bearing conjugated with photoactive,54 electronically active,55 and catalytically active37b, 56 auxiliaries have been reported as examples of such advanced supramolecular functional materials that show enhanced performance or emergent properties not accessible by unimolecular systems. Metalated amino acids and peptides that conjugate with functional organometallics have potent abilities as such supramolecular materials; however, little research on such peptides has been reported as yet.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Self‐Assembly of NCN‐Pincer Pd‐Complex‐Bound Norvalines

Ogata¹,

Sasano²,

Yokoi³

et al. 2013

Chemistry A European J

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The NCN-pincer Pd-complex-bound norvalines Boc-D/L-[PdCl(dpb)]Nva-OMe (1) were synthesized in multigram quantities. The molecular structure and absolute configuration of 1 were unequivocally determined by single-crystal X-ray structure analysis. The robustness of 1 under acidic/basic conditions provides a wide range of N-/C-terminus convertibility based on the related synthetic transformations. Installation of a variety of functional groups into the N-/C-terminus of 1 was readily carried out through N-Boc- or C-methyl ester deprotection and subsequent condensations with carboxylic acids, R(1)COOH, or amines, R(2)NH2 , to give the corresponding N-/C-functionalized norvalines R(1)-D/L-[PdCl(dpb)]Nva-R(2) 2-9. The dipeptide bearing two Pd units 10 was successfully synthesized through the condensation of C-free 1 with N-free 1. The robustness of these Pd-bound norvalines was adequately demonstrated by the preservation of the optical purity and Pd unit during the synthetic transformations. The lipophilic Pd-bound norvalines L-2, Boc-L-[PdCl(dpb)]Nva-NH-n-C11H23, and L-4, n-C4H9CO-L-[PdCl(dpb)]Nva-NH-n-C11H23, self-assembled in aromatic solvents to afford supramolecular gels. The assembled structures in a thermodynamically stable single crystal of L-2 and kinetically stable supramolecular aggregates of L-2 were precisely elucidated by cryo-TEM, WAX, SAXS, UV/Vis, IR analyses, and single-crystal X-ray crystallography. An antiparallel β-sheet-type aggregate consisting of an infinite one-dimensional hydrogen-bonding network of amide groups and π-stacking of PdCl(dpb) moieties was observed in the supramolecular gel fiber of L-2, even though discrete dimers are assembled through hydrogen bonding in the thermodynamically stable single crystal of L-2. The disparate DSC profiles of the single crystal and xerogel of L-2 indicate different thermodynamics of the molecular assembly process.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Self‐Assembly of NCN‐Pincer Pd‐Complex‐Bound Norvalines

Ogata¹,

Sasano²,

Yokoi³

et al. 2013

Chemistry A European J

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“…Although in a limited number of examples (only six substrates were explored), the group of Nakamura also demonstrated the capacity of the NCN-pincer Pd(II) derivative 7 ( Figure 1) to promote the high-yield formation of five-membered ring lactones from both γ-and β-alkynoic acids (5-exo-dig and 5-endo-dig cyclization, respetively) in pure water [33]. Complex 7 easily generates hydrogen-bonding-based supramolecular gels, with well-organized Pd-arrays, in organic solvents.…”

Section: Cycloisomerization Of Preformed or In Situ Generated Alkynoimentioning

confidence: 99%

Metal-Catalyzed Intra- and Intermolecular Addition of Carboxylic Acids to Alkynes in Aqueous Media: A Review

Francos

Cadierno

2017

Catalysts

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Abstract:The metal-catalyzed addition of carboxylic acids to alkynes is a very effective tool for the synthesis of carboxylate-functionalized olefinic compounds in an atom-economical manner. Thus, a large variety of synthetically useful lactones and enol-esters can be accessed through the intra-or intermolecular versions of this process. In order to reduce the environmental impact of these reactions, considerable efforts have been devoted in recent years to the development of catalytic systems able to operate in aqueous media, which represent a real challenge taking into account the tendency of alkynes to undergo hydration in the presence of transition metals. Despite this, different Pd, Pt, Au, Cu and Ru catalysts capable of promoting the intra-and intermolecular addition of carboxylic acids to alkynes in a selective manner in aqueous environments have appeared in the literature. In this review article, an overview of this chemistry is provided. The synthesis of β-oxo esters by catalytic addition of carboxylic acids to terminal propargylic alcohols in water is also discussed.

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“…Some supramolecular gel catalysts that catalyze the oxidation of alcohols, hydrolysis of esters, aldol reactions and intramolecular cycloaddition of alkynoic acids have recently been reported. 25,[36][37][38] These reports showed the potential applicability of supramolecular gels as catalysts, although they did not mention the differences between the reaction kinetics in the gel phase and in solution. The supramolecular gel of 1 with an excess amount of Pd (OAc) 2 contains free Pd(OAc) 2 in the supramolecular gel phase.…”

Section: Wacker Oxidation In Supramolecular Gelmentioning

confidence: 99%

Palladium ion-induced supramolecular gel formation of tris-urea molecules

Aoyama

Sako

Amakatsu

et al. 2014

Polym J

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A multicomponent supramolecular gel constructed from the self-assembly of pyridyl-substituted tris-urea 1 and Pd(OAc) 2 is reported. A mixture of 1 and Pd(OAc) 2 in dimethyl sulfoxide provided a supramolecular gel after brief ultrasound irradiation. The supramolecular gel changed into a sol/solution upon addition of chelating agents such as diamines and bidentate phosphine ligands. Dissociation of the coordination bonds between 1 and the palladium ion via addition of a chelating agent caused the phase transition. The Wacker oxidation of styrene was performed in the supramolecular gel. The reaction in the gel phase required a longer induction period to produce acetophenone than did the reaction in the homogeneous solution.INTRODUCTION Supramolecular gels have potential applications in a wide range of fields in materials science. 1,2 The development of supramolecular gels through the self-assembly of a small molecule, called a low-molecularweight gelator (LMWG), has attracted significant attention in recent decades. 3-6 LMWGs self-assemble by noncovalent interactions, such as hydrogen bonding, π-π interactions, dipole-dipole interactions and solvophobic interactions, to form three-dimensional networks that immobilize fluids. Intermolecular hydrogen bonds of ureide groups are the common driving force for the formation of supramolecular gels. 7 A variety of LMWGs with mono-urea, 8,9 bis-urea, 10-15 trisurea 16,17 and tetrakis-urea 18 structures have been reported. We have also developed C 3 -symmetric tris-urea LMWGs. [19][20][21][22] Supramolecular gels are generally constructed from a single component of LMWGs; however, some are formed from multiple types of small molecules. 23 A metal-ligand coordination bond is a common aspect of the multicomponent supramolecular gels; the advantage in this case is that gel formation can be easily controlled by controlling the formation and dissociation of the metal-ligand coordination bond. Moreover, the metal center of the resulting gel can potentially function as a catalyst for organic reactions. [24][25][26][27][28][29] We have previously reported multicomponent supramolecular gels of trisurea, in which the gelation ability of phenyl-substituted tris-urea was increased by the addition of a small amount of pyridyl-substituted trisurea and metal ion or bis-carboxylic acid. 30 In this paper, we report supramolecular gel formation from pyridyl-substituted tris-urea in the presence of palladium ions in dimethyl sulfoxide (DMSO). The supramolecular gel underwent a gel to sol/solution phase transition upon the addition of chelating agents for palladium ions. The palladium-catalyzed Wacker oxidation of styrene was performed in the gel phase.

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Pd-complex-bound Amino Acid-based Supramolecular Gel Catalyst for Intramolecular Addition–Cyclization of Alkynoic Acids in Water

Abstract: An NCN-pincer Pd-complex-bound norvaline-based supramolecular gel showed efficient catalytic activities for the intramolecular addition–cyclization of alkynoic acid and phenol derivatives in water to afford the corresponding ene-lactones in good to excellent yields.

Cited by 31 publications

References 47 publications

Synthesis and Self‐Assembly of NCN‐Pincer Pd‐Complex‐Bound Norvalines

Synthesis and Self‐Assembly of NCN‐Pincer Pd‐Complex‐Bound Norvalines

Metal-Catalyzed Intra- and Intermolecular Addition of Carboxylic Acids to Alkynes in Aqueous Media: A Review

Palladium ion-induced supramolecular gel formation of tris-urea molecules

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