Au(I)-Catalyzed Enantioselective 1,3-Dipolar Cycloadditions of Münchnones with Electron-Deficient Alkenes

Melhado, Asa D.; Luparia, Marco; Toste, F. Dean

doi:10.1021/ja074824t

Cited by 187 publications

(76 citation statements)

References 14 publications

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“…However, classical 1,3-dipolar cycloaddition of iminoesters and electrophilic olefins was not described using gold complexes. Only Toste´s group published an efficient 1,3-DC employing alanine, phenylalanine and allylglycine derived azlactones with maleimides and acrylates in the presence of dimetallic type 24 (S)-Cy-Segphos (AuOBz) 2 complex as catalyst (2 mol%) in the absence of base [29,58].…”

Section: Gold-catalyzed 13-dc Of Azomethine Ylidesmentioning

confidence: 99%

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Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Nájera

Sansano

2014

Journal of Organometallic Chemistry

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In this account, we describe the experience of our research group in the implementation of chiral coinage metal complexes into the efficient enantioselective 1,3-DC of azomethine ylides derived from α-amino acids and azlactones with different dipolarophiles. The corresponding chiral metallodipoles were generated in situ and next focused on the synthesis of highly substituted prolines. For this purpose, privileged ligands such as phosphoramidites and binap with silver(I), gold(I) and copper(II) salts are described. Depending from the ligand and mainly from the metal salt it can be possible to control the facial endo/exo-diasteroselectivity and the enantioselectivity of these types of processes. The synthetic processes are also supported by DFT calculations in order to elucidate the most plausible mechanism and the stereochemical results.

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Section: Gold-catalyzed 13-dc Of Azomethine Ylidesmentioning

confidence: 99%

“…However, chiral gold complexes [26,27,28] have not so extensively employed and just a very efficient enantioselective cycloaddition of münchnones with electron-deficient alkenes has been described. In this transformation, followed by an ester/amide formation, ∆ 1 -pyrrolines were obtained in very high enantioselectivity [29].…”

Section: Introductionmentioning

confidence: 99%

Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Nájera

Sansano

2014

Journal of Organometallic Chemistry

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“…12,13 Despite the ever burgeoning literature concerning gold-catalysed reactions, the majority of structurally defined chiral gold complexes are restricted to those bearing chiral phosphane ligands. [14][15][16][17][18][19] Given the fact the use of gold-NHC complexes [20][21][22][23][24][25][26] is now de rigour in synthesis, it is somewhat surprising that reports of structurally characterised, chiral, Au(I)-NHC [27][28][29][30][31][32][33][34][35][36] and Au(I)-ADC/NAC 37 complexes are still comparatively scarce. Likewise, the synthesis and characterisation and catalytic activity of cyclometallated gold(III) complexes is relatively unexplored, with only a handful of examples being cited in the literature.…”

Section: Introductionmentioning

confidence: 99%

Some insights into the gold-catalysed A 3 -coupling reaction

Price

Brisdon

Randall

et al. 2017

Journal of Organometallic Chemistry

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Abstract.A series of cyclometallated and functionalised NHC gold(I) and gold(III) complexes, many of which feature chiral ligands, and their application to A 3 -coupling reactions is presented. Gold(III) complexes were found to be particularly effective catalysts for the coupling in a range of solvents, however no asymmetric induction was obtained when using chiral gold complexes and the rate of product formation was found to be similar even when using different ligand systems. In-situ NMR analysis of these reactions indicates that decomposition of the catalyst occurs during the course of the reaction while TEM studies revealed the presence of gold nanoparticles in crude reaction mixtures. Taken together these data suggest that the gold nanoparticales, rather than the intact gold complexes, could be the catalytically active species, and if so this may have significant implications for other gold-catalysed systems.Dedicated to Dr. Mark Whiteley (an outstanding colleague) on his retirement from the School of Chemistry, University of Manchester.

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“…When the reaction was conducted in the absence of NMM, 4a was formed in a low yield (4%) with the recovery of 3a (96%), and 5a was not formed at all, indicating that a base is essential for the completion of cyclodehydration. [12][13][14][15] On the basis of the assumption that the yield of oxazole derivative 5a could be decreased by the separation of relatively lipophilic 4a from water-soluble DMT-MM, we conducted the reaction in a biphasic solvent system composed of CH 2 Cl 2 -acetone-H 2 O (1 : 1 : 1). As a result, the yield of 5a decreased Regular Article…”

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confidence: 99%

One-Pot Preparation of Oxazol-5(4<i>H</i>)-ones from Amino Acids in Aqueous Solvents

Fujita

Kunishima

2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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A method for one-pot synthesis of oxazol-5(4H)-ones has been developed using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM), which is available for the activation of carboxylic acids in an aqueous solvent. The oxazolones were prepared by the N-acylation of amino acids with carboxylic acids and the subsequent cyclodehydration of the resulting N-acylamino acids by the addition of N,N-diethylaniline. Since both these reactions proceed effectively with the same coupling reagent, DMT-MM, in aqueous solvents, the procedure is simplified and becomes easy to perform. In addition, 5-(triazinyloxy)oxazole derivatives have been synthesized by controlling the basicity of the reaction system. Key words oxazolone; oxazole; dehydrocondensation; cyclodehydration; aqueous solvent Oxazol-5(4H)-ones (henceforth referred to as oxazolones) are useful precursors for the synthesis of substituted heterocyclic compounds, 1) natural products, 2) and chiral amino acids. 3,4)In general, the preparation of oxazolones from amino acids is effected by two-step synthesis: N-acylation of the amino group followed by cyclodehydration involving the activation of the carboxy group. The N-acylation of amino acids can be carried out in an aqueous solvent, typically using Schotten-Baumann conditions, 5) while the cyclodehydration of the resulting N-acylamino acids to form oxazolones is performed under anhydrous conditions with dehydrating reagents, such as carbodiimides and acid anhydrides. Thus, these reactions must be performed in separate vessels. If the latter reaction occurs in an aqueous solvent, both reactions can be conducted in the same vessel using water-soluble amino acids as a starting compound. Therefore, the procedure for preparing oxazolones becomes simplified. In this study, we focused on 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) 6) as a dehydrocondensing reagent because the chemoselective activation of carboxy groups using DMT-MM efficiently proceeds even in an aqueous solvent. 7)We report here a one-pot method for the synthesis of oxazolones from amino acids. In this method, DMT-MM is utilized successfully for both the N-acylation of amino acids with carboxylic acids and the subsequent cyclodehydration of the resulting N-acylamino acids. 8,9) Results and DiscussionTo find the optimum reaction conditions for the one-pot method, we first examined each reaction separately using Lleucine (2a) as a model compound.10,11) After several attempts, we succeeded in finding the optimum reaction conditions for the first reaction. Benzoic acid (1) was treated with DMT-MM in the presence of N-methylmorpholine (NMM) in acetone-H 2 O (3 : 1) at room temperature for 15 min; then an aqueous solution of 2a and NaOH was added (Chart 1). As a result, N-benzoyl-L-leucine (3a) was obtained in a satisfactory yield (91%). The addition of NaOH as a base was found to be essential to complete the coupling reaction.The second reaction needs to follow the final conditions of the former reaction to achie...

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Au(I)-Catalyzed Enantioselective 1,3-Dipolar Cycloadditions of Münchnones with Electron-Deficient Alkenes

Cited by 187 publications

References 14 publications

Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Some insights into the gold-catalysed A 3 -coupling reaction

One-Pot Preparation of Oxazol-5(4<i>H</i>)-ones from Amino Acids in Aqueous Solvents

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