Ruthenium carboxylate complexes as easily prepared and efficient catalysts for the synthesis of β-oxopropyl esters

Hiett, Nicholas P.; Lynam, Jason M.; Welby, Christine E.; Whitwood, Adrian C.

doi:10.1016/j.jorganchem.2010.10.001

Cited by 34 publications

(27 citation statements)

References 41 publications

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“…This prompted us to analyze the reaction mixture by 31 P{ 1 H} NMR spectroscopy. [37] In contrast to our findings, they determined differences in productivities between the complexes [Ru(PPh 3 ) 2 (κ 2 -O 2 CMe) 2 ] (81 %) and [Ru(PPh 3 ) 2 (κ 2 -O 2 CPh) 2 ] (68 %), in the addition of benzoic acid to 1-phenylprop-2-yn-1-ol. The resulting 31 P{ 1 H} NMR spectrum exhibited three signals (Figure 4, a), which could be assigned to the initial catalyst 3c (δ = 29.7 pm), the corresponding benzoate complex 3e (δ = 31.2 ppm), and the mixed carboxylate complex [Ru(CO) 2 -(PPh 3 ) 2 (O 2 CtBu)(O 2 CPh)] (δ = 30.1 ppm).…”

Section: Resultscontrasting

confidence: 99%

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Ruthenium Carboxylate Complexes as Efficient Catalysts for the Addition of Carboxylic Acids to Propargylic Alcohols

et al. 2015

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Ruthenium complexes [Ru(CO) 2 (PPh 3 ) 2 (O 2 CR) 2 ] -3a (R = CH 2 OCH 3 ), 3b (R = iPr), 3c (R = tBu), 3d (R = 2-c C 4 H 3 O), and 3e (R = Ph) -were synthesized by treatment of Ru(CO) 3 -(PPh 3 ) 2 with the corresponding carboxylic acids. The molecular structures of the newly synthesized complexes in the solid state are discussed. Compounds 3a-e were successfully applied as catalysts in the addition of carboxylic acids to propargylic alcohols to give the corresponding β-oxo esters in good to excellent yields even in air. The different carboxylate ligands do not have an influence on the productivities, because the carboxylates exchange rapidly under the applied [a]2939 reaction conditions, as was confirmed by 31 P{ 1 H} NMR spectroscopic studies. The addition of catalytic amounts of Na 2 CO 3 resulted in an increase in β-oxo ester formation. The reaction is tolerant to the use of versatile functional groups on the propargylic alcohols and carboxylic acids, revealing a broad substrate generality. In contrast to most other known catalytic systems, even sterically hindered substrates, including 2,4,6-trimethylbenzoic acid, 1,1-diphenylprop-2-yn-1-ol, or the biologically active steroid ethisterone, were successfully converted.

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Section: Resultscontrasting

confidence: 99%

“…[17,18,37] With this solvent the best results could be obtained (Entry 3, Table 1). The most commonly utilized solvent in β-oxopropyl ester synthesis is toluene.…”

Section: Resultsmentioning

confidence: 99%

Ruthenium Carboxylate Complexes as Efficient Catalysts for the Addition of Carboxylic Acids to Propargylic Alcohols

et al. 2015

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“…2. Several acyl groups were examined instead of the pivaloyl group, and the results revealed that the use of a smaller ester such as acetyl or isobutyryl group resulted in lower yields of 35 and 48%, respectively (Table 2, entries 13,14). To determine the effect of the electronic state of the ester of the outcome of the reaction, we also investigated several non-and monosubstituted benzoyl groups.…”

Section: Resultsmentioning

confidence: 99%

“…[9][10][11] Based on the importance of α-acyloxyketones to chemistry, the development of a concise synthetic method for the preparation of α-acyloxyketone derivatives is important. Although a wide variety of synthetic methods have been investigated to date, 12,13) reports pertaining to the direct synthesis of α-acyloxyketone III by the oxidation of alkyne I are rare, most likely because of the difficulties associated with suppressing the over-oxidation of the product and controlling the regioselectivity of the reaction [14][15][16] (Chart 1). To allow for the direct synthesis of α-acyloxyketone III from alkyne I, several researchers directed their attention towards the transition metal-catalyzed migration of propargylic esters [17][18][19][20] to affect a facile oxidative transformation.…”

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confidence: 99%

Synthesis of α-Acyloxyketone Derivatives <i>via</i> the Platinum-Catalyzed Migration of Propargylic Esters

Tsukano

Yamamoto

Takemoto

2015

CHEMICAL & PHARMACEUTICAL BULLETIN

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The synthesis of α-acyloxyketones via the migration of a propargylic ester followed by the intramolecular nucleophilic addition of the resulting allene was achieved using a cationic platinum catalyst. The optimized conditions for this transformation were determined to be 3 mol% of Pt(cod)Cl 2 , 3 mol% of AgNTf 2 , and 3 eq of water in toluene at 100°C, and these conditions were successfully applied to the synthesis of a wide variety of α-aryl-α-acyloxyketones. The mechanism of this reaction was evaluated in detail based on the results of isotope labeling experiments using H 2 18 O.Key words platinum; propargylic ester migration; α-acyloxyketone α-Acyloxyketone, which is a protected form of α-hydroxyketone, is a fundamental structure that can be found in a broad range of natural products and bioactive compounds, including hainanmurpanin, 1) paniculatin 2) and murpaniculol senecioate 3) (Fig. 1). α-Acyloxyketone has also been used as a simple starting material for the stereoselective synthesis of a variety of different structures, including numerous 1,2-diols 4-8) and heterocyclic systems.9-11) Based on the importance of α-acyloxyketones to chemistry, the development of a concise synthetic method for the preparation of α-acyloxyketone derivatives is important. Although a wide variety of synthetic methods have been investigated to date, 12,13) reports pertaining to the direct synthesis of α-acyloxyketone III by the oxidation of alkyne I are rare, most likely because of the difficulties associated with suppressing the over-oxidation of the product and controlling the regioselectivity of the reaction 14-16) (Chart 1). To allow for the direct synthesis of α-acyloxyketone III from alkyne I, several researchers directed their attention towards the transition metal-catalyzed migration of propargylic esters [17][18][19][20] to affect a facile oxidative transformation. [21][22][23][24][25][26][27][28][29][30] For example, in 1991, Schick and Mahrwald 21) reported that the treatment of propargyl acetate 1 with PdCl 2 (MeCN) 2 gave a 1 : 1 mixture of α-acyloxyketone 2 and α,β-unsaturated ketone 3 via the rearrangement of the acetyl group (Chart 2(a)). Ohfune et al. 24)also reported the synthesis of α-acyloxy-α′-siloxyketone 4 using a gold catalyst (Chart 2(b)). Under Ohfune's conditions, it was observed that substrates without a silyl group did not undergo the reaction, and it was therefore assumed that the silyl group was essential for stabilizing the β cation of reaction intermediate 5 (or 6). Although these reactions provided facile access to the α-acyloxyketones 2 and 4 from the readily accessible propargyl esters 1 and 3, several opportunities still remained to improve on this reaction in terms of the selectivity and substrate scope. For improving the scope of this reaction, we focused on enhancing the π-acidity of the transition metal catalyst (i.e., palladium, gold or platinum catalyst) by decreasing its electron density. [17][18][19][20] If allene 9, which was derived from 7, could be strongly activated by a π-a...

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“…Immobilization of homogeneous catalysts on a solid support enables easy recovery and recycling of homogeneous catalysts and avoids their disadvantages with respect to handling and reusability of the catalyst [29]. Recently, ruthenium complexes have been developed as suitable catalysts in organic synthesis [30][31][32][33][34][35]. Also, Schiff base complexes of ruthenium(III) are used as potential catalysts for olefin epoxidation [36].…”

Section: Introductionmentioning

confidence: 99%

Epoxidation of alkenes with NaIO4 catalyzed by an efficient and reusable natural polymer-supported ruthenium(III) salophen catalyst

2015

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Ruthenium carboxylate complexes as easily prepared and efficient catalysts for the synthesis of β-oxopropyl esters

Cited by 34 publications

References 41 publications

Ruthenium Carboxylate Complexes as Efficient Catalysts for the Addition of Carboxylic Acids to Propargylic Alcohols

Ruthenium Carboxylate Complexes as Efficient Catalysts for the Addition of Carboxylic Acids to Propargylic Alcohols

Synthesis of α-Acyloxyketone Derivatives <i>via</i> the Platinum-Catalyzed Migration of Propargylic Esters

Epoxidation of alkenes with NaIO4 catalyzed by an efficient and reusable natural polymer-supported ruthenium(III) salophen catalyst

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