Regioselective hydrations of 1-aryl-3-en-1-ynes using gold and platinum catalysts: selective production of 2-en-1-ones and 3-en-1-ones

Mokar, Bhanudas Dattatray; Liu, Rai‐Shung

doi:10.1039/c4cc02786h

Cited by 22 publications

(15 citation statements)

References 49 publications

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“…38) Intermediates D and E would then be converted to α-acyloxy ketone H via sequential proto-demetallation 39) and hydrolysis reactions. Substrate 11r reacted much more effectively than 11q (Table 2, entries 16,17).…”

Section: Resultsmentioning

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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Section: Resultsmentioning

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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“…Step-1: 2 Yield: 88%; colorless oil; R f = 0.3 (15% EtOAc/hexanes); 1 H NMR (500 MHz, CDCl 3 ): δ 7.26 (m, 2H), 7.16 (m, 3H), 5.38 (q, J = 6.8 Hz, 1H), 4.13 (t, J = 6.1 Hz, 1H), 2.80-2.76 (m, 2H), 2.05 (bs, 1H), 1.64 (s, 3H), 1.55 (d, J = 6.8 Hz, 3H); 13 C NMR (75 MHz, CDCl 3 ): δ 138.5, 136. 8,129.0,127.9,125.9,120.4,78.2,41.7,12.7,11.7;IR (neat):  max 3395,2922,1494,1381,1012,737,695 Step-2: 3 Yield: 88%; colorless oil; R f = 0.5 (10% EtOAc/hexanes); 1 H NMR (500 MHz, 76.9, 41.9, 24.7,23.9,22.5,22.4;IR (neat):  max 3395,2925,1495,1446,1271,1140,916,740 198.5,141.0,138.8,135.3,129.1,128.3,126.4,43.8,26.0,23.1,21.7,21.3;IR (neat):  max 2931, 1660,1495,1379,1273,1187,703…”

Section: (E)-3-methyl-1-phenylpent-3-en-2-one (4c)mentioning

confidence: 99%

“…Step-1: 16 Yield: 83%; colorless oil; R f = 0.3 (15% EtOAc/hexanes); 1 H NMR (500 MHz, 1,130.0,129.9,129.4,127.5,113.9,74.5,55.2,30.1,9.7;IR (neat):  max 3448,2923,2842,1602,1506,1246,1173,1032,940,824 8,161.3,141.9,129.8,127.1,123.7,114.2,55.2,33.7,8.2;IR (neat):  max 2932,2843,1655,1594,1507,1250,1174,1116,1029,981,826…”

Section: (E)-1-(4-methoxyphenyl)pent-1-en-3-one (4ab)mentioning

confidence: 99%

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Nazarov cyclization of divinyl ketones bearing an ester group at the β-position: a remarkable effect of α-substitution and alkene geometry on regioselectivity

et al. 2016

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The Nazarov cyclization of divinyl ketones with an ester at the β-position was examined with particular reference to where the cyclic double bond forms. We observed unprecedented regioselectivity, dictated by the subtle substitution patterns at the α-position and alkene geometry of α,β and mostly, this selectivity is regardless of substitutions at α'- and β'-positions. The major implications of these observations are an aromatic group at the α-position with E-olefin geometry provides a cyclopentenone in which the double bond is not in conjugation with an ester, whereas Z-olefin provides a cyclopentenone in which the double bond is in conjugation with an ester; and divinyl ketones bearing an ester group at the β-position and an alkyl group at the α-position with E-olefin geometry provide a cyclopentenone in which the double bond is in conjugation with the ester.

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“…[7] Despite of theseg reat achievements, developing ah ighly efficient catalytic system is desirable and challenging, especially with regards to regioselective hydration and hydro-alkoxylation of internal alkynes. [8] Directing-group strategies have been employedt oc ontrol hydration of both alkyl-and aryl-substituted alkynes. [8a, d] For example, Hammond and coworkers developed an Au III -catalyzed hydration of 3-alkynoates to provide g-ketoesters in high yields with highr egioselectivity.…”

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confidence: 99%

Mutual Cooperation in the Formal Allyl Alcohol Nucleophilic Substitution and Hydration of Alkynes for the Construction of γ‐Substituted Ketones

Huang

Wang

Liu

et al. 2016

Chemistry A European J

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Mutual cooperation in the formal allyl alcohol nucleophilic substitution reaction and hydration of an alkyne has been utilized in the presence of a gold catalyst to give a series of γ-functionalized ketones with high to excellent yields. This reaction actually involved an intramolecular O-H insertion cyclization of an alkyne to form the dihydrofuran intermediate, which was followed by the nucleophilic addition ring-opening of a dihydrofuran to give the target compound.

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Regioselective hydrations of 1-aryl-3-en-1-ynes using gold and platinum catalysts: selective production of 2-en-1-ones and 3-en-1-ones

Abstract: Regiocontrolled hydrations of 1-aryl-3-en-1-ynes have been accomplished with IPrAuOTf and PtCl2/CO to yield 3-en-1-ones and 2-en-1-ones efficiently; our experimental data indicates that the sizes of catalysts play an important role.

Cited by 22 publications

References 49 publications

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

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

Nazarov cyclization of divinyl ketones bearing an ester group at the β-position: a remarkable effect of α-substitution and alkene geometry on regioselectivity

Mutual Cooperation in the Formal Allyl Alcohol Nucleophilic Substitution and Hydration of Alkynes for the Construction of γ‐Substituted Ketones

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