- Solvent Isotope Effects on the Kinetics of Nucleophilic Addition of Water to a β-Nitrostyrene
-
The hydrolysis rate of 3,4-(methylenedioxy)-β-nitrostyrene (S) has been measured in H2O and in 99percent D2O buffer solutions from pH -0.9 to 10.6.The kinetic solvent isotope effect (KSIE), k(H2O)/k(D2O), is 6.2 at pH 2.5, where k is independent of pH in both solvents and attains a higher value, approximately 22, at about pH 6.2.The isotope effects ki(H2O)/ki(D2O) on the rate constants for the individual steps of the mechanism have been determined and their contributions to the overall KSIE evaluated.Accordingly, the KSIE on the pH-rate plateau at pH 1-4 can be separated into two factors: 5.0 for K12, the ionization constant of S as a pseudo-base in water; and 1.4 for k3H, the rate constant for rate-controlling protonation of the resulting anion by H3O(1+).At pH 6.2, the higher KSIE (7.6) on k3H2O becomes important while the uncatalyzed addition of water to the double bonds is partly rate controlling.The rate at the midpoint of a proton-inventory plot (49.5percent D2O) shows a negative deviation from linearity of 18percent.
- Crowell, Thomas I.
-
-
Read Online
- Biphenyl-Based Bis(thiourea) Organocatalyst for Asymmetric and syn -Selective Henry Reaction
-
A scalable, efficient and chromatography-free synthesis of a new enantiopure C 2-symmetric bis(thiourea) catalyst was accomplished from a readily available starting material. The developed strategy could be conducted on a multi-gram scale. Both the prepared enantiomers of the bis(thiourea) organocatalyst have been tested in the asymmetric Henry reaction under thoroughly optimized conditions during which an unusual solvent effect on enantioselectivity was found. The corresponding adducts were obtained in excellent yields with good to excellent enantioselectivities. The achieved high reactivity and enantioselectivity in the nitroaldol reaction of nitroalkanes with aromatic aldehydes suggests promising potential for this catalyst. Moreover, a significant syn-diastereoselectivity was observed.
- Otevrel, Jan,Bobal, Pavel
-
supporting information
p. 593 - 603
(2017/01/25)
-
- Vasicine from Adhatoda vasica as an organocatalyst for metal-free Henry reaction and reductive heterocyclization of o-nitroacylbenzenes
-
Vasicine, a quinazoline alkaloid, from the leaves of Adhatoda vasica, has been utilized as an efficient catalyst for metal and base free Henry reaction of various aldehydes with nitro alkanes. The method can be used in the synthesis of various β-nitro alcohols under mild reaction conditions without use of hazardous organic solvents and expensive catalysts. Vasicine is also applied successfully for one pot synthesis of 2,1-benzisoxazoles from o-nitroacylbenzenes in good yields under mild conditions.
- Sharma, Sushila,Kumar, Manoranjan,Bhatt, Vinod,Nayal, Onkar S.,Thakur, Maheshwar S.,Kumar, Neeraj,Singh, Bikram,Sharma, Upendra
-
supporting information
p. 5003 - 5008
(2016/10/25)
-
- Application of natural feedstock extract: The Henry reaction
-
For the first time, we have successfully performed the Henry reaction in neat 'Natural Feedstock Extract' at room temperature. Herein, we used two most abundant natural feedstock extracts such as 'Water Extract of Banana' (WEB) and 'Water Extract of Rice Straw Ash' (WERSA). This protocol is highly advantageous owing to the employment of natural feedstock as green reaction media resulting in significant novelty and advancement with respect to green and sustainable chemistry.
- Surneni, Naresh,Barua, Nabin C.,Saikia, Bishwajit
-
supporting information
p. 2814 - 2817
(2016/06/09)
-
- Polymer supported DMAP: An easily recyclable organocatalyst for highly atom-economical Henry reaction under solvent-free conditions
-
Polymer supported catalysts are regarded as a borderline class of catalysts, which retains the advantages of homogeneous catalysts while securing the ease of recovery by simple filtration and workup of heterogeneous systems. Additionally, such catalysts are less hygroscopic due to the long polymer backbone. Here we have demonstrated that a catalytic amount of polymer supported DMAP (10 mol%) can lead to excellent conversion of an equimolar mixture of aldehyde and nitroalkane exclusively into β-nitroalcohols via the Henry reaction. Unlike most of the commonly used catalysts, polymer supported DMAP can be recovered by simple filtration and reused several times, thereby reducing the operational cost. High synthetic efficiency, total atom economy, near quantitative yields, mild reaction conditions, operational simplicity, easy recovery and reusability of the catalyst, solvent-free reaction conditions and avoidance of traditional reaction workup make the protocol highly significant from Green and Sustainable Chemistry perspectives.
- Das, Diparjun,Pathak, Gunindra,Rokhum, Lalthazuala
-
p. 104154 - 104163
(2016/11/17)
-
- Kinetic resolution of racemic amino alcohols through intermolecular acetalization catalyzed by a chiral Bronsted acid
-
The kinetic resolution of racemic secondary alcohols is a fundamental method for obtaining enantiomerically enriched alcohols. Compared to esterification, which is a well-established method for this purpose, kinetic resolution through enantioselective intermolecular acetalization has not been reported to date despite the fact that the formation of acetals is widely adopted to protect hydroxy groups. By taking advantage of the thermodynamics of acetalization by the addition of alcohols to enol ethers, a highly efficient kinetic resolution of racemic amino alcohols was achieved for the first time and in a practical manner using a chiral phosphoric acid catalyst.
- Yamanaka, Takuto,Kondoh, Azusa,Terada, Masahiro
-
supporting information
p. 1048 - 1051
(2015/02/19)
-
- Ethyl acrylate conjugated polystyryl-diphenylphosphine - An extremely efficient catalyst for Henry reaction under solvent-free conditions (SolFC)
-
Over the last few decades, the fast-growing development of polymer supported reagents has led to the synthesis of a variety of reagents on solid support. Some of the major advantages of using such reagents are that they are less hygroscopic, easy to recover, and can be recycled. Here, we have demonstrated that in situ generated ethyl acrylate conjugated polystyryl-diphenylphosphine (PDPP-EA) derived from the reaction of a mixture of polystyryl-diphenylphosphine and ethyl acrylate in a stoichiometric ratio can efficiently catalyze the synthesis of β-nitroalcohols from the reaction of aldehydes and nitroalkanes under solvent-free conditions (SolFC).
- Rokhum, Lalthazuala,Bez, Ghanashyam
-
p. 300 - 306
(2013/06/05)
-
- Henry reaction in aqueous media at neutral pH
-
An efficient method for the synthesis of β-nitro alcohols from nitro alkanes and aldehydes in aqueous phosphate buffer under neutral pH conditions at room temperature is reported. In the case of higher nitro alkanes, the reaction showed very good diastereoselectivity to give syn β-nitro alcohols in preference to their anti products. Copyright
- Bora, Pranjal P.,Bez, Ghanashyam
-
p. 2922 - 2929
(2013/06/27)
-
- Direct Henry reactions with modified calcium oxide as solid catalyst
-
Commercial CaO was modified simply with benzyl bromide. The modified CaO had good water resistance, and characterization by FTIR and TG revealed the modifier was chemically bonded to the CaO surface. Commercial CaO and CaO modified with benzyl bromide were investigated as catalysts for the Henry reaction between benzaldehyde and nitromethane. It was found that the catalytic activity of the modified CaO was greatly improved, with high conversion of benzaldehyde to the (E)-phenyl nitroolefin and 1-phenyl-2-nitroethanol, and with different selectivity from commercial CaO. The effect of modification and reaction conditions on yield, selectivity, and mechanism were studied thoroughly.
- Tang, Ying,Gu, Xuefan,Meng, Mei,Xu, Jingfang
-
p. 3715 - 3725
(2013/10/22)
-
- Cascade formation of isoxazoles: Facile base-mediated rearrangement of substituted oxetanes
-
Give me five! Nitro compounds and oxetan-3-one react through an intriguing cascade sequence to give isoxazole-4-carbaldehydes using inexpensive reagents in a one-pot procedure (see scheme; Ms=methanesulfonyl). A variety of 3-substituted isoxazole-4-carbaldehydes were obtained in high overall yields.
- Burkhard, Johannes A.,Tchitchanov, Boris H.,Carreira, Erick M.
-
supporting information; scheme or table
p. 5379 - 5382
(2011/07/08)
-
- Synthesis of amino tetrahydrofuran lignan via an N,O-heterocyclic compound as an intermediate
-
Tetrahydrofuran aminolignans bearing an amino group at the 8 position were synthesized via an N,O-heterocyclic compound that had been obtained by silylnitronate cycloaddition.
- Hirao, Haruna,Yamauchi, Satoshi,Ishibashi, Fumio
-
p. 741 - 745
(2007/10/03)
-
- Anionic Activation of Organic Compounds by Adsorption on Alumina and Alumina-KF
-
Condensations of acidic carbon compounds with piperonal (1) were achieved by adsorption on neutral alumina without solvent for the more acidic compounds and on Al2O3-KF for the less acidic compounds; dry Michael condensations also took place on Al2O3-KF.
- Villemin, Didier
-
p. 1092 - 1093
(2007/10/02)
-