2768-42-5Relevant academic research and scientific papers
[2.2]Paracyclophane-derived N-acyloxazol-2(3H)-one as a suitable planar chiral auxiliary for the enantioselective synthesis of β-hydroxy acids
Fringuelli, Francesco,Piermatti, Oriana,Pizzo, Ferdinando,Ruzziconi, Renzo
, p. 38 - 39 (2000)
The synthesis of optically active (+)-(R)-[2.2]paracyclophano[4,5-d]-oxazol-2(3H)-one is described. The aldol reaction of N-acyl derivatives of this planar chiral auxiliary with beazaldehyde occurs with good diastereo- and enantioselectivity.
Ultrasound in enzymatic resolution of ethyl 3-hydroxy-3-phenylpropanoate
Ribeiro, Carlos Magno R.,Passaroto, Elisa N.,Brenelli, Eugênia C.S.
, p. 6477 - 6479 (2001)
The enzymatic hydrolysis of ethyl-3-hydroxy-3-phenylpropanoate using ultrasound bath and PCL, PLE and CRL enzymes was studied. The application of ultrasound bath led to an appreciative decrease in the reaction time of enzymatic hydrolysis without a signif
Studies toward stereoselective bionanocatalysis on gold nanoparticles
Jedrzejewska, Hanna,Ostaszewski, Ryszard
, p. 12 - 16 (2013)
As yet, different enzymes were immobilized on gold nanoparticles both through adsorption and covalent binding. However, there is only one evaluation if such immobilization influenced enzyme enantioselectivity, which is an essential parameter in biocatalys
Siloxy Esters as Traceless Activators of Carboxylic Acids: Boron-Catalyzed Chemoselective Asymmetric Aldol Reaction**
Fujita, Taiki,Kanai, Motomu,Mitsunuma, Harunobu,Sameera, W. M. C.,Yamane, Mina
supporting information, p. 24598 - 24604 (2021/10/14)
The catalytic asymmetric aldol reaction is among the most useful reactions in organic synthesis. Despite the existence of many prominent reports, however, the late-stage, chemoselective, catalytic, asymmetric aldol reaction of multifunctional substrates is still difficult to achieve. Herein, we identified that in situ pre-conversion of carboxylic acids to siloxy esters facilitated the boron-catalyzed direct aldol reaction, leading to the development of carboxylic acid-selective, catalytic, asymmetric aldol reaction applicable to multifunctional substrates. Combining experimental and computational studies rationalized the reaction mechanism and led to the proposal of Si/B enediolates as the active species. The silyl ester formation facilitated both enolization and catalyst turnover by acidifying the α-proton of substrates and attenuating poisonous Lewis bases to the boron catalyst.
Stereoselective acetate aldol reactions of α-silyloxy ketones
Lorente, Adriana,Pellicena, Miquel,Romea, Pedro,Urpí, Fèlix
, p. 1023 - 1035 (2015/01/30)
TiCl4-mediated aldol reactions of chiral methyl α-silyloxy ketones with a variety of aldehydes provide the corresponding 1,4-syn aldol adducts with moderate to high stereocontrol. This transformation represents a new approach to substrate-controlled acetate aldol reactions and complements the 1,4-anti asymmetric induction produced by the related α-benzyloxy ketones. This new approach could be useful in the design of more efficient syntheses of natural products.
Substrate evaluation of rhodococcus erythropolis SET1, a nitrile hydrolysing bacterium, demonstrating dual activity strongly dependent on nitrile sub-structure
Coady, Tracey M.,Coffey, Lee V.,O'Reilly, Catherine,Lennon, Claire M.
supporting information, p. 1108 - 1116 (2015/02/19)
Assessment of Rhodococcus erythropolis SET1, a novel nitrile hydrolysing bacterial isolate, has been undertaken with 34 nitriles, 33 chiral and 1 prochiral. These substrates consist primarily of β-hydroxy nitriles with varying alkyl and aryl groups at the β position and containing in several compounds different substituents α to the nitrile. In the case of β-hydroxy nitriles without substitution at the α position, acids were the major products obtained, along with recovered nitrile after biotransformation, as a result of suspected nitrilase activity of the isolate. Unexpectedly, amides were found to be the major hydrolysis product when the β-hydroxy nitriles possessed a vinyl group at this position. To probe this behaviour further, additional related substrates were evaluated containing electron-withdrawing groups at the α position, and amide was also observed upon biotransformation in the presence of SET1. Therefore this novel isolate has also demonstrated NHase activity with nitriles that appears to be substrate-dependent.
Heterogeneous versus homogeneous copper(II) catalysis in enantioselective conjugate-addition reactions of boron in water
Kitanosono, Taku,Xu, Pengyu,Kobayashi, Shu
supporting information, p. 179 - 188 (2014/01/06)
We have developed CuII-catalyzed enantioselective conjugate-addition reactions of boron to α,β-unsaturated carbonyl compounds and α,β,γ,δ-unsaturated carbonyl compounds in water. In contrast to the previously reported CuI catalysis that required organic solvents, chiral CuII catalysis was found to proceed efficiently in water. Three catalyst systems have been exploited: cat. 1: Cu(OH)2 with chiral ligand L1; cat. 2: Cu(OH)2 and acetic acid with ligand L1; and cat. 3: Cu(OAc)2 with ligand L1. Whereas cat. 1 is a heterogeneous system, cat. 2 and cat. 3 are homogeneous systems. We tested 27 α,β-unsaturated carbonyl compounds and an α,β-unsaturated nitrile compound, including acyclic and cyclic α,β-unsaturated ketones, acyclic and cyclic β,β- disubstituted enones, acyclic and cyclic α,β-unsaturated esters (including their β,β-disubstituted forms), and acyclic α,β-unsaturated amides (including their β,β-disubstituted forms). We found that cat. 2 and cat. 3 showed high yields and enantioselectivities for almost all substrates. Notably, no catalysts that can tolerate all of these substrates with high yields and high enantioselectivities have been reported for the conjugate addition of boron. Heterogeneous cat. 1 also gave high yields and enantioselectivities with some substrates and also gave the highest TOF (43 200 h-1) for an asymmetric conjugate-addition reaction of boron. In addition, the catalyst systems were also applicable to the conjugate addition of boron to α,β,γ, δ-unsaturated carbonyl compounds, although such reactions have previously been very limited in the literature, even in organic solvents. 1,4-Addition products were obtained in high yields and enantioselectivities in the reactions of acyclic α,β,γ,δ-unsaturated carbonyl compounds with diboron 2 by using cat. 1, cat. 2, or cat. 3. On the other hand, in the reactions of cyclic α,β,γ,δ-unsaturated carbonyl compounds with compound 2, whereas 1,4-addition products were exclusively obtained by using cat. 2 or cat. 3, 1,6-addition products were exclusively produced by using cat. 1. Similar unique reactivities and selectivities were also shown in the reactions of cyclic trienones. Finally, the reaction mechanisms of these unique conjugate-addition reactions in water were investigated and we propose stereochemical models that are supported by X-ray crystallography and MS (ESI) analysis. Although the role of water has not been completely revealed, water is expected to be effective in the activation of a borylcopper(II) intermediate and a protonation event subsequent to the nucleophilic addition step, thereby leading to overwhelmingly high catalytic turnover. Copyright
Stereoselective synthesis of (S)-dapoxetine: A chiral auxiliary mediated approach
Khatik, Gopal L.,Sharma, Ratnesh,Kumar, Varun,Chouhan, Mangilal,Nair, Vipin A.
, p. 5991 - 5993 (2013/10/22)
An imidazolidin-2-one chiral auxiliary mediated acetate aldol reaction was explored in the enantioselective synthesis of (S)-dapoxetine (SSRI). The diastereoselective aldol adduct was transformed to highly enantiopure (S)-dapoxetine with overall good yield.
Reversal of selectivity in acetate aldol reactions of N-acetyl-(S)-4- isopropyl-1-[(R)-1-phenylethyl]imidazolidin-2-one
Khatik, Gopal L.,Kumar, Varun,Nair, Vipin A.
supporting information; experimental part, p. 2442 - 2445 (2012/07/03)
Synergistic effects of the exo- and endocyclic chiral centers of an imidazolidinone-based auxiliary were investigated in the perspective of acetate aldol reactions. The reversal in diastereoselectivity was accomplished by lithium and titanium enolate reactions, which proceed through proposed open and closed transitions states, respectively. The aldol adducts were used in the stereoselective synthesis of fluoxetine.
Asymmetric induction by (S)-4-isopropyl-1-phenylimidazolidin-2-thione in titanium-mediated aldol reactions and its application in enantioselective synthesis of (R)-baclofen
Khatik, Gopal L.,Khurana, Ravi,Kumar, Varun,Nair, Vipin A.
, p. 3123 - 3132 (2011/10/31)
The usefulness of (S)-4-isopropyl-1-phenylimidazolidin-2-thione as a chiral auxiliary in stereoselective propionate and acetate aldol reactions is discussed. Further, the enantioselective synthesis of (R)-baclofen by acetate aldol reaction using the chiral auxiliary was demonstrated. Georg Thieme Verlag Stuttgart New York.
