Probing the “additive effect” in the proline and proline hydroxamic acid catalyzed asymmetric addition of nitroalkanes to cyclic enones

Hanessian, Stephen; Govindan, Subramaniyan; Warrier, Jayakumar

doi:10.1002/chir.20201

Cited by 34 publications

(15 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[187,188] A linear correlation was obtained when piperidine was used as an additive (3-7 mol %), but a significant NLE was evident when the additive was trans-2,5-dimethylpiperazine or quinine. The NLE curve consisted of a (+)-NLE (for proline < 20 % ee), a (À)-NLE (for proline > 80 % ee), and a flat profile for proline between 20-80 % ee.…”

Section: Reviews 482 Wwwangewandteorgmentioning

confidence: 99%

Nonlinear Effects in Asymmetric Catalysis

Satyanarayana¹,

Abraham²,

Kagan³

2008

Angew Chem Int Ed

493

273

View full text Add to dashboard Cite

There is a need for the preparation of enantiomerically pure compounds for various applications. An efficient approach to achieve this goal is asymmetric catalysis. The chiral catalyst is usually prepared from a chiral auxiliary, which itself is derived from a natural product or by resolution of a racemic precursor. The use of non-enantiopure chiral auxiliaries in asymmetric catalysis seems unattractive to preparative chemists, since the anticipated enantiomeric excess (ee) of the reaction product should be proportional to the ee value of the chiral auxiliary (linearity). In fact, some deviation from linearity may arise. Such nonlinear effects can be rich in mechanistic information and can be synthetically useful (asymmetric amplification). This Review documents the advances made during the last decade in the use of nonlinear effects in the area of organometallic and organic catalysis.

show abstract

Section: Reviews 482 Wwwangewandteorgmentioning

confidence: 99%

Nonlinear Effects in Asymmetric Catalysis

Satyanarayana¹,

Abraham²,

Kagan³

2008

Angew Chem Int Ed

493

273

View full text Add to dashboard Cite

show abstract

“…Eine interessante ( S )‐Prolin‐katalysierte asymmetrische konjugierten Addition von Nitroalkan an Enone in CHCl 3 wurde im Jahr 2000 beschrieben 187. 188 Mit Piperidin als Additiv (3–7 Mol‐%) resultiert eine lineare Korrelation, während mit trans‐ 2,5‐Dimethylpiperazin oder Chinin als Additiven ein deutlicher NLE festgestellt wurde. Die NLE‐Kurve war uneinheitlich mit einem (+)‐NLE für Prolin mit ee <20 %, einem (−)‐NLE für Prolin mit ee >80 % und einem flachen Profil für Prolin zwischen 20 und 80 % ee .…”

Section: Nichtlineare Effekte Durch Teillöslichkeitunclassified

Nichtlineare Effekte in der asymmetrischen Katalyse

2008

View full text Add to dashboard Cite

Zahlreiche Anwendungen in der Chemie erfordern die Synthese enantiomerenreiner Verbindungen. Einen effizienten Ansatz hierfür bietet die asymmetrische Katalyse. Hierbei wird der chirale Katalysator gewöhnlich aus einem chiralen Auxiliar erzeugt, das z. B. von einem Naturstoff abgeleitet wurde oder aus der Racematspaltung racemischer Vorstufen stammt. Die Verwendung nicht‐enantiomerenreiner chiraler Auxiliare in der asymmetrischen Katalyse scheint aus präparativer Sicht ungünstig, da man erwarten sollte, dass der Enantiomerenüberschuss (ee) des Reaktionsprodukts zum ee‐Wert des chiralen Auxiliars proportional ist (Linearität). Tatsächlich kann es jedoch zu Abweichungen von der Linearität kommen. Derartige nichtlineare Effekte können sehr aufschlussreich für den Mechanismus einer Reaktion sein und außerdem in der Synthesechemie genutzt werden (asymmetrische Verstärkung). Dieser Aufsatz fasst die Fortschritte der letzten zehn Jahre bei der Anwendung des nichtlinearen Effekts in der metallorganischen und organischen Katalyse zusammen.

show abstract

“…[1] One of the most studied Michael acceptors are a,bunsaturated ketones, because the adducts obtained contain interesting functionalities suitable for their further transformation into relevant products, such as pyrrolidines, aminoalkanes, and aminocarbonyl compounds. Organocatalytic enantioselective conjugate addition of nitroalkanes to cyclic and acyclic aliphatic a,b-unsaturated ketones has been extensively studied by using proline derivatives, [2] imid-A C H T U N G T R E N N U N G azolines, [3] guanidines, [4] and spiro-ammonium salts as catalysts. [5] Bifunctional thioureas bearing a primary amine have also been described as useful catalysts for this reaction, [6] and even aluminum and magnesium complexes have been reported to promote that enantioselective transformation.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Conjugate Addition of Nitro Compounds to α,β‐Unsaturated Ketones: An Experimental and Computational Study

Manzano

Andrés

Álvarez

et al. 2011

Chemistry A European J

View full text Add to dashboard Cite

A series of chiral thioureas derived from easily available diamines, prepared from α-amino acids, have been tested as catalysts in the enantioselective Michael additions of nitroalkanes to α,β-unsaturated ketones. The best results are obtained with the bifunctional catalyst prepared from L-valine. This thiourea promotes the reaction with high enantioselectivities and chemical yields for aryl/vinyl ketones, but the enantiomeric ratio for alkyl/vinyl derivatives is very modest. The addition of substituted nitromethanes led to the corresponding adducts with excellent enantioselectivity but very poor diastereoselectivity. Evidence for the isomerization of the addition products has been obtained from the reaction of chalcone with [D(3)]nitromethane, which shows that the final addition products epimerize under the reaction conditions. The epimerization explains the low diastereoselectivity observed in the formation of adducts with two adjacent tertiary stereocenters. Density functional studies of the transition structures corresponding to two alternative activation modes of the nitroalkanes and α,β-unsaturated ketones by the bifunctional organocatalyst have been carried out at the B3LYP/3-21G* level. The computations are consistent with a reaction model involving the Michael addition of the thiourea-activated nitronate to the ketone activated by the protonated amine of the organocatalyst. The enantioselectivities predicted by the computations are consistent with the experimental values obtained for aryl- and alkyl-substituted α,β-unsaturated ketones.

show abstract

Probing the “additive effect” in the proline and proline hydroxamic acid catalyzed asymmetric addition of nitroalkanes to cyclic enones

Cited by 34 publications

References 39 publications

Nonlinear Effects in Asymmetric Catalysis

Nonlinear Effects in Asymmetric Catalysis

Nichtlineare Effekte in der asymmetrischen Katalyse

Enantioselective Conjugate Addition of Nitro Compounds to α,β‐Unsaturated Ketones: An Experimental and Computational Study

Contact Info

Product

Resources

About