NMR spectroscopic and theoretical evidence of cinchona alkaloid- ketopantolactone complex formation in aprotic solvents: Implications for the mechanism of Pt-catalyzed enantioselective hydrogenation of activated ketones

Research output: Article

32 Citations (Scopus)

Abstract

NMR spectroscopy (standard 2D NMR spectroscopic methods and diffusion-ordered NMR spectroscopy) and theoretical calculations (ab initio modeling at the density functional level and natural bond orbital analysis) were used to verify formation of supramolecular complexes between the pairs O-methylcinchonine-ketopantolactone (KPL) and β-isocinchonine-KPL in deuterobenzene solution. The first direct evidence was found on the interaction of the lone pair of the quinuclidine N atom and the prochiral keto-carbonyl group of the KPL. Strong nN → π* interactions were observed between the nonbonding orbital of the quinuclidine N atom and the π* antibonding orbitals of the C{double bond, long}O bonds. The complex was demonstrated experimentally to be stabilized not only by the H bonds between H 5 of the chiral modifier and the KPL, but also, depending on the structure of the cinchona alkaloid, by those between H8 and H9 and the KPL. In aprotic solvents, this type of experimentally verified adduct may be present on the Pt surface and participate in chiral induction in the Orito reaction.

Original languageEnglish
Pages (from-to)266-276
Number of pages11
JournalJournal of Catalysis
Volume246
Issue number2
DOIs
Publication statusPublished - márc. 10 2007

Fingerprint

Cinchona Alkaloids
alkaloids
Ketones
ketones
Nuclear magnetic resonance spectroscopy
Hydrogenation
hydrogenation
Nuclear magnetic resonance
Quinuclidines
orbitals
Atoms
nuclear magnetic resonance
spectroscopy
adducts
atoms
induction
keto-pantoyllactone
interactions

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

@article{121966791cd549b899958520692af398,
title = "NMR spectroscopic and theoretical evidence of cinchona alkaloid- ketopantolactone complex formation in aprotic solvents: Implications for the mechanism of Pt-catalyzed enantioselective hydrogenation of activated ketones",
abstract = "NMR spectroscopy (standard 2D NMR spectroscopic methods and diffusion-ordered NMR spectroscopy) and theoretical calculations (ab initio modeling at the density functional level and natural bond orbital analysis) were used to verify formation of supramolecular complexes between the pairs O-methylcinchonine-ketopantolactone (KPL) and β-isocinchonine-KPL in deuterobenzene solution. The first direct evidence was found on the interaction of the lone pair of the quinuclidine N atom and the prochiral keto-carbonyl group of the KPL. Strong nN → π* interactions were observed between the nonbonding orbital of the quinuclidine N atom and the π* antibonding orbitals of the C{double bond, long}O bonds. The complex was demonstrated experimentally to be stabilized not only by the H bonds between H 5′ of the chiral modifier and the KPL, but also, depending on the structure of the cinchona alkaloid, by those between H8 and H9 and the KPL. In aprotic solvents, this type of experimentally verified adduct may be present on the Pt surface and participate in chiral induction in the Orito reaction.",
keywords = "Chiral induction, Cinchona, Enantioselective hydrogenation, Intermediate complex, Ketopantolactone, Molecular modeling, NMR, Supramolecular complex",
author = "T. Martinek and Tibor Varga and F. F{\"u}l{\"o}p and M. Bart{\'o}k",
year = "2007",
month = "3",
day = "10",
doi = "10.1016/j.jcat.2006.11.033",
language = "English",
volume = "246",
pages = "266--276",
journal = "Journal of Catalysis",
issn = "0021-9517",
publisher = "Academic Press Inc.",
number = "2",

}

TY - JOUR

T1 - NMR spectroscopic and theoretical evidence of cinchona alkaloid- ketopantolactone complex formation in aprotic solvents

T2 - Implications for the mechanism of Pt-catalyzed enantioselective hydrogenation of activated ketones

AU - Martinek, T.

AU - Varga, Tibor

AU - Fülöp, F.

AU - Bartók, M.

PY - 2007/3/10

Y1 - 2007/3/10

N2 - NMR spectroscopy (standard 2D NMR spectroscopic methods and diffusion-ordered NMR spectroscopy) and theoretical calculations (ab initio modeling at the density functional level and natural bond orbital analysis) were used to verify formation of supramolecular complexes between the pairs O-methylcinchonine-ketopantolactone (KPL) and β-isocinchonine-KPL in deuterobenzene solution. The first direct evidence was found on the interaction of the lone pair of the quinuclidine N atom and the prochiral keto-carbonyl group of the KPL. Strong nN → π* interactions were observed between the nonbonding orbital of the quinuclidine N atom and the π* antibonding orbitals of the C{double bond, long}O bonds. The complex was demonstrated experimentally to be stabilized not only by the H bonds between H 5′ of the chiral modifier and the KPL, but also, depending on the structure of the cinchona alkaloid, by those between H8 and H9 and the KPL. In aprotic solvents, this type of experimentally verified adduct may be present on the Pt surface and participate in chiral induction in the Orito reaction.

AB - NMR spectroscopy (standard 2D NMR spectroscopic methods and diffusion-ordered NMR spectroscopy) and theoretical calculations (ab initio modeling at the density functional level and natural bond orbital analysis) were used to verify formation of supramolecular complexes between the pairs O-methylcinchonine-ketopantolactone (KPL) and β-isocinchonine-KPL in deuterobenzene solution. The first direct evidence was found on the interaction of the lone pair of the quinuclidine N atom and the prochiral keto-carbonyl group of the KPL. Strong nN → π* interactions were observed between the nonbonding orbital of the quinuclidine N atom and the π* antibonding orbitals of the C{double bond, long}O bonds. The complex was demonstrated experimentally to be stabilized not only by the H bonds between H 5′ of the chiral modifier and the KPL, but also, depending on the structure of the cinchona alkaloid, by those between H8 and H9 and the KPL. In aprotic solvents, this type of experimentally verified adduct may be present on the Pt surface and participate in chiral induction in the Orito reaction.

KW - Chiral induction

KW - Cinchona

KW - Enantioselective hydrogenation

KW - Intermediate complex

KW - Ketopantolactone

KW - Molecular modeling

KW - NMR

KW - Supramolecular complex

UR - http://www.scopus.com/inward/record.url?scp=33846915708&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33846915708&partnerID=8YFLogxK

U2 - 10.1016/j.jcat.2006.11.033

DO - 10.1016/j.jcat.2006.11.033

M3 - Article

AN - SCOPUS:33846915708

VL - 246

SP - 266

EP - 276

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

IS - 2

ER -