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Enantioselective catalysis
Riant O.
ACTUALITE CHIMIQUE
(4-5): 39-44 APR-MAR 2003
Abstract:
Considerations on the evolution and the impact of enantioselective catalysis
on both academic research and industrial applications are presented here. Many
industrial companies have now decided to bet on this area for future developments
in industrial organic synthesis. Actual trends in the academic research shows
the necessity for the evolution of this speciality area toward the discovery
of new concepts as well as the proper use of new combinatorial technics.
Palladium-catalyzed
cross-coupling reaction of a chiral ferrocenyl zinc reagent with aromatic bromides:
Application to the design of chiral octupoles for second harmonic generation
Mamane V, Ledoux-Rak I, Deveau S, Zyss J, Riant O
SYNTHESIS-STUTTGART
(3): 455-467 MAR 2003
Abstract:
Palladium catalyzed cross coupling reaction of a chiral ferrocenylzinc reagent
with aryl bromides allowed the introduction of a planary chiral ferrocenyl subunit
on an aryl fragment. Using this method, new C-3 symmetric chiral architecture
bearing organometallic donor-acceptor fragments were assembled starting from
a common tris aldehyde precursor. The non-linear optical properties were measured
using the Harmonic Light Scattering method and the potentiality for the new
chromophores to behave as octupoles is also discussed.
Synthesis of poly-ferrocene
heterocycles by cycloaddition of mono- or bis(ferrocenecarbonyl)acetylenes and
bis[1,2]dithiolo[1,4]thiazinethiones
Barriga S, Marcos CF, Riant O, Torroba T
TETRAHEDRON
58 (49): 9785-9792 DEC 2 2002
Abstract:
Cycloaddition of a bis[1,2]dithiolo[1,4]thiazine ketothione and mono- or bis(ferrocenecarbonyl)acetylenes
under catalysis by scandium triflate gave mono- and bis-ferrocenecarbonyl-1,3-dithiolylidene[1,2]dithiolo[1,4]thiazines.
Cycloaddition of a bis-dithiolothiazine dithione and bis-ferrocenylbutynedione
gave 3,5-di(bis-ferrocenecarbonyl-1,3-dithiolylidene)[1,4]thiazine, a structure
related to extended tetrathiafulvalenes. (C) 2002 Elsevier Science Ltd. All
rights reserved.
New efficient copper
fluoride-based catalyst for enantioselective hydrosilylation of ketones in aerobic
conditions
Courmarcel J, Mostefai N, Sirol S, Choppin S, Riant O
ISRAEL JOURNAL OF CHEMISTRY
41 (4): 231-240 2001
Abstract:
A new copper(II) fluoride-chiral diphosphines catalytic system was developed.
This one is very efficient and selective for the hydrosilylation of several
substituted or unsubstituted aromatic ketones in so far as moderate to excellent
enantioselectivities were obtained. An oxygen acceleration effect was observed
that led us to propose a practical protocol with a low amount of catalyst.
Efficient enantioselective
hydrosilylation of ketones catalyzed by air stable copper fluoride-phosphine
complexes
Sirol S, Courmarcel J, Mostefai N, Riant O
ORGANIC LETTERS
3 (25): 4111-4113 DEC 13 2001
Abstract:
Copper(II) fluoride-chiral diphosphine systems catalyze the hydrosilylation
of several ketones with moderate to excellent enantioselectivities. An oxygen
acceleration effect was observed and led to a practical protocol with low catalyst
loading.
[2+2+2] cyclotrimerisation
of bisaryl acetylene bearing ferrocenyl units with planar chirality: synthesis
of enantiopure conjugated polyferrocene complexes
Mamane V, Gref A, Lefloch F, Riant O
JOURNAL OF ORGANOMETALLIC CHEMISTRY
637: 84-88 Sp. Iss. SI DEC 3 2001
Abstract:
A new family of highly symmetric and fully conjugated hexaferrocenyl complexes
were prepared by a [2 + 2 + 2] cyclotrimerisation reaction of the corresponding
alkyne monomers. The preliminary electrochemical behaviour of the new complexes
was also evaluated by cyclic voltametry. (C) 2001 Elsevier Science BN. All rights
reserved.
Enantioselective pinacol
coupling of aldehydes mediated and catalyzed by chiral titanium complexes
Bensari A, Renaud JL, Riant O
ORGANIC LETTERS
3 (24): 3863-3865 NOV 29 2001
Abstract:
Starting from easily available chiral Schiff bases, a straightforward synthesis
of air-stable titanium(IV) complexes was devised. Asymmetric pinacol coupling
of aromatic aldehydes mediated and catalyzed by the corresponding low valent
complexes afforded the chiral diols with high yields and enantioselectivities
up to 91%.
Asymmetric synthesis
of chiral ferrocenyl fulleropyrrolidines as potential building blocks for new
materials
Mamane V, Riant O
TETRAHEDRON
57 (13): 2555-2561 MAR 26 2001
Abstract:
Asymmetric [3+2] cycloaddition of chiral ferrocenyl substituted azomethine ylides
to C-60 leads to the corresponding fulleropyrrolidines with high diastereoselectivities.
This methodology has been applied to the preparation of a C-2-symmetric enantiopure
fullerene dimer. (C) 2001 Elsevier Science Ltd. All rights reserved.
A new class of ferrocene-based
1,2-bis(phosphanes) possessing only planar chirality
Argouarch G, Samuel O, Riant O, Daran JC, Kagan HB
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(16): 2893-2899 AUG 2000
Abstract:
Chiral 1,2-bis(phosphanes) 13, devoid of individual chiral centers, have been
prepared in three steps from chiral sulfoxide 10. Their corresponding rhodium
complexes were used as catalysts for asymmetric hydrogenation, giving high ee
values (less than or equal to 95%) in the reduction of itaconic acid or its
ester. A cationic rhodium complex involving coordination of two molecules of
13b and one molecule of oxygen has been isolated and its crystal structure established.
Application of the Siegrist
condensation to the synthesis of conjugated enantiopure bis(styryl)ferrocenes
Skibniewski A, Bluet G, Druze N, Riant O
SYNTHESIS-STUTTGART
(3): 459-462 MAR 1999
Abstract:
Enantiopure polyunsaturated bis(ferrocenyl)aldehydes 7a-c were prepared from
the chiral ferrocenylimine 2b. The key reaction is a Siegrist condensation between
2b and bis-methylarenes 4a-c. Sequential introduction of two different styryl
groups also gave the tris-unsaturated ferrocenecarboxaldehyde 9.
Asymmetric synthesis
and electrochemical behaviour of a C-2 chiral bisferrocenyl orthoquinone
Neo AG, Gref A, Riant O
CHEMICAL COMMUNICATIONS
(21): 2353-2354 NOV 7 1998
Abstract:
A new chiral bisferrocenyl quinone with C-2 symmetry was prepared by asymmetric
synthesis; further condensation with 1,2-diamines led to enantiopure polyaromatic
heterocycles into which two ferrocene units are fused.
A straightforward asymmetric
synthesis of enantiopure 1,2-disubstituted ferrocenes
Riant O, Argouarch G, Guillaneux D, Samuel O, Kagan HB
JOURNAL OF ORGANIC CHEMISTRY
63 (10): 3511-3514 MAY 15 1998
An efficient asymmetric
synthesis of 2-substituted ferrocenecarboxaldehydes
Riant O, Samuel O, Flessner T, Taudien S, Kagan HB
JOURNAL OF ORGANIC CHEMISTRY
62 (20): 6733-6745 OCT 3 1997
Abstract:
Ferrocenecarboxaldehyde is readily transformed into the acetal of (S)-1,2,4-butanetriol
(1,3-dioxane structure) and further methylated to give acetal 15. This can then
be ortho-lithiated using t-BuLi with very high diastereoselectivity (98% de).
Electrophilic quenching provided a large array of compounds of established stereochemistry.
Controlled hydrolysis leads to many ortho-substituted ferrocenecarboxaldehydes
(98% ee) which themselves are starting materials in the synthesis of various
classes of enantiopure ferrocene derivatives with planar chirality of predictable
absolute configuration.
Stereoselective synthesis
of some chiral alpha-ferrocenyl carbenium ions
Brunner A, Taudien S, Riant O, Kagan HB
CHIRALITY
9 (5-6): 478-486 1997
Abstract:
The synthesis of chiral ferrocenyl carbocations is described starting from enantiopure
orthosubstituted ferrocenylcarboxaldehydes. Secondary or tertiary carbocations
have been prepared by ionization of an alcohol precursor. The stereochemistry
of secondary alpha-ferrocenylcarbenium ions has been defined. Preliminary tests
as Lewis acid catalysts have been performed. (C) 1997 Wiley-Liss, Inc.
Asymmetric synthesis
of a chiral tetradentate ligand based on a bis[diphenylphosphinoferrocenyl]
moiety. Electrochemical behavior of free ligand and its Ru-II and Cu-I complexes
MassonSzymczak A, Riant O, Gref A, Kagan HB
JOURNAL OF ORGANOMETALLIC CHEMISTRY
511 (1-2): 193-197 APR 5 1996
Abstract:
alpha-diphenylphosphino carboxaldehyde 4, prepared by asymmetric synthesis,
was reacted with ethane diamine to give bisimine bisphosphine 5. Ruthenium(II)
complex 6 and copper(I) complex 8 were easily formed and their electrochemical
properties studied.
Towards new ferrocenyl
ligands for asymmetric catalysis
Kagan HB, Diter P, Gref A, Guillaneux D, Szymczak AM, Rebiere F, Riant O, Samuel
O, Taudien S
PURE AND APPLIED CHEMISTRY
68 (1): 29-36 JAN 1996
Abstract:
Some new approaches for asymmetric synthesis of chiral ferrocenyl ligands are
described. Many types of ferrocene compounds with planar chirality were prepared
through diastereoselective ortholithiation, thanks to a chiral sulfoxide or
chiral acetal auxiliary. Various mono- and diphosphines may be subsequently
generated. In the sulfoxide route, a key intermediate is pure monolithioferrocene.
A convenient procedure was set up, involving the isolation of stable tri-n-butylstannyl-ferrocene
as a precursor of monolithioferrocene. The species Fc(2)PH (Fc = ferrocenyl)
and its borane protected derivative allowed to synthesize chiral diphosphines
where the usual PPh(2) groups are replaced by the PFc(2) fragment.
Synthesis of a chiral
carbocations linked to a ferrocene unit
Taudien S, Riant O, Kagan HB
TETRAHEDRON LETTERS
36 (20): 3513-3516 MAY 15 1995
Abstract:
Orthosubstituted ferrocene carboxaldehydes (100% ee) were transformed into carbinols
by addition of a Grignard reagent. Treatment by strong acids (HPF6, CF3SO3H,
etc) gave isolated chiral carbocations which are good Lewis acid catalysts for
various reactions such as Diels-Alder reaction.
Asymmetric base-catalysed
cycloaddition between anthrone and some dienophiles
Riant O, Kagan HB, Ricard L
TETRAHEDRON
50 (15): 4543-4554 APR 11 1994
Abstract:
Anthrone has been found to react with N-methylmaleimide in the presence of catalytic
amounts of various chiral beta-aminoalcohols. The cycloadduct 3a has been obtained
in excellent yield with enantiomeric excess of up to 61%. Its absolute configuration
has been assigned by X-ray crystallography. Several features of the reaction
have been studied: variation of dienophile; competition between cycloaddition
and formation of the optically active Michael adduct 4; solvent and temperature
effects. Mechanistic studies are in agreement with a concerted [4+2] process,
providing an unique case of a base-catalyzed asymmetric Diels-Alder reaction.
A general asymmetric-synthesis
of ferrocenes with planar chirality
Riant O, Samuel O, Kagan HB
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
115 (13): 5835-5836 JUN 30 1993
Synthesis and hightly
diastereoselective ortho-lithiation of ferrocenyl sulfoxides - application to
the synthesis of ferrocenyl derivatives with planar chirality
Rebiere F, Riant O, Ricard L, Kagan HB
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH
32 (4): 568-570 APR 1993
Catalytic asymmetric
diels-alder reactions
Kagan HB, Riant O
CHEMICAL REVIEWS
92 (5): 1007-1019 JUL-AUG 1992
Asymmetric diels-alder
reaction catalysed by some chiral lewis-acids
Rebiere F, Riant O, Kagan HB
TETRAHEDRON-ASYMMETRY
1 (3): 199-214 1990
Synthesis of methomyl
derivatives as new photosensitive molecular probes
Aranda G, Riant O
SYNTHETIC COMMUNICATIONS
20 (5): 733-750 1990
Asymmetric diels-alder
reaction catalyzed by chiral bases
Riant O, Kagan HB
TETRAHEDRON LETTERS
30 (52): 7403-7406 1989