Česká společnost chemická, pobočka Brno
Vás zve na přednášku, která se koná v místnosti 132, 1.NP, budova A11,
Kamenice 5, Přírodovědecká fakulty Masarykovy univerzity, Brno
ve čtvrtek 1. prosince 2011 ve 14:00 hod.
PROF. MARTIN KOTORA
CHARLES UNIVERSITY IN PRAGUE, CZECH REPUBLIC
INSTITUTE OF ORGANIC CHEMISTRY AND BIOCHEMISTRY, CZECH REPUBLIC
Axially Chiral Bipyridine N,N’-Dioxides as Catalysts in Enantioselective
Reactions
N,N´-dioxides with axially chiral bipyridine framework belong to the group of strong Lewis bases
that can activate silane and used in several enantioselective reactions such as allylation, epoxide
ring opening, conjugated addition, etc. giving rise to products with high asymmetric induction.
We have developed a simple and efficient method for preparation of new symmetrically and
unasymmetrically substituted axially chiral bis(tetrahydroisoquinolyl) N,N-dioxides 1 and 2, based
on CpCo(CO)2 catalyzed cyclotrimerization of 1,7,9,15-hexadecatetrayne with appropriate nitriles
under microwave irradiation followed by oxidation (Scheme 1).1,2
.
The prepared chiral bis(tetrahydroisoquinolyl) N,N´-dioxides 1 and 2 were tested as catalysts in
enantioselective allylation of variously substituted aromatic aldehydes, α,β−unsaturated aldehydes,
and dienals with allyltrichlorosilane to provide chiral homoallyl alcohols (Scheme 2). Some of the
prepared homoallyl alcohols were used as intermediates for syntheses of several natural
compounds, e.g. (S)-goniothalamin. Both symmetrically and unsymmetrically substituted chiral
bis(tetrahydroisoquinolyl) N,N´-dioxides exhibited high catalytic activity as well as high
asymmetric induction (up to 99%).1,3
The course of the reaction and asymmetric induction strongly
depends on the solvent used and could be related to different reaction mechanisms in each group of
solvents.3c,4
The prepared catalysts have also been preliminarily tested for epoxide ring opening
with SiCl4.5
Scheme 1
N
N
R
R
N
N
O
O
O
CpCo(CO)2
MW
O
N
N
O
O
O
oxid.
21
R CN
Scheme 2
SiCl3
R
OH
R H
O
-78 or -40 °C,
1-6 h
∗
+
Catalyst 1 or 2
(1-5 mol%)
up to 99 % ee
R = aryl
= aryl-CH=CH=
alkyl-CH=CH=
aryl-CH=CH-CH=CH=
alkyl-CH=CH-CH=CH-
References
1. Kadlčíková, A.; Hrdina, R.; Valterová, I.; Kotora, M. Adv. Synth. Catal. 2009, 35, 1279.
2. Kadlčíková, A.; Kotora, M. Molecules 2009, 14, 2918.
3. (a) Hrdina, R.; Dračínský, M.; Valterová, I.; Hodačová, J.; Císařová, I.; Kotora, M. Adv. Synth. Catal. 2008, 350,
1449. (b) Vlašaná, K.; Hrdina, R.; Valterová, I.; Kotora, M. Eur. J. Org. Chem. 2010, 7040. (c) Kadlčíková, A.;
Kotora, M.; Valterová, I.; Ducháčková, L.; Roithová J. Chem. Eur. J. 2010, 16, 9442.
4. Hrdina, R.; Opekar, F.; Roithová, J.; Kotora, M. Chem. Commun. 2009, 2314.
5. Kadlčíková, A.; Vlašaná, K.; Kotora, M. Collect. Czech. Chem Comm. 2011,76, 415.