4th EucheMs chemistry congress

wednesday, 29-Aug 2012
s769
chem. Listy 106, s587–s1425 (2012)
organic Chemistry, Polymers – i
General synthetic methods – iii
o - 3 6 3
Convenient SiLyLAtion of PhenoLS By uSinG
ChLoroSiLAneS in Br/MG-exChAnGe reACtion
G. StrLe 1 , J. CerKovniK 1
1 University of Ljubljana, Faculty of Chemistry and Chemical
Technology, Ljubljana, Slovenia
Preparation of aryl Grignards bearing unprotected OH group
in halogen-magnesium exchange reaction represent a synthetic
chalenge. [1, 2] Some literature data for preparation of
trialkylsilyl-substituted phenols by other synthetic methods are
available, however, there is no reports on direct preparation of
silyl-substituted phenols bearing one or two hydrogen atoms on
silicon atom. Namely, such compounds are usually unstable under
reaction conditions and readily lose silyl functional group by
forming phenols.
Herein, we wish to report efficient direct silylation of
bromo-substituted phenols in a Br/Mg-exchange reaction by
using various disubstituted chlorosilanes in presence of catalytic
amounts of LiCl. [2] Chlorosilane act at the same time as Lewis
acid activating magnesium for bromine exchange to in situ
generate Grignard reagent, and as an electrophilic reagent. By
applying this method we successfully isolated various
substituted alkylsilyl-, dialkylsilyl-, alkylphenylsilyl- and
diphenylsilylphenols in satisfactory to good yields. This approach
can be also extended to various heterocyclic compounds bearing
a hydroxy group like pyridines and quinolines.
Recently we have found an efficient direct catalytic
transformation of some silyl hydrotrioxides (ROOOH). [3] To
prepare some polymer-bound silylated substrates we were
challenged with the preparation silyl-substituted phenols. In this
contribution attempts to prepare polymer-bound substrates via
silyl-substituted phenols will also be discussed.
references:
1. a) Gottardo, C.; Aguirre, A. Tetrahedron Lett. 2002, 43,
7091.
b) Kopp, F.; Krasovskiy, A.; Knochel, P. Chem. Commun.
2004, 2288.
2. Piller, F. M.; Metzger, A.; Schade, M. A.; Haag, B. A.;
Gavryushin, A.; Knochel, P. Chem. –Eur. J. 2009, 15,
7192.
3. Bergant, A.; Cerkovnik, J.; Plesnicar, B.; Tuttle, T. J. Am.
Chem. Soc. 2008, 130, 14086.
Keywords: Grignard reaction; Silanes; Electrophilic
substitution; Synthesis design; Polymers;
General synthetic methods – iV
4 th EucheMs chemistry congress
o - 3 6 4
C-h ACtivAtion reACtionS At SP2- And
SP3-CArBon CenterS
t. BACh 1
1 Technische Universität München, Lehrstuhl für Organische
Chemie I, Garching, Germany
C-H activation reactions at sp2-carbon centers allow for the
direct, regioselective introduction of substituents into arenes and
hetarenes. Particular focus of our work in this area is the installation
of alkyl groups into biologically relevant heterocycles. [1]
In the area of C-H activation at sp3-carbon centers we have
studied the diastereoselective amination reaction in the benzylic
position of chiral substrates. [32] One of the ultimate goals in C-H
activation chemistry is the regio- and enantioselective activation
of aliphatic C-H bonds. Towards this goal, we have developed
transition metal catalysts, to which a ligand with a hydrogen
bonding site is attached. [3] Hydrogen bonding allows to perfectly
position the substrate in an enzyme-like approach. Most recent
results will be discussed.
references:
1. L. Jiao, T. Bach, J. Am. Chem. Soc. 2011, 133,
12990–12993.
2. A. Nörder, P. Herrmann, E. Herdtweck, T. Bach, Org. Lett.
2010, 12, 3690–3692.
3. P. Fackler, C. Berthold, F. Voss, T. Bach, J. Am. Chem.
Soc. 2010, 132, 15911–15913.
Keywords: amination; C-H activation; enantioselectivity;
homogenous catalysis; hydrogen bonds;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc