ICHAC-XI, International Conference on Heteroatom Chemistry
Caen (France), 14-19 June 2015
FACILE SYNTHESIS OF
CYCLIC SILANOL STEREOISOMERS
Number
(to be
inserted by
us)
Hisayuki Endo, Nobuhiro Takeda, and Masafumi Unno*
Department of Chemistry and Chemical Biology, Faculty of Science and Technology,
Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, JAPAN
[email protected], http://element.chem-bio.st.gunma-u.ac.jp/index-e.html
Cyclic silanols, or cyclooligosiloxanes with plural hydroxyl groups, have been known for more
than five decades, and recently their applications as precursors to well-defined silsesquioxanes,
e.g. cage silsesquioxanes,1 laddersiloxanes,2 and supramolecular aggregates3 have been shown.
Amaong four stereoisomers possible for the cyclic silnaols (Scheme 1), all-cis isomer was
exclusively obtained by the hydrolytic condensation starting from substituted trichlorosilanes or
trialcoxysilanes.
R
R
R
OH
OH
R
R
R
R
R
OH
R
HO
O
HO
Si
O
O
O Si
Si
Si
O
Si
Si
O Si
O
O Si
Si O Si O
Si O Si O
Si O Si O OH
Si O Si O OH
R
R
HO
HO
HO
R
HO
OH
HO HO
R
OH
R
OH
R
R
all-cis
cis-trans-cis
cis-cis-trans
all-trans
Scheme 1. Stereoisomers of cyclic silanols
In 2005, we reported the first synthesis of all four isomers by utlizing stereospecific
transformation from cyclic siloxanes.4 Following our report, Kawakami’s group published the
isomerization reaction of phenyl-substituted cyclic silanols. In this presentation, we will report
the isomerization of isobutyl-substituted all-cis cyclic silanols to obtain other stereoisomers
(Scheme 2). Plausible reaction mechanism and applications of cyclic silanols are also described.
R
R
R
R
R
R
Stereoisomerization
R
O Si O Si
O Si O Si
Si O Si O
OH
Si O Si O
OH
HO HO
OH
HO
all-cis
HO
OH
all-cis
R
HO
R
R
R
OH
OH
OH
OH
R
R O Si O Si
R O Si O Si
R O Si O Si
Si O Si O
Si O Si O
Si O Si O
OH
R
R
R
HO
HO
HO HO
HO
R
R
OH
cis-trans-cis
cis-cis-trans
all-trans
Scheme 2. Stereoisomerization reaction
References
1
Unno, M.; Suto, A.; Takada, K.; Matsumoto, H. Bull. Chem. Soc. Jpn., 2000, 73, 215.
Unno, M.; Suto, A.; Matsumoto, T. Russ. Chem. Rev., 2013, 82, 289.
3
Unno, M.; Takada, K.; Matsumoto, H. Chem. Lett., 2000, 29, 242.
4
Unno, M.; Kawaguchi, Y.; Kishimoto, Y.; Matsumoto, H. J. Am. Chem. Soc., 2005, 127, 2256.
5
Ito, R.; Kakihana, Y.; Kawakami, Y. Chem. Lett., 2009, 38, 364.
2