A facile and efficient synthesis of organocyclosiloxanes

Article abstract of DOI:10.1080/10426500307895

A new facile preparative method for the synthesis of organocyclosiloxanes is reported. Ring closure of the dichlorosilanes with NaHCO₃ and pyridine gave mixture of organocyclosiloxanes with cyclotrisiloxane as a main product.

Full text of DOI:10.1080/10426500307895

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Phosphorus, Sulfur, and Silicon and the Related
Elements
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A Facile and Efficient Synthesis of
Organocyclosiloxanes
Vjacheslav V. Zuev a b & Alexei V. Kalinin a
a Institute of Macromolecular Compounds , Russian Academy of Sciences , Bolshoi, Sankt
Petersburg, Russia
b Sankt Petersburg State Technological Institute , Technical University , Moskovskii, Sankt
Petersburg, Russia
Published online: 27 Oct 2010.
To cite this article: Vjacheslav V. Zuev & Alexei V. Kalinin (2003) A Facile and Efficient Synthesis of Organocyclosiloxanes,
Phosphorus, Sulfur, and Silicon and the Related Elements, 178:6, 1289-1294, DOI: 10.1080/10426500307895
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Phosphorus, Sulfur, and Silicon, 178:1289–1294, 2003
C
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print
DOI: 10.1080/10426500390200585
A FACILE AND EFFICIENT SYNTHESIS
OF ORGANOCYCLOSILOXANES
Vjacheslav V. Zueva,b and Alexei V. Kalinina
Institute of Macromolecular Compounds, Russian Academy
of Sciences, Bolshoi, Sankt Petersburg, Russia;a and Sankt
Petersburg State Technological Institute (Technical University),
Moskovskii, Sankt Petersburg, Russiab
(Received September 28, 2002; accepted November 23, 2002)
A new facile preparative method for the synthesis of organocyclosilox-
anes is reported. Ring closure of the dichlorosilanes with NaHCO3 and
pyridine gave mixture of organocyclosiloxanes with cyclotrisiloxane as
a main product.
Keywords: Cyclization; cyclosiloxaness; dichlorosilanes; organosilicon
compounds
Organocyclosiloxanes have attracted considerable attention because
of their utility as monomers in synthesis of polysiloxanes.1 Polysilox-
anes are commercially the most important type of inorganic/organic
polymeric materials. Living anionic ring-opening polymerization of cy-
clotrisiloxanes has been used to prepare narrow molecular weight dis-
tribution polysiloxanes. Regio specific anionic ring-opening polymer-
ization of monosubstituted cyclotrisiloxanes has been used to prepare
highly regular polysiloxanes. Polydisperse high molecular weight linear
polysiloxanes often are prepared by acid-catalyzed ring-opening poly-
merization of cyclotetrasiloxanes.
In principle, organocyclosiloxanes can be prepared by any reaction
in which silicon-oxygen bonds are formed.2 Among reactions of sil-
icon functional derivatives with substances which can provide oxy-
gen to form Si O Si bonds, the most important for the synthesis of
organocyclosiloxanes is the hydrolysis of difunctional derivatives of sil-
icon (organodichlorosilanes, organoalkoxysilanes, etc). In most cases
Address correspondence to Vjacheslav V. Zuev, Institute of Macromolecular
Compounds, Russian Academy of Sciences, Bolshoi pr. 31,199004, Sankt Petersburg,
Russian Federation. E-mail: zuev@hq.macro.ru
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V. V. Zuev and A. V. Kalinin
organocyclosiloxanes are formed together with linear siloxanols, in vari-
able proportions, depending the conditions of the hydrolysis. A disad-
vantage of this reaction is that in this process the cyclotrisiloxanes
(most important monomers for polymerization) are formed only in very
low yields (up to 1%) because of their high-strength structure.3 Recently
a new synthetic methods was proposed for the synthesis of cyclotrisilox-
anes starting from dichlorosilanes by using dimethylsulfoxide4 or gal-
lium triiodide5 with yields of cyclotrisiloxanes up to 50% (all cyclosilox-
anes in yields up to 80%).
An initial requirement for this research was to develop a simple,
clean, and efficient synthesis of a variety of organocyclosiloxanes de-
rived from dichlorosilanes by using cheap reagents. It is known from
the patent literature that metal salts can be used as oxygen sources in
the synthesis of cyclosiloxanes. For example, Me2SiCl2 and Na2CO3 in
column at 300–400 C from a mixture of cyclosiloxanes in 98% yield.6 In
almost the same conditions, diethyldichlorosilane with NaHCO3 pro-
duces a trimeric cyclosiloxane (Et2SiO)3 in low yield.7 In a Russian
patent,8 NaHCO3 or KHCO3 was used in similar conditions for synthe-
sis various cyclosiloxanes starting from dichlorosilanes. High temper-
ature conditions may lead to the degradation of starting materials and
products having sensitive substituents.
RESULTS AND DISCUSSION
We report in this article an experimentally simple new approach to the
synthesis of organocyclosiloxanes starting from dichlorosilanes using
NaHCO3 as source of oxygen and pyridine as acceptor of HCl. The re-
action was carried out in solution at room temperature with equimolar
quantities of pyridine, dichlorosilane, and sodium bicarbonate and gave
a mixture of organocyclosiloxanes with 95–99% yields. Diethyl ether,
acetone, hexane, benzene, toluene, ethyl acetate, among others, may be
used as solvents. One requirement, but not a stringent one, is that this
solvent should be good both for starting dichlorosilane and for result-
ing cyclosiloxanes. However, it also is possible to carry out this reaction
without any solvent.
where n = 3,4,5,6

A Facile and Eficient Synthesis of Organocyclosiloxanes
1291
The yields and contents of different rings in the synthesis of
organocyclosiloxanes are described in Table I. The spectral and ana-
lytical data on of organocyclosiloxanes synthesized for the first time
are given in Table II. Yields of cyclotrisiloxanes ranged from 33 to 67%.
To the best our knowledge, this is the highest yield in one-pot synthesis
of cyclotrisiloxanes from dichlorosilanes.
In conclusion, the procedure reported here represents a new syn-
thetic approach to the organocyclosiloxanes. The easy availability of the
starting materials, the simplicity of this short and clean procedure, and
the good yields of products render this process particularly attractive.
EXPERIMENTAL
All starting materials were obtained from Reachim (USSR or Russia)
and distilled or recrystallized prior to use. The solvents used for reac-
tions are dried by standard methods. Dichloro- -naphthylmethylsilane
was synthesized by the reaction of a Grignard reagent prepared
from -bromonaphtalene with methyltrichlorosilane.9 Dichloromethyl-
6,60,7,70,8,80,9,90-octafluoro-4-oxa-nonylsilane was synthesized from
methyldichlorosilane and allyl ether of 2,20,3,30,4,40,5,54-octafluoropen-
tanol by published hydrosilylation reactions.10
Melting points were measured on a Boetius apparatus (DDR). IR
1
spectra were recorded on a Bruker IFS-88 spectrometer. H,13C, and
29Si NMR spectra were taken on a Bruker DPX-300 instrument.
Dimethylcyclosiloxanes
To 8.4 g (0.1 mmol) of water free NaHCO3 and 7.9 g (0.1 mmol) dry
pyridine in 80 ml ethyl acetate 12.9 g (0.1 mmol) dimethyldichlorosi-
lane in 50 ml ethyl acetate was added dropwise throughout 1 h. After
stirring for 3 h at room temperature, the solution was filtered and the
residue was washed with 30 ml ethyl acetate. The solvent was evapo-
rated. The distillation of residue 7.9 g (99% yield) gave 4.38 g (60%) of
hexamethylcyclotrisiloxane, 1.46 g (20%) of octamethylcyclotetrasilox-
ane, 1.10 g (15%) of decamethylcyclopentasiloxane, and 0.36 g (5%) of
a mixture of cyclohexacyclooctasiloxanes.
Phenylmethylcyclosiloxanes
To 8.4 g (0.1 mmol) of water free NaHCO3, and 7.9 g (0.1 mmol) dry
pyridine in 80 ml acetone, 19.1 g (0.1 mmol) methylphenyldichlorosilane
in 30 ml acetone was added dropwise throughout 1 h. After stirring

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V. V. Zuev and A. V. Kalinin
for 3 h at room temperature, the solution was filtered and the residue
was washed with 30 ml acetone. The solvent was evaporated. The dis-
tillation of residue 13.4 g (98.5% yield) in vacuo gave 4.26 g (33%) of
trimethyltriphenylcyclotrisiloxane and 8.45 g (65.5%) of tetramethyl-
tetraphenylcyclotetrasiloxane.
Diphenylcyclosiloxanes
To 30.5 g (0.363 mmol) of water free NaHCO3, and 28.5 g (o.363 mmol)
dry pyridine in 250 ml toluene 91.8 g (0.363 mmol) diphenyldichlorosi-
lane in 90 ml toluene was added dropwise throughout 1 h. After stirring
for 3 h at room temperature, the solution was filtered and the residue
was washed with 200 ml benzene for complete disolution of silicon-
organic derivatives. The combined benzene and toluene solution was
washed with water (2 450 ml). The organic layer was separated and,
after adding of 200 ml of ethanol, was evaporated. Crystalline residue
was recrystallized from ethyl acetate to give 48 g (67.2%) of hexaphenyl-
cyclotrisiloxane and 21.8 g (30.3%) of octaphenyltetracyclosiloxane.
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