close

Вход

Забыли?

вход по аккаунту

?

Group Transfer Polymerization of Acrylic Acid Esters with Alkylthio- or Arylthiosilanes as Initiators.

код для вставкиСкачать
room temperature has only recently been made possible by
group transfer polymerization."] This industrially promising process is initiated by a Michael addition, e.g., of the
0-silylketene acetal 1 , to methyl methacrylate 2 in the
presence of anionic catalysts. Examples of such catalysts
are (Me2N),S'Me3Sie (TASF) and (Me,N),S'He
(TASHFz). Chain growth is achieved by repeated Michael
additions in which the silyl group is transferred to the end
of the chain. This leads to formation of the living polymer
3 with an 0-silylketene acetal end group, which can be desilylated, e.g. by methanolysis.
5
+
MeHOSiMe3
Procedure
Me
5 : A mixture of 3 (5.1 g, 11.17 mmol) and 2 (2.77 g, 11.17 mmol) was heated
i n 500 mL of boiling THF. This furnished a brown suspension, from which
OMe
I
Received: August 4, 1986;
supplemented: September 19, 1986 [Z 1890 [E]
German version: Angew. Chem. 98 (1986) I 1 15
[ I ] a) K. Wieghardt, W. J. Kiippers, J. Weiss, Inorg. Chem. 24 (1985) 3067. b)
P. W. R Corfield, C . Ceccarelli, M. D. Click, J. W.-Y. Moy, L. A. Ochroymowycz. D. B. Rorabacher, J Am. Chem. Soc. I07 (1985) 2399: c) A.
J. Blake, R. 0. Could, A. J. Lavery, M. Schroder, Angew. Chem. 98 (1986)
282; Angew Chem. In/ Ed. Engl. 25 (1986) 274, and references cited
therein.
121 Cf. also [la, bl and C . Baldoli, P. DelButtero, S. Maiorana, A. Papagni, J .
Chem. Soc. Chem. Commufi. 1985. I181 : P. Singh, G. Arora, Heterocycles
23 (1985) 2815; J. S. Bradshaw, J. Y. K. Hui, J . Hererocycl. Chem. 11
(1974) 649. Special condensation reagents o r ions, e.g. Cs2C0, [3a] or
benzyltrimethylammoniuni ions [3b], can in some cases drastically increase the yield; the separation problems, however, could not be circumvented.
13) a) 1. Buter, R. M. Kellogg, J. Org. Chem. 46 (1981) 4481; b) W. N. Setzer,
C. A. Ogle, G. S. Wilson, R. S. Glass, Inorg. Chem. 22 (1983) 266.
[4] D. Sellmann, L. Zapf, Angew. Chem. 96 (1984) 799; Angew. Chem. f n t .
Ed. Engl. 23 (1984) 807.
[5] D. Sellmann, U. Kleine-Kleffmann, J . Organomet. Chem. 247 (1983)
307.
[6] Cf. also the systematic influence of the PR3 ligands on the alkylation of
[Ru(PR,),dttd] (PR, = PMe,, PPh,; dttd'O = 2,3,8,9-dibenzo-I,4,7,1O-tetrathia-2,8-decadiene(2-)): D. Sellmann, M. Waeber, G. Huttner, L. Zsolnai, Inorg. Chim. Arta I18 ( I 986) 49.
Group Transfer Polymerization of
Acrylic Acid Esters with Alkylthio- or Arylthiosilanes
as Initiators
C02Me
>
2
the solvent was completely removed. The reddish-brown residue was extracted with 2 x 50 m L EtzO, taken up in 300 mL of THF, treated with 8 mL
of conc. HCI, and heated to boiling for ca. 2 h until a yellow solution was
obtained. Removal of the solvent furnished a yellow powder, which was
washed with 2 x 25 mL of E t 2 0 and then dissolved in 200 mL of CH2C12.
Extraction of the CH2C12 solution with 2 x 50 mL of H 2 0 , drying over
NaSO,, evaporation to a fifth of the original volume, and cooling, afforded
a yellow solid. Recrystallization from 50 m L of CH2C12 at 30°C- -30°C
yielded 2.85 g ( 5 5 % ) of analytically pure 5 in the form of colorless crystals;
m.p. 161°C: 'H-NMR (270 MHz, CD2CIZ):6(C6H,)=7.3 (m, 4), 7.2 (m, 4);
6(CH2)=3.1 (m, 8), 2.7 (m, 8); MS (FD): m / z 456 (Ma).
On using half the quantities of substrates mentioned above, yields of up to
75% could be obtained; the one-pot process with the educts FeC12.4H20,
ChH4(SH)2.LiOH, C O and 2 afforded 5 in 45% yield.
TASHFZ
+Me
:3
CH30H
>
3
+ MeOSiMe;,
MezC+CHz-F+H
I
COZMe
C02Me n
In the case of acrylic acid esters, polymers with narrow
molecular weight distribution are obtained only with electrophilic catalysts such as ZnIz (at room temperature) or
diisobutylaluminum chloride (at - 78 'C).[*] However, the
Zn1,-catalyzed polymerization of ethyl acrylate fails to
provide a living polymer."
We report here on the first use of alkylthio- and arylthiosilanes 4 as initiators for the group transfer polymerization of acrylic acid esters 5.14'I n order to perform the
polymerization, a mixture of initiator and catalyst in the
proper solvent is treated with the monomer, the reaction
temperature being kept constant by a thermostat. After
quantitative conversion, the polymers 6 are desilylated by
methanolysis. In the case of initiation with 4 b and 4d, the
trimethylsilyl protective group at the front of the chain is
cleaved with CH,OH/HCI.
H
R'SSiMe,
+
n
4
+
6
By Manfred T. Reetz,* Ralph Ostarek,
Karl-Erwin Piejko, Dieter Arlt, and Bruno Bomer
The polymerization of methacrylic acid esters to living
polymers with narrow molecular weight distribution at
[*] Prof. Dr. M. T. Reetz, Dr. R. Ostarek
Fachbereich f h e m i e der Universitat
Hans-Meerwein-Strasse, D-3550 Marburg (FRG)
Dr. K.-E. Piejko, Prof. Dr. D. Arlt, Dr. B. Bomer
Dayer AG, 5090 Leverkusen, Bayerwerk (FRG)
1108
0 VCH Verlaqrge.yell.ychaJrmbH. 0-6940 Weinherm, 1986
The results listed in Table 1 show that the anionic catalyst TASHFz leads to polymers with relatively broad molecular weight distributions (No. I, 2). In contrast, use of
electrophilic catalysts affords polymers with narrow molecular weight distributions"] (No. 3-8). The somewhat
high molecular weights of the polymers prepared with 4c
0570-#833/86/1212-/108 $ 02.50/0
Angew Chem. In!. Ed. Engl 25 (19861 No. 12
Table I Group transfer polymerization o f acrylates 5 with alkylthio- or arylthiosilanes 4 as initiators. TASHF' =(Me-.N)?SOHF?, THF=tetrahydrofurdn.
R'
No.
1
2
3
4
5
6
7
4a
4b
4c
4b
4d
4b
4b
4b
8
R'
Initiator
(mmol)
Me
CH2C'H20SiMel
Ph
CH2CH20SiMe,
CH?C02SiMe,
CHZCHzOSiMe*
CHrCHzOSiMe3
CH2CH20SiMe3
(5.3)
(3.0)
(2.0)
(1.9)
(2.1)
5b
5b
5b
5b
5b
(0.73)
5a
(153)
(0.76)
5b
5b
nBu
nBu
nBu
nBu
nBu
Me
nBu
nBu
Monomer [a]
(mmol)
(40)
(30)
(34)
(36)
(36)
(55)
(14800)
(36)
Catalyst (mmol)
(0.1)
(0.2)
(0.4)
(3.6)
(0.2)
(0.2)
TASHFl
TASHFl
Zn12
(;BU)~AICI
Znll
Zn12
Zn12
Znl-.
(157)
(0.2)
Solvent
[a1
CH3CN
THF
toluene
CH2CI2
toluene
toluene
toluene
toluene
t
[h]
1
1
3
2
3
6
24
4
T
["C]
M,(calc) [b]
[kg.mol-']
M,,(obs) [c]
hkg-mol-'j
22
22
I .0
1.4
2.4
2.5
2.3
I .5
I I
13 [el
12
3.0 iq
6.9
14.2
8.6
0
-78
0
0
6.6
0
12.5
22
6.1
D
[d]
I .44
2.0
1.16 [el
1.14
-
[o
1.15
1.08
1.10
[aJ Concentration of the monomer = 3 rnol L - '. [b] Calculated from monomer/initiator ratio. (cl Determined by gel permeation chromatography with universal
calibration. [d] For the definition of polydispersity D see [S]. [el Sample contained oligomers which were not taken into account in the calculation ofahe molecular
weight dihtribution. [fl M,, from the sulfur content of the polymer, D not determined.
as initiator and diisobutylaluminum chloride as catalyst relative to the expected value (M,(calc)) can be attributed to
an incomplete initiation under the given conditions (No. 3
and 4, respectively). In combination with ZnI, as catalyst,
however, the alkylthiosilanes 4a, 4b, and 4d afford polyacrylates having molecular weights which correspond to the
monomer/initiator ratio in the sense of a stoichiometric
polymerization; the molecular weight distribution is also
narrow ( N o . 5-7).
In the polymerization of 5b with 4b in the presence of
ZnIz (22"C), further monomer was added at room temperature three hours after termination of polymerization. This
led to a continuation of the polymerization with quantitative formation of a polymer having a molecular weight distribution which is only slightly broadened ( D = 1.25).
The polymers prepared with the functional initiators 4b
and 4d have, after cleavage of the trimethylsilyl group, a
hydroxy- and carboxy end group, respectively, which can
be used for further reactions such as coupling reactions
with other functionalized polymers.
CH2SSiMe3
I
2 n 5b
d
'
CH2S+CH2
7
8 L
-
r
OSiMe,
C H 2 a 0
coZnau J n - 1
Bu
H
The ethylenedi(thiosi1ane) 7 as initiator leads to a polymer 8 with two silylketene acetal end groups and narrow
molecular weight distribution ( D = 1.07; determined on the
desilylated product; reaction with ZnI, as catalyst at 22°C
in toluene). In the case of the polymerization of the acrylate 5 (Rz=2-ethylhexyl) with 7, anionic catalysts were
also tested. TASHFz furnished only poor results, whereas
nBuaNF (THF/room temperature) afforded uniform polymers (e.g., D = 1.07; M,=2.21 kg mol-'; M,(calc)= 1.95
kg mol - I).
In summary, alkylthiosilanes are excellent initiators for
the polymerization of acrylates. In combination with ZnIz
as catalyst, living polymers with narrow molecular weight
distribution are obtained. The ready accessibility of functionalized initiators1"' enables the simple preparation of
well defined functionalized polyacrylates which are suitable for the synthesis of block and graft polymers.
Received. August 1 I , 1986,
revised: October I , 1986 [ Z 1898 I € ]
German version' Angew. Chem 98 (1986) I I16
Angew Chein. Ini. Ed. Engl. 2 s (19861 N u . I2
[ I ] 0 . W. Webster, W. R. Hertler, D. Y. Sogah, W. B. Farnham, T. V. RajanBabu, J . Am. Chem. Soc. 105 (1983) 5706; 0. W. Webster, W. B. Farnham,
D. Y. Sogah, Eur. Pat.-Anm. 0068887 (1983), Du Pont.
[2] W. R. HertIer, D. Y. Sogah, 0. W. Webster, B. M. Trost, Macromolecule.\
17(1984) 1417.
131 The authors 121 report that renewed addition of acrylate after termination
of polymerization does not lead to a continuation of polymerization.
[4] M. T. Reetz, R. Ostarek, E. E. Piejko, DOS 3 504 168 (1986). Bayer AC.
[ S ] The molecular weight distribution can be characterized by the polydispersity D ; D=M,/M, (ratio of the weight average molecular weight to
the number average molecular weight). With D values of < 1.2 one speaks
of narrow molecular weight distributions.
[6] See, e.g., W. P. Weber: Silicon Reagentsfor Organic Synrherrs. Springer,
Berlin 1983, Chapter 21.
Enantioselective Synthesis of a-Substituted
Primary Amines by Nucleophilic Addition to
Aldehyde-SAMP Hydrazones**
By Dieter Enders,* Heinrich Schubert. and
Christoph Nubling
The SAMPIRAMP hydrazone method enables highly
diastereoselective and enantioselective C C couplings at the
a-position to the carbonyl group of ketones and aldehydes."] We recently reported on the extension of this
method to the enantioselective synthesis of [I-substituted
primary amines I by a-alkylating, reductive amination of
aldehydes (reaction A),"' and on the reductive amination
of unsymmetrical ketones to a-substituted primary amines
I1 (Reaction B)."' We have now succeeded in opening u p a
very flexible entry to the amines I1 via a C C coupling reaction (Reaction C). The new method is based on a nucleophilic addition to SAMP (or the enantiomeric RAMP)
hydrazones of aldehydes (Scheme 1).
The aldehydes 1 , after conversion into the SAMP hydrazones ( S ) - 2 ,are treated with organolithium compounds in
ether or tetrahydrofuran (TH F) at - 78 "C. The reductive
N-N cleavage of the hydrazines ( S R ) - 3 or ( S S ) - 3 , formed
by selective diastereofacial addition at the C N double
bond, with Raney nickel affords the a-substituted primary
amines (R)-or (S)-4 together with ( ( S ) - 5 )in total yields of
[*I
Prof. Dr. D. Enders, Dr. H. Schubert [+I, DipLChem C. Nubling
lnstitut fur Organische Chemie der Technischen Hochschule
Professor-Pirlet-Strasse I , D-5 100 Aachen (FRG)
['I
Present address: Henkel KG, Henkel-Strasse 67, D-4000 thsseldorf
(FRC).
This work was supported by the Fonds der Chemischen Industrie, by the
Minister fur Wissenschaft und Forschung des Landes Nordrhein-Westfalen, and by BASF AG, Degussa AG, and Bayer AG. C. N . thanks the
Stiftung Volkswagenwerk for a Kekule Fellowship. We thank Prof. W .
A. Kdnrg. Hamburg, for valuable help with the G C ee-determination.
[**I
0 VCH Verlagsgesellrcha~mbH. 0-6940 Weinheim. 1986
OS70-0833/86/12I2-1109 $ 02.50/0
1 I09
Документ
Категория
Без категории
Просмотров
0
Размер файла
230 Кб
Теги
acid, acrylic, initiator, group, esters, transfer, alkylthio, polymerization, arylthiosilanes
1/--страниц
Пожаловаться на содержимое документа