Reactions of hexaorganyldigermoxanes with O-trimethylsilyl carbamates

Article abstract of DOI:10.1023/A:1011302004605

Hexa-n-butyl-and hexaisopentyldigermoxanes but not hexaphenyldigermoxane react with O-trimethylsilyl N,N-diethylcarbamate and trimethylsilyl piperidinocarboxylate to give O-triorganylgermyl carbamates.

Full text of DOI:10.1023/A:1011302004605

Russian Chemical Bulletin, International Edition, Vol. 50, No. 4, pp. 743—744, April, 2001
743
Reactions of hexaorganyldigermoxanes with
O-trimethylsilyl carbamates
N. A. Ryzhkova« and N. V. Komarov
Kuban´ State University,
149 ul. Stavropol´skaya, 350040 Krasnodar, Russian Federation.
Fax: +7 (861 2) 69 9502. E-mail: silan@chem.kubsu.ru
Hexa-n-butyl- and hexaisopentyldigermoxanes but not hexaphenyldigermoxane react with
O-trimethylsilyl N,N-diethylcarbamate and trimethylsilyl piperidinocarboxylate to give
O-triorganylgermyl carbamates.
Key words: hexaalkyldigermoxanes, O-trimethylsilyl N,N-dialkylcarbamates, N,N-di-
alkylcarbamoyloxy(trialkyl)germanes, N,N-diethylcarbamoyloxy(triphenyl)germane.
Earlier,1 we discovered that Î-trialkylsilyl carbam-
Table 1. Physicochemical constants of carbamates 3a—c
ates react with organotin oxides and organyldistannoxanes
to give Î-di(tri)organylstannyl carbamates.
20
Com-
pound
B.p.
/°C
(p/Torr)
nD
Found
Calculated
1H NMR,
(%)
N
δ*
Taking into account the availability and high reac-
tivities of Î-trimethylsilyl carbamates (1), it was of
interest to study their reactions with hexaorganyl-
digermoxanes (2) as a new possible alternative2 method
for the synthesis of Î-triorganylgermyl carbamates (3).
Although organogermanium oxides and organyldi-
germoxanes are less basic and therefore much less reac-
tive than their organotin analogs, they react with some
compounds, involving the Ge—O bond.3
Ñ
H
3a
3b
3c
158—160
(3)
171—172
(7)
1.4533
1.4564
1.4581
61.24 10.58 3.11
60.93 10.40 3.38
59.05 10.41 3.18
59.76 10.71 3.49
2.52
(t)
2.62
(q)
2.63
(q)
120
(1)
56.92
9.95 3.80
56.73 10.29 3.89
* Chemical shifts of the signals from the Hx atoms in the
1H NMR spectra of R3GeOC(O)N(CHx2R´)2.
Results and Discussion
Carbamates 3 are viscous liquids with slight odor.
Our study showed that heating of hexaisopentyl- and
hexa-n-butyldigermoxanes (2a,b) at 150—160 °Ñ with
equimolar amounts of trimethylsilyl piperidinocarboxylate
(1a) or Î-trimethylsilyl N,N-diethylcarbamate (1b) af-
fords carbamates 3 in up to 60% yield (Scheme 1).
Their IR spectra show an intense absorption band at
–1
–1
1660 cm
(Ñ=Î) and a broad band at 860 cm
(Ge—O). The 1H NMR spectra contain signals at
δ 2.5—2.6 for the equivalent protons of the N-linked
methylene groups. The spectral pattern in the δ range
from 0.3 to 1.5 ppm is complicated because multiplets
from various groups overlap.
Scheme 1
It was established that digermoxanes 2 react with
carbamates 1 five to six times more slowly than
distannoxanes,2 the yield of target products 3 being
reduced to 50—60% (the yields of Î-trialkylstannyl
carbamates were 70—80%).
When aliphatic radicals in digermoxane 2 are re-
placed by aromatic ones, no arylgermyl carbamates 3 are
formed. Thus, after heating of carbamate 1 with an
equimolar amount of hexaphenyldigermoxane (4) in tolu-
ene and without solvent for 1—5 h only the start-
ing compounds were recovered. This can be due
to steric hindrances and lesser basicity and nu-
cleophilicity of digermoxane 4 compared to di-
germoxanes 2.
O
2 Me3SiOCNR´2
+
R3GeOGeR3
1a,b
2a,b
O
2 R3GeOCNR´2
3a—c
+
Me3SiOSiMe3
R = Me2CHCH2CH2 (2a, 3a, 3b), Bu (2b, 3c);
NR´2 = N(CH2)5 (1a, 3a), NEt2 (1b, 3b, 3c)
Carbamates 3 were identified by IR spectroscopy;
their physicochemical constants were also compared
with those of compounds obtained by an independent
method, namely, by carboxylation of trialkylgermyl ha-
lides in the presence of secondary amines2 (Table 1).
Î-Triphenylgermyl N,N-diethylcarbamate (5) was
obtained in 60% yield according to Scheme 2.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 713—714, April, 2001.
1066-5285/01/5004-743 $25.00 © 2001 Plenum Publishing Corporation

744
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 4, April, 2001
Ryzhkova and Komarov
Scheme 2
Triisopentylgermyl piperidinocarboxylate (3a) was obtained
by heating a mixture of hexaisopentyldigermoxane (3.3 g,
0.0056 mol) and carbamate 1a (2.3 g, 0.0112 mol) at 150—160 °C
for 4 h. Vacuum distillation gave compound 3a (3.2 g, 59%),
Ph3GeCl
+
CO2
+
2 Et2NH
O
20
b.p. 149—150 °Ñ (2 Torr), nD 1.4522. IR, ν/cm–1: 1660
(C=O); 860 (Ge—O).
Î-Tri-n-butylgermyl N,N-diethylcarbamate (3c) was ob-
tained analogously from hexa-n-butyldigermoxane (1.6 g,
0.003 mol) and carbamate 1b (1.2 g, 0.006 mol). The yield of 3c
Ph3GeOCNEt2
+ Et2NH•HCl
5
20
was 1.06 g (49%), b.p. 120 °Ñ (1 Torr), nD 1.4576. IR,
ν/cm–1: 1660 (Ñ=Î); 855 (Ge—O).
Experimental
Î-Triphenylgermyl N,N-diethylcarbamate (5). A stirred so-
lution of chlorotriphenylgermane (8.83 g, 0.026 mol) and di-
ethylamine (7.3 g, 0.1 mol) in 50 mL of THF was saturated with
dry carbon dioxide at 20—25 °Ñ. The precipitate that formed
was filtered off, the filtrate was concentrated, and the residue
was recrystallized from pentane to give compound 5 (6.4 g,
59%) as needle-like crystals, m.p. 164 °Ñ. Found (%): C, 66.81;
H, 6.12; N, 2.84. C23H25GeNO2. Calculated (%): C, 65.78;
H, 5.96; N, 3.34. IR, ν/cm–1: 1650 (C=O); 855 (Ge—O).
Reactions of carbamates 1a,b with hexaphenyldigermoxane
The solvents and the starting reagents were thoroughly dried
and purified by distillation before use.
The starting hexaorganyldigermoxanes 2 were prepared by
alkaline hydrolysis of triorganylgermanium halides.4 The physi-
cochemical constants of the compounds obtained corresponded
to the literature data.5
Î-Trimethylsilyl carbamates 1 were synthesized by carboxy-
lation of chlorotrimethylsilane in the presence of the corre-
sponding secondary amines in anhydrous benzene.6
(4). A.
A mixture of hexaphenyldigermoxane (4) (2.8 g,
4.5 mmol) and carbamate 1b (1.7 g, 9 mmol) in 10 mL of
toluene was kept in an oil bath at 150—160 °Ñ for 4 h.
Cooling the reaction mixture gave compound 4 (2.6 g, 93%)
as a crystalline precipitate, m.p. 183 °Ñ. (cf. Ref. 5: m.p.
183—184 °Ñ).
IR spectra were recorded on a LOMO IKS-29 spectrometer
–1
(4200—400 cm–1) with an accuracy of ±5 cm
.
1H NMR spectra were recorded on a Tesla BS 587a instru-
ment (80 MHz) in CDCl3 with HMDS as the internal standard.
Î-Trimethylsilyl N,N-diethylcarbamate (1b). Carbon diox-
ide was bubbled for 0.5 h through a solution of diethylamine
(58.5 g, 0.8 mol) in 100 mL of anhydrous benzene with vigorous
stirring and cooling with ice water, and then chlorotri-
methylsilane (43.4 g, 0.4 mol) was added in small portions. The
precipitate that formed was filtered off and washed with ben-
zene. The filtrates were combined and concentrated in vacuo,
B.
A mixture of hexaphenyldigermoxane (4) (2.37 g,
3.8 mmol) and carbamate 1a (3.05 g, 15.2 mmol) in 10 mL of
toluene was kept in an oil bath at 150—160 °Ñ for 5 h.
Compounds 4 (2.18 g, 92%, m.p. 183 °Ñ) and 1a (2.89 g, 95%,
20
b.p. 64—65 °C (2 Torr), nD 1.4425) were recovered.
and the residue was fractionated in vacuo to give compound 1b
References
20
(52.8 g, 70%), b.p. 44—45 °Ñ (3 Torr), nD
1.4203. IR,
ν/cm–1: 1697 (C=O); 1068 (Si—O—C). Cf. Ref. 6: b.p. 36 °Ñ
1. N. A. Boldyreva, N. V. Komarov, and A. A. Andreev,
Zh. Obshch. Khim., 1988, 45, 1932 [J. Gen. Chem. USSR,
1988, 45 (Engl. Transl.)].
2. N. V. Komarov and N. A. Ryzhkova, Tezisy dokladov
Vserossiiskoi konferentsii po metalloorganicheskoi khimii [Abstrs.,
All-Russia Conf. on Organometallic Chemistry], Nizhnii
Novgorod, 1995, 1, p. 32 (in Russian).
3. R. Ingam, S. Rosenberg, H. Gilman, and F. Rijkens, Chem.
Rev., 60, 459; Organogermanium Compounds. A Survey of the
Literature from January 1950 to July 1960, Inst. of Organic
Chemistry.
4. K. A. Kocheshkov, N. N. Zemlyanskii, N. I. Sheverdina, and
E. M. Panov, Metody elementoorganicheskoi khimii. Germanii,
olovo, svinets [Methods of Organoelement Chemistry. Germa-
nium, Tin, and Lead], Nauka, Moscow, 1968, 704 pp. (in
Russian).
5. V. F. Mironov and T. K. Gar, Organicheskie soedineniya
germaniya [Organogermanium Compounds], Nauka, Moscow,
1967, 301 pp. (in Russian).
6. D. Knausz, A. Meszticzky, L. Szakacs, B. Csakvari, and
K. Ujszaszy, J. Organomet. Chem., 1983, 256, 11.
7. Y. Yamamoto and D. S. Tarbell, J. Org. Chem., 1971,
36, 2954.
20
(1.5 Torr), nD 1.4202.
Trimethylsilyl piperidinocarboxylate (1a) was prepared analo-
gously from chlorotrimethylsilane (27.2 g, 0.25 mol) and piperi-
dine (42.5 g, 0.5 mol). The yield of 1a was 46.8 g (66%),
b.p. 95 °Ñ (8 Torr), nD20 1.4493. Found (%): C, 53.14; H, 9.02;
N, 6.86; Si, 13.63. C9H19NO2Si. Calculated (%): C, 53.71;
H, 9.45; N, 6.96; Si, 13.96. IR, ν/cm–1: 1690 (C=O); 1080
(Si—O—C). Cf. Ref. 7: b.p. 64—65 °Ñ (2 Torr); IR (CCl4),
ν/cm–1: 1675 (C=O).
Î-Triisopentylgermyl N,N-diethylcarbamate (3b). A. Dried
carbon dioxide was passed through a solution of diethylamine
–1
(2.9 g, 0.04 mol) in 50 mL of THF at a rate of 0.5 L min for
0.5 h; then, a solution of triisopentylgermyl chloride (6.4 g,
0.02 mol) in 30 mL of THF was added. The reaction mixture
was diluted with an equal volume of diethyl ether, and the
precipitate that formed was filtered off. The filtrate was concen-
trated and distilled in vacuo to give compound 3b (5.4 g, 67%),
20
b.p. 171—172 °Ñ (7 Torr), nD 1.4564. Found (%): C, 59.05;
H, 10.41; N, 3.18. C20H43GeNO2. Calculated (%): C, 59.76;
H, 10.71; N, 3.49. IR, ν/cm–1: 1660 (C=O); 860 (Ge—O).
B.
A mixture of hexaisopentyldigermoxane (3.7 g,
0.0063 mol) and carbamate 1b (2.4 g, 0.0126 mol) was heated at
150—155 °C for 3 h. Vacuum fractionation of the reaction
mixture gave compound 3b (2.93 g, 61%), b.p. 145—146 °Ñ
Received July 12, 2000;
in revised form December 5, 2000
(2 Torr), nD 1.4546. IR, ν/cm–1: 1660 (C=O); 860 (Ge—O).
20