Reactivity of N-(chlorodimethylgermyl)methyl and N-(chlorodimethylsilyl) methyl derivatives of lactams and amides toward Grignard reagents

Article abstract of DOI:10.1007/s11176-005-0010-y

N-[(Chlorodimethylgermyl)methyl]lactams and -amides containing a five-coordinate germanium atom react with Grignard reagents chemoselectively by the Ge-Cl bond to form four-coordinate germanium compounds. The method of competitive reactions was used to es

Full text of DOI:10.1007/s11176-005-0010-y

Russian Journal of General Chemistry, Vol. 74, No. 9, 2004, pp. 1356 1358. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004,
pp. 1462 1465.
Original Russian Text Copyright
2004 by Bylikin, Shipov, Kramarova, Artamkina, Negrebetskii, Baukov.
Reactivity of N-(Chlorodimethylgermyl)methyl
and N-(Chlorodimethylsilyl)methyl Derivatives
of Lactams and Amides toward Grignard Reagents
S. Yu. Bylikin, A. G. Shipov, E. P. Kramarova,
O. B. Artamkina, Vad. V. Negrebetskii, and Yu. I. Baukov
Russian State Medical University, Moscow, Russia
Received Decmber 6, 2002
Abstract N-[(Chlorodimethylgermyl)methyl]lactams and -amides containing a five-coordinate germanium
atom react with Grignard reagents chemoselectively by the Ge Cl bond to form four-coordinate germanium
compounds. The method of competitive reactions was used to establish that respective five-coordinate
germanium and silicon compounds are almost equally reactive toward Grignard reagents but much more
reactive than model four-coordinate germanium and silicon compounds.
Five-coordinate silicon [1] and tin compounds [2]
are characteristically more reactive in certain reactions
compared with model compounds containing four-
coordinate germanium and silicon. For instance,
(O Si)-chelate N-[(halodimethylsilyl)methyl]lactams
exhibit a higher silylating activity toward carbonyl
compounds compared with halotrimethylsilanes [3]
and are more reactive than the latter in exchange reac-
tions with compounds Me3SiY (Y = OAc, Hlg) [4].
Germanium(V) chlorides Ib and Id, like their si-
licon analogs, chemoselectively react with Grignard
reagents by the Ge Cl bond to form N-(benzyldi-
methylgermyl)methyl and N-(trimethylgermyl)methyl
derivatives IIb and IId, respectively, in which, ac-
cording to the IR spectra, the intramolecular coordina-
tion O Ge is lacking. Note that similar chemoselec-
tivity have been observed in the reaction of N-[(chloro-
dimethylgermyl)methyl]-N-methylacetamide
with
butyllithium [8].
The method of competitive reactions was used to
reveal a higher reactivity of N-[(chlorodimethylsilyl)-
methyl]lactams compared with chlorotrimethylsilane
toward benzylmagnesium chloride. Therewith, the re-
lative reactivity of the lactams increases with increasing
size of the lactam ring, i.e. with enhancing O Si co-
ordination interaction in the starting chloride [5].
The facility of formation of germyl chlorides Ib
and Id in the reactions of N-(trimethylsilyl)lactams
and -amides with chloro(chloromethyl)dimethylger-
mane [8, 9] and the fairly high yields of compounds
IIb and IId make us to consider this reaction feasible
for preparative synthesis of N-[(organyldimethylger-
myl)methyl]lactams and -amides.
Compared with five-coordinate silicon and tin com-
pounds, there germanium analogs have received much
less study [6], and relative reactivities of five- and
four-coordinate germanium compounds, as well as of
such germanium compounds and structurally related
compounds of the other Group 14 elements have
never been reported.
R2
R2
R1
R3MgX R1
O
N
O
\Me
N
.
/
.
M/
CH2
/
/
/
CH2MMe2R3
Me
Cl
Ia Id
IIa IId
In the present work we studied the reactions of N-
(chlorodimethylgermyl)methyl-substituted hexahydro-
azepin-2-ones Ib and Id1 and N-(S)-(1-phenylethyl)-
acetamide with Grignard reagents (methylmagnesium
iodide and benzylmagnesium chloride), as well as
compared the reactivities of these compounds with
those of N-(chlorodimethylsilyl)methyl derivatives
Ia and Ic and chlorotrimethylgermane toward the
same Grignard reagents.
M = Si (a, c), Ge (b, d); R1, R2 = (CH2)5 (a, b); R1 =
Me(Ph)CH, R2 = Me (c, d); R3 = Bn (a, b), Me (c, d);
Hlg = Cl (a, b), I (c, d).
1
For preliminary commication on the reaction of N-[(chloro-
dimethylgermyl)methyl]hexahydroazepin-2-one with methyl-
magnesium iodide, see [7].
1070-3632/04/7409-1356 2004 MAIK Nauka/Interperiodica

REACTIVITY OF N-(CHLORODIMETHYLGERMYL)METHYL
1357
By the method of competitive reactions we deter-
mined the relative reactivities of germyl chlorides Ib
and IId and their silicon analogs Ia and Ic toward
benzylmagnesium chloride and methylmagnesium
iodide, respectively, as well as of germyl chloride Ib
and chlorotrimethylgermane toward benzylmagnesium
chloride. The product ratios were determined by GLC.
Competitive reactions of five-coordinate germanium
chlorides Ib and Id with their silicon analogs Ia and Ic and
chlorotrimethylgermane
Grignard
reagent
Reagents
Molar ratio
Ia, Ib
Ic, Id
PhCH2MgCl IIa: IIb = 1: 1.05 0.03
The resulting molar ratios of substituted benzyldi-
methyl and trimethylgermanes and -silanes at a 5:5:1
ratio of the starting reagents and Grignard reagent
(solvent diethyl ether benzene, 1:1) are listed in
the table.
As seen from the table, five-coordinate silicon and
germanium derivatives are much more reactive than
their four-coordinate element analogs. With silicon
derivatives, this effect is weaker, which is probably
explained both by the larger size and higher polari-
zability of the germanium atom compared with silicon
and by slightly different reaction conditions (the
molar ratios of the reagents and Grignard reagent were
5:5:1 with germyl derivatives and 1:1:1 with silyl
derivatives).
MeMgI
IIc: IId = 1: 1.13 0.03
Me3SiCl, Ia PhCH2MgCla Me3SiCH2Ph : IIa = 1: 1.55b
Me3GeCl, Ib PhCH2MgCl Me3GeCH2Ph : IIb=
1: 3.4 0.1
Me3SiCl,
Me3GeCl
PhCH2MgCl Me3SiCH2Ph : Me3GeCH2Ph =
1: 2.6 0.2
a
b
Molar ratio 1:1:1.
Data of [5].
13C NMR spectra were obtained on a Varian XL-400
spectrometer (400.1 and 100.6 MHz, respectively) in
the pulse mode with subsequent Fourier transform,
internal reference TMS.
The specific rotations were measured on an A1-
EPO polarimeter in 0.5-dm cells.
Replacement of the silicon atom by germanium,
too, enhances the reactivity, but the molar ratio of the
reaction products is markedly higher only for four-co-
ordinate element derivatives [1:2.6 for Me3SiCH2Ph
and Me3GeCH2Ph against 1:1.05 for compounds IIa
and IIb]. The observed leveling of the reactivity of
five-coordinate element derivatives probably results
from the relatively stronger elongation of the M Cl
bond in silicon compounds on the extension of the
coordination sphere of the central atom from 4 to 5
compared with their germanium analogs. The rate
effect of such factors as the dependence of the coor-
dination strength on the nature of the chelating ligand
and the different solubility of the reagents under
heterogeneous reaction conditions should also not be
excluded. Apparently, there reasons explain the fact
that the difference in the reactivities of compounds Ic
and Id (1:1.13) toward the more active (and, con-
sequently, less selective) methylmagnesium iodide is
slightly larger that the difference in the reactivities of
compounds Ia and Ib (1:1.05) toward benzylmag-
nesium chloride.
The products of competitive reactions were ana-
lyzed by GLC on a Chrom-4 chromatograph (column
1000 5 mm, packing 10% SE-30 on silica gel, carrier
gas helium, thermal conductivity detector).
The starting (O M)-chelate (M = Si, Ge) N-[(chlo-
rodimethylsilyl)methyl]hexahydroazepin-2-one
and
N-[(chlorodimethylgermyl)methyl]hexahydroazepin-
2-one (Ia, Ib) were prepared by the reactions of N-
(trimethylsilyl)hexahydroazepin-2-one with chloro-
(chloromethyl)dimethylsilane and -germane [4, 10].
(O Si)-Chelate N-(S)-[(chlorodimethylsilyl)methyl]-N-
(1-phenylethyl)acetamide (Ic) was prepared by the re-
action of N-(S)-(1-phenylethyl)acetamide with chloro-
(chloromethyl)dimethylsilane in the presence of tri-
ethylamine [11].
N-[(Benzyldimethylsilyl)methyl]hexahydroazepin-
2-one (IIa) and benzyltrimethylgermane were syn-
thesized as described in [5, 12], respectively.
(O Ge)-Chelate N-(S)-[(chlorodimethylger-
myl)methyl]-N-(1-phenylethyl)acetamide (Id).
A
Thus, the resulting data suggest enhanced reactivity
of five-coordinate germanium derivatives compared
with chlorotrimethylgermane toward Grignard re-
agents, as well as an only slight difference in the re-
activities of five-coordinate silicon and germanium
compounds.
solution of 1.3 g of chloro(chloromethyl)dimethyl-
germane and 1.63 g of N-(trimethylsilyl)-N-(S)-(1-
phenylethyl)acetamide in 10 ml of o-xylene was
heated under reflux for 3 h and then reduced by half
in a vacuum. The crystals that formed were filtered off,
washed with hexane, and dried to obtain 1.76 g (81%)
of compound Id, mp 86 87 C (from toluene),
[ ]2D0 +42 (MeCN, 12 mg/ml). IR spectrum (CHCl3),
EXPERIMENTAL
The IR spectra of 3% solutions in CHCl3 were
1
1
1
measured on a Specord IR-75 instrument. The H and
, cm : 1590 s, 1500 w. H NMR spectrum (CDCl3),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

1358
BYLIKIN et al.
Competitive reactions. A solution of 1 mmol of
*
, ppm: 0.89 d (3H, GeMe2), 1.68 d (3H, C CH3,
3JHH 6.9 Hz), 2.25 s (3H, CH3CO), 2.51 d, 2.81 d (2H, organomagnesium compound in 10 ml of diethyl ether
NCH2, JHH 14.0 Hz), 5.12 q (1H, *C CH, JHH
6.9 Hz), 7.2 7.4 m (5H, C6H5). Found, %: C 49.91; H
6.48; Ge 22.92. C13H20ClGeNO. Calculated, %: C
49.67; H 6.41; Ge 23.10.
was added dropwise to a mixture of 5 mmol of germyl
chloride Ib or Id and 5 mmol of silyl chloride Ia or
Ic, or 5 mmol of Me3GeCl in 10 ml of benzene. The
mixture was stirred for 0.5 h at room temperature and
then decomposed with water. The aqueous layer was
treated with 10 ml of diethyl ether. The combined
organic layers were evaporated in a vacuum, and the
residue was analyzed by GLC to determine the molar
ratios of the reaction products (see table).
2
3
N-[(Benzyldimethylgermyl)methyl]hexahydro-
azepin-2-one (IIb). A solution of PhCH2MgCl, ob-
tained from 0.32 g of Mg and 1.5 ml of benzyl chlo-
ride in 15 ml of diethyl ether, was added to a solution
of 2.64 g of germyl chloride Ib in 10 ml of benzene.
The reaction mixture was heated under reflux for
10 min, cooled, and made weakly acidic with 10%
HCl. The organic layer was separated, and the
aqueous layer was treated with diethyl ether (2
10 ml). The combined organic layers were dried with
MgSO4, the solvent was removed in a vacuum, and
the residue was fractionated to obtain 1.9 g (59%) of
compound IIb as a colorless liquid, bp 201 202 C
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,
1
1
cm : 1620 s. H NMR spectrum (CDCl3), , ppm:
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compound IIb from a solution of 8.1 g of chlorosilane
Ic in 50 ml of benzene and MeMgI obtained from
0.8 g of Mg and 2.1 ml of 35 ml of diethyl ether;
yield 4.4 g (59%), colorless liquid, bp 155 156 C
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1
1
14 mg/ml). IR spectrum (CHCl3), , cm : 1630 s. H
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1.58 d (3H, *C CH3, JHH 6.8 Hz), 2.25 s (3H,
3
2
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*
3
5.09 q (1H, C CH, JHH 6.8 Hz), 7.2?7.4 m (5H,
C6H5). Found, %: C 67.29; H 9.30; N 5.47. C14H23
NOSi. Calculated, %: C 67.41; H 9.29; N 5.62.
N-(1-Phenylethyl)-N-(S)-[(trimethylgermyl)me-
thyl]acetamide (IId) was prepared similarly to com-
pound IIb from 3.14 g of germyl chloride Id in 25 ml
of benzene and MeMgI (from 0.29 g of Mg and
0.75 g of MeI in 10 ml of diethyl ether), yield 1.7 g
(58%), colorless liquid, bp 164 165 C (7 mm Hg),
n2D0 1.5252, [ ]2D0 41 (MeCN, 15 mg/ml). IR spec-
trum (CHCl3), , cm : 1625 s. H NMR spectrum
(CD3C6D5), , ppm: 0.15 s (3H, GeMe2), 1.15 d (3H,
*C CH3, JHH 6.8 Hz), 1.87 s (3H, CH3CO), 2.36 d,
1
1
3
2
2.55 d (2H, NCH2, JHH 13.9 Hz), 4.57 q (1H,
*C CH, JHH 6.8 Hz), 6.9 7.1 m (5H, C6H5). Found,
3
%: C 57.06; H 7.62; N 4.59. C14H23GeNO. Calculated,
%: C 57.21; H 7.89; N 4.77.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004