Reaction of iodo(trimethyl)silane with N,N-dimethyl carboxylic acid amides

Article abstract of DOI:10.1134/S1070428010060035

The reactions of iodo(trimethyl)silane with N,N-dimethylformamide and N,N-dimethylacetamide Me₂NCOR (R = H, Me) at a molar ratio of 1: 2 involved mainly cleavage of the N-C(=O) bond with formation of up to 80% of N,N-dimethyltrimethylsilylamine Me₃SiNMe₂ and the corresponding acyl iodide RCOI. In the reaction with N,N-dimethylformamide, formyl iodide HCOI was detected for the first time by gas chromatography-mass spectrometry. The contribution of Me-N bond cleavage, leading to N-methyl-N-trimethylsilyl derivative Me(Me₃Si)NCOR and methyl iodide was considerably smaller. Another by-product was the corresponding N-methyl imide MeN(COR)₂ formed by reaction of the initial amide with acyl iodide. The primary intermediate in the reaction of iodo(trimethyl)silane with DMF and DMA is quaternary ammonium salt [Me₂(Me₃Si)N ⁺COR] I^- which decomposes via dissociation of the N-CO and N-Me bonds.

Full text of DOI:10.1134/S1070428010060035

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 6, pp. 791–793. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © M.G. Voronkov, I.P. Tsyrendorzhieva, A.V. Lis, V.I. Rakhlin, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46,
No. 6, pp. 801–803.
Reaction of Iodo(trimethyl)silane with N,N-Dimethyl
Carboxylic Acid Amides
M. G. Voronkov, I. P. Tsyrendorzhieva, A. V. Lis, and V. I. Rakhlin
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: vir@irioch.irk.ru
Received December 18, 2009
Abstract—The reactions of iodo(trimethyl)silane with N,N-dimethylformamide and N,N-dimethylacetamide
Me2NCOR (R = H, Me) at a molar ratio of 1:2 involved mainly cleavage of the N–C(=O) bond with formation
of up to 80% of N,N-dimethyltrimethylsilylamine Me3SiNMe2 and the corresponding acyl iodide RCOI. In the
reaction with N,N-dimethylformamide, formyl iodide HCOI was detected for the first time by gas chromatog-
raphy–mass spectrometry. The contribution of Me–N bond cleavage, leading to N-methyl-N-trimethylsilyl
derivative Me(Me3Si)NCOR and methyl iodide was considerably smaller. Another by-product was the corre-
sponding N-methyl imide MeN(COR)2 formed by reaction of the initial amide with acyl iodide. The primary
intermediate in the reaction of iodo(trimethyl)silane with DMF and DMA is quaternary ammonium salt
[Me2(Me3Si)N+COR]I– which decomposes via dissociation of the N–CO and N–Me bonds.
DOI: 10.1134/S1070428010060035
We previously noted similarity in the reactivities of
acyl iodides and iodo(trimethyl)silane [1] which was
carboxamide. N,N-Dimethyltrimethylsilylamine was
isolated by distillation of the reaction mixture in 32
introduced by us for the first time into organic and
(R = H) or 25% yield (R = Me). Subsequent distillation
organometallic synthetic practice [2–6]. We recently
of the residue was not performed to avoid thermolysis.
showed that reactions of acyl iodides RCOI (R = Me,
However, by gas chromatography–mass spectrometry
Ph) with N,N-dimethylformamide (DMF) and N,N-di-
we identified 61% of Me3SiNMe2, 11% of MeI,
5% of HCOI, 1% of MeN(CHO)2, and 11% of
methylacetamide (DMA) involve elimination of one
methyl group from the nitrogen atom with formation of
Me(Me3Si)NCHO (R = H) and 76% of Me3SiNMe2,
the corresponding N-methyl dicarboximide (including
3% of MeI, and 5% MeN(COMe)2 (R = Me). In both
cases, the still residue contained ~40% of unreacted
mixed one). The process is accompanied by transacyla-
tion, i.e., acyl group exchange between the reagents [7].
initial amide which was taken in excess. No iodo-
We now report that iodo(trimethyl)silane reacts
with excess DMF or DMA (molar ratio 1:2) under
mild conditions (boiling methylene chloride, 5 h) to
give N,N-dimethyltrimethylsilylamine as a result of
cleavage of the N–(C=O) bond (Scheme 1).
(trimethyl)silane (expected product of the reverse
reaction) was detected. Thus the overall yield of
Me3SiNMe2 was 83% for R = H and 77% for R = Me.
Interestingly, the reaction of Me3SiI with DMF
afforded N-methyl-N-trimethylsilylformamide as a re-
sult of cleavage of the Me–N bond (Scheme 2).
Scheme 1.
O
O
Scheme 2.
Me3SiI +
Me3SiNMe2 +
O
O
R
NMe2
R
I
Me3SiI
+
MeI +
SiMe3
H
NMe2
H
N
R = H, Me.
Me
This reaction is reversible, but the equilibrium can
be displaced almost completely toward the products
using a considerable excess of the initial N,N-dimethyl
In this case iodo(trimethyl)silane reacts with DMF
in a way similar to acyl iodides [7]. It was even more
791

VORONKOV et al.
792
surprising that we detected formyl iodide HCOI among
the products by GC–MS. The possibility for the exist-
ence of formyl iodide was so far doubtful. The forma-
tion of HCOI was also confirmed by the presence of
N-formyl-N-methylformamide among the products
(Scheme 3). Analogous elimination of one methyl
group from DMF by the action of acyl iodides was
described by us previously [7].
Reaction of iodo(trimethyl)silane with N,N-di-
methylformamide. Iodo(trimethyl)silane, 7.25 g
(0.036 mol), was added dropwise to a solution of
5.29 g (0.072 mol) of N,N-dimethylformamide in
10 ml of methylene chloride, and the mixture was
stirred for 5 h at 40°C. Distillation gave 1.35 g (32%)
of Me3SiNMe2, bp 80–112°C; published data [8]:
bp 86°C, nD20 = 1.3950. Mass spectrum, m/z (Irel, %):
117 (40) [M]+, 73 (100), 61 (5), 45 (20), 15 (9); and
1.44 g (40%) of initial DMF, bp 150–160°C; published
data [9]: bp 153°C, nD20 = 1.4305. Mass spectrum, m/z
(Irel, %): 73 (100) [M]+, 58 (30), 44 (90), 15 (45).
According to the GC–MS data, the still residue,
3.49 g, contained [fraction, %; mass spectrum, m/z
(Irel, %)]: 11% (0.47 g) of MeI, 142 (100) [M]+, 127
(40), 15 (86); 5% (0.22 g) of HCOI, 156 (15) [M]+,
127 (35), 29 (80); 61% (2.14 g) of Me3SiNMe2, 117
(40) [M]+, 73 (100), 57 (5), 45 (20), 15 (10); 11%
(0.49 g) of Me2NCHO, 73 (100) [M]+, 58 (30), 44 (90),
15 (45); 1% (0.06 g) of MeN(CHO)2, 87 (30) [M]+, 72
(24), 57 (35), 29 (72), 15 (40); and 11% (0.49 g) of
MeN(SiMe3)CHO, 131 (40) [M]+, 116 (17), 102 (35),
73 (60) 58 (25), 29 (7), 15 (10).
Scheme 3.
O
O
O
O
+
MeI +
H
I
H
NMe2
H
N
H
Me
The reaction of Me3SiI with DMA involves only
processes shown in Schemes 1 and 3, which lead to
formation of Me3SiNMe2 and MeN(COMe)2, respec-
tively. The primary intermediate in the reactions of
iodo(trimethyl)silane with DMF and DMA is the
adduct [Me2(Me3Si)N+COR] I– (Schemes 1, 2). This
labile quaternary ammonium salt readily undergoes
decomposition via cleavage of the N–C=O and N–CH3
bonds as a result of attack by iodide ion on the most
electrophilic carbonyl carbon atom and (to a lesser
extent) on the carbon atom in the N-methyl group. The
decomposition products are, respectively, N,N-di-
methyltrimethylsilylamine and N-methyl-N-trimethyl-
silylcarboxamide. Cleavage of the most reactive N–Si
bond, which should lead to the initial reactants, does
not occur due to the presence of excess initial N,N-di-
methyl carboxamide.
Reaction of iodo(trimethyl)silane with N,N-di-
methylacetamide. Iodo(trimethyl)silane, 12.4 g
(0.062 mol), was added dropwise under stirring to
10.8 g (0.124 mol) of N,N-dimethylacetamide in 10 ml
of methylene chloride, and the mixture was stirred for
5 h at 35°C. Distillation gave 2.13 g (29%) of
Me3SiNMe2, bp 80–120°C. Mass spectrum, m/z
(Irel, %): 117 (10) [M]+, 102 (70), 87 (12), 73 (59), 58
(15), 44 (12), 15 (3); and 4.03 g (40%) of initial DMA,
bp 160–168°C; published data [10]: bp 165°C, nD20
=
EXPERIMENTAL
1.4380. Mass spectrum, m/z (Irel, %): 87 (50) [M]+, 72
(20), 58 (5), 44 (100), 30 (15), 15 (30). According to
the GC–MS data, the still residue, 4.5 g, contained
[fraction, %; mass spectrum, m/z (Irel, %)]: 3% (0.16 g)
of MeI, 142 (100) [M]+,127 (40), 15 (86); 76% (3.44 g)
of Me3SiNMe2, 117 (40) [M]+, 73 (100), 57 (5), 45
(20), 15 (10); 15% (0.79 g) of Me2NCOMe, 87 (60)
[M]+, 72 (20), 57 (35), 44 (100), 15 (40); 5% (0.24 g)
of MeN(COMe)2, 115 (10) [M]+, 100 (35), 72 (34), 57
(15), 4 (100), 29 (22), 15 (30); and 1% (0.07 g) of
MeN(SiMe3)2, 175 (2), 87 (20), 73 (100), 44 (35).
1
The H, 13C, and 29Si NMR spectra were recorded
on a Bruker DPX-400 spectrometer at 400.1, 100.61,
and 79.5 MHz, respectively, using CDCl3 as solvent
and cyclohexane as internal reference. Gas chromato-
graphic–mass spectrometric analysis was performed
on a Hewlett–Packard HP 5890 gas chromatograph
coupled with an HP 5971A mass-selective detector
(electron impact, 70 eV; Ultra-2 column, stationary
phase 5% of phenylmethylsilicone; injector tempera-
ture 250°C, oven temperature programming from 70 to
280°C at a rate of 20 deg/min). Gas chromatographic
analysis was performed on a Tsvet-500 chromatograph
equipped with a thermal conductivity detector and
a glass column, 3 m×4 mm, packed with 10% of
PSM-1000 on Inerton-Super (0.125–0.150 mm); car-
rier gas helium.
This study was performed under financial support
by the Council for Grants at the President of the Rus-
sian Federation (project no. NSh-255.2008.3) and by
the Presidium of the Siberian Division of the Russian
Academy of Sciences (integration project no. 97).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 6 2010

REACTION OF IODO(TRIMETHYL)SILANE WITH N,N-DIMETHYL CARBOXYLIC
793
4. Voronkov, M.G., Pavlov, S.F., and Dubinskaya, E.I., Izv.
Akad. Nauk SSSR, Ser. Khim., 1975, no. 3, p. 657.
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