A convenient synthesis and some characteristic reactions of novel propiolamidinium salts

Article abstract of DOI:10.1055/s-0030-1258353

Starting from N,N,N,N,N,N-hexaalkylguanidinium chlorides and terminal alkynes, a series of new orthoamide derivatives of alkynecarboxylic acids were prepared. The orthoamides were converted into propiolamidinium chlorides by reaction with benzoyl chloride

Full text of DOI:10.1055/s-0030-1258353

PAPER
265
A Convenient Synthesis and Some Characteristic Reactions of Novel
Propiolamidinium Salts
S
ynthesisandReactions
e
of Propiola
r
midiniu
n
m
Salts er Weingärtner,a Willi Kantlehner,b Gerhard Maas*a
a
Institute of Organic Chemistry I, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
Fax +49(731)5022803; E-mail: gerhard.maas@uni-ulm.de
b
Faculty of Chemistry, Organic Chemistry, University of Applied Research Aalen, Beethovenstraße 1, 73430 Aalen, Germany
Fax +49(7361)5762250; E-mail: willi.kantlehner@htw-aalen.de
Received 8 September 2010; revised 27 October 2010
yield; stronger alkylation reagents, including methyl tri-
flate, did not produce better results.4
Abstract: Starting from N,N,N¢,N¢,N¢¢,N¢¢-hexaalkylguanidinium
chlorides and terminal alkynes, a series of new orthoamide deriva-
tives of alkynecarboxylic acids were prepared. The orthoamides
were converted into propiolamidinium chlorides by reaction with
benzoyl chloride and into propiolamidinium triflates by reaction
with triethylsilyl trifluoromethanesulfonate. Propiolamidinium
salts undergo conjugate addition reactions with sec-amines and
thiols. Treatment of terminal alkyne chlorides with silver(I) oxide
afforded a silver complex, which can apparently adopt the composi-
tion of either a bisalkynyl silver complex [Ag(CCC(NMe2)2)2]AgCl2
or a monoalkynyl silver complex [ClAgCCC(NMe2)2].
Kantlehner and coworkers took another approach, namely
electrophile-induced deamination of a propiolic acid
orthoamide. However, their synthesis of propiolamidini-
um chloride 3a-Cl (see Scheme 2 below) from benzoyl
chloride and 3,3,3-tris(dimethylamino)-1-phenylprop-1-
yne remains the only example of this method so far report-
ed.5
We explored another approach to salts 3 without success:
the reaction of alkynyl lithium or alkynyl Grignard com-
pounds with chlorotetramethylformamidinium chloride6
did not afford the desired propiolamidinium salts. In this
context, it must be remembered that the reaction of phenyl
lithium and higher alkyl lithium compounds with this
chloroformamidinium salt also did not take the expected
addition/substitution pathway, but instead gave products
derived from radical intermediates.7 Coupling of the chlo-
roformamidinium salt with terminal alkynes under
Sonogashira conditions was also unsuccessful.
Key words: alkynes, amidinium salts, orthoamides, hexamethyl-
guanidinium chloride, silyl triflates
Acetylenic iminium (1), amidium (2), and amidinium (3)
salts combine in one organic cation two reactive function-
al groups (Figure 1). It can be expected that due to the
electron-deficient C≡C triple bond and to a susceptibility
of the ambident functionality toward nucleophilic re-
agents, these salts are potentially useful building blocks in
organic synthesis. In fact, a variety of chemical transfor-
mations have been reported for acetylenic iminium salts
1.1,2 Amidium salts 2, although readily obtained by O-
alkylation of alkynecarboxylic acid amides, have been ex-
plored to a much lesser extent,3 and very little is known
about the chemistry of alkynyl amidinium salts (also
called propiolamidinium salts) 3.
We returned, therefore, to alkynyl orthoamides as poten-
tial precursors of propiolamidinium salts 3. It has been re-
ported that terminal alkynes can be converted into alkynyl
orthoamides by subsequent treatment with sodium hy-
dride (80% in mineral oil) and hexamethylguanidinium
chloride (HMG-Cl; 5a) in tetrahydrofuran.8 As we were
facing low yields in some cases and it appeared that the
+NR3
1 R2 = alkyl, aryl
2 R2 = OR
2
R1
1. BuLi, THF, –78 °C, 15 min
3 R2 = NR2
R2
X–
+NR2
2
Cl–
2.
, 25 °C, 17 h
Figure 1
R22N
NR2
2
(5a R2 = Me; 5b R2 = Et)
Even reports on the synthesis of propiolamidinium salts
are scarce. An obvious approach would be the N-alkyla-
tion of propiolamidines, R1C≡CC(=NR)(NR2). However,
Viehe and Baum have found this transformation not to be
proficient, in contrast to the N-protonation using perchlo-
ric acid. The reaction of N,N-dimethyl-N¢-methylpropiol-
amidine and methyl iodide was sluggish and gave N,N¢-
tetramethylphenylpropiolamidinium iodide in very low
R1
C(NR2
)
2 3
R1
4a–g
66–87%
6a–g
a R1 = Ph, R2 = Me
b R1 = c-Pr, R2 = Me
c R1 = t-Bu, R2 = Me
d R1 = SiMe3, R2 = Me
e R1 = SiEt3, R2 = Me
f R1 = Si(i-Pr)3, R2 = Me
g R1 = Ph, R2 = Et
+NMe2
NaCCH
NMe2
MeCN, 24 h, 40 °C
H
NMe2
NMe2
6h (69%)
Me2N
NMe2
– NaCl
Cl–
5a
SYNTHESIS 2011, No. 2, pp 0265–0272
x
x
.
x
x
.2
0
1
1
Advanced online publication: 07.12.2010
DOI: 10.1055/s-0030-1258353; Art ID: T18210SS
Scheme 1 Synthesis of alkynyl orthoamides 6a–h
© Georg Thieme Verlag Stuttgart · New York

266
W. Weingärtner et al.
PAPER
quality of sodium hydride in mineral oil affected the product, we isolated the bis(orthoamide) derivative of
yields, we switched from sodium to lithium acetylides.
acetylenedicarboxylic acid (see Kantlehner et al.8).
Hence, we made use of sodium acetylide, but the reaction
was carried out in acetonitrile as a dipolar solvent to in-
crease the solubility of both starting materials.
Terminal alkynes 4 were lithiated quantitatively with n-
butyllithium in tetrahydrofuran and immediately convert-
ed into the corresponding alkynyl orthoamides 6a–g with
the hexaalkylguanidinium salts 5a and 5b (Scheme 1 and The ester-substituted alkyne orthoamide 6i (see Scheme 4
Table 1). Similar reactions of organolithium compounds below) could also not be prepared in this way because of
with 5a have been described previously.9 The lithium polymerization of the lithiated propiolic ester. Therefore,
acetylides are soluble in tetrahydrofuran and react at an 6i was synthesized as published from tris(dimethylami-
acceptable rate with guanidinium salts 5 suspended in tet- no)ethoxymethane and ethyl propiolate.11
rahydrofuran. In contrast, sodium acetylides are formed
slowly due to the low solubility of sodium hydride in tet-
rahydrofuran and subsequently react slowly with guani-
dinium salts 5, suspended in tetrahydrofuran, to afford
The orthoamides 6b, 6c, and 6h were successfully con-
verted into the novel propiolamidinium chlorides 3b, 3c,
and 3h-Cl by treatment with benzoyl chloride, following
the procedure established for 3a-Cl (Scheme 2 and
orthoamides 6.
Table 2).5 Because the propiolamidinium chloride salts
The terminal alkynyl orthoamide 6h could not be prepared 3-Cl are hygroscopic, they were converted into the more
effectively in the same way because the (mono)lithium stable propiolamidinium tetraphenylborate salts 3-BPh4
acetylide readily underwent irreversible disproportion- by an anion-exchange reaction.
ation in tetrahydrofuran at 0 °C to form the insoluble, less
Unfortunately, the benzoyl chloride method was not ap-
reactive dilithium acetylide and acetylene.10 As the main
plicable to trialkylsilyl-substituted alkynyl orthoamides
Table 1 Alkynyl Orthoamides 6a–h
Product Molecular formulaa
Yield Bpb
1H NMR (d)c
13C{1H} NMR (d)d
IR (cm–1)e
vC≡C
(%)
(°C/mbar)
6a
6b
6c
6d
6e
C15H23N3 (245.36)
C12H23N3 (209.33)
C13H27N3 (225.37)
C12H27N3Si (241.45)
C15H33N3Si (283.53)
79
105/0.05f 2.55 (s, 18 H, NCH3), 7.29–7.32
40.0 (NCH3), 85.2, 85.8 (C≡C), 94.2
2218
(m, 3 H, PhH), 7.49–7.51 (m, 2 H, (CN(CH3)2), 113.2, 128.0, 128.2,
PhH)
131.9 (CPh)
75
78
82
87
95/0.3
90/0.2
95/0.1
105/0.1
0.68–0.80 (m, 4 H, CH2 cp). 1.29– –0.6 (CH cp), 8.6 (CH2 cp), 39.9
1.36 (m, 1 H, CH cp), 2.44 (s, 18 (NCH3), 70.7 (NCC≡C), 89.3
H, NCH3)
2231
(NCC≡C), 93.6 (CN(CH3)2)
1.28 (s, 9 H, CH3), 2.44 (s, 18 H, 27.5 (C(CH3)3), 31.4 (C(CH3)3), 39.9 2235
NCH3)
(NCH3), 73.8 (NCC≡C), 93.4
(CN(CH3)2), 94.8 (NCC≡C)
0.19 (s, 9 H, Si(CH3)3), 2.44 (s, 18 0.2 (SiCH3), 39.8 (NCH3), 89.5
H, NCH3)
2161
2160
(SiC≡C), 93.7 (CN(CH3)2), 100.7
(NCC≡C)
0.63 (q, J = 7.9 Hz, 6 H,
4.6 (SiCH2CH3), 7.3 (SiCH2), 39.8
SiCH2CH3), 1.02 (t, J = 7.9 Hz, 9 (NCH3), 86.9 (SiC≡C), 93.9
H, CH2CH3), 2.46 (s, 18 H, 6
NCH3)
(CN(CH3)2), 101.8 (NCC≡C)
6f
C18H39N3Si (325.61)
C21H35N3 (329.52)
71
66
135/0.01 1.10–1.12 (m, 21 H, Si(i-Pr)), 2.47 11.4 (SiCHCH3), 18.8 (CHCH3), 39.9 2160
(s, 18 H, NCH3)
(NCH3), 85.7 (SiC≡C), 94.0
(CN(CH3)2), 102.7 (NCC≡C)
6g
160/0.01 1.09 (t, J = 7.1 Hz, 18 H,
16.0 (CH2CH3), 43.9 (NCH2CH3),
2221
CH2CH3), 2.91 (q, J = 7.1 Hz, 12 83.8 (NCC≡C), 89.7 (NCC≡C), 96.0
H, NCH2CH3), 7.26–7.28 (m, 3 H, (CN(CH3)2), 123.9, 127.6, 128.7,
PhH), 7.40–7.42 (m, 2 H, PhH)
131.4 (CPh)
6h
C9H19N3 (169.27)
69
65/5
2.12 (s, 1 H, C≡CH), 2.48 (s, 18 H, 40.3 (NCH3), 73.7 (1JC,H = 263 Hz,
2280,
3304
(ºCH)
NCH3)c
C≡CH), 79.7 (NCC≡C), 94.2
(CN(CH3)2)d
a Since the orthoamides are rather moisture-sensitive oily compounds, no combustion analysis was carried out.
b Kugelrohr distillation.
c Carried out at 400.13 MHz in CDCl3 (6h: in C6D6); cp = cyclopropyl.
d Carried out at 100.61 MHz in CDCl3 (6h: in C6D6); cp = cyclopropyl; assignments were made on the basis of HMBC experiments.
e Film.
f Oily 6a slowly crystallized as off-white needles (mp 28–30 °C).
Synthesis 2011, No. 2, 265–272 © Thieme Stuttgart · New York

PAPER
Synthesis and Reactions of Propiolamidinium Salts
267
Table 2 Propiolamidinium Salts 3
Product Molecular formula Yield (%) CHN
Calcd
Mp (°C)
1H NMR (d)a
13C{1H} NMR (d)b
IR (cm–1)c
Found
–
C≡C
C=N+
d
3b-Cl
3c-Cl
3h-Cl
C10H17ClN2
(200.71)
85
–
–
–
>121 (dec.) 0.90–0.94 (m, 2 H, CH2 0.4 (CH cp), 10.7 (CH2 cp), 2223
cp), 1.07–1.12 (m, 2 H, 44.0 (NCH3), 64.9
CH2 cp), 1.50–1.57 (m, (NCC≡C), 116.1(NCC≡C),
1 H, CH cp), 3.38 (s, 12 152.3 (C+(N(CH3)2)2)
H, +NCH3)
1614
d
d
C11H21ClN2
(216.75)
87
–
–
>177 (dec.) 1.13 (s, 9 H, CH3), 3.52 28.9 (C(CH3)3), 29.7
2224
1619
(s, 12 H, +NCH3)
(C(CH3)3), 44.2 (NCH3),
69.7 (NCC≡C), 118.8
(NCC≡C), 152.3
(C+(N(CH3)2)2)
C7H13ClN2
(160.64)
84
89
> 93 (dec.) 3.31 (s, 12 H, +NCH3), 44.6 (NCH3), 71.4
5.24 (s, 1 H, C≡CH) (NCC≡C), 99.7 (HC≡C),
153.0 (C+(N(CH3)2)2)
2090
1619
3a-OTf C14H17F3N2O3S
C, 47.99; C, 47.83; 125–126
3.47 (s, 12 H, +NCH3), 44.4 (NCH3), 77.3
7.44–7.48 (m, 2 H,
PhH), 7.55–7.63 (m, 3 117.8, 129.1, 132.2, 132.7
H, PhH)
(CPh), 152.3 (C+(N(CH3)2)2)
2219
(350.36)
H, 4.89;
N, 8.00
H, 5.15;
N, 8.00
(NCC≡C), 107.6(NCC≡C), 1615
e
3b-OTf C11H17F3N2O3S
85
80
C, 42.03;
H, 5.45;
N, 8.91
–
yellow oil
1.02–1.05 (m, 2 H, CH2 0.3 (CH cp), 10.5 (CH2 cp), 2221
cp), 1.14–1.18 (m, 2 H, 43.4 (NCH3), 64.8 (NCC≡C), 1616
CH2 cp), 1.57–1.64 (m, 116.5 (NCC≡C), 152.7
1 H, CH cp), 3.34 (s, 12 (C+(N(CH3)2)2)
H, +NCH3)
(314.32)
3c-OTf C12H21F3N2O3S
C, 43.63; C, 43.55; 66–67
1.34 (s, 9 H, CH3), 3.35 28.9 (C(CH3)3), 29.6
2230
1622
(330.37)
H, 6.41;
N, 8.48
H, 6.39;
N, 8.39
(s, 12 H, +NCH3)
(C(CH3)3), 43.7 (NCH3),
68.7 (NCC≡C), 119.4
(NCC≡C), 152.8
(C+(N(CH3)2)2)
3d-OTf C11H21F3N2O3SSi 82
C, 38.14; C, 38.07; 71–73
0.32 (s, 9 H, SiCH3),
–1.1 (SiCH3), 43.8 (NCH3), 2169
(346.44)
H, 6.11;
N, 8.09
H, 6.04;
N, 7.84
3.40 (s, 12 H, +NCH3) 90.2 (NCC≡C), 117.9
(NCC≡C), 151.6
1627
(C+(N(CH3)2)2)
3e-OTf C14H27F3N2O3SSi 86
C, 43.28; C, 43.13; 80–82
0.75 (q, J = 7.9 Hz, 6 H, 3.5 (SiCH2), 7.3 (CH2CH3), 2170
(388.52)
H, 7.00;
N, 7.21
H, 7.09;
N, 7.15
SiCH2CH3), 1.03 (t, J = 43.9 (NCH3), 91.2
1627
7.9 Hz, 9 H,
(NCC≡C), 116.7(NCC≡C),
SiCH2CH3), 3.43 (s, 12 151.6 (C+(N(CH3)2)2)
H, +NCH3)
3f-OTf C17H33F3N2O3SSi 81
C, 47.42; C, 47.24; 103–105
1.11–1.12 (m, 18 H,
CHCH3), 1.16–1.24
(m, 3 H, SiCHCH3),
10.9 (SiCH), 18.5
2165
1627
(430.60)
H, 7.72;
N, 6.51
H, 7.79;
N, 6.69
(CHCH3), 44.0 (NCH3),
92.1 (NCC≡C), 116.2
3.42 (s, 12 H, +NCH3) (NCC≡C), 151.5
(C+(N(CH3)2)2)
3g-OTf C18H25F3N2O3S
88
82
C, 53.19; C, 53.08; 46–47
1.44 (t, J = 7.2 Hz, 12 13.3 (CH3), 48.6 (NCH2),
2217
1586
(406.46)
H, 6.20;
N, 6.89
H, 6.32;
N, 6.69
H, CH2CH3), 3.81 (q,
J = 7.2 Hz, 8 H,
77.7 (NCC≡C), 105.0
(NCC≡C), 118.0, 129.1,
+NCH2CH3), 7.46–7.56 132.4, 132.8 (CPh), 151.3
(m, 2 H, PhH), 7.58–
7.62 (m, 3 H, PhH)
(C+(N(CH3)2)2)
e
3h-OTf C8H13F3N2O3S
C, 35.03;
H, 4.48;
N, 10.21
–
red oil
3.45 (s, 12 H, +NCH3), 44.0 (NCH3), 70.6
4.33 (s, 1 H, C≡CH) (NCC≡C), 97.0 (HC≡C),
151.5 (C+(N(CH3)2)2)
2115
1627
(274.26)
a Carried out at 400.13 MHz in CDCl3 (3h-Cl: in CD3CN); cp = cyclopropyl.
b Carried out at 100.61 MHz in CDCl3 (3h-Cl: in CD3CN); d (CF3) = 120.8 (q, 1JC,F = 319 Hz); NMR assignments were confirmed by 2D cor-
relation spectra.
c Neat (ATR measurement).
d The hygroscopic chlorides 3b, 3c, and 3h-Cl were converted into tetraphenylborates 3b, 3c, and 3h-BPh4 for elemental analysis (see experi-
mental section).
e Elemental analyses of oils 3b and 3h-OTf were not successful; the composition was confirmed by mass spectrometry (CI): 3b-OTf: m/z = 165
[Mcat]+; 3h-OTf: m/z = 125 [Mcat]+.
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268
W. Weingärtner et al.
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PhCOCl
Table 3 Reaction of Orthamide 6d with Trimethylsilyl Halides and
Triflate
+NMe2
NMe2
Et2O, 0 °C, 1 h
X–
R
C(NMe2)3
R
– PhCONMe2
Me3Si-X
Et2O, r.t., 1 h
+NMe2
NMe2
NMe2
NMe2
NMe2
6
3-X
TMS
TMS
NaBPh4,
MeCN
X = Cl (81–91%)
X = BPh4
X–
6d
3d-X
R = Ph (a), c-Pr (b), t-Bu (c), H (h)
Scheme 2 Synthesis of novel propiolamidinium chlorides 3-Cl and
tetraphenylborates 3-BPh4
X
Yield of 3d-X (%)a
Cl
Br
I
n/ab
47
6d–f, which suffered unspecific decomposition. We were
pleased to find that orthoamides 6a–h all underwent clean
deamination upon treatment with triethylsilyl trifluo-
romethanesulfonate (triflate), and alkynyl amidinium tri-
flates 3a–h-OTf were obtained in high yields (Scheme 3,
Table 2). During work-up, the by-product, (dimethylami-
no)triethylsilane, was easily removed in vacuo. Triethyl-
silyl triflate is to be preferred over trimethylsilyl triflate
(vide infra), because the latter unavoidably contains traces
of triflic acid, which give rise to the formation of the di-
alkylammonium triflate that is hard to separate from the
amidinium salt.
67
OTf
77
a The crude product was recrystallized from Et2O/CH2Cl2 at –20 °C.
b The formation of the propiolamidinium chloride was observed as an
off-white precipitate, which slowly decomposed.
of 6d in tetrahydrofuran, the propiolamidinium salt 3d-
OTf immediately precipitated as a brown powder.
It should be added that the stability of the propiolamidin-
ium salts derived from 6d was closely related to the anion
used, with the chloride salt showing the lowest stability.
However, the electrophile was also important, since an
analogous reaction with benzoyl triflate was not success-
ful.
Et3SiOTf
Et2O, 0 °C, 1 h
+NR2
2
R1
C(NR2
)
2 3
R1
– Et3SiNR2
81–93%
NR2
2
2
TfO–
6a–h
As found in previous studies,4,5 propiolamidinium salts 3
appear to be very reluctant to undergo common cycload-
dition reactions. They did not participate in Diels–Alder
reactions with cyclopentadiene (even under heating in
acetonitrile), and were not amenable to 1,3-dipolar cy-
cloaddition reactions with ethyl diazoacetate or oxazoli-
um mesoionic reagents.
3a-OTf – 3h-OTf
a R1 = Ph, R2 = Me
b R1 = c-Pr, R2 = Me
c R1 = t-Bu, R2 = Me
d R1 = SiMe3, R2 = Me
e R1 = SiEt3, R2 = Me
f R1 = Si(i-Pr)3, R2 = Me
g R1 = Ph, R2 = Et
h R1 = H, R2 = Me
Scheme 3 Synthesis of propiolamidinium triflates 3a–h-OTf
Under the same reaction conditions, orthoamide 6i was
cleaved at the Calkyne–CN bond, and hexamethylguanidini-
um triflate (5c) was isolated in high yield (Scheme 4). The
reason for this different behavior is not yet known.
On the other hand, the propiolamidinium salts underwent
diastereoselective Michael-type nucleophilic addition
with sec-amines. As an example, the reaction of salts 3
with morpholine afforded the b-morpholino-propeneami-
dinium salts 7 in high yields (Scheme 5), with syn-addi-
tion being observed exclusively (the configuration was
established by NOE NMR experiments). Whereas syn-ad-
dition is the rule for Michael additions of this kind, it must
also be kept in mind that the cations of salts 7 represent vi-
namidinium systems, which, due to the push-pull substi-
tution of the enaminic double bond, can easily assume the
most stable configuration irrespective of the geometry of
the addition step.
+NMe2
Et3SiOTf
Et2O, –11 °C, 1 h
NMe2
EtO2C
NMe2
NMe2
Me2N
NMe2
TfO–
5c
91%
6i
Scheme 4 Et3SiOTf-induced cleavage of alkynyl orthoamide 6i
The highly electrophilic silyl triflates were found to be the
best reagents for effective deamination of orthoamides
6a–h. A comparison of the TMS triflate with the TMS ha-
lides was made for the transformation of the trimethylsi-
lyl-substituted alkynyl orthoamide 6d (Table 3). It was
evident that the yield diminished with decreasing silylat-
ing power of the reagent. Silyl halides could be used to
prepare the bromide and iodide salts, however, the chlo-
ride salts could not be isolated. The bromide and iodide
salts were obtained as oils. We were also unable to pro-
vide analytically pure bromides or chlorides by recrystal-
lization. When Me3SiOTf was added slowly to a solution
Such an addition reaction was previously reported by
Weingarten,12 whereby, 3-phenylpropiolamidinium ace-
tate, which resulted from the reaction of acetic acid with
orthoamide 6a, was trapped in situ by conjugate addition
of dimethylamine. Other synthetic routes to propeneami-
dinium salts have been based on condensation reactions.13
Propiolamidinium salts 3 also reacted with thiols through
conjugate addition. Examples with cyclohexylmercaptan
(8a) and benzenethiol (8b) are shown in Scheme 6. The
reaction with propiolamidinium chloride 3a-Cl afforded a
mixture of E/Z-isomeric salts 9a and 10a, respectively. In
Synthesis 2011, No. 2, 265–272 © Thieme Stuttgart · New York

PAPER
Synthesis and Reactions of Propiolamidinium Salts
269
+NMe2
Assignment of the E- or Z-configuration of propeneami-
dinium salts 10a by NOE experiments was not reliable
due to the presence of closely spaced H signals of the
H
morpholine
+NMe2
NMe2
Me2N
MeCN, r.t., 4 h
1
X–
R
91-93%
phenyl and the phenylthio groups. However, the similarity
N
R
X–
1
of the H and 13C NMR chemical shifts compared with
O
(E)- and (Z)-9a (Table 4) allowed us to assume the same
configuration for the major vs. the minor isomers in both
cases. It should also be mentioned that the relevant 1H and
13C NMR data assigned to the two diastereomers of 10a
are, in all details, analogous to those of a related propene-
iminium salt, 4-(1-methyl-3-phenyl-3-phenylthio-2-pro-
pen-ylidene)morpholinium triflate.14 Additionally, we
were able to assign characteristic NMR chemical shifts of
(E)- and (Z)-10a based upon computationally calculated
molecular structures of (E)- and (Z)-9a (see the Support-
ing Information).
3a,b,d
7a,b,d
a: R = Ph, X = BPh4
b: R = c-Pr, X = BPh4
d: R = SiMe3, X = OTf
Scheme 5 Conjugate addition of morpholine to propiolamidinium
salts 3a-BPh4, 3b-BPh4 and 3d-OTf
contrast to salts 7, formation of the Z-isomer predominat-
ed in both cases. For the isomeric 3-cyclohexylthioprop-
eneamidinium chlorides 9a, the configurational
assignment was accomplished by selective NOE experi-
ments, which revealed perturbation effects between the
olefinic proton and the neighboring 1H nuclei. For exam-
ple, irradiation at d = 6.32 ppm [2-H for the major isomer
(Z)-9a] resulted in through-space interactions with the
signals at d = 3.36 [N(CH3)2] and 7.47 ppm (PhH).
The terminal alkyne 3h offered the opportunity to meta-
late the acetylenic C–H bond, paving the way to other
alkynyl amidinium salts that are substituted or functional-
ized at the remote acetylenic carbon atom. Bertrand and
R−SH
SR +NMe2
NMe2
Ph +NMe2
NMe2
(8a R = C6H11, 8b R = Ph)
+NMe2
CHCl3, 60 °C, 6 h or 4 h
9a R = C6H11
10a R = Ph
+
Ph
Ph
RS
> 98%
Cl–
NMe2
Cl–
Cl–
H
H
3a-Cl
(E)-9a, 10a
(Z)-9a,10a
9a 15
10a 20
:
:
85
80
Scheme 6 Conjugate addition of cyclohexylmercaptan (8a) and benzenethiol (8b) to propiolamidinium chloride 3a-Cl
Table 4 1H and 13C NMR Data of Salts 9a and 10aa
+NMe2
Ph
3
2
1
9a R = C6H11
10a R = Ph
NMe2
RS
Compd 1H NMR d (ppm)
13C NMR d (ppm)
2-H
NCH3
3.05
PhH
R
C-1
C-2
C-3
NCH3
Other signals
(E)-9a 6.05
167.1
109.2
162.3
25.3, 25.4, 32.3 (CH2); 45.2
(SCH); 127.8, 129.2, 131.0,
136.3 (CPh)
7.42–7.49 1.02–1.71 (5 CH2)
2.70–2.81 (SCH)
42.8–43.7b
(Z)-9a
6.32
3.36
166.6
166.2
118.0
109.2
156.2
164.2
25.0, 25.6, 33.8 (CH2); 45.5
(SCH); 127.7, 129.0, 130.4,
136.4 (CPh)
(E)-10a 5.29
(Z)-10a 6.72
3.04, 3.15c
127.7, 128.7, 129.3, 130.4,
130.7, 131.3, 134.9 (CPh)d
7.14–7.63 (Ph, SPh)
42.3–43.2b
3.43
166.0
118.4
154.8
128.2, 128.5, 128.6, 129.2,
130.5, 130.7, 131.1, 135.7
(CPh)
a Recorded in CDCl3 with TMS as internal standard. NMR data for 9a were recorded with a Bruker DRX 400, data for 10a were recorded with
an AMX 500 spectrometer.
b The NCH3 signals were strongly broadened due to coalescence.
c Two broadened, symmetrical NCH3 signals.
d One 13C signal for CPh in (E)-10a coincides with a signal of (Z)-10a.
Synthesis 2011, No. 2, 265–272 © Thieme Stuttgart · New York

270
W. Weingärtner et al.
PAPER
co-workers15 have just reported that 2-ethynyl-1,3-di-
methylimidazolium iodide, which can be considered as a
special type of an alkynyl amidinium salt, is readily met-
alated with silver oxide to give the complex [(1,3-
Me2ImC≡C)2Ag]I, which was characterized by an X-ray
crystal structure analysis and used for transmetalation re-
actions.
were recorded with an AMX 500 spectrometer operating at 500.1
MHz for 1H and 125.7 MHz for 13C. The solvent signals served as
internal standard for NMR spectroscopic measurements. IR spectra
were obtained with a Bruker Vector 22 FT-IR spectrophotometer
using a Harrick Scientific MVP ATR unit equipped with a ZnSe
crystal. Melting points were determined with a Büchi Melting Point
B-540 apparatus and are uncorrected. Elemental analyses were per-
formed with an Elemental Vario Micro Cube. The HRMS spectrum
for 11 was recorded with a Bruker Daltonics micrOTOF-Q instru-
ment (ESI).
+
NMe2
Me2N
Me2N
Hexamethylguanidinium chloride (5a) and hexaethylguanidinium
chloride (5b) were prepared according to the literature procedure20
and dried over P2O5 for 3 d at 165 °C in vacuo (0.01 mbar).
Ag
NMe2
[AgCl2]–
Sodium acetylide (NaCCH) was purchased as an 18% slurry in xy-
lene from Acros Organics, the xylene was removed in vacuo. The
crude sodium acetylide was washed several times with anhydrous
hexane, filtered off through a sintered glass filter and dried at 60 °C
in vacuo (0.5 mbar) for 3 h.
Ag2O
CH2Cl2, r.t., 15 h
+NMe2
NMe2
11a
H
or
63%
Cl–
Me2N
Me2N
3h–Cl
AgCl
Triethylsilyl- and triisopropylsilylacetylene (4e and 4f) were syn-
thesized according to a slightly modified literature procedure.21 To
form the reactive mono-lithium acetylide species, a solution of n-
BuLi (1 M in Et2O, 0.25 mol, 250 mL) was slowly added to a satu-
rated solution of acetylene in THF (50 mL containing approx. 2.5
equiv of acetylene) through a double-ended needle at –78 °C.
11b
Scheme 7 Conversion of ethynyl orthoamide 7h into silver complex
11a and/or 11b
Cylohexylmercaptan (8a) and benzenethiol (8b) were dried with
CaCl2, and distilled at 40 mm pressure in a stream of argon.
By partial analogy, we found that salt 3h-Cl reacts
smoothly with silver(I) oxide to give the stable silver(I)
bisacetylide complex 11 (Scheme 7). The proposed struc-
ture, a linear [Ag(CCC(NMe2)2)2]+ cation and an [AgCl2]–
anion, which should be associated through an Ag–Ag in-
teraction (see Wang and Lin;16 silver alkynyl complexes
forming metallic clusters are also known17), is in agree-
All other reagents were purchased from commercial suppliers and
used without further purification.
Alkynyl Orthoamides 6; Typical Procedure
To a solution of an alkyne 4 (12.0 mmol) in THF (12 mL) cooled to
–78 °C was slowly added BuLi (2.5 M in hexane, 4.80 mL) via a sy-
ment with elemental analysis and mass spectra. To our ringe. The reaction mixture was kept for 15 min at –78 °C and then
allowed to warm to r.t. Hexamethyl- or hexaethylguanidinium chlo-
ride (5a or 5b, 11.5 mmol) was swiftly added, and the suspension
was vigorously stirred at ambient temperature for 17 h. The precip-
itated LiCl was filtered through a sintered glass filter under an argon
atmosphere, and the solvent was then removed at 40 °C/175 mbar.
The residue was carefully distilled in a Kugelrohr apparatus to af-
ford colorless or light-yellow oils. Alkynyl orthoamides can be
surprise, however, a single-crystal X-ray structure analy-
sis revealed the structure of monoacetylide silver complex
11b (note that 11a and 11b have the same relative elemen-
tal composition). In the crystal structure, two symmetry-
related molecules of 11b form a dimer with a four-mem-
bered cyclic Ag–Cl···Ag–Cl core. It appears, therefore,
that in solution an equilibrium exists between complexes stored in Schlenk tubes under an argon atmosphere in a freezer at
11a and 11b16 and that the ESI(+) mass spectrum reveals
–20 °C. For yields, physical and spectroscopic data, see Table 1.
only the cation of complex 11a. Further studies on this is-
3,3,3-Tris(dimethylamino)propyne (6h)
sue, as well as on metalation and transmetalation reac-
Sodium acetylide (1.87 g, 39 mmol) was suspended in anhydrous
MeCN (20 mL). HMG-Cl (6.00 g, 33 mmol) was added, and the
tions, are underway.18
slurry was stirred for 1 d at 40 °C. The precipitated NaCl was fil-
tered off through a sintered glass filter under an argon atmosphere
and the MeCN was quickly removed at 40 °C/80 mbar. The residue
In summary, we have developed a novel method to pre-
pare propiolamidinium triflates 3a–g-OTf, including an
improved procedure for the preparation of alkynyl ortho-
was distilled in a Kugelrohr apparatus (65 °C/5 mbar) to afford a
amides from terminal alkynes and hexaalkylguanidinium
highly hygroscopic yellow oil, which quickly crystallized as off-
chlorides. These alkynyl orthoamides are versatile syn-
thetic building blocks in their own right.9b,19 It is hoped
that propiolamidinium salts 3 will prove to be useful sub-
strates for further transformations.
white needles.
Yield: 3.85 g (69%); mp 24–26 °C.
Propiolamidinium Chlorides 3-Cl; Typical Procedure
To a solution of alkynyl orthoamide 6a–c or 6h (4.0 mmol) in Et2O
(25 mL) was slowly added a solution of freshly distilled benzoyl
chloride (0.48 mL, 4.1 mmol) in Et2O (8 mL) at 0 °C. The reaction
mixture was stirred for 40 min, during which time a white powdery
precipitate formed. The liquid phase was removed by pipette, and
the precipitate was washed several times with Et2O. The light-
brown solid was dried and recrystallized from CH2Cl2/Et2O to af-
ford propiolamidinium chlorides 3 as off-white powders (see
Table 2). The synthesis of 3a-Cl by this method has already been
described.5 For elemental analysis, the propiolamidinium chlorides
All reactions were carried out in rigorously dried glassware under
an atmosphere of argon, making use of Schlenk techniques, and tak-
ing into account the moisture-sensitivity of the orthoamides and
amidinium salts. Solvents were dried by established procedures and
stored over molecular sieves (4 Å for Et2O, CH2Cl2, pentane, and
THF, 3 Å for EtOAc and acetonitrile). Trimethyl and triethylsilyl
triflate were freshly distilled prior to use. NMR spectra were record-
ed with a Bruker DRX 400 spectrometer operating at 400.1 MHz for
1H and 100.6 MHz for 13C. NOE experiments and 2D NMR spectra
Synthesis 2011, No. 2, 265–272 © Thieme Stuttgart · New York

PAPER
Synthesis and Reactions of Propiolamidinium Salts
271
3-Cl were converted into non-hygroscopic tetraphenylborate salts
3-BPh4 (vide infra).
13C NMR (DMSO-d6): d = 39.4 (NCH3), 120.6 (q, 1JC–F = 322 Hz,
CF3), 162.3 {C+[N(CH3)2]3}.
MS (CI): m/z (%) = 144 (100) [Mcat]+, 145 (8) [Mcat + H]+.
Propiolamidinium Tetraphenylborates 3; Typical Procedure
Propiolamidinium chloride 3a–c or 3h-Cl (4.0 mmol) was dissolved
in an adequate quantity of MeCN. A solution of sodium tetraphe-
nylborate (1.37 g, 4.0 mmol) in MeCN (5 mL) was added and the
mixture was stirred for 15 min at 60 °C. The precipitated NaCl was
hot-filtered off, the filtrate was evaporated in vacuo, and the crude
product was recrystallized from MeCN to afford the tetraphenylbo-
rate.
Anal. Calcd for C8H18F3N3O3S (293.31): C, 32.76; H, 6.19; N,
14.33. Found: C, 32.75; H, 6.00; N, 14.13.
N,N,N¢,N¢-Tetramethyl(3-morpholino-3-phenylprop-2-
yne)amidinium Tetraphenylborate (7a)
To a solution of tetraphenylborate salt 3a-BPh4 (1.04 g, 2.0 mmol)
in MeCN (14.0 mL) was slowly added dried morpholine (0.175 mL,
2.0 mmol), and the mixture was stirred for 4 h at ambient tempera-
ture. The solution was concentrated in vacuo, and the white precip-
itate was filtered off and recrystallized form EtOAc to afford 7a as
white crystals.
3a-BPh4
Yield: 1.89 g (91%); mp 172–173 °C.
Anal. Calcd for C37H37BN2 (520.51): C, 85.38; H, 7.16; N, 5.38.
Found: C, 85.12; H, 7.18; N, 5.28.
Yield: 1.13 g (93%); mp 181–182 °C.
IR (ATR): 3056, 2957, 2865, 1585, 1553, 1480, 1447, 1397, 1343,
1265, 1242, 1220, 1154, 1118, 1062, 1032, 903, 821 cm–1.
3b-BPh4
Yield: 1.69 g (87%); mp 140–141 °C.
+
1H NMR (DMSO-d6): d = 2.71 (s, 12 H, NCH3), 3.23–3.25 (m,
Anal. Calcd for C34H37BN2 (484.48): C, 84.29; H, 7.70; N, 5.78.
Found: C, 84.09; H, 7.71; N, 5.65.
4 H, CH2 morpholino), 3.69–3.71 (m, 4 H, CH2 morpholino), 4.86
(s, 1 H, C=CH), 6.77–6.79 (m, 4 H, PhH), 6.91–6.94 (m, 8 H, PhH),
7.17–7.18 (m, 8 H, PhH), 7.35–7.33 (m, 2 H, PhH), 7.55–7.52 (m,
3 H, PhH).
3c-BPh4
Yield: 1.78 g (89%); mp 157–158 °C.
13C NMR (DMSO-d6): d = 41.5 (NCH3), 49.2 (NCH2), 65.6
3
Anal. Calcd for C35H41BN2 (500.52): C, 83.99; H, 8.26; N, 5.60.
Found: C, 83.70; H, 8.19; N, 5.43.
(OCH2), 88.8 (C=CH), 121.5, 125.2 (q, JB,C = 2.7 Hz, BCCPh),
1
128.9, 129.0, 130.8, 134.1, 135.5 (CPh), 164.3 (q, JB,C = 49.5 Hz,
BCPh), 167.1 {C+[N(CH3)2]2}, 169.4 (C=CH).
3h-BPh4
Anal. Calcd for C41H46BN3O (607.63): C, 81.04; H, 7.63; N, 6.92.
Found: C, 80.36; H, 7.80; N, 6.92.
Yield: 1.49 g (84%); mp >183 °C (dec.).
Anal. Calcd for C31H33BN2 (444.42): C, 83.78; H, 7.48; N, 6.30.
Found: C, 83.64; H, 7.52; N, 6.27.
N,N,N¢,N¢-Tetramethyl(3-morpholino-3-cyclopropylprop-2-
yne)amidinium Tetraphenylborate (7b)
Prepared as for 7a.
Propiolamidinium Triflates 3; Typical Procedure
To a cooled solution (0 °C) of triethylsilyl trifluoromethane-
sulfonate (0.91 mL, 4.0 mmol) in pentane (12 mL) was slowly add-
ed a solution of alkynyl orthoamide 6a–h (4.0 mmol) in Et2O (5
mL) from a cooled dropping funnel.
Yield: 1.04 g (91%); mp 171–172 °C.
IR (ATR): 3052, 2983, 2888, 2853, 1573, 1532, 1441, 1421, 1399,
1372, 1267, 1238, 1150, 1121, 1060, 1025, 953, 906, 876 cm–1.
1H NMR (DMSO-d6): d = 0.34–0.37 (m, 2 H, CH2 cp), 0.93–0.97
(m, 2 H, CH2 cp), 1.52–1.57 (m, 1 H, CH cp), 2.97 (s, 12 H, NCH3),
3.55–3.57 (m, 4 H, CH2 morpholino), 3.66–3.68 (m, 4 H, CH2 mor-
pholino), 4.46 (s, 1 H, C=CH), 6.77–6.80 (m, 4 H, PhH), 6.91–6.94
(m, 8 H, PhH), 7.17–7.18 (m, 8 H, PhH).
3a-OTf and 3c–g-OTf
A yellow oil separated from the above Et2O–pentane solution, and
the mixture was kept stirring for 30 min at 0 °C. The supernatant
phase was decanted, and the residual oil was solidified by anhy-
drous Et2O trituration and by scratching the inner wall of the flask
with a glass rod. The crude solid product was taken up in CH2Cl2
and again slowly precipitated by addition of Et2O. The solid was
dried in vacuo to afford the salts as tan-colored powders.
13C NMR (DMSO-d6): d = 6.9 (CH2 cp), 12.6 (CH cp), 41.4 (NCH3),
47.5 (NCH2), 65.7 (OCH2), 83.1 (C=CH), 121.5, 125.3 (q,
1
3JB,C = 2.7 Hz, BCCPh), 135.5 (CPh), 164.3 (q, JB,C = 49.5 Hz,
BCPh), 167.1 {C+[N(CH3)2]2}, 169.4 (C=CH).
3b-OTf and 3h-OTf
Anal. Calcd for C38H46BN3O (571.60): C, 79.85; H, 8.11; N, 7.35.
Found: C, 79.63; H, 8.24; N, 7.29.
A deeply colored oil separated from the organic phase, and the mix-
ture was kept stirring at 0 °C for 15 min. The supernatant organic
phase was thoroughly removed by pipette and the residual oil was
triturated several times with anhydrous pentane in an ultrasonic
bath. For yields, physical and spectroscopic data, see Table 2.
N,N,N¢,N¢-Tetramethyl(3-morpholino-3-trimethylsilylprop-2-
yne)amidinium Trifluoromethanesulfonate (7d)
Yield: 0.77 g (87%); mp 121–122 °C.
IR (ATR): 2966, 2910, 2864, 1582, 1521, 1399, 1255, 1222, 1140,
1116, 1030, 952, 914, 829 cm–1.
1H NMR (CDCl3): d = 0.33 (s, 9 H, SiCH3), 3.09–3.12 (m, 12 H,
NCH3), 3.33–3.55 (m, 4 H, CH2 morpholino), 3.74–3.77 (m, 4 H,
CH2 morpholino), 4.38 (s, 1 H, C=CH).
Compound 6i
In the case of orthoamide 6i, N,N,N¢,N¢,N¢¢,N¢¢-hexamethylguani-
dinium triflate (5c) was isolated as a white powder, which was re-
crystallized from MeCN and dried for 6 h at 60 °C in vacuo (0.01
mbar).
13C NMR (CDCl3): d = 0.1 (SiCH3), 42.1 (NCH3), 51.2 (NCH2),
Yield: 1.07 g (91%); mp 177–178 °C.
1
67.0 (OCH2), 89.9 (C=CH), 120.9 (q, JC–F = 319 Hz, CF3), 168.2
IR (ATR): 2919, 1597, 1479, 1409, 1280, 1222, 1164, 1025,
897 cm–1.
{C+[N(CH3)2]2}, 174.0 (C=CH).
Anal. Calcd for C15H30F3N3O4SSi (433.56): C, 41.55; H, 6.97; N,
9.69. Found: C, 41.60; H, 6.88; N, 9.65.
1H NMR (DMSO-d6): d = 3.01 (NCH3).
Synthesis 2011, No. 2, 265–272 © Thieme Stuttgart · New York

272
W. Weingärtner et al.
PAPER
N,N,N¢,N¢-Tetramethyl(3-cyclohexylthio-3-phenylprop-2-
yne)amidinium Chloride (E/Z-9a)
References
(1) For selected references for cycloaddition reactions, see:
(a) Nikolai, J.; Schlegel, J.; Regitz, M.; Maas, G. Synthesis
2002, 497. (b) Gerster, H.; Espenlaub, S.; Maas, G.
Synthesis 2006, 2251. (c) Gerster, H.; Maas, G. Z.
Naturforsch., B 2008, 63, 384.
(2) For selected references for reaction with nucleophiles, see:
(a) Maas, G.; Mayer, T. Synthesis 1991, 1209.
(b) Reinhard, R.; Glaser, M.; Neumann, R.; Maas, G. J. Org.
Chem. 1997, 62, 7744. (c) Schlegel, J.; Maas, G. J. Prakt.
Chem. 2000, 342, 235. (d) Reisser, M.; Maier, A.; Maas, G.
Eur. J. Org. Chem. 2003, 2071. (e) Reisser, M.; Maas, G.
J. Org. Chem. 2004, 69, 4913. (f) Rahm, R.; Espenlaub, S.;
Werz, U. R.; Maas, G. Heteroat. Chem. 2005, 16, 437.
(3) (a) Viehe, H. G.; Baum, J. S. Chimia 1975, 29, 300.
(b) Baum, J. S.; Viehe, H. G. J. Org. Chem. 1976, 41, 183.
(c) François, J.-P.; Gittos, M. W. Synth. Commun. 1979, 9,
741.
(4) Baum, J. S. Postdoctoral Technical Report; UCL Louvain:
Belgium, 1975.
(5) Kantlehner, W.; Lehmann, H.; Stahl, T.; Kaim, W. Chem.-
Ztg. 1991, 115, 183.
(6) Eilingsfeld, H.; Neubauer, G.; Seefelder, M.; Weidinger, H.
Chem. Ber. 1964, 97, 1232.
(7) Hobbs, C. F.; Weingarten, H. J. Org. Chem. 1971, 36, 2881.
(8) Kantlehner, W.; Speh, P.; Lehmann, H.; Bräuner, H. J.;
Haug, E.; Mergen, W. W. Chem.-Ztg. 1990, 114, 176.
(9) (a) Hobbs, C. F.; Weingarten, H. J. Org. Chem. 1971, 36,
2885. (b) Kantlehner, W.; Haug, E.; Stieglitz, R.; Frey, W.;
Kress, R.; Mezger, J. Z. Naturforsch., B 2002, 57, 399.
(10) Midland, M. J. Org. Chem. 1975, 40, 2250.
(11) Kantlehner, W.; Kreß, R.; Mezger, J.; Ladendorf, S.
Z. Naturforsch., B 2005, 60, 227.
(12) Weingarten, H. Tetrahedron 1968, 24, 2767.
(13) (a) Jutz, Ch.; Müller, E. Angew. Chem. 1966, 78, 747.
(b) Art, J.-F.; Janousek, Z.; Viehe, H. G. Synth. Commun.
1990, 20, 3031.
To a solution of 3a-Cl (710 mg, 3.0 mmol) in CHCl3 (2.0 mL) was
added cyclohexylmercaptan (8a) (370 mL, 3.0 mmol), and the mix-
ture was stirred for 4 h at 60 °C. The solution was concentrated in
vacuo, and the yellow crude product was triturated several times
with Et2O in an ultrasonic bath to afford 9a as a yellow sticky oil
(isomeric mixture, Z/E = 85:15).
Yield: 943 mg (99%). For spectroscopic data, see Table 4.
For elemental analysis, the chloride salts E/Z-9a were converted
into the tetraphenylborate salts (see procedure above), which were
recrystallized from CHCl3.
Anal. Calcd for C43H49BN2S (636.74): C, 81.11; H, 7.76; N, 4.40.
Found: C, 81.08; H, 7.70; N, 4.47.
N,N,N¢,N¢-Tetramethyl(3-phenyl-3-phenylthioprop-2-yne)ami-
dinium Chloride (E/Z-10a)
To a solution of 3a-Cl (710 mg, 3.0 mmol) in CHCl3 (2.0 mL) was
added benzenethiol (8b; 310 mL, 3.0 mmol) and the mixture was
stirred for 6 h at 60 °C. The solution was concentrated in vacuo, and
the residual yellow oil was triturated several times with Et2O in an
ultrasonic bath to afford 10a as a bright yellow solid (isomeric mix-
ture, Z/E = 80:20).
Yield: 1.02 g (98%). For spectroscopic data, see Table 4.
For elemental analysis, chloride salts E/Z-10a were converted into
the tetraphenylborate salts (see procedure above), which were re-
crystallized from CHCl3.
Anal. Calcd for C43H43BN2S (630.69): C, 81.89; H, 6.87; N, 4.44.
Found: C, 81.82; H, 6.82; N, 4.43.
Complex 11
Salt 3h-Cl (870 mg, 5.4 mmol) was dissolved in CH2Cl2 (25 mL),
and silver(I) oxide (625 mg, 2.7 mmol) was added. The mixture was
stirred for 15 h and then reduced to three-quarter of its volume. The
gray-brown crude solid was collected and dissolved in refluxing an-
hydrous CHCl3 (125 mL). The solution was filtered hot, allowed to
cool and placed in a refrigerator at – 32 °C to precipitate 11 as an
off-white powder.
(14) Maas, G.; Würthwein, E.-U.; Singer, B.; Mayer, T.; Krauss,
D. Chem. Ber. 1989, 122, 2311.
(15) Asay, M.; Donnadieu, B.; Schoeller, W. W.; Bertrand, G.
Angew. Chem. Int. Ed. 2009, 48, 4796; Angew. Chem. 2009,
121, 4890.
(16) Wang, H. M. J.; Lin, I. J. B. Organometallics 1998, 17, 972.
(17) Rais, D.; Yau, J.; Mingos, D. M. P.; Vilar, R.; White, A. J.
P.; Williams, D. J. Angew. Chem. Int. Ed. 2001, 40, 3464;
Angew. Chem. 2001, 113, 3572.
(18) Details of the crystal structure analysis of 11b will be
reported elsewhere. The bond lengths in the organic part of
the complex suggest a rather small degree of electron
delocalization toward the bond structure of a
Yield: 910 mg (63%); mp >159 °C (dec.).
IR (ATR): 2934, 2079, 1597, 1471, 1408, 1394, 1285, 1172, 1025,
886 cm–1.
1H NMR (DMSO-d6): d = 3.22 (s, NCH3).
13C NMR (DMSO-d6): d = 42.8 (NCH3), 94.2 (CCAg), 151.9
{C[N(CH3)2]2}; CAg not observed.
+
HRMS (ESI, +): m/z calcd for C14H24AgN4 : 355.1052; found:
355.1046.
Anal. Calcd for C14H24Ag2Cl2N4 (535.01): C, 31.43; H, 4.52; N,
10.47. Found: C, 31.61; H 4.56; N, 10.52.
[bis(dimethylamino)allenylidene] silver(I) complex
(compare lit.15).
(19) Kantlehner, W.; Vettel, M.; Lehmann, H.; Edelmann, K.;
Stieglitz, R.; Ivanov, I. C. J. Prakt. Chem. 1998, 340, 408.
(20) Kantlehner, W.; Haug, E.; Mergen, W. W.; Speh, P.; Maier,
T.; Kapassakalidis, J. J.; Bräuner, H.-J.; Hagen, H. Liebigs
Ann. Chem. 1984, 108.
Acknowledgment
This research was funded by the Bundesministerium für Bildung
und Forschung (BMBF, FKZ 01 RI 05179). We thank Chemische
Fabrik Karl Bucher GmbH (Waldstetten, Bayern) and BASF SE
(Ludwigshafen/Rhein) for chemicals.
(21) Marino, J. P.; Nguyen, H. H. J. Org. Chem. 2002, 67, 6841.
Synthesis 2011, No. 2, 265–272 © Thieme Stuttgart · New York