Syntheses and stability of alkynyl s,n-acetals derived from 2-propynals

Article abstract of DOI:10.1080/10426500902947765

Two types of synthetic methods for S,N-acetals derived from 2-propynals were described. Thioformamides, lithium acetylides, and alkylating agents were the key substrates. In the first method, methylation of thioformamides with MeOTf followed by reacting w

Full text of DOI:10.1080/10426500902947765

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Phosphorus, Sulfur, and Silicon
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Syntheses and Stability of
Alkynyl S,N-Acetals Derived
from 2-Propynals
Toshiaki Murai a , Kozue Fukushima a , Yukiyasu Ohta
a & Yuichiro Mutoh a
a Department of Chemistry, Faculty of Engineering ,
Gifu University , Gifu, Japan
Published online: 06 Jun 2009.
To cite this article: Toshiaki Murai , Kozue Fukushima , Yukiyasu Ohta & Yuichiro
Mutoh (2009) Syntheses and Stability of Alkynyl S,N-Acetals Derived from 2-Propynals,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:6, 1462-1480, DOI:
10.1080/10426500902947765
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Phosphorus, Sulfur, and Silicon, 184:1462–1480, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500902947765
Syntheses and Stability of Alkynyl S,N-Acetals Derived
from 2-Propynals
Toshiaki Murai, Kozue Fukushima, Yukiyasu Ohta,
and Yuichiro Mutoh
Department of Chemistry, Faculty of Engineering, Gifu University, Gifu,
Japan
Two types of synthetic methods for S, N-acetals derived from 2-propynals were de-
scribed. Thioformamides, lithium acetylides, and alkylating agents were the key
substrates. In the first method, methylation of thioformamides with MeOTf fol-
lowed by reacting with lithium acetylides led to the title compounds. As an alter-
native method, the direct addition of lithium acetylides to thioformamides gave
lithium thiolates, which was then alkylated. With these two methods, a wide range
of derivatives including bis-S, N-acetals were provided, and their stability was in-
fluenced by the substituents at the alkynyl carbon atom. The introduction of silyl
group enhanced the stability effectively.
Keywords Alkynyl S, N-acetals; alkynylation; thioiminium salts
INTRODUCTION
Alkynyl S, S-acetals derived from 2-propynals are important synthetic
units leading to a wide variety of alkynes and allenes.1 Similarly,
N,N-acetals derived from 2-propynals have been prepared2 and used
as key precursors leading to propargylamines.3 In contrast, only
one article has described acyclic alkynyl S, N-acetals4 to the best of
our knowledge before our studies,5 although cyclic derivatives are
synthesized.6 For example, the addition of lithium phenylacetylide
to 3-methylbenzothiazolium iodide gives 2-alkynylbenzothiazole
Received 7 January 2008; accepted 3 March 2008.
Dedicated to Professor Marian Mikolajczyk,CBMiM PAN in Lo´dz´, Poland, on the oc-
ꢀ
ꢀ
casion of his 70th birthday.
This work was supported in part by Grant-in-Aid for Scientific Research on Priority
Area (No. 19027021, “Synergy of Elements”) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan.
Address correspondence to Toshiaki Murai, Department of Chemistry, Faculty of En-
gineering, Gifu University, Yanagido, Gifu 501-1193, Japan. E-mail: mtoshi@gifu-u.ac.jp
1462

Alkynyl S, N-Acetals Derived from 2-Propynals
1463
derivative where the sulfur and nitrogen atoms are within a five-
membered ring.6b
During the course of our studies on the reactivity of thioamides,7
alkynylation of the thioiminium salts 2 derived from the thiofor-
mamides 1 with lithium acetylides 3 was found to give the alkynyl
S, N-acetals 4 with high efficiency (Scheme 1).5 We report herein the
detail of two types of synthetic methods leading to alkynyl S, N-acetals
and their stability.
SCHEME 1
RESULTS AND DISCUSSION
The reaction of thioiminium salt 2a generated in situ from thiofor-
mamide 1a and methyl triflate (MeOTf) with lithium acetylide 3a gave
alkynyl S, N-acetal 5 in 92% yield (Table I). Thus, the reactions of in
situ generated thioiminium salt 2a with various lithium acetylides
were carried out. In almost all cases, the S, N-acetals were obtained
in moderate to high yields without any purification. Aliphatic lithium
acetylide 3c with an acetal skeleton 3d were used, and the correspond-
ing S, N-acetals 7 and 8 were obtained. The use of 3e and 3f derived from
enynes also gave S, N-acetals 9 and 10 in high yields. When aromatic
lithium acetylides were used in this reaction, the yields of the products
were not greatly affected by the electron-donating and -withdrawing
groups on the aryl groups (Table I). The reaction with 3j derived from
1-naphthylacetylene8 proceeded smoothly to give the desired product
14 in 97% yield.
Then, the reactions of thioformamides 1 with various substituents
at the nitrogen atom with MeOTf and lithium acetylides 3 were exam-
ined, and a wide range of thioiminium salts participated in the reaction
(Table II). N,N-Diethyl thioformamide (1b),9 N,N-diphenyl thiofor-
mamide (1c), and N,N-dibenzyl thioformamide (1d) worked well as
a starting thioamide affording the acetals 15, 16, and 17. Simi-
larly, the use of thioformamides having two different substituents
on the nitrogen atom gave the desired acetals 18 and 19. 4-
Morpholinecarbothioaldehyde (1g)10 was also applied to this reaction,
and the corresponding S, N-acetal 20 was formed. S, N-Acetals with

1464
T. Murai et al.
TABLE I Synthesis of S, N-Acetals by the Reaction of Thioiminium
Salts with Lithium Acetylidesa
RC CLi 3
S,N–acetal yieldb
RC CLi 3
S,N-acetal yieldb
ME3SiC CLi 3a
Ph3SiC CLi 3b
n-BuC CLi 3c
PhC CLi 3g
4-MeOC6H4C CLi 3h
4-FC6H4C CLi 3i
1-naphthylC CLi 3j
aThe reaction was carried out as follows unless otherwise noted: Thioformamide 1a
(1.0 mmol) was treated with methyl triflate (1.0 mmol) in Et2O (2 mL) at 0◦C for 30s.
Then, to the reaction mixture was added an Et2O solution of the lithium acetylides 3
(1.5 mmol) at 0◦C, and the mixture was stirred at room temperature for 0.5 h. bCrude
yield. cLithium acetylide 3l (1.2 mmol) was used.
ethylthio group 21 and 23 were readily synthesized by using EtOTf
instead of MeOTf (Table II).
The synthesis of the alkynyl S, N-acetals was carried out by the
alternative method shown in Scheme 2 and Table III. The addition of
methyl iodide (23a) to lithium thiolate derived from thioformamide 1a
and lithium acetylide 3a led to S, N-acetal 5 in 87% yield. Several types

Alkynyl S, N-Acetals Derived from 2-Propynals
1465
TABLE II Synthesis of S, N-Acetals by the Reaction of Thioiminium
Salts with Lithium Acetylidesa
thiloformamide 1
3
S, N-acetal yieldb
thioformamide 1
3
S, N−acetal yieldb
1g
1gcd
aThe reaction was carried out as follows unless otherwise noted: Thioformamide 1
(1.0 mmol) was treated with methyl triflate (1.0 mmol) in Et2O (2 mL) at 0◦C for 30s.
Then, to the reaction mixture was added an Et2O solution of the lithium acetylides 3
(1.5 mmol) at 0◦C, and the mixture was stirred at room temperature for 0.5 h. bCrude
yield. cEtOTf was used. dLithium acetylide 3b (1.2 mmol) was used.
of lithium acetylides 3 and alkyl halides 23 were applied to the present
reaction. Ethyl iodide (23b), n-propyl iodide (23c), and n-butyl iodide
(23d) could be used as alkylating agents to give the corresponding S, N-
acetals 24, 25, and 26 in moderate yields.
The reaction of lithium thiolates formed in situ from lithium
acetylides 3a and 3c with allyl bromide (23e) proceeded smoothly un-
der the identical conditions leading to S, N-acetals 27 and 28. Handling
of these products should be carried out in a well-ventilated hood since
they stink more heavily than any other S, N-acetals. The reaction of
SCHEME 2

1466
T. Murai et al.
TABLE III Synthesis of S, N-Acetals by the Reaction of Lithium
Thiolates with Alkyl Haldilesa
substrate
S,N-acetal yieldb
substrate
S, N-acetal yieldb
c
1a
1a
3a
23d
c
3a
c
23a
1a
3a
1a
3a
23b
23e
c
1a
1a
3c
23e
c
3g
c
23a
d
f
1g
1a
d
f
3a
3a
d
f
23b
23f
e
g
1g
1a
e
g
g
3a
3m
e
23c
23a
aThe reaction was carried out as follows unless otherwise noted: Thioformamide
1a (1.0 mmol) was treated with lithium acetylides 3 (1.5 mmol) in Et2O (2 mL) at
−78◦C and the mixture was stirred at room temperature for 0.5 h. Then, to the
reaction mixture was added alkyl halides 5 (2 mmol) at 0◦C, and the mixture was
stirred at room temperature for 2 h. bCrude yield. cThe reaction mixture was
stirred for 1 h. dThioformyl morpholine 1g was used. eThe reaction mixture was
stirred for 1.5 h. f BnBr (1 equiv) was added to lithium thiolate, and then the
mixture was stirred at room temperature for 4 h. gThe reaction mixture was
stirred for 0.5 h.
thioformamide possessing morpholyl group 1g and lithium acetylide
3a also formed the corresponding lithium thiolate. Then, the ethylation
of the lithium thiolate gave S, N-acetal 22 in 84% yield. The use of ex-
actly 1 equiv of benzyl bromide (23f) was necessary for the synthesis of
S, N-acetal 29. The use of excess 23f resulted in the further benzylation

Alkynyl S, N-Acetals Derived from 2-Propynals
1467
of 29. Instead of lithium acetylides, phenyllithium (3m) was used for
the synthesis of phenyl S, N–acetal,11 which could not be obtained by
the method via the thioiminium salt shown in Scheme 1. The reaction
of 1a, 3m, and 23a gave 30 with the contamination of a small amount
of benzaldehyde. The purification of 30 was not successful. A similar
reaction with 1-naphthyllithium did not give the desired products, but
the complex mixture was formed. These indicated that aromatic S, N-
acetals were less stable than alkynyl S, N-acetals. In other words, the
alkynyl group played important roles to enhance the stability of S, N-
acetals.
The introduction of the sec-alkyl group to the sulfur atom of S, N-
acetals was carried out (Scheme 3). To an Et2O solution of lithium
thiolate generated in situ from thioformamide 1a and 3a, 12-crown-4-
ether at 0◦C was added, and this was stirred at this temperature for
30 min. To the reaction mixture was added isopropyl iodide at 0◦C,
and this was stirred at the same temperature for 1 h. After workup,
the desired alkynyl S, N–acetal 31 was obtained in 75% yield. When no
additive was present, 31 was not formed. The use of TMEDA as the
additive gave 31 rather in lower yield (46%).
SCHEME 3
Finally, bis-S, N-acetals linked through alkyl groups were synthe-
sized (Scheme 4). The reaction of lithium thiolate derived from 1 and
3a with 1,2-diiodoethane (32a) was carried out. To obtain the desired
product 33, the various combinations of the molar ratio of 1a, 3a, and
32a were tested, but they usually gave a complex mixture. This may be
partly because of the instability of 33 and/or an initially formed inter-
mediate. 1,3-Diiodopropane (32b) was then used. The reaction mixture
(1a:3a:9b:TMEDA = 3:4.5:1:5) was stirred for 4 h, and the desired
bis-S, N-acetal 34 with two S, N-acetal groups in one molecule was ob-
tained quantitatively. A similar reaction of lithium thiolate derived
from lithium phenylacetylide (3g) and thioformamide 1a gave the de-
sired bis-S, N-acetal 35 in a mixture with other unidentified products.
The reaction of lithium thiolates bearing ethynylcyclohexen-1-yl and 3-
methylbut-3-en-1-ynyl groups with 1,3-diiodopropane (32b) worked in

1468
T. Murai et al.
SCHEME 4
a similar way to give corresponding bis-S, N-acetals 36 and 37. On the
basis of NMR spectra of the crude samples, they contained several types
of unidentified compounds. The further purification of the crude sam-
ples resulted in the decomposition of 36 and 37. Therefore, the stability
of these bis-S, N-acetals depends on the substituents at the alkynyl
carbon atom, and TMS group has contributed to the enhancement of
the stability of the products. A similar effect of silyl group has been
observed for the synthesis of alkynyl hemithioacetals. The addition of
alcohols and ethanethiol to the formyl group of 3-(trimethylsilyl)-2-
propynal gives hemithioacetals 41 (Figure 1) in high yields.12
The reaction of 1a with lithium (trimethylsilyl)acetylide (3a) fol-
lowed by the addition of 1,5-diiodopentane (32c) or 1,6-diiodohexane
(32d) gave the corresponding product 38 or 39 quantitatively. In ad-
dition, the α,αꢀ -dibromo-o-xylene (32e) was also used to lead to the
corresponding bis-S, N-acetal 40 in high yield. The purification of bis-
S, N-acetals shown in Scheme 4 by column chromatography on silica
gel and alumina resulted in the partial decomposition of the products,
but those derived from 3a showed purity higher than 90%.

Alkynyl S, N-Acetals Derived from 2-Propynals
1469
FIGURE 1 Hemiacetals and hemithioacetals.
In summary, two types of synthetic protocols leading to alkynyl S, N-
acetals have been demonstrated. The reaction of thioiminium salts de-
rived from thioformamides and MeOTf with lithium acetylides gives the
desired acetals. Alternatively, the direct addition of lithium acetylides
to thioformamides generates lithium thiolates followed by the addi-
tion of alkyl halides to lead to alkynyl S, N-acetals. The versatility
of these starting materials allows the construction of diverse sets of
alkynyl S, N-acetals. To improve the yields of the products, the use of
12-crown-4 ether and TMEDA is effective. These methods also lead to
bis-S, N-acetals. The stability of alkynyl S, N-acetals is enhanced by the
introduction of silyl groups to the alkynyl carbon atoms.
EXPERIMENTAL
Melting points were measured by a Yanagimoto micro melting point
apparatus (uncorrected). IR spectra were obtained on a JASCO FT/IR
410 spectrophotometer. 1H (399.7 MHz), 13C (100.4 MHz), and 19F
(376.0 MHz) NMR spectra were measured on a JEOL a-400 spectrom-
eter. The 1H and 13C chemical shifts are reported in δ values with
reference to Me4Si and CDCl3 as internal standards, respectively. The
19F chemical shifts are expressed in δ values deshielded with respect
to CF3COOH as an external standard. All spectra were acquired in the
proton-decoupled mode. Mass (MS) and high-resolution mass spectra
(HRMS) were measured on a SHIMAZU GCMS QP 1000, a JEOL
GC-mate II mass spectrometer, or a JEOL JMS-700 spectrometer.
Elemental analyses were carried out at the Elemental Analysis Center
of Kyoto University. All the manipulations were carried out under Ar
atmosphere.
Synthesis of Alkynyl S,N-Acetals via Thioiminium Salts:
General Procedure
To a dried Et2O solution of thioformamide 1 methyl triflate (1 equiv.)
was added at room temperature, and the mixture was stirred for

1470
T. Murai et al.
30 sec at this temperature. To the reaction mixture an Et2O solution
of lithium acetylide 3 (1.5 equiv.) prepared from acetylene and BuLi
(1.6 M hexane solution) at 0◦C was added, and this was stirred for
0.5 h at room temperature. The resulting mixture was poured into a
saturated aqueous solution of NaHCO3, and extracted with Et2O. The
organic layer was dried over MgSO4 and concentrated in vacuo to give
S, N-acetal in purity higher than 95%.
N,N-Dimethyl-1-(methylthio)-3-(trimethylsilyl)-2-propyn-1-
amine (5)
Red oil; IR (neat) 2958, 2860, 2825, 2783, 2163, 1489, 1251 cm−1
;
1H NMR (CDCl3)δ = 0.20 (s, 9H, SiMe3), 2.22 (s, 3H, SMe), 2.35 (s,
6H, NMe2), 4.70 (s, 1H, CH); 13C NMR (CDCl3)δ = −0.07 SiMe3), 14.9
(SMe), 40.6 (NMe2), 64.3 (CH), 92.2, 99.5 (C C); MS (EI) m/z 201 (M+);
Anal. Calcd. for C9H19NSSi: C, 53.67; H, 9.51. Found: C, 53.93; H,
9.37%.
N,N-Dimethyl-1-(methylthio)-3-(triphenylsilyl)-2-propyn-1-
amine (6)
Orange oil; IR (neat) 2958, 2860, 2825, 2782, 2162, 1508, 1046 cm−1; 1H
NMR (CDCl3)δ = 2.23 (s, 3H, SMe), 2.41 (s, 6H, NMe2), 4.81 (s, 1H, CH),
7.23–7.63 (m, 9H, Ar), 7.64-7.70 (m, 6H, Ar); 13C NMR (CDCl3)δ = 15.0
(SMe), 40.9 (NMe2), 64.4 (CH), 87.4, 104.5 (C C), 127.9, 129.9, 133.3,
135.5 (Ar); MS (EI) m/z 388 (M+).
N,N-Dimethyl-1-(methylthio)-2-heptyn-1-amine (7)
Dark brown oil; IR (neat) 3389, 2957, 2934, 2861, 2824, 2780, 2233,
1655, 1631, 1574, 1456, 1343, 1279, 1214, 1158, 1095, 1021, 960, 820,
724, 688, 661 cm–1; 1H NMR (CDCl3)δ = 0..84 (t, J = 7.3 Hz, 3H, CH3),
1.35 (m, 2H, CH2), 1.44, (m, 2H, CH2), 2.09 (s, 3H, SCH3), 2.21 (dt,
J = 2.0, 6.8 Hz, 2H, CH2), 2.28 (s, 6H, N(CH3)2), 4.61 (t, J = 2.0 Hz,
1H, CH); 13C NMR (CDCl3)δ = 13.7 (CH3), 15.1 (SCH3), 18.6, 22.1, 30.9
(CH2), 40.7 (N(CH3)2), 64.3 (CH), 74.8, 88.1 (C C); MS (EI) m/z 185
(M+); HRMS (EI) calcd. for C10H19NS (M+) 185.1238, found 185.1264.
N,N-Dimethyl-1-(methylthio)-4,4-diethoxy-2-butyn-1-amine (8)
Dark brown oil; IR (neat) 3410, 2977, 2931, 2884, 2827, 2783, 2362,
2238, 1660, 1583, 1561, 1454, 1390, 1355, 1329, 1279, 1213, 1130, 1053,

Alkynyl S, N-Acetals Derived from 2-Propynals
1471
1013, 824 cm–1; 1H NMR (CDCl3)δ = 1.18 (t, J = 7.1 Hz, 6H, CH3), 2.17
(s, 3H, SCH3), 2.32, (s, 6H, N(CH3)2), 3.55 (dq, J = 2.4, 7.3 Hz, 2H, CH2),
3.68 (dq, J = 2.4, 7.8 Hz, 2H, CH2), 4.65 (d, J = 1.5 Hz, 1H, CH), 5.31 (d,
J = 1.5 Hz, 1H, OCH); 13C NMR (CDCl3)δ 15.1 (SCH3), 40.7 (N(CH3)2),
60.9 (CH3), 63.7 (CH2), 73.4 (CH), 80.1, 82.7 (C C), 91.3 (OCH); MS
(EI) m/z 231 (M+); HRMS (EI) calcd. for C11H21NO2S (M+) 231.1293,
found 231.1296.
N,N-Dimethyl-1-(methylthio)-3-(cyclohex-1-yl)-2-propyn-1-
amine (9)
Red oil; IR (neat) 3395, 3024, 2933, 2857, 2827, 2778, 2361, 2178, 1661,
1435, 1343, 1259, 1217, 1158, 1135, 1047, 1016, 917, 840, 823, 800, 665,
634, 618 cm–1; H NMR (CDCl3)δ = 1.60 (m, 4H, CH2), 2.12 (m, 4H,
1
CH2), 2.22 (s, 3H, SCH3), 2.37(s, 6H, N(CH3)2), 4.80 (s, 1H, CH), 6.14
(m, 1H, C CHCH2); 13C NMR (CDCl3)δ = 14.1 (SCH3), 21.4, 22.2, 25.6,
29.3 (CH2), 40.6 (N(CH3)2), 64.6 (CH), 74.3, 89.4 (C C), 120.0 (C CH),
135.4 (C CH); MS (EI) m/z 209 (M+); HRMS (EI) calcd. for C12H19NS
(M+) 209.1238, found 209.1259.
N,N,4-Trimethyl-1-(methylthio)-4-penten-2-yn-1-amine (10)
Red oil; IR (neat) 3304, 3096, 2975 ,2945, 2920, 2860, 2825, 2781, 2372,
2219, 2104, 1803, 1614, 1453, 1373, 1342, 1289, 1212, 1159, 1094, 1046,
1016, 963, 899, 824 cm–1; H NMR (CDCl3)δ = 1.84 (s, 3H, CH3), 2.16
1
(s, 3H, SCH3), 2.30 (s, 6H, N(CH3)2), 4.72 (s, 1H, CH), 5.18 (s, 1H,
C CH2), 5.25 (s, 1H, C CH2); 13C NMR (CDCl3)δ = 14.7 (SCH3), 23.3
(CH3), 40.4 (N(CH3)2), 64.1 (CH), 82.8, 88.4 (C C), 122.1 (CH2 =C),
125.9 (CH2 C); MS (EI) m/z 169 (M+); HRMS (EI) calcd. for C9H15NS
(M+) 169.2871, found 169.0910.
N,N-Dimethyl-1-(methylthio)-3-phenyl-2-propyn-1-amine (11)
Dark red oil; IR (neat) 2943, 2860, 2825, 2781, 2189, 1489, 1028 cm−1
;
1H NMR (CDCl3)δ = 2.31 (s, 3H, SMe), 2.42 (s, 6H, NMe2), 4.90 (s, 1H,
CH), 7.25–7.34 (m, 3H, Ar), 7.42–7.50 (m, 2H, Ar); 13C NMR (CDCl3)δ =
15.0 (SMe), 40.7 (NMe2), 64.5 (CH), 84.0, 87.4 (C C), 128.2, 128.4,
131.8, 132.0 (Ar); MS (EI) m/z 205 (M+).

1472
T. Murai et al.
N,N-Dimethyl-1-(methylthio)-3-(4-methoxyphenyl)-2-propyn-
1-amine (12)
Brown oil: IR (neat) 3285, 2940, 2836, 2780, 2219, 2180, 1656, 1605,
1569, 1509, 1455, 1291, 1249, 1173, 1106, 1031, 832, 803 cm−1; 1H NMR
(CDCl3)δ = 2.10 (s, 3H, SCH3), 2.43 (s, 6H, N(CH3)2), 3.8 (s, 3H, OCH3),
4.90 (s, 1H, CH), 6.83 (d, J = 8.8 Hz, 2H, Ar), 7.39 (d, J = 8.8 Hz, 2H,
Ar); 13C NMR (CDCl3)δ = 14.9 (SCH3), 40.7 (N(CH3)2), 55.3 (OCH3),
64.7 (CH), 75.8, 82.6, 87.4 (C), 113.9, 133.2, 159.7 (Ar); MS (EI) m/z 236
(M+); HRMS (EI) calcd. for C13H17NOS (M+) 235.1031, found 235.1039.
N,N-Dimethyl-1-(methylthio)-3-(4-fluorophenyl)-2-propyn-1-
amine (13)
Brown oil: IR (neat) 3404, 3048, 2943, 2859, 5824, 2778, 2226, 1894,
1660, 1600, 1561, 1506, 1469, 1453, 1437, 1226, 1156, 1042, 1015, 836
cm–1; H NMR (CDCl3)δ = 2.20 (s, 3H, SCH3), 2.35 (s, 6H, N(CH3)2),
1
4.80 (s, 1H, CH), 6.90–6.95 (m, 2H, Ar), 7.34–7.41 (m, 2H, Ar); 13C NMR
(CDCl3)δ = 15.0 (SCH3), 40.7 (N(CH3)2), 64.5 (CH), 83.8, 86.3 (C C),
2
1
115.5, 118.5 (Ar), 133.9 (Ar, JCF = 37.1 Hz), 162.6 (Ar, JCF = 249.6
Hz); MS (EI) m/z 224 (M++ 1), 176 (M+ – SCH3), 133 (M+ – SCH3
– N(CH3)2); HRMS (EI) calcd. for C12H14FNS (M+) 223.0831, found
223.0822.
N,N-Dimethyl-1-(methylthio)-3-(1-naphthyl)-2-propyn-1-
amine (14)
Red oil: IR (neat) 3294, 3057, 2942, 2858, 2824, 2779, 2361, 1937, 1662,
1586, 1507, 1452, 1395, 1335, 1260, 1210, 1157, 1094, 1026, 799, 773
cm–1; H NMR (CDCl3)δ = 2.44 (s, 3H, SCH3), 2.51 (s, 6H, N(CH3)2),
1
5.04 (s, 1H, CH), 7.39–7.43 (1H, Ar), 7.49–7.59 (2H, Ar), 7.69–7.71 (1H,
Ar), 7.83 (t, J = 7.6 Hz, 2H, Ar), 8.32 (d, J = 7.8 Hz, 1H, Ar); 13C NMR
(CDCl3)δ = 15.1 (SCH3), 40.9 (N(CH3)2), 64.8 (CH), 85.5, 89.0 (C C),
120.2, 125.2, 126.1, 126.4, 126.9, 128.3, 128.9, 130.8, 133.1, 133.3 (Ar);
MS (EI) m/z 208 (M+ – SCH3); HRMS (EI) calcd. for C16H17NS (M+)
255.1082, (M+ – SCH3) 208.1126, found 208.1090.
N,N-Diethyl-1-(methylthio)-3-phenyl-2-propyn-1-amine (15)
Dark brown oil; IR (neat) 3399, 3061, 2970, 2918, 2826, 2341, 1664,
–1
1598, 1490, 1442, 1383, 1258, 1194, 1157, 1115, 1069, 756, 690 cm
;
1H NMR (CDCl3)δ = 1.05 (t, J = 7.1 Hz, 6H, CH3), 2.18 (s, 3H, SCH3),

Alkynyl S, N-Acetals Derived from 2-Propynals
1473
2.66 (dq, J = 13.7, 6.7 Hz, 2H, CH2) 2.76 (dq, J = 13.7, 6.7 Hz, 2H,
CH2), 5.0 (s, 1H, CH) 7.18-7.23 (m, 3H, Ar), 7.36–7.39 (m, 2H, Ar);
13C NMR (CDCl3)δ = 13.6 (CH3), 14.6 (SCH3), 44.3 (CH2), 60.9 (CH),
85.4, 86.4(C C), 122.7, 128.2, 128.3, 131.7 (Ar); MS (EI) m/z 234 (M+);
HRMS calcd. for C14H19NS (M+) 233.1238, found 233.1254.
N,N-Diphenyl-1-(methylthio)-3-(trimethylsilyl)-2-propyn-1-
amine (16)
Dark brown oil; IR (neat) 3395, 3060, 3036, 2959, 2917, 2173, 1945,
1691, 1591, 1495, 1450, 1412, 1357, 1250, 1184, 1097, 1074, 1030, 1014,
846, 750, 697, 671 cm–1; H NMR (CDCl3)δ = 0.11 (s, 9H, Si(CH3)3),
1
2.12 (s, 3H, SCH3), 5.89 (s, 1H, CH), 7.02–7.07 (m, 2H, Ar), 7.10–7.13 (m,
4H, Ar), 7.25–7.29 (m, 4H, Ar); 13C NMR (CDCl3)δ = –0.35 (Si(CH3)3)
14.7 (SCH3), 57.6 (CH), 93.7, 99.9 (C C), 123.1, 123.5, 128.9, 145.8
(NPh2); MS (EI) m/z 325 (M+); HRMS (EI) calcd. for C19H23NSSi (M+)
325.1321, found 325.1313.
N,N-Di(phenylmethyl)-1-(methylthio)-3-phenyl-2-propyn-1-
amine (17)
Dark brown oil; IR (neat) 3435, 3084, 3061, 3027, 2977, 2918, 2835,
2340, 1951, 1879, 1809, 1677 1600, 1542, 1492, 1454, 1443, 1363, 1258,
1205, 1156, 1119, 1071, 1028, 957, 913, 859, 823, 780, 755, 698, 670,
609, 528, 485, cm–1; H NMR (CDCl3)δ = 2.20 (s, 3H, SCH3), 3.78 (d,
1
J = 13.7 Hz, 2H, CH2Ph), 3.94 (d, J = 13.7 Hz, 2H, CH2Ph), 4.86 (s,
1H, CH), 7.24–7.27 (m, 2H, Ar), 7.31–7.33 (m, 7H, Ar), 7.39–7.40 (m,
4H, Ar), 7.46–7.49 (m, 2H, Ar); 13C NMR (CDCl3)δ = 14.5 (SCH3), 54.0
(CH2Ph), 59.2 (CH), 84.4, 87.2 (C C), 122.6, 127.2, 128.3, 128.4, 128.5,
129.0, 131.9, 138.9 (Ar; The signals due to several aromatic carbon
atoms were overlapped.); MS (EI) m/z 358 (M+); HRMS (EI) calcd. for
C24H23NS (M+) 357.1551, found 357.1543.
N-(2-Propenyl)-N-phenylmethyl-1-(methylthio)-3-phenyl-2-
propyn-1-amine (18)
Dark brown oil; IR (neat) 3399, 3061, 3028, 2919, 2833, 2362, 1952,
1874, 1674, 1640, 1598, 1491, 1442, 1416, 1365, 1259, 1205, 1116,
1071, 1027, 994, 920, 756, 691 cm–1; H NMR (CDCl3)δ = 2.22 (s, 3H,
1
SCH3), 3.29 (dd, J = 5.4, 14.2 Hz, 1H, CH2CH=CH2), 3.44 (dd, J =
6.4, 14.2 Hz, 1H, CH2CH=CH2), 3.84 (m, 2H, CH2Ph), 4.97 (s, 1H,
CH), 5.17 (d, J = 10.2 Hz, 1H, CH2CH=CH2), 5.28 (d, J = 17.1 Hz,

1474
T. Murai et al.
1H, CH2CH=CH2), 5.86 (m, 1H, CH2CH=CH2), 7.20–7.49 (m, 10H,
Ar); 13C NMR (CDCl3)δ = 14.4 (SCH3), 53.0 (NCH2), 53.9 (NCH2), 59.5
(CH), 84.5, 87.0 (C C), 118.0 (CH=CH2), 122.6, 127.1, 128.2, 128.3,
129.0, 131.8, 132.1 (Ar), 135.8 (CH=CH2), (Ar); MS (EI) m/z 307 (M+);
HRMS (EI) calcd. for C20H21NS (M+) 307.4524, found 307.1411.
N-Methy-N-phenyl-1-(methylthio)-3-phenyl-2-propyn-1-
amine (19)
Orange solid; mp 75.8–78.0 (dec.); IR (KBr) 3422, 3060, 2987, 2912,
2817, 2592, 2372, 2222, 1964, 1895, 1822, 1770, 1685, 1595, 1505, 1489,
1472, 1454, 1440, 1424, 1364, 1350, 1304, 1289, 1265, 1224, 1184, 1098,
1070, 1032, 992, 965, 921, 762, 749, 691, 616, 762, 749, 691, 616, 533,
1
517, 503 cm–1; H NMR (CDCl3)δ = 2.16 (s, 3H, SCH3), 3.08 (s, 3H,
CH3), 5.98 (s, 1H, CH), 6.83–6.87 (m, 1H, Ar), 6.96–6.98 (m, 2H, Ar),
7.25–7.30 (m, 5H, Ar), 7.43–7.45 (m, 2H, Ar); 13C NMR (CDCl3)δ = 14.7
(SCH3), 33.3 (CH3), 59.0 (CH), 84.2, 87.2(C C), 115.5, 119.4, 122.2,
128.3, 128.6, 129.2, 131.8, 148.5 (Ar); MS (EI) m/z 267 (M+), HRMS (EI)
calcd for C17H17NS (M+); found 267.1067. Anal. Calcd. for C17H17NS:
C, 76.36; H, 6.41; N, 5.24, Found C, 76.66; H, 6.54; N, 5.24%.
N-(1-Methylthio-3-phenyl-2-propyn-1-yl)morpholine (20)
Dark brown oil; IR (neat) 3395, 3055, 2958, 2917, 2854, 2825, 2758,
2688, 2223, 1970, 1712, 1656, 1598, 1490, 1443, 1341, 1325, 1291, 1258,
1116, 1071, 1030, 999, 980, 861 757, 691, 563 cm–1; 1H NMR (CDCl3)δ =
2.27 (s, 3H, SCH3), 2.79 (m, 4H, CH2), 3.76 (t, J = 4.9 Hz, 4H, CH2),
4.83 (s, 1H, CH), 7.44–7.47 (m, 2H, Ar) 7.25–7.33 (m, 3H, Ar); 13C NMR
(CDCl3)δ = 14.7 (SCH3), 49.0 (CH2NCH2), 63.5 (CH), 66.8 (CH2OCH2),
83.3, 88.0 (C C), 128.3, 128.6, 131.4, 131.8 (Ar); MS (EI) m/z 247 (M+);
HRMS (EI) calcd. for C14H17NOS (M+) 247.1031, found 247.1015.
N-[1-Ethylthio-3-(trimethylsilyl)-2-propyn-1-yl]morpholine (21)
Orange oil: IR (neat) 3423, 2961, 2927, 2898, 2855, 2827, 2758, 2683,
2360, 2246, 2165, 1974, 1664, 1612, 1452, 1322, 1292, 1251, 1201, 1118,
1070, 1057, 1008, 989, 845, 789, 761, 734 cm–1; H NMR (CDCl3)δ =
1
0.14 (s, 9H, Si(CH3)3), 1.24 (t, J = 7.6 Hz, 3H, CH3), 2.65 (m, 6H, CH2),
3.69 (t, J = 4.4 Hz, 4H, CH2), 4.65 (s, 1H, CH); 13C NMR (CDCl3)δ =
–0.06 (Si(CH3)3), 15.0, 25.5 (SCH2CH3), 48.8 (CH2NCH2), 62.0 (CH),
66.8 (CH2OCH2), 92.6, 99.0 (C C); MS (EI) m/z 196 (M+ – SCH2CH3);

Alkynyl S, N-Acetals Derived from 2-Propynals
1475
HRMS (EI) calcd. for C10H18NOSSi (M+ – CH2CH3) 228.0878, found
228.0883.
N-[1-Ethylthio-3-(triphenylsilyl)-2-propyn-1-yl]morpholine (22)
Pale yellow oil: IR (neat) 3399, 3068, 2961, 2925, 2854, 2165, 2027,
1956, 1884, 1822, 1588, 1485, 1451, 1429, 1376, 1321, 1291, 1252, 1189,
1115, 989, 709, 699, 507 cm–1; 1H NMR (CDCl3)δ = 1.14 (t, J = 7.3 Hz,
3H, CH3), 2.57–2.67 (m, 6H, CH2), 3.63 (t, J = 4.6 Hz, 4H, CH2), 4.72
(s, 1H, CH), 7.24–7.33 (m, 10H, Ar), 7.53–7.57 (m, 5H, Ar); 13C NMR
(CDCl3)δ = 14.9, 25.5 (SCH2CH3), 49.1 (CH2NCH2), 62.1 (CH), 66.9
(CH2OCH2), 87.8, 104.3 (C C), 128.1, 130.1, 133.3, 135.6 (Ar).
Synthesis of Alkynyl S,N-Acetals via Lithium Thiolates:
General Procedure
To a dried Et2O solution of lithium acetylide 3 (1.5 equiv.), thiofor-
mamide 1 was added at −78◦C, and this was stirred at room tempera-
ture for 0.5 h. To the reaction mixture, alkyl halides (2 equiv.) at 0◦C
was added, and this was stirred at room temperature for 2 h. The result-
ing mixture was poured into a saturated aqueous solution of NaHCO3,
and extracted with Et2O. The organic layer was dried over MgSO4 and
concentrated in vacuo to give S, N-acetals in purity higher than 90%.
N,N-Dimethyl-1-(ethylthio)-3-(trimethylsilyl)-2-propyn-1-
amine (24)
Brown oil: IR (neat) 3399, 2959, 2861, 2824, 2782, 2163, 1665, 1452,
–1
1445, 1251, 1208, 1158, 1075, 1045, 1018, 988, 843, 760, 699 cm
;
1H NMR (CDCl3)δ = 0.15 (s, 9H, Si(CH3)3), 1.24 (t, J = 7.5 Hz, 3H,
CH3), 2.31 (s, 6H, N(CH3)2), 2.66 (q, J = 7.5 Hz, 2H, CH2), 4.73 (s,
1H, CH); 13C NMR (CDCl3)δ = 0.13 (Si(CH3)3), 15.2 (CH3), 25.7 (CH2),
40.5 (N(CH3)2), 63.2 (CH), 91.8, 100.0 (C C); MS (EI) m/z 154 (M+
–
SCH2CH3).
N,N-Dimethyl-1-(propylthio)-3-(trimethylsilyl)-2-propyn-1-
amine (25)
Brown oil: IR (neat) 2959, 2861, 2825, 2782, 2341, 2163, 1625, 1454,
1407, 1250, 1073, 1046, 1021, 988, 843, 760, 515, 413 cm–1; H NMR
1
(CDCl3)δ = 0.15 (s, 9H, Si(CH3)3), 0.96 (t, J = 7.4 Hz, 3H, CH3), 1.60
(sext, J = 7.4 Hz, 2H, CH2CH3), 2.31 (s, 6H, N(CH3)2), 2.63 (t, J = 7.4

1476
T. Murai et al.
Hz, 2H, SCH2), 4.71 (s, 1H, CH); 13C NMR (CDCl3)δ = –0.06 (Si(CH3)3),
13.6, 23.5, 33.7 (CH2CH2CH3), 40.7 (N(CH3)2), 63.4 (CH), 91.7, 100.2
(C C).
N,N-Dimethyl-1-(butylthio)-3-(trimethylsilyl)-2-propyn-1-
amine (26)
Brown oil: IR (neat) 3407, 2957, 2861, 2782, 2163, 1740, 1625, 1453,
–1
1250, 1074, 1022, 843, 760, 698 cm
;
1H NMR (CDCl3)δ = 0.16 (s,
9H, Si(CH3)3), 0.88 (t, J = 7.3 Hz, 3H, CH3), 1.38 (sext, J = 7.3
Hz, 2H, CH2CH3), 1.56 (quint, J = 7.3 Hz, 2H, CH2CH2CH3), 2.31
(s, 6H, N(CH3)2), 2.64 (dt, J = 2.7, 7.3 Hz, 2H, SCH2),4.70 (s, 1H,
CH); 13C NMR (CDCl3)δ = –0.06 (Si(CH3)3), 13.7, 22.1, 31.4, 32.2
(CH2CH2CH2CH3), 40.6 (N(CH3)2), 63.5 (CH), 91.7, 100.2 (C C); MS
(EI) m/z 212 (M+ – CH2CH3).
N,N-Dimethyl-1-(2-propenylthio)-3-(trimethylsilyl)-2-propyn-1-
amine (27)
Brown oil: IR (neat) 3387, 3071, 2958, 2860, 2824, 2782, 2341, 2163,
–1
1636, 1456, 1338, 1251, 1076, 1026, 989, 844, 760 cm
;
1H NMR
(CDCl3)δ = 0.12 (s, 9H, Si(CH3)3), 2.23 (s, 6H, N(CH3)2), 3.22 (m, 2H,
SCH2), 4.60 (s, 1H, CH), 5.07 (m, 2H, CHCH2), 5.77 (ddt, J = 17.1,
9.8, 7.1 Hz, 1H, CHCH2); 13C NMR (CDCl3)δ = –0.04 (Si(CH3)3), 34.1
(SCH2), 40.5 (N(CH3)2), 62.1 (CH), 92.0, 99.9 (C C), 117.1 (CHCH2),
134.2 (CHCH2).
N,N-Dimethyl-1-(2-propenylthio)-2-heptyn-1-amine (28)
Orange oil: IR (neat) 3855, 3823, 3737, 3651, 3366, 3081, 2957, 2934,
2861, 2823, 2780, 2342, 2233, 1832, 1663, 1634, 1577, 1456, 1431, 1400,
–1
1379, 1340, 1217, 1158, 1096, 1046, 1009, 989, 916 cm
;
1H NMR
(CDCl3)δ = 0.86 (t, J = 7.3 Hz, 3H, CH3), 1.42 (m, 4H, CH2CH2), 2.21
(dt, J = 2.1, 7.1 Hz, 2H, CH2), 2.28 (s, 6H, N(CH3)2), 3.22 (m, 2H, SCH2),
4.59 (t, J = 2.0 Hz, 1H, CH), 5.05 (m, 2H, CHCH2), 5.78 (ddt, J = 17.3,
9.5, 7.1 Hz, 1H, CHCH2); 13C NMR (CDCl3)δ = 13.5 (CH3), 18.4, 21.9,
30.7 (CH2) 34.1 (SCH2), 40.4 (N(CH3)2), 62.0 (CH), 75.0, 87.9 (C C),
116.9 (CHCH2), 134.3 (CHCH2); MS (EI) m/z 169 (M+ – CH2CHCH2).

Alkynyl S, N-Acetals Derived from 2-Propynals
1477
N,N-Dimethyl-1-(phenylmethylthio)-3-(trimethylsilyl)-2-
propyn-1-amine (29)
Orange oil: IR (neat) 3412, 3061, 3029, 2953, 2782, 2163, 1947, 1870,
1624, 1495, 1454, 1407, 1250, 1070, 1029, 844, 762, 699 cm–1; 1H NMR
(CDCl3)δ = 0.19 (s, 9H, Si(CH3)3), 2.32 (s, 6H, N(CH3)3), 3.81 (d, J =
13.2 Hz, 1H, CH2Ph), 3.90 (d, J = 13.2 Hz, 1H, CH2Ph), 4.56 (s, 1H,
CH), 7.22–7.34 (m, 5H, Ar); 13C NMR (CDCl3)δ = –0.05 (Si(CH3)3), 35.3
(CH2Ph), 40.5 (N(CH3)2), 62.4 (CH), 92.3, 99.7 (C C), 126.9, 128.2,
129.0, 138.4 (Ar); MS (EI) m/z 154 (M+ – SCH2Ph); HRMS (EI) calcd.
for C15H23NSSi (M++ 1) 278.1320, found 278.1414.
N,N-Dimethyl-1-(1-methylethylthio)-3-(trimethylsilyl)-2-
propyn-1-amine (31)
The thioformamide (0.085 mL, 1 mmol), a dried Et2O solution (4 mL)
of alkynyllithium (1.5 mmol) at −78◦C was added, and this was stirred
at room temperature for 1 h. To the reaction mixture was added 12-
crown-4-ether (0.243 mL, 1.5 mmol) at 0◦C, and this was stirred at this
temperature for 0.5 h. Then, isopropyl iodide (0.2 mL, 2 mmol) was
added at 0◦C, and this mixture was stirred at this temperature for 1 h.
The resulting mixture was poured into a saturated aqueous solution of
NaHCO3, and extracted with Et2O. The organic layer was dried over
MgSO4 and concentrated in vacuo to give 31 (0.171 g, 75%) in purity
higher than 90% as a brown oil: IR (neat) 3415, 2957, 2864, 2783,
2162, 1626, 1451, 1407, 1383, 1365, 1247, 1096, 1049, 1023, 842, 759
cm–1; H NMR (CDCl3)δ = 0.17 (s, 9H, Si(CH3)3), 1.28 (d, J = 6.8 Hz,
1
3H, CHCH3), 1.32 (d, J = 6.8 Hz, 3H, CHCH3), 2.34 (s, 6H, N(CH3)3),
3.08 (septet, J = 6.8 Hz, 1H, CH(CH3)2), 4.73 (s, 1H, CHC C); 13C
NMR (CDCl3)δ = –0.05 (Si(CH3)3), 23.9 (CH3) 35.2 (CH(CH3)2), 40.5
(N(CH3)2), 62.2 (CHC C), 91.4, 100.4 (C C); MS (EI) m/z 154 (M+
– SCH(CH3)2); HRMS (EI) calcd. for C11H23NSSi (M++ 1) 230.1320,
found 230.1415(M++ 1).
3,9-Bis(dimethylamino)-1,11-bis(trimethylsilyl)-4,8-
dithiaundeca-1,10-diyne (34)
The thioformamide (0.128 mL, 0.5 mmol) was added an Et2O solution
(5 mL) of alkynyllithium (2.25 mmol) at −78◦C, and this was stirred at
room temperature for 0.5 h. To the reaction mixture, 1,3-diiodopropane
(0.057 mL, 0.5 mmol) and TMEDA (0.37 mL, 2.5 mmol) at 0◦C was
added, and this was stirred at room temperature for 4 h. The resulting
mixture was poured into a saturated aqueous solution of NaHCO3,

1478
T. Murai et al.
and extracted with Et2O. The organic layer was dried over MgSO4 and
concentrated in vacuo to give 34 (0.267 g, quant.) in purity higher than
90% as a brown oil: IR (neat) 2956, 2860, 2824, 2782, 2362, 2162, 1717,
–1
1625, 1453, 1338, 1250, 1209, 1159, 1076, 1046, 1025, 988, 844 cm
;
1H NMR (CDCl3)δ = 0.15 (s, 18H, Si(CH3)3), 1.89 (quint, J = 7.2 Hz,
2H, CH2), 2.31 (s, 12H, N(CH3)2), 2.75 (t, J = 7.2 Hz, 4H, CH2), 4.71 (s,
2H, CH); 13C NMR (CDCl3)δ = –0.09 (Si(CH3)3), 30.2, 30.3, 30.5 (CH2),
40.5 (N(CH3)2), 63.5 (CH), 91.9, 99.9 (C C); MS (EI) m/z 414 (M+).
3,11-Bis(dimethylamino)-1,13-bis(trimethylsilyl)-4,10-
dithiatrideca-1,12-diyne (38)
The thioformamide (0.77 mL, 3 mmol) was added a dried Et2O solution
(20 mL) of alkynyllithium (10.8 mmol) at −78◦C, and this was stirred at
room temperature for 0.5 h. To the reaction mixture, 1,3-diiodopropane
(0.45 mL, 3 mmol) and TMEDA (2.2 mL, 15 mmol) at 0◦C was added,
and this was stirred at room temperature for 4 h. The resulting mix-
ture was poured into a saturated aqueous solution of NaHCO3, and
extracted with Et2O. The organic layer was dried over MgSO4 and con-
centrated in vacuo to give 38 (1.852 g, quant.) in purity higher than
80% as a brown oil: IR (neat) 2954, 2859, 2824, 2781, 2360, 2162, 1627,
1454, 1337, 1250, 1208, 1158, 1075, 1046, 1021, 988, 844 cm–1; 1H NMR
(CDCl3)δ = 0.14 (s, 18H, Si(CH3)3), 0.78–0.92 (bm, 2H, CH2), 2.14–2.24
(bm, 4H, CH2), 2.29 (s, 12H, N(CH3)2), 2.61–2.64 (bm, 4H, CH2), 4.68 (s,
2H, CH); 13C NMR (CDCl3)δ = –0.09 (Si(CH3)3), 28.3, 29.6, 31.4 (CH2),
40.5 (N(CH3)2), 63.4 (CH), 91.8, 100.0 (C C); MS (EI) m/z 411 (M+
–
2CH3 –1).
3,12-Bis(dimethylamino)-1,14-bis(trimethylsilyl)-4,11-
dithiatetradeca-1,13-diyne (39)
The thioformamide (0.77 mL, 9 mmol), a dried Et2O solution (20 mL) of
alkynyllithium (10.8 mmol) at −78◦C was added, and this was stirred
at room temperature for 0.5 h. To the reaction mixture was added 1,6-
diiodohexane (0.49 mL, 3 mmol) and TMEDA (2.2 mL, 15 mmol) at
0◦C, and this was stirred at room temperature for 4 h. The resulting
mixture was poured into a saturated aqueous solution of NaHCO3,
and extracted with Et2O. The organic layer was dried over MgSO4 and
concentrated in vacuo to give 39 (1.811 g, quant.) in purity higher than
90% as a brown oil: IR (neat) 2952, 2858, 2824, 2781, 2162, 1717, 1664,
1453, 1335, 1250, 1208, 1075, 1046, 1023, 988, 844, 760, 698 cm–1; 1H
NMR (CDCl3)δ = 0.13 (s, 18H, Si(CH3)3), 1.36 (bm, 4H, CH2), 1.56 (bm,

Alkynyl S, N-Acetals Derived from 2-Propynals
1479
4H, CH2), 2.29 (s, 12H, N(CH3)2), 2.62 (bt, J = 7.0 Hz, 4H, CH2), 4.68
(s, 2H, CH); 13C NMR (CDCl3)δ –0.07 (Si(CH3)3), 28.6, 29.9, 31.5 (CH2),
40.5 (N(CH3)2), 63.4 (CH), 91.7, 100.1 (C C); MS (EI) m/z 456 (M+),
302 (M+ –CHN(CH3)2C CSiMe3); HRMS (EI) calcd. for C14H28N1S2Si1
(M+ – CHN(CH3)2C CSiMe3) 302.1435, found 302.1427.
1,2-Bis[3-(dimethylamino)-5-(trimethylsilyl)-2-thiapent-4-yn-1-
yl]benzene (40)
The thioformamide (0.26 mL, 3 mmol) was added a dried Et2O solution
(10 mL) of alkynyllithium (3.9 mmol) at −78◦C, and this was stirred
at room temperature for 0.5 h. To the reaction mixture, α, αꢀ -dibromo-
o-xylene (0.264 g, 1 mmol) and TMEDA (0.74 mL, 5 mmol) at 0◦C was
added, and this was stirred at room temperature for 4 h. The resulting
mixture was poured into a saturated aqueous solution of NaHCO3 and
extracted with Et2O. The organic layer was dried over MgSO4 and
concentrated in vacuo to give 40 (0.528 g, quant.) in purity higher than
90% as a brown oil: IR (neat) 2951, 2898, 2859, 2824, 2781, 2360, 2342,
2160, 1625, 1453, 1416, 1339, 1249, 1205, 1158, 1076, 1045, 1025, 986,
1
844, 760 cm–1; H NMR (CDCl3)δ = 0.12 (s, 18H, Si(CH3)3), 2.27 (s,
12H, N(CH3)2), 3.96 (dq, J = 2.3, 13.3 Hz, 4H, CH2), 4.51 (d, J = 3.6
Hz, 2H, CH), 7.10–7.12 (m, 2H, Ar), 7.19–7.21 (m, 2H, Ar); 13C NMR
(CDCl3)δ = 0.02 (Si(CH3)3), 32.58, 32.63 (CH2), 40.48, 40.50 (N(CH3)2),
62.64, 62.75 (CH), 92.38, 92.42, 99.56, 99.65 (C C), 127.31, 130.68,
130.71, 136.59 (Ar); MS (EI) m/z 430 (M+ – N(CH3)2–1); HRMS (EI)
calcd. for C23H37N2S2Si2 (M+ – CH3) 461.1937, found 461.1924.
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