Rhodium-Catalyzed Highly Regioselective and Stereoselective Intermolecular Hydrosilylation of Internal Ynamides under Mild Conditions

Article abstract of DOI:10.1021/acs.joc.8b00695

A rhodium-catalyzed highly regio- and stereoselective intermolecular hydrosilylation of internal ynamides has been developed. With the neutral rhodium complex [Rh(CO)₂Cl]₂ as a catalyst and the bulky silanes as reactants, various ynamides underwent hydrosilylation smoothly at room temperature with an excellent β-regioselectivity and anti-stereoselectivity. The synthetically versatile β-silyl (Z)-enamide products could be further transformed to diverse useful building blocks. Several possible mechanisms are proposed to rationalize this unique formal trans-addition-type selectivity.

Full text of DOI:10.1021/acs.joc.8b00695

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Note
Rhodium-Catalyzed Highly Regio- and Stereoselective Intermolecular
Hydrosilylation of Internal Ynamides under Mild Conditions
Nan Zheng, Wangze Song, Tiexin Zhang, Ming Li, Yubin Zheng, and Lingyue Chen
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b00695 • Publication Date (Web): 08 May 2018
Downloaded from http://pubs.acs.org on May 8, 2018
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The Journal of Organic Chemistry
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Rhodium-Catalyzed
Intermolecular Hydrosilylation of Internal Ynamides under Mild
Conditions
Highly
Regio-
and
Stereoselective
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Nan Zheng,†, ‡ Wangze Song,†,* Tiexin Zhang,† Ming Li,† Yubin Zheng,‡ and Lingyue Chen†
† State Key Laboratory of Fine Chemicals, School of Pharmaceutical Science and Technology, Dalian University of
Technology, Dalian, 116024, P. R. China.
‡ School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, P. R. China.
Supporting Information Placeholder
ABSTRACT: A rhodiumꢀcatalyzed highly regioꢀ and stereoselective intermolecular hydrosilylation of internal ynamides has been
developed. With the neutral rhodium complex [Rh(CO)2Cl]2 as catalyst and the bulky silanes as reactants, various ynamides underwent
hydrosilylation smoothly at room temperature with excellent β regioselectivity and anti stereoselectivity. The synthetically versatile βꢀsilyl
(Z)ꢀenamide products could be further transformed to diverse useful building blocks. Several possible mechanisms are proposed to
rationalize this unique formal transꢀadditionꢀtype selectivity.
Silylꢀsubstituted organic molecules are widely applied in
organic synthesis, materials and polymer science due to their nonꢀ
toxicity, stability, easy accessibility and diverse transformations.1
Therefore, various metalꢀcatalyzed hydrosilylation of unsaturated
functional groups, such as alkenes, alkynes, carbonyls, imines,
epoxides and so on, have been developed in recent years.2 Among
these transformations, alkyne hydrosilylation could provide the
vinylsilanes by the most straightforward and atomꢀeconomic
strategy.3 Vinylsilanes, as valuable synthetic precursors, are
frequently used to participate in different crossꢀcoupling reactions,
TamaoꢀFleming oxidations, electrophilic substitutions and group
transfer polymerizations,4 which furthermore highlight the notable
significance of alkyne hydrosilylation. However, there still exist
tremendous challenges for alkyne hydrosilylation. First, the
substrate scopes are limited to the terminal alkynes and
symmetrical alkynes.2,5 If unsymmetrical internal alkynes are used
as substrates, the regioꢀ and stereoselectivity for alkyne
hydrosilylation would drop dramatically. Second, most previous
studies focused on the normal and electronꢀpoor internal alkynes.6
Only a few electronꢀrich internal alkyne hydrosilylations were
reported under harsh conditions.7 In addition, how to control the
regioꢀ and stereoselectivity for alkyne hydrosilylation is still the
critical issue. Four possible isomers could be acquired from
alkyne hydrosilylation (Scheme 1a). Limited protocols are used to
obtain a single product with high regioꢀ and stereoselectivity.
Highly polarized or electronꢀdeficient alkynes may give certain
initial selectivities,6 which could be further improved by internal
directing group approach or intramolecular hydrosilylation.8 But
these substrates are complicated and usually hard to access. It is
important to develop a general and novel control strategy to
achieve high regioꢀ and stereoselectivities. Third, recent examples
on intermolecular hydrosilylation of internal alkynes mainly based
on the catalysts like ruthenium,5d,6d,7c,8a,8b platinum,5e,6c,8c,8e
iridium,5c,7b cobalt,7d,7e,8d manganese5a and other metals or
metalloids,7a which generally require heating, ligands or additives.
Consequently, it is quite urgent and meaningful to develop the
new alkyne hydrosilylation which could occur smoothly under
mild conditions without sophisticated promoting regents.
Scheme 1. Design of Intermolecular Hydrosilylation of
Unsymmetrical Internal Alkyne
Despite the rhodium also a good catalyst in other silylation
reaction,9 the rhodiumꢀcatalyzed intermolecular regioꢀ and
stereoselective hydrosilylation of electronꢀrich internal alkynes
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remains limitedly known today. Owing to our combined interest
in the ynamides chemistry10 and rhodiumꢀcatalyzed reactions,11
we herein report the Rh(I)ꢀcatalyzed intermolecular
hydrosilylation of internal ynamides (Scheme 1b). Remarkably,
the hydrosilylation of internal ynamides could undergo efficiently
in room temperature with high regioꢀ and stereoselectivities to
afford βꢀsilyl (Z)ꢀenamide products. Based on the mechanism
studies, the chelation between carbonyl oxygen of ynamides and
Rh catalyst may play the crucial control role. Several possible
mechanisms are proposed to rationalize this unique formal transꢀ
additionꢀtype selectivity.
1
2
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4
5
6
7
8
Table 1. Optimization of Reaction Conditionsa
entry
catalyst
solvent
yield [%]b
β/αc
Z/Ec
1
[Rh(CO)2Cl]2
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
DCM
80
> 20:1
15:1
-
9
2
[Rh(COD)2]BF4
[Rh(COD)Cl]2
[Ir(COD)Cl]2
trace
0d
-
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3
-
-
In order to achieve the hydrosilylation reaction for electronꢀrich
internal alkynes, ynamide 1a as the representative substrate and
triethylsilane (2a) were chosen as model substrates to optimize the
reaction parameters.12 Rh(I) was first employed to catalyze this
hydrosilylation (Table 1, entries 1ꢀ3). Only neutral catalyst
[Rh(CO)2Cl]2 worked efficiently at room temperature to afford
desired βꢀsilyl (Z)ꢀenamide 3a with good regioꢀ and
stereoselectivity.13 The cationic catalyst [Rh(COD)2]BF4 failed to
mediate the reaction well. Another neutral catalyst [Rh(COD)Cl]2
resulted in the decomposition of ynamide. Ir(I) as catalyst
provided the hydrogenation product exclusively in good yield and
stereoselectivity (Table 1, entry 4). Neutral [Cp*Ru(cod)Cl] could
not give any desired hydrosilylation product, and the cationic
[Cp*Ru(MeCN)3]PF6 gave the lower regioꢀ and stereoselectivity
(Table 1, entries 5 and 6). Chloroplatinic acid or platinichloride
were demonstrated to be ineffective for this transformation (Table
1, entries 7 and 8). It is noteworthy that previously wellꢀdefined Ir,
Ru catalysts demonstrated to be either less selective or inactive at
room temperature for ynamide hydrosilylation, which features this
complementary approach for rhodiumꢀcatalyzed system. Other
solvents could maintain the good regioselectivity but did not
further improve the efficiency and stereoselectivity (Table 1,
entries 9ꢀ12).
4
76e
trace
61
-
11:1
-
5
[Cp*Ru(COD)Cl]
[Cp*Ru(MeCN)3]PF6
H2PtCl6·6H2O
Na2PtCl6·6H2O
[Rh(CO)2Cl]2
-
6
2.4:1
-
6.2:1
-
7
trace
trace
64
8
-
-
9
> 20:1
> 20:1
> 20:1
> 20:1
4.9:1
4.4:1
6.5:1
3.7:1
10
11
12
[Rh(CO)2Cl]2
CHCl3
THF
60
[Rh(CO)2Cl]2
71
[Rh(CO)2Cl]2
Toluene
55
a.Reaction conditions: 1a (1.0 equiv), 2a (2.0 equiv), solvent (0.1 M), catalyst (2.5
mol %), at rt under N2 for 12 h. b.Yields were determined by 1H NMR of the crude
mixture with an internal standard. c.The ratio of α/β and E/Z were determined by
1H NMR of the crude mixture. d.The starting material decomposed. e.Only the (Z)ꢀ
hydrogenation product was detected in good NMR yield. Cp*
pentamethylcyclopentadiene, COD = 1,5ꢀcyclooctadiene.
=
reaction still occurred for triisopropylsilyl (TIPS) substituted
ynamide at mild conditions. It provided a unique way to access β,
βꢀdisilylated enamide, which was usually hard to prepare under
other harsh conditions. Other tertiary silanes, such as
dimethylphenylsilane (2m) and methyldiphenylsilane (2n) were
efficient for this hydrosilylation of ynamides. Secondary silane
(diphenylsilane) and primary silane (phenylsilane) could not
attend this transformation efficiently. The complex mixtures were
acquired using 2o or 2p as hydrosilylating regents. In addition, we
also explored the variation of acyclic ynamides, including Nꢀ
sulfonyl or carboxyl ynamdies. Neither triethylsilane nor
triphenylsilane could react with acyclic ynamides to afford
desired hydrosilylation products. If an extra carbon was
introduced between the alkyne and the nitrogen of amide, the
reaction failed to occur. It discloses that the position of amide
connected with alkyne is crucial for this hydrosilylation.
With the optimized condition in hand, we explored the
substrate scope for Rhꢀcatalyzed βꢀanti selective hydrosilylation
of ynamides (Scheme 2). Aliphatic and aromatic tertiary silanes
were successfully applied to this protocol. A variety of achiral and
chiral ynamides with alkyl or aryl substituents could attend the
reaction smoothly at room temperature to give (Z)ꢀconfigured
products with excellent βꢀregioselectivity (more than 20:1) and
high antiꢀstereoselectivity (up to more than 20:1). Triethylsilane
(2a) was firstly investigated as silicon source. The electronic
effect was not obvious for aryl substituted ynamides (3b and 3c).
If pyrrolidinone was used instead of oxazolidinone, the yield and
stereoselectivity of 3d significantly dropped to 66% and 5:1 with
extended reaction time. The bulky groups introduced to the
adjacent position of ynamides could be well tolerated for this
hydrosilylation (3e and 3f). The structure of 3e was
unambiguously confirmed by Xꢀray crystallographic analysis.14
However, the low yields and stereoselectivities for tꢀbutyl
substituted ynamides (1g) were observed, which may due to the
combination of unfavorable steric and electronic factors. Besides
tꢀbutyl substituted ynamides, we also investigated nꢀbutyl and
cyclohexyl substituted ynamides. The inseparable mixture (Z/E =
1:1) were obtained for these alkylꢀsubstituted ynamides.
(TMSO)3SiH (2h), as the typical alkoxysilane, failed to attend this
Subsequently, the applicability of this reaction was examined.
It was very easy to remove the silyl groups from the obtained
vinylsilane products under mild conditions.7a Treating 3f with 1.5
equiv silver fluoride in room temperature, corresponding (E)ꢀ
enamides 4f were acquired and the olefin configurations were
perfectly maintained. The (E)ꢀenamides 4f could be further
transformed to chiral αꢀfluorinated imides in one step according to
the known literature.15 The Hiyama crossꢀcoupling reaction is the
typical organosiliconꢀbased crossꢀcoupling. We screened different
conditions and found triethylsilane derivate 3f could not achieve
this crossꢀcoupling with 4ꢀiodoanisole efficiently, because the
transmetalation was reluctant to occur without the activating agent
(such as fluoride or hydroxide) in organosilicons (Scheme 3).16
Rhꢀcatalyzed
hydrosilylation.
Encouragingly,
when
triphenylsilane (2i) was used as silicon source, the
stereoselectivities were as high as triethylsilane (3i, 3j, 3k and 3l).
The yield of paraꢀmethylꢀphenyl substituted ynamide (1j) was
similar with the phenyl one. Both yields and stereoselectivities
could be increased for alkyl substituted ynamides (1k and 1l).
Noticeably, although β, βꢀdisilylated enamide was unstable,13 the
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The Journal of Organic Chemistry
Scheme 2. Substrate Scope of the Hydrosilylation of Ynamides with Silanea
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a.Standard conditions unless otherwise noted: 1 (0.2 mmol), 2 (0.4 mmol), MeCN (2 mL), [Rh(CO)2Cl]2 (2.5 mol %), at rt under N2 for 12 h. Combined isolated yields
were shown. The ratio of α/β and E/Z were determined by 1H NMR of the crude mixture. The ratio of β/α > 20:1 unless otherwise noted. b.For 24 h. c.For 18 h, TIPS =
triisopropylsilyl. d.Inseparable mixture.
The Rhꢀcatalyzed hydrosilylation of internal ynamides could
result in excellent regioꢀ and stereoselectivities under mild
conditions. To further understand this Rhꢀcatalyzed process, we
investigated the mechanism. We firstly concluded one possible
isomerization process may be involved to afford the βꢀsilyl (Z)ꢀ
enamide products 3.6b, 9b The initial hydrosilylation provides βꢀ
silyl (E)ꢀenamides 3’. Then the second hydrosilylation followed
by βꢀhydride elimination gives βꢀsilyl (Z)ꢀenamides. βꢀSilyl (E)ꢀ
enamide 3a’ was treated under the standard condition in order to
demonstrate this mechanism. Unfortunately, no reaction occurred
under the standard condition. Hence the isomerization mechanism
may be excluded (for details, see the SI).
The CrabtreeꢀOjima mechanism is the most classic and
ubiquitous mechanism suitable for the hydrosilylation of alkynes
and alkenes.17 But it fails to explain the results why
triphenylsilane 2i works better than triethylsilane 2a for some
substrates in this Rhꢀcatalyzed hydrosilylation of ynamides (for
details, see the SI).
We rationalize that a ketene iminium intermediate forming in
situ may be an alternative explanation for affording βꢀsilyl (Z)ꢀ
1
enamide products.7a,12,18 From the HꢀNMR study (for details, see
the SI), the Rh carbonyl complex A is generated firstly. It could
activate the ynamide to attack silane in intermediate B, generating
the ketene iminium species C in situ.19 Then the hydride
selectively attacks the ketene iminium C by pathway (a) due to
the combination of steric and βꢀsilicon effect, which determines
the (Z)ꢀenamides geometry.7a For the TIPSꢀsubstituted ynamide 1l,
β, βꢀsilylꢀdisubstituted ketene iminium intermediate would be
formed. Triphenyl group is more bulky than the triisopropyl one,
which control the hydride attacking by pathway (a) efficiently.
Although the alkyl group is less steric hindrance than aryl group,
the poor selectivity was acquired for treating tꢀbutylꢀsubstituted
ynamide 1g with triethylsilane 2a. It may be due to the
unfavorable electronic factors. Although the reason for these
interesting phenomena is not clear at this stage, we also consider
the critical factor may change depending on the substrate (Scheme
4).
Scheme 3. Application of Rh-catalyzed Hydrosilylation of
Internal Ynamides
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(19 mg, 1.5 eq, 0.15 mmol). The mixture was stirred at room
Scheme 4. Plausible Ketene Iminium Mechanism
temperature for 12 h. Then the mixture was concentrated in vacuo
and purified with flash column chromatography (5% EtOAc in PE)
to give the pure product 4f (21.5 mg, 81%) as white solid.
1
2
3
4
5
6
7
8
O
O
H Rh
Rh
Si
R1
O
Si-H
Rh(I)
O
O
O
R1
N
R1
N
N
General Procedure of the Stoichiometric Reactions for
Mechanism Investigation. To a solution of 1a (7.48 mg, 0.04
mmol) in CD3CN (0.4 mL) under N2 was added [Rh(CO)2Cl]2
A
B
(a)
[N]
1
R1
Si
R1
R1
H
(15.5 mg, 1 eq, 0.04 mmol). The mixture was tested by HꢀNMR
[N]
unfavor (b)
favor (a)
H
Rh
at 0, 3, 6, 12 h.
Si
H
Si
[N]
(Z)ꢀ3ꢀ(2ꢀphenylꢀ2ꢀ(triethylsilyl)vinyl)oxazolidinꢀ2ꢀone
(3a).
C
1
cis-addition
trans-addition
(b)
46.1 mg, Z/E = 15:1. 76% yield. Yellow oil. H NMR (400 MHz,
CDCl3, TMS): δ 7.29ꢀ7.25 (m, 2H), 7.22ꢀ7.20 (m, 1H), 7.11ꢀ7.08
(m, 2H), 6.65 (s, 1H), 4.42 (t, J = 8.0 Hz, 2H), 3.85 (t, J = 8.0 Hz,
2H), 0.92 (t, J = 8.0 Hz, 9H), 0.65 (q, J = 8.0 Hz, 6H). 13C NMR
(125 MHz, CDCl3): δ 157.4, 143.7, 136.7, 136.0, 128.0, 128.0,
126.0, 62.1, 47.4, 7.6, 4.4. IR (KBr) ν 2955, 2359, 1761, 1598,
1398, 1265, 1080, 741, 703 cmꢀ1. HRMS (EIꢀTOF) m/z: [M]+
Calcd for C17H25NO2Si 303.1655; Found 303.1664.
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In summary, we have developed a rhodiumꢀcatalyzed highly
regioꢀ and stereoselective intermolecular hydrosilylation of
internal ynamides under mild conditions. This reaction is unique
to provide a straightforward and efficient entry to access the
related βꢀsilyl (Z)ꢀenamides. With the neutral rhodium complex
[Rh(CO)2Cl]2 as catalyst and the bulky silanes as reactants,
various ynamides underwent hydrosilylation smoothly at room
(Z)ꢀ3ꢀ(2ꢀ(4ꢀmethoxyphenyl)ꢀ2ꢀ(triethylsilyl)vinyl)oxazolidinꢀ2ꢀ
1
one (3b). 46.6 mg, Z/E > 20:1. 70% yield. Yellow oil. H NMR
(500 MHz, CDCl3, TMS): δ 7.02 (d, J = 10.0 Hz, 2H), 6.81 (d, J =
10.0 Hz, 2H), 6.60 (s, 1H), 4.41 (t, J = 10.0 Hz, 2H), 3.82 (t, J =
10.0 Hz, 2H), 3.80 (s, 3H), 0.92 (t, J = 10.0 Hz, 9H), 0.65 (q, J =
10.0 Hz, 6H). 13C NMR (125 MHz, CDCl3): δ 158.0, 157.5, 136.6,
135.9, 129.8, 129.0, 113.4, 62.1, 56.2, 47.5, 7.6, 4.3. IR (KBr) ν
2956, 2359, 1762, 1590, 1265, 1110, 742, 701 cmꢀ1. HRMS (EIꢀ
TOF) m/z: [M]+ Calcd for C18H27NO3Si 333.1760; Found
333.1764.
temperature with excellent
β
regioselectivities and anti
stereoselectivities. The synthetically versatile βꢀsilyl (Z)ꢀenamide
products could be further transformed to the useful building
blocks. Based on the detailed mechanism study, several possible
mechanisms are proposed. The high regioꢀ and stereoselectivities
may be derived from the strong coordination between the
ynamides and rhodium, followed by the hydride selectively
attacking the ketene iminium intermediate. The comprehensive
mechanistic studies and advanced theoretical calculations for the
catalysts and intermediates are underway in our laboratory.
(Z)ꢀ3ꢀ(2ꢀ(4ꢀchlorophenyl)ꢀ2ꢀ(triethylsilyl)vinyl)oxazolidinꢀ2ꢀ
1
one (3c). 46.5 mg, Z/E = 18:1. 69% yield. Yellow oil. H NMR
(500 MHz, CDCl3, TMS): δ 7.24 (d, J = 10.0 Hz, 2H), 7.02 (d, J =
10.0 Hz, 2H), 6.65 (s, 1H), 4.42 (t, J = 10.0 Hz, 2H), 3.85 (t, J =
10.0 Hz, 2H), 0.92 (t, J = 10.0 Hz, 9H), 0.64 (q, J = 10.0 Hz, 6H).
13C NMR (125 MHz, CDCl3): δ 157.3, 142.3, 137.1, 134.2, 132.0,
129.4, 128.1, 62.1, 47.2, 7.6, 4.4. IR (KBr) ν 2957, 2305, 1762,
1481, 1264, 749, 705 cmꢀ1. HRMS (EIꢀTOF) m/z: [M]+ Calcd for
C17H24ClNO2Si 337.1265; Found 337.1257.
EXPERIMENTAL SECTION
General Information. Unless otherwise noted, all reactions in
nonꢀaqueous media were conducted under a positive pressure of
dry nitrogen in glassware that had been oven dried prior to use.
Anhydrous solutions were transferred via an oven dried syringe or
cannula. All solvents were dried prior to use unless noted
otherwise. Thin layer chromatography was performed using
precoated silica gel plates and visualized with UV light at 254 nm.
Flash column chromatography was performed with silica gel (40ꢀ
(Z)ꢀ1ꢀ(2ꢀphenylꢀ2ꢀ(triethylsilyl)vinyl)pyrrolidinꢀ2ꢀone
(3d).
1
39.7 mg, Z/E = 5:1. 66% yield. Yellow oil. Major isomer: H
NMR (500 MHz, CDCl3, TMS): δ 7.50ꢀ7.33 (m, 5H), 7.28 (s, 1H),
3.86 (t, J = 10.0 Hz, 2H), 2.60 (t, J = 10.0 Hz, 2H), 2.24 (t, J =
10.0 Hz, 2H), 0.98 (t, J = 10.0 Hz, 9H), 0.81 (q, J = 10.0 Hz, 6H).
13C NMR (125 MHz, CDCl3): δ 175.1, 146.4, 130.3, 128.2, 127.1,
126.5, 126.1, 49.4, 31.3, 18.5, 6.8, 5.3. IR (KBr) ν 2876, 1710,
1461, 1384, 1265, 737, 703 cmꢀ1. HRMS (EIꢀTOF) m/z: [M]+
Calcd for C18H27NOSi 301.1862; Found 301.1870.
60 ꢁm). H and 13C nuclear magnetic resonance spectra (NMR)
1
were obtained on a Bruker Avance II 400 MHz or Bruker Avance
III 500 MHz recorded in ppm (δ) downfield of TMS (δ=0) in
CDCl3 unless noted otherwise. Signal splitting patterns were
described as singlet (s), doublet (d), triplet(t), quartet (q), quintet
(quint), multiplet (m), and broad (br) with coupling constants (J)
in hertz (Hz). High resolution mass spectra (HRMS) were
performed by Micromass apparatus (TOF mass analyzer type) on
an Electron Impact (EI) mass spectrometer or Agilent apparatus
(TOF mass analyzer type) on an Electron Spray Injection (ESI)
mass spectrometer. Melting points were determined by XPꢀ4
melting point apparatus. Optical rotations were measured on a
Rudolph Autopol IV automatic polarimeter.
General Procedure of Rhodium-catalyzed Hydrosilylation.
Standard conditions: To a vial containing [Rh(CO)2Cl]2 (2.0 mg,
0.025 eq, 0.005 mmol) in MeCN (2 mL) under N2 was added 3ꢀ
(phenylethynyl)oxazolidinꢀ2ꢀone (37.4 mg, 1 eq, 0.2 mmol) and
triethylsilane (46.5 mg, 2 eq, 0.4 mmol). The mixture was stirred
at room temperature for 12 h. Then the mixture was concentrated
in vacuo and purified with flash column chromatography (10%
EtOAc in PE) to give the pure product (46.1 mg, 76%) as yellow
oil.
(Z)ꢀ(S)ꢀ4ꢀbenzylꢀ3ꢀ(2ꢀphenylꢀ2ꢀ(triethylsilyl)vinyl)oxazolidinꢀ2ꢀ
one (3e). 58.2 mg, Z/E > 20:1. 74% yield. White solid, mp = 115ꢀ
o
1
116 C. [α]ꢁꢀꢂ= +30.8 (c = 0.52, CH2Cl2). H NMR (400 MHz,
CDCl3, TMS): δ 7.37ꢀ7.12 (m, 10H), 6.44 (s, 1H), 4.30ꢀ4.14 (m,
3H), 3.23 (t, J = 8.0 Hz, 1H), 2.83ꢀ2.77 (m, 1H), 0.97 (t, J = 8.0
Hz, 9H), 0.74 (q, J = 8.0 Hz, 6H). 13C NMR (125 MHz, CDCl3): δ
156.8, 143.2, 143.1, 135.6, 135.1, 129.1, 129.1, 128.0, 127.8,
127.3, 126.3, 66.5, 60.4, 38.3, 7.6, 3.6. IR (KBr) ν 2961, 2359,
1759, 1420, 1265, 1110, 748, 704 cmꢀ1. HRMS (EIꢀTOF) m/z:
[M]+ Calcd for C24H31NO2Si 393.2124; Found 393.2133.
(Z)ꢀ(S)ꢀ4ꢀphenylꢀ3ꢀ(2ꢀphenylꢀ2ꢀ(triethylsilyl)vinyl)oxazolidinꢀ2ꢀ
one (3f). 61.4 mg, Z/E > 20:1. 81% yield. White solid, mp = 48ꢀ
o
1
49 C. [α]ꢁꢀꢂ= +94.3 (c = 0.32, CH2Cl2). H NMR (500 MHz,
CDCl3, TMS): δ 7.40ꢀ7.36 (m, 3H), 7.35ꢀ7.29 (m, 2H), 7.22ꢀ7.14
(m, 3H), 6.99 (d, J = 5.0 Hz, 2H), 6.09 (s, 1H), 4.89ꢀ4.86 (m, 1H),
4.67 (t, J = 10.0 Hz, 1H), 4.29ꢀ4.26 (m, 1H), 0.92 (t, J = 10.0 Hz,
9H), 0.71 (q, J = 10.0 Hz, 6H). 13C NMR (125 MHz, CDCl3): δ
156.9, 143.6, 143.2, 137.5, 134.6, 129.3, 129.1, 127.9, 127.8,
126.8, 126.2, 69.5, 63.1, 7.6, 3.5. IR (KBr) ν 2955, 2359, 1762,
1539, 1441, 1263, 1102, 876, 749 cmꢀ1. HRMS (EIꢀTOF) m/z:
[M]+ Calcd for C23H29NO2Si 379.1968; Found 379.1967.
General Procedure of Protodesilylation. To a solution of 3f
(37.9 mg, 0.1 mmol) in MeOH (1 mL) under N2 was added AgF
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The Journal of Organic Chemistry
(Z)ꢀ3ꢀ(2ꢀphenylꢀ2ꢀ(triphenylsilyl)vinyl)oxazolidinꢀ2ꢀone
(3i).
ASSOCIATED CONTENT
1
69.7 mg, Z/E = 16:1. 78% yield. Yellow oil. H NMR (500 MHz,
CDCl3, TMS): δ 7.57ꢀ7.55 (m, 6H), 7.40ꢀ7.35 (m, 5H), 7.35ꢀ7.29
(m, 6H), 7.00ꢀ6.98 (m, 4H), 3.61 (t, J = 10.0 Hz, 2H), 3.34 (t, J =
10.0 Hz, 2H). 13C NMR (125 MHz, CDCl3): δ 156.9, 143.2, 139.4,
136.1, 134.3, 129.7, 129.2, 127.9, 127.6, 125.8, 122.9, 62.2, 46.9.
IR (KBr) ν 2920, 2851, 1765, 1590, 1390, 1102, 700 cmꢀ1. HRMS
(EIꢀTOF) m/z: [M]+ Calcd for C29H25NO2Si 447.1655; Found
447.1650.
1
2
3
4
5
6
7
8
Supporting Information
The Supporting Information is available free of charge on the
1
ACS Publications website. Other plausible mechanism, H NMR,
13C NMR spectra of new compounds and Xꢀray crystallographic
data for 3e.
AUTHOR INFORMATION
(Z)ꢀ3ꢀ(2ꢀ(pꢀtolyl)ꢀ2ꢀ(triphenylsilyl)vinyl)oxazolidinꢀ2ꢀone (3j).
1
Corresponding Author
66.4 mg, Z/E = 17:1. 72% yield. Yellow oil. H NMR (400 MHz,
9
CDCl3, TMS): δ 7.57ꢀ7.55 (m, 6H), 7.38ꢀ7.26 (m, 9H), 6.88ꢀ6.76
(m, 4H), 3.59 (t, J = 8.0 Hz, 2H), 3.34 (t, J = 8.0 Hz, 2H), 2.19 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 156.9, 139.2, 136.5, 136.1,
134.4, 129.7, 129.0, 128.3, 127.9, 127.7, 123.7, 62.1, 47.1, 20.9.
IR (KBr) ν 2986, 1760, 1595, 1428, 1399, 1107, 1039, 744 cmꢀ1.
HRMS (ESIꢀTOF) m/z: [M+Na]+ Calcd for C30H27NO2SiNa
484.1703; Found 484.1703.
*wzsong@dlut.edu.cn
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Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
This work was supported by grants from the Doctoral Program
Foundation of Liaoning Province (Nos. 20170520378,
20170520274), the Fundamental Research Funds for the Central
Universities (Nos. DUT16RC(3)114, DUT18LK25) and National
Natural Science Foundation of China (Nos. 21702025,
51703018). We thank Prof. Baomin Wang (Dalian University of
Technology) for his enthusiastic help and Mr. He Zhao (Dalian
University of Technology) for Xꢀray crystal analysis.
(Z)ꢀ3ꢀ(2ꢀ(triphenylsilyl)hexꢀ1ꢀenꢀ1ꢀyl)oxazolidinꢀ2ꢀone
(3k).
o
59.8 mg, Z/E > 20:1. 70% yield. White solid, mp = 106ꢀ107 C.
1H NMR (500 MHz, CDCl3, TMS): δ 7.63ꢀ7.61 (m, 6H), 7.42ꢀ
7.36 (m, 9H), 7.20 (s, 1H), 3.49 (t, J = 10.0 Hz, 2H), 3.22 (t, J =
10.0 Hz, 2H), 2.07 (t, J = 5.0 Hz, 2H), 1.24ꢀ1.22 (m, 2H), 1.07ꢀ
1.04 (m, 2H), 0.65 (t, J = 5.0 Hz, 3H). 13C NMR (125 MHz,
CDCl3): δ 157.0, 136.8, 136.1, 134.4, 129.8, 128.0, 121.4, 62.0,
47.2, 36.8, 33.4, 22.3, 13.6. IR (KBr) ν 2956, 2359, 1761, 1476,
1399, 1107, 761, 639 cmꢀ1. HRMS (EIꢀTOF) m/z: [M]+ Calcd for
C27H29NO2Si 427.1968; Found 427.1965.
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one (3l). 78.0 mg, Z/E > 20:1. 74% yield. White solid, mp = 119ꢀ
120 oC. 1H NMR (500 MHz, CDCl3, TMS): δ 7.68 (d, J = 5.0 Hz,
6H), 7.43ꢀ7.37 (m, 9H), 6.40 (s, 1H), 3.88 (t, J = 10.0 Hz, 2H),
3.36 (t, J = 10.0 Hz, 2H), 1.20ꢀ1.15 (m, 3H), 1.06 (d, J = 10.0 Hz,
18H). 13C NMR (125 MHz, CDCl3): δ 155.7, 151.7, 149.2, 135.1,
132.4, 128.9, 126.9, 60.7, 46.5, 17.9, 10.9. IR (KBr) ν 2943, 2341,
1749, 1428, 1108, 882, 740 cmꢀ1. HRMS (EIꢀTOF) m/z: [MꢀiPr]+
Calcd for C29H34NO2Si2 484.2128; Found 484.2133.
(Z)ꢀ3ꢀ(2ꢀ(dimethyl(phenyl)silyl)ꢀ2ꢀphenylvinyl)oxazolidinꢀ2ꢀone
1
(3m). 45.2 mg, Z/E = 15:1. 70% yield. Yellow oil. H NMR (400
and Tin. Synthesis 2005, 2005, 853. (c) Brunner, H.
A New
MHz, CDCl3, TMS): δ 7.63ꢀ7.62 (m, 2H), 7.39ꢀ7.18 (m, 8H), 6.77
(s, 1H), 3.84 (t, J = 8.0 Hz, 2H), 3.38 (t, J = 8.0 Hz, 2H), 0.34 (s,
6H). 13C NMR (125 MHz, CDCl3): δ 157.6, 144.2, 139.5, 137.2,
134.4, 130.1, 129.0, 128.8, 127.0, 125.0, 113.6, 62.6, 47.3, 0.0. IR
(KBr) ν 2986, 2359, 1758, 1417, 1265, 1111, 814, 747 cmꢀ1.
HRMS (ESIꢀTOF) m/z: [M+Na]+ Calcd for C19H21NO2SiNa
346.1234, found 346.1239.
Hydrosilylation MechanismꢀNew Preparative Opportunities. Angew.
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(Z)ꢀ3ꢀ(2ꢀ(methyldiphenylsilyl)ꢀ2ꢀphenylvinyl)oxazolidinꢀ2ꢀone
1
(3n).55.4 mg, Z/E = 17:1. 70% yield. Yellow oil. H NMR (400
MHz, CDCl3, TMS): δ 7.66ꢀ7.64 (m, 4H), 7.40ꢀ7.38 (m, 6H),
7.22ꢀ7.16 (m, 6H), 3.66 (t, J = 8.0 Hz, 2H), 3.33 (t, J = 8.0 Hz,
2H), 0.39 (s, 3H). 13C NMR (125 MHz, CDCl3): δ 156.9, 143.3,
138.4, 136.2, 134.9, 129.6, 128.4, 128.1, 127.1, 126.3, 112.8, 62.0,
46.9, ꢀ0.5. IR (KBr) ν 2985, 1759, 1398, 1109, 1039, 747, 703 cmꢀ
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408.1390; Found 408.1392.
(E)ꢀ(S)ꢀ4ꢀphenylꢀ3ꢀstyryloxazolidinꢀ2ꢀone (4f). 21.5 mg, E/Z >
20:1. 81% yield. White solid, mp = 122ꢀ123 oC. [α]ꢀꢁꢂ= +91.3 (c =
1.45, MeOH). 1H NMR (500 MHz, CDCl3, TMS): δ 7.44ꢀ7.40 (m,
2H), 7.39ꢀ7.31 (m, 4H), 7.22 (t, J = 10.0 Hz, 2H), 7.17ꢀ7.13 (m,
3H), 5.58 (d, J = 15.0 Hz, 1H), 5.16 (dd, J = 5.0, 10.0 Hz, 1H),
4.78 (t, J = 10.0 Hz, 1H), 4.20 (dd, J = 5.0, 10.0 Hz, 1H). 13C
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128.6, 126.7, 125.9, 125.6, 123.0, 113.0, 70.8, 58.6. IR (KBr) ν
2986, 2359, 1760, 1403, 1265, 747 cmꢀ1. Compound 4f is known
compound, and the proton and carbon spectrum is fully consistent
with literature reported.15
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