Synthesis of novel α-acyloxycarboxamides containing vinylbis(silanes) through three-component Passerini reactions

Article abstract of DOI:10.1007/s13738-016-1018-4

A three-component efficient procedure is described for the synthesis of novel α-acyloxycarboxamides containing bis(trimethylsilyl)ethenyl group from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde, aromatic carboxylic acids and isocyanides, via the Passeri

Full text of DOI:10.1007/s13738-016-1018-4

J IRAN CHEM SOC
DOI 10.1007/s13738-016-1018-4
ORIGINAL PAPER
Synthesis of novel α‑acyloxycarboxamides containing
vinylbis(silanes) through three‑component Passerini reactions
Vahideh Raeisdasteh Hokmabad1 · Hassan Abbasi1 · Kazem D. Safa1
Received: 5 October 2016 / Accepted: 24 November 2016
© Iranian Chemical Society 2016
Abstract A three-component efficient procedure is described
for the synthesis of novel α-acyloxycarboxamides containing
bis(trimethylsilyl)ethenyl group from 4-[2,2-bis(trimethylsilyl)
ethenyl]benzaldehyde, aromatic carboxylic acids and iso-
cyanides, via the Passerini reaction. This reaction proceeds
smoothly and cleanly under mild conditions in H2O and
[bmim]BF4 at room temperature and led to products in good
yields. The silylated aldehyde was obtained via Peterson ole-
fination reaction of terephthalaldehyde with tris(trimethylsilyl)
methyllithium in THF at 0 °C.
of ketones and isoxazoline derivatives as well as for a vari-
ety of important organosilicon reagents, such as acylsilanes,
epoxysilanes, silanols [10–15]. Recently, we described the
synthesis of new organosilicon compounds containing the
vinylbis(silane) group and converted them to amines [16].
Multicomponent reactions are special types of synthetically
useful organic reactions in which three or more reagents
are combined to react in a one-pot procedure [17, 18]. This
allows for high atom economy, a minimization of the forma-
tion of by-products, and decreases costs and is less time con-
suming [19]. They have been extensively studied over the past
few years, since these processes represent an efficient way of
assembling complex molecules in one pot, thus exemplify-
ing many of the desired features of an ideal synthesis. Among
MCRs, isocyanide-based multicomponent reactions (IMCRs)
have attracted much attention because of the advantages that
they offer to the field of the combinatorial chemistry [20–23].
The IMCRs are particularly interesting because they are more
versatile and diverse than the remaining MCRs [24, 25]. The
Passerini reaction (first described in 1921, Scheme 1) [26]
is the most fundamental MCR involving isocyanides that
provide α-acyloxycarboxamides by combining three build-
ing blocks in one step: a carboxylic acid, an aldehyde and
an isocyanide. This reaction has been involved as a key step
in the total synthesis of natural products due to the fact that
the α-acyloxycarboxamide is a frequently recurring motif in
many pharmacologically interesting natural products [27–30].
Keywords Passerini reaction · 4-[2,2-bis(trimethylsilyl)
ethenyl]benzaldehyde · Carboxylic acid · Isocyanide ·
Water · [bmim]BF4
Introduction
Since the discovery of the high biological potential of sev-
eral classes of organosilicon compounds, in the 1960s, it is
obvious that the organosilicon compounds, in principle, can
exhibit high and specific biological activity. In the mean-
time, some biologically active organosilicon compounds have
already found practical application as therapeutic agents in
medicine and as reference drugs in experimental pharma-
cology [1–6]. Vinylsilanes and vinylbis(silanes) are impor-
tant synthetic reagents in organic synthesis [7–9] because
the C(sp2)–Si bonds undergo numerous transformations
[8]. Vinylbis(silanes) are useful reagents for the preparation
Experimental
* Kazem D. Safa
Materials and instruments
dsafa@tabrizu.ac.ir
1
4-[2,2-Bis(trimethylsilyl)ethenyl]benzaldehyde and [bmim]
BF4 were prepared based on the reported procedures [16,
Organosilicon Research Laboratory, Faculty of Chemistry,
University of Tabriz, Tabriz 5166616471, Iran
1 3

J IRAN CHEM SOC
uid was further washed with DCM and dried at 80 °C
under reduced pressure to reuse in subsequent runs.
2. A mixture of 4-[2,2-bis(trimethylsilyl)ethenyl]benzal-
dehyde (1a, 1 mmol), a carboxylic acid derivative (2,
1 mmol) and an isocyanide (3, 1 mmol) in 2 ml H2O
was stirred at room temperature for a certain period of
time (Table 1) to complete the reaction (monitored by
TLC). The precipitate was collected by suction, subse-
quently rinsed with n-hexane and dried to give product.
Scheme 1 Mechanism of Passerini reaction
31, 32]. Other starting materials and solvents were pur-
chased from Merck and were used without further purifica-
tion. The FTIR spectra were recorded on a Bruker-Tensor
Analyses and spectra
1
270 spectrometer. The H NMR and 13C NMR spectra
were recorded on a Bruker FT-400 MHz spectrometer at
room temperature and with CDCl3 as the solvent for H
(tert‑Butylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)phe‑
nyl) methyl 2‑chlorobenzoate (4a) White powder (silica
gel, n-hexane/ethyl acetate 10:2, Rf = 0.6), m.p. 72–76 °C.
FTIR (KBr, cm−1): 838.77, 1256.87 (Si–CH3), 1695.24,
1724.89 (CO), 2890, 2961.39, 3072.29 (CH), 3308.68
1
NMR, tetramethylsilane (TMS) served as internal stand-
ard (δ = 0). Mass spectra were obtained with a GC-Mass
Agilent, quadrupole model 5973 N instrument, operating
at 70 eV. Melting points were measured with Barnstead
international capillary melting point apparatus. Elemental
analyses were carried out with an Elementar Vario EL III
instrument.
1
(NH). H NMR (400 MHz, CDCl3, δ/ppm): −0.08 (s, 9H,
SiMe3), 0.17 (s, 9H, SiMe3), 1.35 (s, 9H, t-Bu), 6.20 (s, 1H,
CH=), 6.31 (s, 1H, NH), 7.18 (d, J = 8 Hz, 1H, Ar), 7.35–
7.49 (m, 5H, Ar), 7.70 (s, 1H, CH =), 7.90 (d, J = 8 Hz,
1H, Ar). 13C NMR (400 MHz, CDCl3, δ/ppm): −0.53, 0.95
(SiMe3), 27.60 (CH3), 50.58 (N–C), 74.86 (CH), 125.70,
127.24, 127.44, 127.57, 128.70, 129.17, 132.50, 132.68,
133.57, 142.51 (Ar), 146.50, 152.92 (vinyl. C), 164.07 (CO
of amide), 166.42 (CO of ester). MS (m/z (EI), %): 515
([M]+), 139 (100), 213 (61.02), 73.10 (42.84, [SiMe3]+),
416.10 (39.01). Anal. Calc. for C27H38ClNO3Si2: C 62.82,
H 7.42, N, 2.71. Found: C 62.61, H 7.29, N 2.63%.
General procedure for synthesis of 4a–4k
1. A mixture of 4-[2,2-bis(trimethylsilyl)ethenyl]ben-
zaldehyde (1a, 1 mmol), a carboxylic acid derivative
(2, 1 mmol) and an isocyanide (3, 1 mmol) in 2 ml
[bmim]BF4 was stirred at room temperature for a cer-
tain period of time (Table 1) to complete the reaction
(monitored by TLC). The product was extracted three
times with 10 ml portions of diethyl ether, and the
combined ethereal phases were washed with brine and
dried over sodium sulfate. The solvent was removed
under reduced pressure, and the product was purified
by column chromatography on silica gel using an ethyl
acetate–hexane eluent. The rest of the viscous ionic liq-
(tert‑Butylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)
phenyl) methyl benzoate (4b) White powder (silica gel,
n-hexane/ethyl acetate 9:1, Rf = 0.5), m.p. 71–74 °C. FTIR
(KBr, cm−1): 837.62, 1256.40 (Si–CH3), 1666, 1725 (CO),
1
2844.62, 2958.44, 3083.91 (CH), 3283 (NH). H NMR
Table 1 Synthesis of α-acyloxycarboxamides containing 2,2-bis(trimethylsilyl)ethenyl group (4a–k)
Entry
R1
R2
Product
Yield (%)/H2O
Time (h)/H2O
Yield (%)/[bmim]BF4
Time (h)/[bmim]BF4
1
t-Bu
2-Cl
4a
4b
4c
4d
4e
4f
95
94
95
97
95
93
97
96
98
97
92
2
83
85
75
87
87
72
87
85
90
85
75
10
13
12
10
18
15
9
2
t-Bu
H
2
3
t-Bu
2-Me
3,4,5-trimethoxy
2-NO2
4-NO2
3-Cl
4
4
t-Bu
2
5
t-Bu
3
6
t-Bu
3
7
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
4g
4h
4i
1.5
3
8
4-Cl
9
9
3-F
1.5
2
12
15
18
10
11
3-NO2
4-Br
4j
4k
5
1 3

J IRAN CHEM SOC
(400 MHz, CDCl3, δ/ppm): −0.08 (s, 9H, SiMe3), 0.17 (s,
9H, SiMe3), 1.35 (s, 9H, t-Bu), 6.21 (s, 1H, CH), 6.33 (s,
1H, NH), 7.1 (d, J = 8 Hz, 2H, Ar), 7.30 (m, 1H, Ar), 7.40
(m, 5H, Ar), 7.7 (s, 1H, CH =), 7.89 (d, J = 8 Hz, 1H,
Ar); 13C NMR (400 MHz, CDCl3, δ/ppm): −0.5, −0.91
(SiMe3), 27.58 (CH3), 50.60 (N–C), 75.90 (CH), 125.7,
125.9, 127.14, 130.2, 131.08, 131.9, 133.45, 142.4 (Ar),
146.42, 152.95 (vinyl. C), 163.09 (CO of amide), 166.11
(CO of ester); MS (m/z (EI), %): 481 ([M]+), 105.10 (100),
179.10 (79.02), 382.20 (61.61), 73.10 (42.56, [SiMe3]+).
Anal. Calc. for C27H39NO3Si2: C 67.31, H 8.16, N, 2.91.
Found: C, 67.15, H 7.97, N 2.77%.
(tert‑Butylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)phe‑
nyl)methyl 2‑nitrobenzoate (4e) White powder (silica gel,
n-hexane/ethyl acetate 10:2, Rf = 0.4), m.p. 111–113 °C.
FTIR (KBr, cm−1): 839.21, 1253.31 (Si–CH3), 1675.58,
1
1740.9 (CO), 2960.87, 3076.38 (CH), 3329.39 (NH). H
NMR (400 MHz, CDCl3, δ/ppm): −0.08 (s, 9H, SiMe3),
0.17 (s, 9H, SiMe3), 1.36 (s, 9H, t-Bu), 6.02 (s, 1H, NH),
6.15 (s, 1H, CH), 7.18 (d, J = 8 Hz, 2H, Ar), 7.36 (d,
J = 8 Hz, 2H, Ar), 7.69 (m, 3H, Ar, CH =), 7.85 (m, 2H,
Ar). 13CNMR (400 MHz, CDCl3, δ/ppm): −0.56, 0.91
(SiMe3), 27.47 (CH3), 50.78 (N–C), 76.50 (CH), 122.81,
125.2, 125.8, 127.19, 129.83, 131.44, 132.02, 147.19 (Ar),
146.5, 152.8 (vinyl. C), 162.61 (CO of amide), 165.63
(CO of ester). MS (m/z (EI), %): 526 ([M]+), 73.10 (100,
[SiMe3]+), 182.90 (68.67), 184.90 (67.18), 261.10 (59.13).
Anal. Calc. for C27H38N2O5Si2: C 61.56, H, 7.27, N 5.32.
Found: C 61.37, H 7.04, N 5.12%.
(tert‑Butylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)phe‑
nyl) methyl 2‑methyl benzoate (4c) White powder (silica
gel, n-hexane/ethyl acetate, 9:1, Rf = 0.6), m.p. 84–87 °C.
FTIR (KBr, cm−1), 838.8, 1249.95 (Si–CH3), 1658.04,
1724.49 (CO), 2910, 2960.9, 3081.28 (CH), 3283.97 (NH).
1H NMR (400 MHz, CDCl3, δ/ppm): −0.07 (s, 9H, SiMe3),
0.18 (s. 9H, SiMe3), 1.33 (s, 9H, t-Bu), 2.60 (s, 3H, CH3),
5.83 (s, 1H, NH), 6.16 (s, 1H, CH), 7.20 (d, J = 8 Hz,
2H, Ar), 7.28 (t, J = 8 Hz, 2H, Ar), 7.44 (t, J = 8 Hz, 3H,
Ar), 7.72 (s, 1H, CH =), 7.9 (d, J = 8 Hz, 1H, Ar). 13C
NMR (400 MHz, CDCl3, δ/ppm): −0.53, 0.90 (SiMe3),
20.70 (CH3), 27.6 (CH3), 50.5 (N–C), 74.9 (CH), 124.88,
125.79, 127.23, 129.50, 130.48, 130.80, 131.42, 131.80,
133.72, 142.50 (Ar), 146.5, 152.9 (vinyl. C), 164 (CO of
amide), 166.4 (CO of ester). MS (m/z (EI), %): 495 ([M]+),
119.10 (100), 193.10 (57.89), 396.20 (45.04), 73.10 (30.28,
[SiMe3]+). Anal. Calc. for C28H41NO3Si2: C 67.83, H 8.34,
N 2.83. Found: C 67.43, H 8.09, N 2.69%.
(tert‑Butylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)phe‑
nyl) methyl 4‑nitrobenzoate (4f) White powder (silica gel,
n-hexane/ethyl acetate 10:2, Rf = 0.4), m.p. 146–149 °C.
FTIR (KBr, cm−1): 839.63, 1258.8 (Si–CH3), 1662.70,
1731.56 (CO), 2863.49, 2961.58, 3086.81 (CH), 3429.12
1
(NH). H NMR (400 MHz, CDCl3, δ/ppm): −0.07 (s, 9H,
SiMe3), 0.18 (s, 9H, SiMe3), 1.30 (s, 9H, t-Bu), 5.48 (s,
1H, NH), 6.14 (s, 1H, CH), 7.23 (d, J = 8 Hz, 2H, Ar),
7.45 (d, J = 8 Hz, 2H, Ar), 7.7 (s, 1H, CH =), 8.28 (q,
J = 20 Hz, 4H, Ar). 13C NMR (400 MHz, CDCl3, δ/ppm):
−0.57, 0.93 (SiMe3), 27.5 (CH3), 50.8 (N–C), 75.5 (CH),
122.6, 126.05, 127.51, 130, 132.70, 133.89, 143.15, 149.70
(Ar), 147.06, 152.5 (vinyl. C), 162.6 (CO of amide), 165.6
(CO of ester). MS (m/z (EI), %): 526 ([M]+), 73.10 (100,
[SiMe3]+), 182.90 (68.67), 184.90 (67.18), 261.10 (59.13).
Anal. Calc. for C27H38N2O5Si2: C 61.56, H, 7.27, N, 5.32.
Found: C 61.33, H 7.19, N 5.15%.
(tert‑Butylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinylphe‑
nyl) methyl 3,4,5‑trimethoxy benzoate (4d) White pow-
der (silica gel, n-hexane/ethyl acetate 10:1, Rf = 0.6),
m.p. 131–133 °C. FTIR (KBr, cm−1): 840.87, 1255.72
(Si–CH3), 1665.60, 1723.48 (CO), 2860.8, 2959.7, 3082
(CH), 3308.59 (NH). 1H NMR (400 MHz, CDCl3, δ/ppm):
−0.15 (s, 9H, SiMe3), 0.10 (s, 9H, SiMe3), 1.25 (s, 9H,
t-Bu), 3.82 (s, 9H, OMe), 5.64 (s, 9H, NH), 6.05 (s, 1H,
CH), 7.13 (d, J = 8 Hz, 2H, Ar), 7.26 (s, 2H, Ar), 7.36
(d, J = 8 Hz, 2H, Ar), 7.63 (s, 1H, CH=). 13C NMR
(400 MHz, CDCl3, δ/ppm): −0.54, 0.9 (SiMe3), 27.62
(CH3), 50.5 (N–C), 55.23, 59.9 (O–CH3), 75.01 (CH),
106.08, 123.32, 125.84, 127.29, 133.48, 142.62, 152.02
(Ar), 146.6, 152.8 (vinyl. C), 163.8 (CO of amide), 166.2
(CO of ester). MS (m/z (EI), %): 571 ([M]+), 195.10
(100), 269.10 (38.44), 472.20 (27.03), 73.10 (20.74,
[SiMe3]+). Anal. Calc. for C30H45NO6Si2: C 63.01, H 7.93,
N 2.45. Found: C 62.78, H 7.73, N 2.34%.
(Cyclohexylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)
phenyl) methyl 3‑chlorobenzoate (4g) White powder (sil-
ica gel, n-hexane/ethyl acetate 10:2, Rf = 0.5), m.p. 141–
143 °C. FTIR (KBr, cm−1): 839.97, 1251.14 (Si–CH3),
1657.88, 1731.61 (CO), 2856.34, 2933.28, 3084.54 (CH),
3308.68 (NH). 1H NMR (400 MHz, CDCl3, δ/ppm): −0.06
(s, 9H, SiMe3), 0.18 (s, 9H, SiMe3), 1.05–1.92 (m, 10H, 5
CH2 of cyclohexyl), 3.81 (m, 1H, CH of cyclohexyl), 5.75
(d, J = 8 Hz, 1H, NH), 6.24 (s, 1H, CH), 7.21 (d, J = 8 Hz,
2H, Ar), 7.42 (m, 3H, Ar), 7.56 (d, J = 8 Hz, 1H, Ar), 7.70
(s, 1H, CH =), 7.98 (d, J = 8 Hz, 1H, Ar), 8.05 (s, 1H, Ar).
13C NMR (400 MHz, CDCl3, δ/ppm): −0.55, 0.95 (SiMe3),
23.62, 24.37, 31.76 (CH2 of cyclohexyl), 47.29 (N–C),
75.08 (CH), 125.88, 126.96, 127.34, 128.82, 128.89,
1 3

J IRAN CHEM SOC
130.11, 132.54, 132.93, 133.71, 142.78 (Ar), 146.71,
152.73 (vinyl. C), 163.05 (CO of amide), 165.99 (CO of
ester). MS (m/z (EI), %): 541 ([M]+), 139 (100), 73.10
(86.99, [SiMe3]+), 213 (71.80), 141 (33.80). Anal. Calc.
for C29H40ClNO3Si2: C, 64.23, H, 7.44, N, 2.58. Found: C
64.09, H 7.38, N 2.46%.
(silica gel, n-hexane/ethyl acetate 10:2, Rf = 0.5), m.p.
129–132 °C. FTIR (KBr, cm−1): 839.97, 1251.13 (Si–
CH3), 1655.73, 1732.42 (CO), 2858.58, 2934.96, 3086.25
(CH), 3265.11 (NH). 1H NMR (400 MHz, CDCl3, δ/
ppm): −0.06 (s, 9H, SiMe3), 0.18 (s, 9H, SiMe3), 1.2–
1.93 (m, 10H, 5 CH2 of cyclohexyl), 3.81 (m, 1H, CH of
cyclohexyl), 5.62 (d, J = 8 Hz, 1H, NH), 6.25 (s, 1H, CH),
7.24 (t, J = 8 Hz, 2H, Ar), 7.46 (d, J = 8 Hz, 2H, Ar),
7.69 (t, J = 8 Hz, 2H, Ar), 8.43 (t, J = 8 Hz, 2H, Ar), 8.90
(s, 1H, Ar). 13C NMR (400 MHz, CDCl3, δ/ppm): −0.55,
0.95 (SiMe3), 23.62, 24.35, 31.8 (CH2 of cyclohexyl),
47.47 (N–C), 75.5 (CH), 123.77, 125.9, 126.09, 127.7,
130.22, 132.47, 143.15, 147.02 (Ar), 147.2, 152.5 (vinyl.
C), 163 (CO of amide), 165.67 (CO of ester). MS (m/z
(EI), %): 552 ([M]+), 73.10 (100, [SiMe3]+), 261.10
(53.32), 187.10 (30.92), 276.10 (23.38), 203.10 (20.12).
Anal. Calc. for C29H40N2O5Si2: C, 63.01, H, 7.29, N,
5.07. Found: C 62.84, H 7.07, N 4.91%.
(Cyclohexylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)
phenyl) methyl 4‑chlorobenzoate (4h) White powder (sil-
ica gel, n-hexane/ethyl acetate 10:1, Rf = 0.5), m.p. 112–
114 °C. FTIR (KBr, cm−1): 843.11, 1260.99 (Si–CH3),
1686.10, 1727.15 (CO), 2855.23, 2935.06, 3083.6 (CH),
3284.06 (NH). 1H NMR (400 MHz, CDCl3, δ/ppm): −0.07
(s, 9H, SiMe3), 0.18 (s, 9H, SiMe3), 1.02–1.92 (m, 10H, 5
CH2 of cyclohexyl), 3.80 (m, 1H, CH of cyclohexyl), 5.76
(d, J = 8 Hz, 1H, NH), 6.23 (s, 1H, CH), 7.2 (d, J = 8 Hz,
2H, Ar), 7.44 (d, J = 8 Hz, 4H, Ar), 7.7 (s, 1H, CH =),
8.02 (d, J = 8 Hz, 2H, Ar). 13C NMR (400 MHz, CDCl3,
δ/ppm): −0.66, 0.8 (SiMe3), 23.49, 24.26, 31.66 (CH2 of
cyclohexyl), 47.17 (N–C), 74.81 (CH), 125.74, 126.68,
127.70, 130.08, 130.40, 132.90, 138.95, 142.64 (Ar),
146.60, 152.62 (vinyl. C), 163.26 (CO of amide), 166.03
(CO of ester). MS (m/z (EI), %): 541 ([M]+), 139 (100),
73.10 (86.99, [SiMe3]+), 213 (71.80), 141 (33.80). Anal.
Calc. for C29H40ClNO3Si2: C, 64.23, H, 7.44, N, 2.58.
Found: C 64.03, H 7.32, N 2.41%.
(Cyclohexylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)
phenyl) methyl 4‑bromobenzoate (4K) Yellow powder
(silica gel, n-hexane/ethyl acetate 10:2, Rf = 0.5), m.p.
182–184 °C. FTIR (KBr, cm−1): 814.25, 1248.46 (Si–
CH3), 1684.42, 1728.67 (CO), 2856.60, 2934.16, 3066.35
(CH), 3304.75 (NH). 1H NMR (400 MHz, CDCl3, δ/
ppm): −0.074 (s, 9H, SiMe3), 0.18 (s, 9H, SiMe3), 1.2–
1.92 (m, 10H, 5 CH2 of cyclohexyl), 3.79 (m, 1H, CH
of cyclohexyl), 5.74 (d, J = 8 Hz, 1H, NH), 6.23 (s, 1H,
CH), 7.20 (d, J = 8 Hz, 2H, Ar), 7.43 (d, J = 8 Hz, 2H,
Ar), 7.61 (d, J = 8 Hz, 2H, Ar), 7.7 (s, 1H, CH =), 7.95
(d, J = 8 Hz, 2H, Ar). 13C NMR (400 MHz, CDCl3, δ/
ppm): −0.53, 0.97 (SiMe3), 23.65, 24.39, 31.79 (CH2 of
cyclohexyl), 47.28 (N–C), 74.95 (CH), 125.86, 127.34,
130.31, 130.65, 130.87, 130.95, 134,157 (Ar), 142.7,
152.7 (vinyl. C), 166.09 (CO of ester). MS (m/z (EI),
%): 587 ([M+2]+), 73.10 (100, [SiMe3]+), 207 (85.6),
182.9 (43.87), 184.90 (42.48), 281 (41.84). Anal. Calc.
for C29H40BrNO3Si2: C, 59.37 H, 6.87, N, 2.39. Found: C
58.98, H 6.68, N 2.19%.
(Cyclohexylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)
phenyl) methyl 3‑fluorobenzoate (4i) White powder (sil-
ica gel, n-hexane/ethyl acetate 10:2, Rf = 0.5), m.p. 122–
124 °C. FTIR (KBr, cm−1): 840.34, 1269.03 (Si–CH3),
1657.60, 1728.69 (CO), 2856.38, 2935.60, 3082.12 (CH),
3269.08 (NH). 1H NMR (400 MHz, CDCl3, δ/ppm): −0.03
(s, 9H, SiMe3), 0.22 (s, 9H, SiMe3), 1.06–1.96 (m, 10H, 5
CH2 of cyclohexyl), 3.84 (m, 1H, CH of cyclohexyl), 5.80
(d, J = 8 Hz, NH), 6.28 (s, 1H, CH), 7.24 (d, J = 8 Hz,
2H, Ar), 7.32 (m, 1H, Ar), 7.49 (m, 3H, Ar), 7.74 (s, 1H,
CH =), 7.80 (s, J = 8 Hz, 1H, Ar), 7.93 (d, J = 8 Hz, 1H,
Ar). 13C NMR (400 MHz, CDCl3, δ/ppm): −0.54, 0.96
(SiMe3), 23.62, 24.62, 31.78 (CH2 of cyclohexyl), 47.28
(N–C), 75.08 (CH), 115.58, 115.8, 119.51, 119.72, 124.55,
125.8, 127.33, 129.22, 133.03, 142.76 (Ar), 146.71, 152.76
(vinyl. C), 162.79 (CO of amide), 165.99 (CO of ester).
MS (m/z (EI), %): 525 ([M]+), 123 (100), 197 (87.50),
73.10 (63.51, [SiMe3]+), 188.10 (26.83). Anal. Calc. for
C29H40FNO3Si2: C, 66.24 H, 7.67, N, 2.66. Found: C 66.02,
H 7.57, N 2.59%.
Results and discussion
α-Acyloxycarboxamides are precursors in the synthesis
of natural products. Recently Pirrung and Sarma reported
the acceleration of the Passerini reaction in water and in
aqueous solutions compared to organic solvents. Simi-
lar results in terms of reaction time and yields were
obtained when ionic liquid such as [bmim]BF4 was used
as solvent for most reactions [33, 34]. Due to interest-
ing properties of silicon-containing organic compounds
(Cyclohexylcarbamoyl)(4‑(2,2‑bis(trimethylsilyl)vinyl)
phenyl) methyl 3‑nitrobenzoate (4j) White powder
1 3

J IRAN CHEM SOC
Table 2 Effect of different solvents on one-pot synthesis of 4a
Entry
Solvent
Time/h
Temp/°C
Yield/%
1
2
3
4
5
6
7
8
CH2Cl2
CH2Cl2
THF
48
48
48
48
42
48
10
2
25
–
Reflux
25
45
–
THF
Reflux
25
40
25
34
83
95
PEG
PEG
60
[bmim]BF4
H2O
25
25
Scheme 2 Preparation of 4-[2,2 bis(trimethylsilyl)ethenyl]benzalde-
hyde via Peterson protocol
Conclusions
and in connection with our continued research on envi-
ronmentally benign methodologies in organic synthe-
sis, we were interested in inserting a silicon atom into
α-acyloxycarboxamides via the Passerini reaction. There-
fore, we apply this methodology to the versatile and effi-
cient one-pot synthesis of α-acyloxycarboxamide deriva-
tives containing the organosilicon groups in H2O and
[bmim]BF4 as solvents at room temperature. Previously,
we reported the synthesis of 4-[2,2-bis(trimethylsilyleth
enyl)]benzaldehyde (1a) by the reaction of (Me3Si)3CLi
with terephthalaldehyde via the Peterson olefination reac-
tion (Scheme 2) [16].
In summary, we have synthesized and characterized novel
α-acyloxycarboxamides containing an organosilicon
groups by the Passerini three-component reaction between
4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde, an iso-
cyanide and carboxylic acids in [bmim]BF4 and H2O as
solvents. This reaction is smoothly and efficiently car-
ried out under mild conditions, and no side reactions were
observed, rendering it a useful protocol for the synthesis of
these compounds.
Acknowledgements Financial support of this work by the Tabriz
University is gratefully appreciated.
The one-pot three-component condensation reactions of
aldehyde 1a with aromatic carboxylic acids 2 and isocya-
nides 3 proceeded smoothly and cleanly under mild condi-
tions in H2O and [bmim]BF4 and led to products in good
yields (Table 1). All of the pure products (4a–4k) were sta-
ble at room temperature for a long time. Elemental analy-
ses and spectroscopic data clearly indicated the formation
of products. Full results are given in Experimental section
(Scheme 3).
We also tested the effect of different solvents on the effi-
ciency of the Passerini reaction using synthesis of 4a as a
model reaction. The results are given in Table 2. According
to the results, it is observed that water and [bmim]BF4 are
suitable solvents for this type of reaction.
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1 3