2
L. Yang et al. / Tetrahedron 75 (2019) 130538
of the fluorophore. Inspired by these excellent ability, we envi-
sioned that blocked N, N-diethylamino based coumarin dye might
be an excellent candidate, on which our fluorescent probes are
based.
The test solution was prepared by adding 30 mL of probe 1
(1 mM) to 3.0 mL of HEPES buffer (10 mM, pH ¼ 7.4, 50% DMSO,
containing 5 mM CTAB (Cetyltrimethylammonium bromide)). Then
stock solutions of each analyte were added into the quartz cell
gradually by using a micro-syringe. Excitation wavelength for test
solution were 439 nm and with slit width as 1 nm.
In this work, we reported the design and synthesis of probe 1, in
which the 2,4-dinitrobenzene group was introduced both as the
detection unit and as a fluorescence quencher. Due to the stronger
SNAr activity of thiophenols, probe 1 would rapidly afford the re-
ported blocked N, N-diethylamino based coumarin dyes by the
addition of thiophenol in aqueous solution. The probe 1 exhibited a
significant fluorescence turn-on signal and showed a high sensi-
tivity and selectivity for thiophenols over other thiols. The unique
recognition mechanism of probe 1 toward PhSH through subse-
quent cyclization process was also demonstrated. Furthermore, the
probe 1 can be used for to detect thiophenols in living cells.
2
.3. Synthetic procedures
The synthetic process were shown in Scheme 1 and the char-
acteristic data of each compound was shown in Figs. S1eS7.
2
.3.1. Synthesis of compound 2
To solution of 8-Hydroxyjulolidine-9-aldehyde (65 mg,
.3 mmol) and 1-Fluoro-2,4-dinitro-benzene (74 mg, 0.4 mmol) in
a
0
acetone (10.0 mL) was added potassium carbonate (138 mg,
1 mmol). The resulting mixture was stirred at 70 C for 4 h. After
ꢂ
2
. Experimental section
removal of the solvent, the solid was purified by silica gel flash
chromatography using CH Cl as eluent to afford compound 2
2.1. Instruments
2
2
(
80 mg, 69% yield) as a yellow solid. HRMS (EI) m/z: calcd for
1H NMR and 13C NMR spectra were determined on Bruker
þ
1
C19H17N O [M þ Na] , 406.1015 found, 406.1015. H NMR
3
6
Ascend™ 400 spectrometer with TMS as internal standard. Mass
spectra data were measured on Bruker Microtof-QIII spectrometry.
Absorption spectra were recorded on Shimadzu UV2600 spectro-
photometer. Luminescence spectra were measured on an Edin-
burgh FS-5 fluorescence spectrophotometer. Cell imaging
experiments were performed with Leica DMI8 inverted fluores-
cence microscope. TLC analysis was performed on silica gel plates
and column chromatography was conducted using silica gel (mesh
(400 MHz, CDCl3)
d
9.65 (s, 1H), 8.89 (d, J ¼ 2.7 Hz, 1H), 8.26 (dd,
J ¼ 9.3, 2.8 Hz, 1H), 7.38 (s, 1H), 6.86 (d, J ¼ 9.3 Hz, 1H), 3.49e3.21
(m, 4H), 2.80 (t, J ¼ 6.3 Hz, 3H), 1.97 (ddd, J ¼ 37.9, 11.8, 6.1 Hz, 4H).
2
.3.2. Synthesis of probe 1
To a solution of compound 2 (80 mg, 0.2 mmol) and 2-cyano-
N,N-dimethylacetamide (28 mg, 0.25 mmol) in a mixture of ethyl
alcohol (10.0 mL) was added piperidine (15.0
lution was stirred at 70 C for 4 h. After removal of the solvent, the
mL). The reaction so-
2
00e300).
ꢂ
3
solid was purified by silica gel flash chromatography using CH OH/
2
.2. Reagents and chemicals
CH
2
Cl
2
(v/v, 1:10) as eluent to afford probe 1 (35.0 mg, 37% yield) as
þ
a red solid. HRMS (EI) m/z: calcd for C24
H
23
N
5
O
6
[M þ 1] , 478.1726;
þ
1
All the chemicals of analytical grade were obtained from com-
found, 478.1700. [M þ Na] , 500.1546; found, 500.1539. H NMR
mercial sources and used as supplied without further purification.
Double distilled water was used throughout the experiments. A
stock solution of probe 1 was prepared as 1 mM in DMSO. Solutions
(400 MHz, CDCl
3
)
d
8.88 (dd, J ¼ 14.4, 2.6 Hz, 1H), 8.28 (dd, J ¼ 9.2,
2.7 Hz, 1H), 8.08 (s, 1H), 7.62 (s, 1H), 6.81 (dd, J ¼ 9.2, 4.1 Hz, 1H),
3.30 (ddd, J ¼ 21.8, 13.7, 8.1 Hz, 4H), 3.11e3.02 (m, 3H), 2.83 (dd,
ꢁ
2
13
of various testing species (2.0 ꢀ 10 M) were prepared from PhSH,
J ¼ 12.1, 5.9 Hz, 2H), 2.07e1.84 (m, 4H), 1.26 (s, 5H). C NMR
GSH, Cys, Hcy, Leu, Met, Pro, NaNO
3
, KNO
3
, Na
2
SO
4
, Na
2
S, Na
2
S
2
O
3
,
3
(101 MHz, CDCl ) d 165.07, 155.64, 143.78, 141.32, 138.04, 126.97,
NaSCN, NaHSO in twice-distilled water.
3
119.87, 116.56, 111.89, 111.29, 99.28, 50.06, 49.39, 29.13, 27.56, 27.40,
ꢂ
ꢂ
Scheme 1. Synthesis of probe 1. (a) 1-Fluoro-2,4-dinitro-benzene, acetone, 70 C, 4 h, yield 69%. (b) 2-cyano-N, N-dimethylacetamide, piperidine, EtOH, 70 C, 4 h, yield 37%. (c) 2-
ꢂ
cyano-N, N-dimethylacetamide, piperidine, EtOH, 70 C, 4 h, yield 37%. (d) Thiophenol, CH
3
CN/HEPES buffer (pH ¼ 7.4), CTAB, r.t., 1 h, yield 27%.