10.1002/cplu.201900316
ChemPlusChem
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(d, J = 7.9 Hz, 1 H), 7.68 (t, J = 7.6 Hz, 1 H), 7.64–7.59 (m, 3 H), 7.49 (t,
J = 7.5 Hz, 1 H), 7.45 (t, J = 7.7 Hz, 2 H), 7.35 (t, J = 7.4 Hz, 1 H) ppm.
13C NMR (126 MHz, CDCl3): δ = 193.51, 144.50, 135.43, 133.58, 133.08,
132.85, 131.19, 129.80, 129.09, 129.03, 128.82, 128.64, 124.95, 123.77,
120.91 ppm; HRMS-ESI [(M+H)+]: m/z calcd for (C15H11OS)+: 239.0525;
found, 239.0513.
127.10 ppm. HRMS-ESI [(M+H)+]: m/z calcd for (C13H9S3)+: 260.9860;
found, 260.9868.
7H-Thieno[2,3-c]thiopyran-7-one (8a). Yield: 77 mg, 70%, orange oil. 1H
NMR (500 MHz, CDCl3) δ = 7.84 (d, J = 5.2 Hz, 1H), 7.67 (d, J = 9.4 Hz,
1H), 7.53 (d, J = 9.4 Hz, 1H), 7.39 (d, J = 5.2 Hz, 1H) ppm; 13C NMR
(126 MHz, CDCl3): δ = 179.40, 146.92, 134.37, 134.21, 129.27, 127.92,
117.89, 114.28 ppm. HRMS-ESI [(M+H)+]: m/z calcd for (C7H5OS2)+:
168.9776; found, 168.9782.
(Z)-3-Benzylidene-4-methylbenzo[c]thiophen-1(3H)-one (4b) Yield: 91
mg, 84%. Orange oil. 1H NMR (500 MHz, CDCl3): δ = 7.79 (d, J = 7.6 Hz,
1 H), 7.74 (s, 1 H), 7.57 (d, J = 7.5 Hz, 2 H), 7.50 (d, J = 7.3 Hz, 1 H),
7.44 (t, J = 7.7 Hz, 2 H), 7.40–7.32 (m, 2 H), 2.82 (s, 3 H) ppm; 13C NMR
(126 MHz, CDCl3): δ = 193.97, 141.20, 137.31, 136.64, 135.19, 135.01,
134.25, 130.14, 129.73, 128.90, 128.68, 128.46, 23.65 ppm; HRMS-ESI
[(M+H)+]: m/z calcd for (C16H13OS)+: 253.0681; found, 253.0678.
5-Phenyl-7H-thieno[2,3-c]thiopyran-7-one (8b). Yield: 96 mg, 90%, red-
dark oil. 1H NMR (500 MHz, CDCl3): δ = 7.85 (d, J = 5.1 Hz, 1H), 7.64 –
7.59 (m, 2H), 7.54 (s, 1H), 7.49 – 7.44 (m, 3H), 7.36 (d, J = 5.1 Hz, 1H)
ppm; 13C NMR (126 MHz, CDCl3) δ = 179.75, 147.69, 145.57, 136.81,
134.72, 131.98, 129.80, 129.32, 128.24, 127.20, 115.61 ppm. HRMS-ESI
[(M+H)+]: m/z calcd for (C13H9OS2)+: 245.0089; found, 245.0093.
(Z)-3-Benzylidene-6-chlorobenzo[c]thiophen-1(3H)-one (4c). Yield: 87
mg, 82%, Amorphous yellow powder, m.p. 95-97 °C. 1H NMR (500 MHz,
CDCl3): δ = 7.91 (d, J = 8.4 Hz, 1 H), 7.81 (d, J = 1.8 Hz, 1 H), 7.62 (dd, J
= 8.4, 1.8 Hz, 1 H), 7.58 (d, J = 7.4 Hz, 2 H), 7.57 (s, 1 H), 7.45 (t, J = 7.7
Hz, 2 H), 7.36 (t, J = 7.4 Hz, 1 H) ppm; 13C NMR (126 MHz, CDCl3): δ =
192.05, 142.63, 135.59, 135.13, 134.38, 133.59, 130.13, 129.81, 129.14,
125.74, 123.48, 121.90 ppm; HRMS-ESI [(M+H)+]: m/z calcd for
(C15H10ClOS)+: 273.0135; found, 273.0138.
In-vitro evaluation of the herbicidal activity of sulfurated
heterocycles
Effects on root morphology
Seed sterilization, vernalization and germination were carried out as
previously reported.[29] Briefly, seeds of Arabidopsis thaliana (L.) Heynh.
ecotype Columbia (Col-0) were sterilized for 3 min in 50% EtOH and
0.5% NaOCl with Triton X-100 at 0.01% and then washed three times in
distilled water. After sterilization, seeds were maintained in 0.1% agar at
4 °C for 72 h to allow vernalization. Then, 24 seeds were sown in square
Petri dishes (100 x 150 mm) containing plant agar (0.8% w/v) medium
enriched with a mixture of micro and macronutrients (Murashige-Skoog,
Sigma-Aldrich) supplemented with 1% sucrose. The plates were placed
vertically in the growth chamber to encourage geotropic growth of roots.
Growing conditions were 22 2 ° C and light intensity of 75 mol m-2s-1.
Immediately after germination, five uniform, 4-d old seedlings were
transferred to a single plate and grown for 14 d with the same medium
containing 0, 25, 50, 100, 200, 400 μM of each heterocyclic derivative.
The molecules were previously dissolved in EtOH and the same amount
of EtOH (0.1% v/v) was added to the control (0 μM). At the end of the
experiments, the whole root system was imaged by scanning (STD 1600,
Régent Instruments Inc., Quebec, Canada) and primary root length
(PRL) and number of lateral roots (NLR) were measured using WinRhizo
Pro system v. 2002a (Instruments Régent Inc., Quebec, Canada).
(Z)-3-(4-Fluorobenzylidene)benzo[c]thiophen-1(3H)-one (4d). Yield: 90
mg, 84%, Amorphous grey powder, m.p. 84-86 °C. 1H NMR (500 MHz,
CDCl3): δ = 7.97 (d, J = 8.5 Hz, 1 H), 7.86 (d, J = 7.6 Hz, 1 H), 7.68 (t, J =
7.6 Hz, 1 H), 7.58 (dd, J = 8.8, 5.3 Hz, 2 H), 7.56 (s, 1 H), 7.50 (t, J = 7.5
Hz, 1 H), 7.14 (t, J = 8.5 Hz, 2 H) ppm; 13C NMR (126 MHz, CDCl3): δ =
206.95, 193.07, 163.62, 144.26, 133.51, 131.44 (d, J = 8.2 Hz), 129.03,
123.64 (d, J = 25.4 Hz), 120.70, 116.15 (d, J = 21.8 Hz) ppm; HRMS-ESI
[(M+H)+]: m/z calcd for (C15H10FOS)+: 257.0431; found, 257.0423.
3-(4-Methoxyphenyl)-1H-isothiochromen-1-one (5e). Yield: 85 mg, 80%,
Amorphous orange powder, m.p. 117-119 °C. 1H NMR (500 MHz, cdcl3)
δ = 8.29 (dd, J = 8.0, 0.5 Hz, 1H), 7.85 – 7.80 (m, 2H), 7.69 (td, J = 7.5,
1.3 Hz, 1H), 7.49 – 7.43 (m, 2H), 6.99 – 6.95 (m, 2H), 6.83 (s, 1H), 3.87
(s, 3H) ppm. 13C NMR (126 MHz, CDCl3) δ = 162.63, 161.22, 153.87,
138.06, 134.95, 129.78, 127.81, 126.97, 125.83, 124.69, 120.30, 114.39,
100.38, 55.56 ppm. HRMS-ESI [(M+H)+]: m/z calcd for (C16H13O2S)+:
269.0631; found, 269.0632.
1
3-Propyl-1H-isothiochromen-1-one (5f). Yield: 85 mg, 78%, brown oil. H
NMR (500 MHz, CDCl3) δ = 7.94 (d, J = 8.2 Hz, 1H), 7.67 (t, J = 7.5 Hz,
1H), 7.43 (t, J = 7.7 Hz, 2H), 7.33 (d, J = 7.8 Hz, 1H), 6.72 (s, 1H), 2.60 (t,
J = 7.5 Hz, 3H), 1.82 – 1.71 (m, 3H), 1.00 (t, J = 7.4 Hz, 4H) ppm; 13C
NMR (126 MHz, CDCl3): δ = 163.21, 157.61, 135.19, 132.85, 132.75,
132.28, 129.86, 128.72, 125.68, 106.24, 35.43, 20.61, 13.57 ppm.
HRMS-ESI [(M+H)+]: m/z calcd for (C12H13OS)+: 205.0681; found,
205.0680.
Effects on shoot development and pigments content
To evaluate the phytotoxic potential of the selected molecules on plant
growth and development, different parameters were considered. In
particular, total fresh weight (FW), leaf number (LN) and pigments
content were evaluated. Regarding the last parameter, total amounts of
chlorophyll a, chlorophyll b, and carotenoids were analyzed and
calculated according to Wellburn.[30] The pigments content was evaluated
according to the following equations:
7H-Thieno[2,3-c]thiopyran-7-thione (7a). Yield: 108 mg, 89%, Amorphous
red powder, m.p. 88-90 °C. 1H NMR (500 MHz, CDCl3) δ = 7.95 (d, J =
5.3 Hz, 1H), 7.65 (d, J = 9.4 Hz, 1H), 7.52 (d, J = 9.4 Hz, 1H), 7.38 (d, J =
5.3 Hz, 1H) ppm; 13C NMR (126 MHz, CDCl3) δ = 196.79, 148.88),
139.52), 138.36, 134.43, 128.38, 121.19 ppm. HRMS-ESI [(M+H)+]: m/z
calcd for (C7H5S3)+: 184.9547; found, 184.9547.
Chla (µg) = (15.65 (DO666 – DO750) – 7.34 (DO653 – DO750))*V
Chlb (µg) = (27.05 (DO653 – DO750) – 11.21 (DO666 – DO750))*V
Ct (X+C) (µg) = (1000 (DO470 – DO750) – 2.86 Chla – 129.2 Chlb)/221)*V
5-Phenyl-7H-thieno[2,3-c]thiopyran-7-thione (7b). Yield: 103 mg, 90%,
Amorphous red powder, m.p. 100-102 °C. 1H NMR (500 MHz, CDCl3): δ
= 7.95 (d, J = 5.3 Hz, 1H), 7.76 (s, 1H), 7.63 – 7.57 (m, 2H), 7.50 – 7.45
(m, 3H), 7.41 (d, J = 5.3 Hz, 1H) ppm. 13C NMR (126 MHz, CDCl3): δ =
196.94, 151.04, 147.21, 141.31, 138.63, 135.55, 130.24, 129.52, 128.62,
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