Journal of Agricultural and Food Chemistry
Article
Figure 1. Examples of fungicides structure.
13C NMR (100 MHz, CDCl3) ppm: 120.9, 122.1, 124.6, 125.2, 126.3,
129.1, 133.1, 135.6, 136.5, 139.1, 153.81, 168.0. HRMS [MH]+ exact
mass calculated for C13H9S2NBr, 321.9354; found, 321.9356.
Data for 2-(4-Iodophenylthio)benzothiazole (5). The product
was isolated as yellow oil after column chromatography using
dichloromethane:petroleum ether (70:30). 1H NMR (400 MHz,
CDCl3) δ: 7.28−7.32 (m, 1H), 7.40−7.45 (m. 3H), 7.56−7.78 (m,
2H), 7.80 (d, J = 8.12 Hz, 1H) 7.89 (dd, J = 8.12 Hz, J = 3.03 Hz, 1H).
13C NMR (100 MHz, CDCl3) ppm: 121.2, 122.5, 124.9, 126,7, 130.2,
130.3, 130.6, 135.7, 136.0, 136.9, 139.4, 154.1. HRMS [MH]+ exact
mass calculated for C13H9S2NI, 369.9221; found, 369.9239.
Figure 2. Methodologies employed for the arylation of 2-
mercaptobenzotiazole.
DMSO (Carlo Erba) was also distilled under nitrogen and stored in
molecular sieve 4 Å (Aldrich). Potato glucose agar (PGA) and
Triadimefon were commercially available and used as received.
Distilled water was sterilized before their use.
Data for 2-(2-Chlorophenylthio)benzothiazole (6). The
product was isolated as brown solid after column chromatography
using dichloromethane:petroleum ether (70:30). 1H NMR (400 MHz,
CDCl3) δ (ppm): 7.28−7.34 (td, 1H, J = 1.17 Hz, J = 8.69 Hz), 7.34−
7.39 (dd, 1 H, overlapping, J = 1.23 Hz, J = 8.38 Hz), 7.39−7.46 (tt,
2H, overlapping, J = 1.23 Hz, J = 8.01 Hz), 7.66−7.72 (dt, 1H, J = 1.48
Hz, J = 7.54 Hz), 7.73−7.78 (dt, 1H, J = 8.26 Hz), 7.78−7.82 (dt, 1H,
J = 1.97 Hz), 7.89−7.95 (dt, 1H, J=8.14 Hz). 13C NMR (100 MHz,
CDCl3) (ppm): 120.93, 122.27, 124.63, 126.26, 128.65, 129.73,
131.71, 131.87, 134.19, 135.87, 136.92, 153.87, 166.97. HRMS [MH]+
exact mass calculated for C13H8S2NCl, 277.9865; found, 277.9860.
Data for 2-(3-Chlorophenylthio)benzothiazole24 (7). The
product was isolated as colorless oil after column chromatography
using dichloromethane:petroleum ether (70:30). 1H NMR (400 MHz,
CDCl3) δ: 7.28−7.34 (J = 1.17 Hz, J = 8.69 Hz, td, 1H), 7.37−7.44 (t,
1H, overlapping, J = 7.77 Hz), 7.37−7.44 (dd, 1H, overlapping, J =
1.23 Hz, J = 8.38 Hz), 7.44−7.50 (tt, 1H, overlapping, J = 1.23 Hz, J =
8.01 Hz), 7.58−7.64 (dt, 1H, J = 1.48 Hz, J = 7.54 Hz), 7.68−7.72 (d,
1H, J = 8.26 Hz), 7.72−7.74 (t, 1H, J = 1.97 Hz), 7.83−8.03 (d, 1H, J
= 8.14 Hz). 13C NMR (100 MHz, CDCl3) ppm: 120.9, 122.3, 124.7,
126.3, 130.4, 130.9, 131.9, 132.9, 134.5, 135.4, 135.7, 153.7. HRMS
[MH]+ exact mass calculated for C13H9S2NCl, 277.9865; found,
277.9860.
Photostimulated Reactions of Dihalobenzenes with Benzo-
thiazole-2-thiolate Ions in DMSO. The following procedure is
representative of these reactions. 2-Mercaptobenzothiazole (1.1
mmol) and t-BuOK (1.1 mmol) were added to 8 mL of degassed
DMSO. Then, after 10 min when no more solid was present,
benzothiazole-2-thiolate ions were ready for use (characterized by a
yellow solution). Substrate (1.0 mmol) was added to the solution and
the reaction mixture irradiated for 180 min. The reaction was then
quenched by adding an excess of water. The solution was then
extracted with dichloromethane and water (25 mL). The organic
extract was analyzed by GC-MS, and the products were isolated by
column chromatography.
A similar procedure was carried out for reactions with substrate
excess, adding 1.0 mmol of 2-mercaptobenzothiazole and t-BuOK and
5.0 mmol of substrate. These reaction mixtures were irradiated for 30
min.
Microwave Assisted Reactions of Dihalobenzenes with
Benzothiazole-2-thiolate Ions in Microwave Oven. 2-Mercapto-
benzothiazole (0.5 mmol) and KOH (0.5 mmol) was added to 2 mL
of water. Then, after 2 min when no more solid was present, the
benzothiazole-2-thiolate ions were ready for use (characterized by a
yellow solution). Substrate (0.6 mmol) was added to the solution and
the reaction mixture irradiated for 2−7 min. The solid was extracted
with dichloromethane. The organic extract was analyzed by GC-MS.
Data for 2-(Phenylthio)benzothiazole (2). The product was
isolated as yellow oil after column chromatography using dichlor-
Data for 2-(4-Fluorophenilthio)benzothiazole (8). The prod-
uct was isolated as brownish solid after column chromatography using
dichloromethane:petroleum ether (70:30); mp 54.3−55.5 °C. 1H
NMR (400 MHz, CDCl3) δ: 7.11−7.21 (m, 2H), 7.22−7.31 (m, 1H),
7.40 (ddd, J = 8.65 Hz, J = 7.30 Hz, J = 1.20 Hz, 1H), 7.65 (d, J = 8.17
Hz, 1H), 7.68−7.73 (m, 2H), 7.86 (d, J = 8.17 Hz, 1H). 13C NMR
(100 MHz, CDCl3) ppm: 117.5, 117.7, 121.1, 122.3, 124.7, 126.8,
135.9, 138.1, 138.2, 154.2, 163.3, 165.8, 169.8. HRMS [MH]+ exact
mass calculated for C13H9S2NF, 262.0155; found, 262.0169.
1
omethane:petroleum ether (70:30). H NMR (400 MHz, CDCl3) δ:
7.27−7.57 (m, 5H), 7.62−7.82 (m, 3H), 7.90 (dd, J = 12.55 Hz, J =
8.17 Hz, 1H). 13C NMR (100 MHz, CDCl3) ppm: 121.1, 121.5, 122.2,
124.7, 124.9, 126.5, 130.3, 130.8, 135.7, 135.9, 153.3. HRMS [MH]+
exact mass calculated for C13H10S2N, 244.0249; found, 244.0317.
Data for 1,4-Bis(2-Mercaptobenzothiazol)benzene (3). The
nucleophile excess was extracted from the reaction mixture by washing
with water. The product was isolated as a white solid after filtrating
and washing the precipitate with ethyl acetate; mp: 197.5−199.3 °C.
1H NMR (400 MHz, DMSO-d6) δ: 7.39 (td, J = 8.14 Hz, J = 1.15 Hz,
2H), 7.49 (td, J = 8.22 Hz, J = 1.27 Hz, 2H), 7.89 (ddd, J = 8.17 Hz; J
= 1.00 Hz, J = 0.54 Hz, 2H), 7.92 (s, 4H), 8.00 (ddd, J = 8.05 Hz, J =
1.17 Hz, J = 0.55 Hz, 2H). 13C NMR (100 MHz, DMSO-d6) ppm:
121.7, 121.9, 125.0, 126.6, 132.1, 135.1, 135.5, 153.2. HRMS [MH]+
exact mass calculated for C20H13S4N2, 408.9962; found, 408.9986.
Data for 2-(4-Bromophenylthio)benzothiazole23 (4). The
product was isolated as white solid after column chromatography
using dichloromethane:petroleum ether (70:30); mp 55.6−56.8 °C.
1H NMR (400 MHz, CDCl3) δ: 7.29 (ddd, J = 7.97 Hz, J = 7.37 Hz, J
= 1.21 Hz, 1H), 7.42 (ddd, J = 8.13 Hz, J = 7.28 Hz, J = 1.25 Hz, 1H),
7.56−7.64 (m, J = 3.00 Hz; J = 1.14 Hz, J = 0.52 Hz, 4H), 7.69 (ddd, J
= 8.28 Hz, J = 0.53 Hz, 1H), 7.89 (dd, J = 8.28 Hz, J = 0.53 Hz, 1H).
Bioassays of Fungicidal Activities. Five bunches of botrytized
grape clusters (Vitis vinifera cv. Chardonnay) were randomly hand-
harvested in a vineyard in the district Barrancas, Maipu, province
́
Mendoza (Argentina) in 2010. Solutions of compounds 2−8 were
prepared with ethanol and were sterilized by filtration with 0.2 μm
GHP HPLC filter membrane. Those solutions were each incorporated
into polystyrene Petri dishes which contained potato glucose agar
(PGA) and the required amount of water to reach the desired
concentration of each compound. Fungal growth in the presence of
each compound was evaluated at four concentrations (12.5, 25, 50,
and 100 μg mL−1) in PGA. Then the culture media were allowed to
solidify. The final concentration of ethanol was 1.2% of the final
volume of media for all treatments and control. For this instance,
ethanol, water, PGA, and HPLC filters, membranes, and syringes were
previously sterilized by autoclave for 15 min at 120 °C. For each
analysis, three replicates were performed. Radial growth was measured
after incubation at 28 °C for 8 days in the dark. For all assays, the fungi
were cultured on PGA/water (positive control) and PGA/water/
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J. Agric. Food Chem. 2015, 63, 3681−3686