3286 J. Agric. Food Chem., Vol. 45, No. 8, 1997
Rouchaud et al.
GC signal 2 times lower than that of monomethylrimsulfuron
′. Monomethyl derivative 4′ of compound 4 was GC detected
32), 324 (compound 3, 36), 260 (3 - SO
85), 231 (3 - SO CH CH , 100). MS (CI): 382 (M - SO
100), 339 (M - SO NCO, 85), 325 (compound 3 + H, 95), 296
(3 - CH CH + H, 76), 245 (3 - SO CH , 42), 231 (3 - SO
CH CH , 72).
N-(4,6-Dimethoxypyrimidin-2-yl)-N-[3-(ethylsulfonyl)-2-
pyridinyl]urea (2) and N-[3-(Ethylsulfonyl)-2-pyridinyl]-4,6-
dimethoxy-2-pyrimidineamine (3). Rimsulfuron (1.0 g, 2.32
mmol) in a mixture (1.4 N in HCl) of methanol (30 mL) and
hydrochloric acid (12 N, 4 mL) was stirred (8 days, 20 °C).
The solid rimsulfuron was first in suspension and at the end
of the reaction was completely dissolved. Methanol was
evaporated under vacuum and water (50 mL) added; the
mixture was brought to pH 7.0 with NaOH and extracted with
2
, 48), 245 (3 - SO
2
CH
+ H,
3
,
1
2
2
3
2
as such (flame photometry) and was made up of a mixture of
2
1
O- and N-methyl derivatives (as shown by H NMR) which
2
3
2
3
2
-
were not separated by TLC and GC. Compounds 2 and 3 were
injected directly into the GC apparatus. Compound 2 also was
transformed in the GC apparatus into compound 3 which was
detected; compound 3 was GC detected as such. For GC
analysis of compound 5, to its TLC-purified extract in ethyl
acetate (2 mL) was added a solution of trifluoroacetic anhy-
dride (Acros; 25%, v/v, in ethyl acetate; 2 mL), the mixture
was carefully heated to boiling (∼5 min) until concentrated to
2
3
0
.1 mL, ethyl acetate was added, and the mixture was
analyzed by GC for trifluoroacetylated 5 [N-(trifluoroacetyl)-
-amino-4,6-dimethoxypyrimidine 5′]. GC conditions were as
2
2 4
ethyl acetate. The ethyl acetate solution was dried (Na SO )
follows: glass column with a 1.80 m × 2 mm internal diameter
and concentrated under vacuum to dryness. The product was
column chromatographed [successively 1/2 ether/hexane (v/v)
and 1/2 ethyl acetate/hexane (v/v)], giving successively com-
packed with 5% SE30 on Gas Chrom Q 80-100 mesh; nitrogen
-
1
carrier gas at 40 mL min ; injection and detection tempera-
tures of 275 °C for rimsulfuron and compounds 1′, 2, and 3
and of 250 °C for compound 5′, and detection of each of these
compounds by electron capture (GC Varian 2700 apparatus);
for compound 4′, injection at 250 °C and detection at 180 °C,
and detection by flame photometry in the sulfur mode (GC
Tracor 550 apparatus). Column temperature and retention
times for each compound were as follows: compound 3 (from
rimsulfuron and compounds 1′, 2, or 3), 245 °C, 3.7 min;
compound 4′, 160 °C, 3.9 min; and compound 5′, 170 °C, 2.7
min. The GC samples from soil extracts of rimsulfuron (as
its monomethyl derivative 1′) and of the rimsulfuron metabo-
lites 2-4 (as its methyl derivative 4′) and 5 (as its trifluoro-
acetyl derivative) were in many cases further analyzed by GC-
MS.
pounds 3 (0.35 g, 1.08 mmol, 47%) and 2 (0.37 g, 1.0 mmol,
1
43%). H NMR (CDCl
3
) spectrum of compound 2: 1.22-1.29
), 3.27 (q, 2H, SO CH CH ), 3.63 (s, 6H,
), 5.71 (s, 1H, pyrimidine H), 7.61, 8.44, 8.89 (m, 3H,
(t, 3H, SO
OCH
2
CH
2
CH
3
2
2
3
3
pyridine H). Spectra of compound 3: IR 3356, 3095, 2956,
1603, 1570, 1516, 1447, 1408, 1372, 1354, 1310, 1273, 1200,
1
1163, 1132, 1059, 1005, 801, 739. H NMR (CDCl
3
): 1.24 (t,
), 3.87 (s, 6H,
), 5.73 (s, 1H, pyrimidine H), 6.35 (br, 1H, NH). MS
3H, SO
OCH
(EI): 324 (M , 45), 309 (M - CH
279 (M - OCH CH , 4), 277 (M - HOCH
- SO H, 19), 245 (M - SO CH , 24), 231 (M - SO
100), 216 (231 - CH , 42), 186 (216 - OCH + H, 35).
2 2 3 2 2 3
CH CH ), 3.17 (q, 2H, SO CH CH
3
+
3
, 4), 295 (M - CH
CH - H, 3), 259 (M
3
CH CH ,
2 3
CH , 9),
2
3
2
3
2
2
3
2
2
3
3
2-Hydroxy-3-(ethylsulfonyl)pyridine (4). Rimsulfuron (4.0 g,
9.3 mmol) in 12 N HCl in water (50 mL) was heated to reflux
(stirring, 3.5 h). The cooled mixture was brought to pH 7 by
careful addition (cooling) of a 4 N NaOH solution in water,
and the aqueous solution (∼80 mL) was repeatedly (4 × 300
mL) extracted with ethyl acetate; the ethyl acetate solution
-
1
IR spectra were recorded in KBr discs in cm (Midac FTIR
-
1
1
apparatus; 4000-400 cm ). H NMR spectra were in parts
per million (δ) in tetramethylsilane (Varian 250 MHz). MS
and GC-MS (VG AutoSpec; Fisons GC 8065) spectra condi-
tions were as follows: 70 eV, electron impact EI and (or)
chemical ionization (CI) with NH
3
; FAB-SIMS in glycerol for
2 4
was dried (Na SO ) and concentrated to dryness under vacuum,
rimsulfuron; m/ e, relative abundance, %.
and the residue was column chromatographed [1/1ethanol/
An a lytica l Sta n d a r d s for Rim su lfu r on a n d Its Me-
ta bolites. Rimsulfuron. The commercial formulation Titus
ether (v/v)], giving compound 4 (1.51 g, 8.07 mmol, 87%). IR:
3423, 3117, 2986, 1699, 1653, 1607, 1539, 1478, 1406, 1366,
1
(25 g; 25% rimsulfuron; Du Pont, Belgium) in ethyl acetate
200 mL) was heated to reflux (7 min, stirring); the hot mixture
1300, 1235, 1127, 976, 774, 737. H NMR (CDCl
3
): 1.27 (t,
(
3H, CH
2 3 2 3
CH ), 3.48 (q, 2H, CH CH ), 6.53 (t, 1H, pyridine H),
was filtered. The solid was reextracted in the same way two
more times, and the filtrates were gathered and concentrated
to dryness in a vacuum rotary evaporator. Recrystallization
in 1/1 ethyl acetate/chloroform (v/v) gave rimsulfuron (5.94 g,
7.79 (t, 1H, pyridine H), 8.32 (t, 1H, pyridine H). MS (EI):
+
187 (M , 71), 158 (M - CH
2
CH
3
, 17), 141 (158 - OH, 23), 123
NOH + H,
(M - SO
100).
2
, 29), 111 (158 - SO + H, 32), 95 (C H
5 3
9
3
1
5%, purity greater than 99% as shown by TLC). IR: 3424,
Mixture of 2-Methoxy-3-(ethylsulfonyl)pyridine and 1-Meth-
yl-3-(ethylsulfonyl)-2-pyridone (4′). 2-Hydroxy-3-(ethylsulfo-
nyl)pyridine 4 (1 g, 5.3 mmol) in methanol (50 mL) was treated
at 20 °C with an ethereal solution of diazomethane until the
yellow color persisted. The mixture was stirred at 20 °C for 2
h and concentrated under vacuum to dryness, and the solid
was purified by column chromatography [2/1 hexane/acetone
277, 3093, 2946, 2789, 1734, 1611, 1586, 1507, 1454, 1375,
1
356, 1318, 1235, 1196, 1171, 1130, 1047, 990, 779, 718.
): 1.33-1.38 (t, 3H, SO CH CH
), 3.98 (s, 6H, OCH ), 5.82 (s, 1H, pyrimidine H),
.18 (br, 1H, NH-pyrimidine), 7.78, 8.62, 8.93 (m, 3H, pyridine-
H), 12.98 (br, 1H, SO NH). MS (EI): 322 (compound 3 - 2H,
8), 231 [C HN (OCH NH(C N), 36], 155 [C HN (OCH
NH , 59], 137 [C HN (OCH - 2H, 18], 123 [C HN (OCH )(O)
H, 14], 109 [C HN (OCH ) + H, 19]. MS FAB-SIMS
glycerol): 432 (M + 1, 100), 340 [M - SO CH CH + 2H, 8),
99 (340 - CONH + 2H, 11), 199 [C HN (OCH NHCONH
H, 83], 182 [C HN (OCH NHCO, 78], 156 [C HN (NH )-
OCH + H, 58].
Monomethylrimsulfuron (1′). Rimsulfuron (1.0 g, 2.32 mmol)
H
NMR (CDCl
SO CH CH
7
3
2
2
3
), 3.75 (q, 2H,
2
2
3
3
2
1
4
2
3
)
2
5
H
3
4
2
3
)
2
-
(v/v)], giving the mixture of compounds 4′ (1.02 g, 5.1 mmol,
1
2
4
2
3
)
2
4
2
3
96%). H NMR (CDCl
3
): 1.19 (t, 3H, SO
2
CH
2
CH
3
), 3.24-3.49
-
(
2
+
(
4
2
3
(m, 2H, SO
2
CH
2
CH
3
), 3.57 (s, 1H, NCH
3
), 3.67 (s, 2H, OCH
3
),
2
2
3
6.31 (t, 1H, pyridine H), 7.02 (m, 0.5H, pyridine H), 7.63 (m,
4
2
3
)
2
2
0.5H, pyridine H), 8.12 (m, 1H, pyridine H). MS (EI): 201
+
4
2
3
)
2
4
2
2
(M , 43), 186 (M - CH
3
, 21), 172 (M - CH
, 18), 142 (156 - CH , 31), 107 (M - HSO
, 78), 78 (C N + H, 100).
2
CH
3
, 24), 156 (M
3
)
2
- OCH
CH
2
CH
3
2
2
CH -
2
3
5 3
H
in ethyl acetate (100 mL) was treated with a solution of
diazomethane in ether until the yellow color persisted. The
mixture was stirred for 20 h (20 °C), maintaining the yellow
color by addition of the diazomethane ethereal solution when
necessary. The solvent was evaporated under vacuum, and
the residue was column chromatographed [10/1 dichloro-
methane/acetic acid (v/v)], yielding methylrimsulfuron (0.91
g, 2.04 mmol, 88%). IR: 3423, 3277, 3092, 2953, 1698, 1597,
2-Amino-4,6-dimethoxypyrimidine (5). To the stirred (20 °C)
mixture of 2-amino-4,6-dihydroxypyrimidine (1 g, 7.87 mmol;
Acros) in methanol (30 mL) was added an ethereal solution of
diazomethane until the yellow color persisted. The mixture
was stirred during 24 h (20 °C), maintaining the yellow color
by addition of the diazomethane solution when necessary. The
solvent was evaporated under vacuum, and the residue was
column chromatographed [1/1 ethanol/hexane (v/v)], yielding
compound 5 (1.05 g, 6.77 mmol, 86%). IR: 3431, 2932, 1653,
1
7
2
561, 1539, 1414, 1366, 1316, 1211, 1171, 1155, 1051, 955, 785,
1
1
50, 720. H NMR (CDCl
.99 (s, 3H, SO NCH ), 3.25 (q, 2H, SO
), 5.67 (s, 1H, pyrimidine H), 7.57, 8.42, 8.86 (m, 3H,
pyridine H), 9.87 (br, 1H, NH-pyrimidine). MS (EI): 381 (M
SO , 3), 352 (M - SO NCH , 2), 338 (M - SO NCO - H,
3
): 1.21-1.28 (t, 3H, SO
2
CH
2
CH
3
),
1622, 1539, 1466, 1418, 1252, 1213, 1165, 1034, 974. H NMR
2
3
2
CH CH ), 3.62 (s, 6H,
2
3
(DMSO-d
7.28 (br, 2H, NH
4), 127 (M - HCN - H, 28), 125 (M - OCH
NH CNH, 38).
6
): 3.70 (s, 6H, OCH
). MS (EI): 155 (M , 100), 139 (M - NH
, 21), 112 (M -
3
), 4.93 (s, 1H, pyrimidine H),
+
OCH
3
2
2
,
2
-
2
2
3
2
2