Ethyl Oxanilates and Pyridones as CHAs
J. Agric. Food Chem., Vol. 54, No. 5, 2006 1869
solid of meta and para aryl substituted ethyl oxanilates, which were
homogeneous, by TLC (18). Ethyl 4′- fluoro oxanilate (4), a member
of this family, was synthesized by thermal condensation of 4-fluoro
aniline and diethyl oxalate. Yield 4.75 g (90%). Mp 118-119 °C (lit.
1
1
(
)
8
18.5 °C). TLC R
t, J ) 6 Hz, 3H, -CH
6 Hz, 2H, H , Hb′ aromatic), 7.95 (d, J ) 6 Hz, 1H, H
.10 (d, J ) 6 Hz, 1H, Ha′ aromatic), 9.44 (s, 1H, NH). IR: 3333 (as.
NH str), 1698 (CdO ester str), 1640 (amide-I band, CdO str), 1400
f
: 0.50. GC R
t
) 7.82 min. HNMR (CDCl
3
): δ 1.65
), 7.40 (t, J
a
aromatic),
3
), 4.70 (q, J ) 6 Hz, 2H, -OCH
2
b
(
(
(
CF str), 1295 (aromatic secondary δCH). EI-MS m/z (rel int %): 211
M , 100), 139 (18), 138 (93), 137 (72), 110 (92), 75 (12), 83 (32), 63
5).
+
A solution of ethyl(chlorocarbonyl) formate (0.25 mol) in CHCl
10 mL) was added over a period of 30 min to a solution of ortho
kept at e10 °C with continuous
3
(
substituted aniline (0.25 mol) in CHCl
3
stirring under an inert atmosphere of nitrogen. The reaction was
followed by TLC (hexane-ethyl acetate (4:1) as developing medium)
until completion. The resultant reaction mixture was poured into ice-
cold water, and a solid residue was obtained after evaporating the CHCl
3
layer. Recrystallization of the residue with ethanol yielded ortho
substituted ethyl oxanilates as white crystalline solids, which was
homogeneous by TLC (18). Ethyl 2′-fluoro oxanilate (2), a member of
this family, was synthesized by condensation between 2-fluoro aniline
and ethyl(chlorocarbonyl) formate. Yield 4.91 g (93%). Mp103 °C.
1
Figure 1. General procedure of synthesis of ethyl oxanilates (ortho/para
and meta substituted) and pyridones.
TLC R
Hz, 3H, CH
f
: 0.63. GC R
t
: 4.79 min. HNMR (CDCl
3
): δ 1.35 (t, J ) 6
), 7.20 (m, 3H, H , Hb′ and
aromatic), 9.15 (s, 1H, NH). EI-MS m/z
3
), 4.35 (q, J ) 6 Hz, 2H, OCH
2
b
H
c
aromatic), 7.50(m, 1H, H
a
+
(
(
rel int %): 211 (M , 14), 139 (40), 111 (100), 91 (18), 84(45), 83
63), 64(41), 63 (36), 57(59), 52(23), 50(16).
A solution of substituted anilines (0.03 mol), p-toluenesulfonic acid,
and ethyl isodehydracetate (0.015 mol) suspended in dry xylene was
heated to reflux for 18-24 h. The resulting suspension was washed
with dilute HCl and water to remove excess aniline and dried over
that govern interaction of CHAs with the macromolecular
receptor in the crop plants controlling pollen formation and its
viability.
In a program of design and development of potential and
targeted CHAs, we have already reported the deployment of
N-acylanilines, anilides, and amino acid analogues in wheat
2 4
anhydrous Na SO . The crude product obtained after the removal of
(
18-21). The present study consisted of synthesis, field
xylene was purified by silica column chromatography using acetone-
hexane (4:6) to furnish N-aryl-5-carbethoxy-4,6-dimethyl-1,2-dihydro-
pyrid-2-ones/pyridones as dark brown oils (19). N-(4-Chlorophenyl)-
evaluation, QSAR analysis, and possible mode of action of 40
test CHAs belong to two chemical classes, viz. ethyl oxanilates
and pyridones, as potential CHAs for chickpea. On the basis of
the preliminary screening, a short list of eight potent CHAs
5
-carbethoxy-4,6-dimethyl-1,2-dihydropyrid-2-one (26), a member of
the pyridone family, was synthesized by thermal condensation of
4
6
1
-chloro aniline and ethyl isodehydracetate using an acid catalyst. Yield
(showing g90% of induction of pollen sterility) were tested
1
.29 g (66%). TLC R
.30 (t, J ) 6 Hz, 3H, OCH
)d), 4.22 (q, J ) 6 Hz, 2H, OCH
C(H)-), 7.00 (d, J ) 6 Hz, 2H, H , H aromatic), 7.37 (d, J ) 6 Hz,
f
0.27. GC R
CH ), 1.80 (s, 3H, dC(CH
), 6.13 (s, 1H, d
t
15.78 min. HNMR (CDCl
3
): δ
for their selectivity in action, and technology has been standard-
ized toward the development of potent molecules as well as
systematic ranking of CHAs on the basis of activity vis- a` -vis
selectivity.
2
3
3
)N-), 2.12
(s, 3H, -C (CH
3
2
b
b′
+
2H, H
a
, Ha′ aromatic). EI-MS: m/z (%) 305 (M , 31), 262 (8), 260
(
(
(
24), 250 (15), 248 (45), 234 (7), 232 (26), 231 (20), 213 (17), 204-
22), 169 (14), 168 (55), 167 (16), 154 (36), 152 (69), 138 (11), 127
12), 113 (35), 111 (100), 77 (35), 75 (58), 67 (16), 65 (17), 63 (17),
MATERIALS AND METHODS
The compounds synthesized numbering 40 analogues belong to two
broad chemical classes, viz. ethyl oxanilates and pyridones. The test
compounds have been prepared by condensation between different
substituted anilines with various esters. Ethyl oxanilates and pyridones
containing variations at the acyl domain were synthesized by condensa-
tion of substituted anilines with appropriate diesters or acid chlorides
or monoesters as described earlier (18-21). The compounds were
purified using physical and chromatographic separation methods. The
53 (30), 52 (47).
Screening of Synthesized Compounds as CHAs on Chickpea (Var
BG 1088). The high-yielding Kabuli variety of chickpea (Cicer
arietinum L.), viz. BG 1088, recommended for North Western Plain
Zone of India, was chosen for evaluation of chemical induction of male
sterility. The experiment was laid out in a randomized block design
with three replicates along with the control. The material was planted
in a row of 2.5 m length with a row-to-row distance of 50 cm and
plant-to-plant distance of 35 cm for each treatment in three replications
at the Indian Agricultural Research Institute experimental farm. The
recommended package of practices was followed throughout the season
for a good crop. Other optimum agronomic practices were also followed
which included recommended fertilizer and irrigation schedule, timely
weeding, and other cultural operations. A solvent suitable for formula-
tion of CHAs was identified on the basis of the solubility characteristics
of the test CHAs. A stock solution of 40 EC (40000 ppm) was prepared
by dissolving 120 mg of CHA in 3 mL of cyclohexanone and Tween-
80 (polyoxysorbitan monooleate) (5%) as emulsifier which was diluted
to working solution of 30 mL by distilled water to prepare 4000 ppm
concentration. Spray emulsion (2000, 1000, 800, and 500-ppm) was
obtained by appropriate serial dilution of stock solution (4000 ppm)
by distilled water. To ensure phytosafety of cyclohexanone, a blank
solvent emulsion was sprayed on the crop well in advance. No serious
1
structures of synthesized compounds were confirmed by IR, H NMR,
and MS. Melting points (mp’s) were determined by using a sulfuric
acid bath and were uncorrected. All test compounds gave correct
elemental analyses using a Euro Vector elemental analyzer (model
EA3011).
General Procedure of Synthesis of Ethyl Oxanilates (1-20) and
Pyridones (21-40). The following methods illustrate the general
scheme of synthesis of the title compounds using different substituted
anilines and various esters (Figure 1).
To a solution of aniline (0.025 mol) and toluene was added diethyl
oxalate (0.03 mol). The reaction mixture was refluxed for 45 min, and
ethanol was collected as an azeotrope. The reaction was followed by
TLC (hexane-ethyl acetate (4:1) as developing medium) until comple-
tion. After cooling of the reaction mixture, a solid residue was obtained,
which was triturated with boiling ethanol to give a white crystalline