Organophosphorus chemistry, part 37: Synthesis and insecticidal activities of some phosphonate adducts derived from 6-(Aryliminomethyl)-furobenzopyran-5- ones

Article abstract of DOI:10.1080/10426501003598614

Dialkyl phosphites attack 6-(Aryliminomethyl)furobenzopyran-5-ones at the imine-carbon atom to give new phosphonate 1:1 adducts. The obtained compounds regenerate the starting materials upon thermolysis under reduced pressure. Structures of the new products were attested by compatible analytical and spectroscopic measurements. Insecticidal activity tests assured that some new compounds show marked potency against adults of Aphis gossypii (Glover), which infests cotton crops. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426501003598614

Phosphorus, Sulfur, and Silicon, 185:2277–2285, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003598614
ORGANOPHOSPHORUS CHEMISTRY, PART 37:
SYNTHESIS AND INSECTICIDAL ACTIVITIES OF SOME
PHOSPHONATE ADDUCTS DERIVED FROM
6-(ARYLIMINOMETHYL)-FUROBENZOPYRAN-5-ONES
Taghrid S. Hafez,1 Hisham Abdallah A. Yosef,1
Hala M. Abou Yousef,2 Eman F. Al-Amrousi,1
and Mohamed Refat H. Mahran1
1Department of Organometallic and Organometalloid Chemistry,
National Research Centre, Dokki, Cairo, Egypt
2Central Agricultural Laboratory of Pesticides, Dokki, Cairo, Egypt
Dialkyl phosphites attack 6-(Aryliminomethyl)furobenzopyran-5-ones at the imine-carbon
atom to give new phosphonate 1:1 adducts. The obtained compounds regenerate the starting
materials upon thermolysis under reduced pressure. Structures of the new products were
attested by compatible analytical and spectroscopic measurements. Insecticidal activity tests
assured that some new compounds show marked potency against adults of Aphis gossypii
(Glover), which infests cotton crops.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental
file.
Keywords 6-(Aryliminomethyl)furobenzopyran-5-ones; insecticidal activities; phosphoryla-
tion; spectroscopic evidence; thermolysis
INTRODUCTION
Phosphonates have become very important compounds by virtue of their recognition
and efficiency as reagents in organic syntheses as well as for their biological and industrial
importance.1,2 Aldehydes,3–6 aldimines,7–10 and ketimines11–14 are suitable substrates for
the preparation of members of this class of compounds. Recently,1 we have reported
on the reaction of 4-methoxy- (1a) and 4,9-dimethoxy-5-oxo-5H-furo[3,2-g]benzopyran-
6-carboxaldehyde (1b) with dialkyl phosphites and trialkyl phosphites.1 This, together
with our growing interest in the organophosphorus chemistry of arylimines derived from
carbonyl compounds,7,8,11–13,15,16 has initiated us to study the behavior of monoarylimines
3a–h towards dialkyl phosphites 4a–c.
Received 27 October 2009; accepted 4 January 2010.
Address correspondence to M. R. H. Mahran, Department of Organometallic and Organometalloid Chem-
istry, National Research Centre, Dokki 12622, Cairo, Egypt. E-mail: mrh mahran@yahoo.com
2277

2278
T. S. HAFEZ ET AL.
RESULTS AND DISCUSSION
Arylimines 3a–h of the present study were essentially prepared by condensing 1a
or 1b with the appropriate aryl amine (aniline, p-chloroaniline, p-bromoaniline, and/or
p-fluoroaniline) in boiling ethanol. While anils 3a, c, and e were prepared according to
established procedures,17,18 monoanils 3b, d, and f–h are now prepared for the first time
(see the Experimental section and Scheme 1).
OCH3
O
CHO
H2N
X
O
O
2
a, X= H
b, X= Cl
c, X= Br
d, X= F
R
- H O
2
1 a , R=H
b, R=OCH3
OCH3
O
O
H
C
N
X
O
R
3a
b
c, R = H
d
e
f,
, R= X= H
, R = H
, R=OCH3
R= OCH3
X=H
X= Cl
X= Br
X= F
X= Cl
X= Br
X= F
g, R= OCH3
h
, R= OCH3
, R = H
Scheme 1
We have now found that monoanils 3a–h react smoothly with the appropriate dialkyl
phosphites 4a–c at 100◦C in the absence of solvent to give the respective phosphonate
1:1 adducts 5a–t in colored crystalline forms. Compatible analytical and spectroscopic
measurements were in good accord with the assigned structures (Scheme 2).
Thus, microanalysis and molecular weight determination (MS) for 4,9-dimethoxy-5-
oxo-5H-furo[3,2-g][1]-6-[(α-diethoxyphosphoryl-α-p-chloroanilino)methyl] benzopyran
5n, taken as a representative example, corresponded to C24H25ClNO8P. A positive chemical
shift at δ = 22.68 ppm was recorded in the 31P NMR spectrum of 5n (vs. 85% H3PO4),
confirming the presence of a phosphorus-to-carbon linkage (phosphonate group)19 in its
structure. The IR spectrum of 5n (KBr, cm−1) revealed the presence of strong absorption
bands at 3293 (NH, free), 1644 (C O, γ -pyrone), 1605, 1537 (C C, furan and aromatic),
1280 (P O, free),20 and 1050 (P O C2H5).20 The strong (C N) band present in the
1
IR spectrum of monoanil 3f at 1611 was absent in the spectrum of 5n. The H NMR
spectrum of 5n (DMSO-d6, δ ppm) showed protons of the ethoxy-CH3 groups attached to

ORGANOPHOSPHORUS CHEMISTRY, PART 37
2279
O
3 a-h + ( R/ O )2 P
OH
( R/ O )2 P
H
, R/= CH
4a
3
b, R/= C2H5
, R/= C H -i
c
3
7
O
P
OCH3
O
O
OR/
OR/
H
C
H
N
X
O
R
X= H
/
a, R = H
R = H
b,
R = C2H5
k, R= OCH3
l, R = OCH3
m, R = OCH3
n, R = OCH3
o, R = OCH3
p, R = OCH3
q, R = OCH3
r, R = OCH3
s, R = OCH3
t, R = OCH3
X= H
X= H
X= Cl
X= Cl
X= Cl
X= Br
X= Br
X= Br
X= F
R/ = C2H5
R/ = C3H7-i
R/ = CH3
5
X= H
X= Cl
X= Cl
X= Br
X= Br
X= Br
X= F
R/ = C3H7-i
/
c, R = H
d, R = H
e, R = H
f, R= H
g, R = H
h, R = H
i, R = H
j, R = H
R = C2H5
/
R/ = C2H5
R/ = C3H7-i
R/ = CH3
R = C3H7-i
R/ = CH3
R/ = C2H5
R/ = C3H7-i
R/ = CH3
R/ = C2H5
R/ = C3H7-i
R/ = C2H5
R/ = C3H7-i
X= F
X= F
R/ = C2H5
R/ = C3H7-i
X= F
Scheme 2
phosphorus (6H) as two triplets (each with 4JHP = 9.00 HZ) at 1.08 and 1.22. Apparently,
the asymmetry of the molecule due to the presence of a stereocenter would render the
two ethoxy groups distereotropic, and hence anisochronous, thus resulting in the observed
splitting pattern.21–23 The expected two quintets due to protons of the ethoxy-CH2- groups
attached to phosphorus (4H) appeared as an obscured multiplet (10H) in the 4.18–3.83
region, wherein two singlets emerge at 4.10 (3H, OCH3) and 4.00 (3H, OCH3). The
spectrum also showed two doublets (each with JHH = 9 HZ) due to protons of the
N C6H4 Cl grouping (AB-system, 4H) at 6.70 (2H) and 7.12 (2H), as well as two
doublets (each with JHH = 2.5 HZ) at 8.40, 8.15 due to the furan ring protons. Signals
2
were also found at 7.30 (1H, γ -pyrone, s), 5.20 (1H, dd, each with JHH = 18 HZ, for
P-CH-NH), and at 6.45 (1H, NH, diffused multiplet, D2O—exchangeable). The main
features of the 13C NMR spectrum of 5n (DMSO, δppm) are the presence of signals at
174.49 (C O), 62.98 (C4 OCH3), 62.88(C9 OCH3), 62.63 (P-O-CH2-), 62.53 (P-O-CH2-),
61.86 (P-O-C-CH3), 61.34 (P-O-C-CH3), 16.28(P-CH), 105.28(C3), and 146.10(C2).
Moreover, structure 5n has been exclusively and unambiguously assigned based
on X-ray crystallographic analysis. An ORTEP projection of single X-ray diffraction of

2280
T. S. HAFEZ ET AL.
OCH2-CH3
O
P
OCH3
O
5
OCH2-CH3
4
3
N
H
Cl
H
6
7
2
O
O
H
9
OCH3
5n
compound 5n is shown in Figure 1. The compound is clearly seen to be a phospho-
nate adduct, resulting from the attack by diethyl phosphite on the C N bond where the
phosphoryl moiety is oriented anti with respect to the arylamino group. Crystal data and
experimental parameters used for the intensity data collection strategy and final results
of the structure determination of compound 5n are represented in Table I. Selected bond
´
lengths (Å) and bond angles (deg) are shown in Tables S1 and S2, respectively (see the
Supplemental Materials, available online).
In the mass spectrum of compound 5n, the molecular ion peak (a, M+) was hardly
conspicuous at m/z 521, 1.69% (523, 0.41%), showing its relative instability under electron
Figure 1 ORTEP projection of single X-ray diffraction of compound 5n.

ORGANOPHOSPHORUS CHEMISTRY, PART 37
2281
Table I Crystal structure and data refinement parameters of compound 5n
Compound
5n
Empirical formula
Formula weight
C24H25ClNO8P
521.890
Crystal system / space group
a / Å
b / Å
Triclinic/P1
10.9425 (10)
11.8380 (11)
13.168 (2)
82.430 (4)
69.323 (4)
64.873 (11)
1444.5 (3)
2
c / Å
α / ◦
β / ◦
γ / ◦
V / Å3
Z
D calc (g/cm3)
1.200
0.23
µ (mm−1
)
Color / shape
Temp (K)
Colorless / needles
298
Theta range for collection
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness of fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
2.910–21.967
3513
2985
1314/0/346
2.228
0.081
0.156
bombardment. Cleavage of M+ at axis x produces the base peak (cation b) at m/z 384,
which ejects a neutral CH2O molecule from one of the methoxyl groups to give ion c
at m/z 354 (356) (Scheme S1, Supplemental Materials). Upon thermolysis under reduced
pressure, compound 5n regenerated the starting materials, namely 4,9-dimethoxy-5-oxo-
5H-furo[3,2-g][1]-6-[p-chlorophenylimino-methyl]benzopyran (3f) and diethyl phosphite
4b.
In terms of the hard-soft-acid-base (HSAB) principle,24–26 dialkyl phosphites 4 are
considered to be soft bases. Therefore, they can induce attack at the azomethine-carbon
atom to yield 5.
INSECTICIDAL ACTIVITY
Pesticidal activities are associated with a variety of organophosphorus com-
pounds,27–30 which are liable to become less effective as a result of building cross-resistance
in pests. Therefore, continuous efforts are devoted towards developing new generations of
these pesticides. This initiated us to study the effect of some selected new phosphonate
adducts (5c, d, e, g, j, n, p, q, and t) against Aphis gossypii (Glover) (see the Supplemental
Materials available online). This sucking aphid pest infests cotton crops worldwide. It
affects cotton yield by direct feeding and fiber quality by excreting honeydew, which
supports growth of harmful microorganisms.31 The slide-dip method32,33 was used in this
study. The average mortality percentage was calculated per each concentration and was
corrected using Abbott’s formula34 if necessary. The corrected percentage mortality rate
of each compound was statistically computed.35

2282
T. S. HAFEZ ET AL.
CONCLUSION
Results of the present study offer a new group of phosphonates (5a–t) de-
rived from furochromones, to which belong many biologically active principles
frequently used as drugs.36,37 They also belong to the pharmacologically interesting
α-aminophosphonates.38–41 The new compounds were prepared by allowing monoanils
3a–h to condense with the appropriate dialkyl phosphites 4. The study also clearly shows
that the γ -pyrone carbonyl group in substrates 3 show marked stability towards attack by
the examined phosphorus reagents, at least under the prevailing experimental conditions.
The phosphonate adduct 5c showed marked pesticidal activity against Aphis gossypii
(Glover), which infests cotton crops.
EXPERIMENTAL
Reactions with dialkyl phosphites were carried out under an atmosphere of dry argon.
Solvents were purified and dried according to usual procedures. Dialkyl phosphites are com-
mercially available (Aldrich) and were freshly distilled before use. Compounds 3a,17 3c,17
and 3e18 were prepared according to known procedures. Melting points were recorded on
an Electrothermal melting point apparatus and were uncorrected. The infrared spectra were
obtained from KBr-disks using a Bru¨ker Vector 22 (Germany) Infrared Spectrophotometer
and/or a Jasco FT/IR-300E Fourier transform infrared spectrophotometer and reported in
cm−1. 1H NMR spectra were recorded on a Varian Mercury VX-300 Spectrometer (at 300
MHz) and/or a Jeol JNM-EX 270 FT Spectrometer (at 270 MHz). Proton chemical shifts (δ)
are reported in ppm downfield from TMS. 13C NMR spectra were recorded on a Jeol JNM-
EX 270 FT Spectrometer (at 68 MHz). 31P NMR spectra were recorded on JNM ECA-500
Spectrometer (vs 85% H3PO4) at 200 MHz. Mass spectra were recorded on a Finnigan
SSQ 7000 Spectrometer and/or a Shimadzu GC MS-Q 1000 EX spectrometer at 70 eV. The
microanalyses were carried out at the Microanalytical Unit, Cairo University, Cairo, Egypt.
Intensity data collection for X-ray diffraction was performed with a Kappa-CCD Enraf No-
nius FR 590 Single Crystal Diffractometer. The structures were solved by direct methods
using the SIR92 program42 and refined using maXus.43 The molecular graphics were made
with ORTEP.44 Crystallographic data (CIF) for the structures reported in this article have
been deposited in the Cambridge Crystallographic Data Centre (CCDC) as supplementary
publication No. 757276. Copies of the data can be obtained, free of charge, on application
to the CCDC, 12 Union Road, Cambridge CB 12EZ, UK. (FAX: + 44(1223)336-033;
E-mail: deposit@ccdc.cam.ac.uk).
Preparation of Monoanils 3b,d and 3f–h
A mixture of 1a (or 1b) (0.005 mol) in ethanol and aryl amine 2a (or 2b,c and d)
(0.005 mol) in ethanol was heated under reflux until no more of the reactants could be
detected (TLC). The reaction mixture was left at room temperature overnight, and the
yellow solid obtained was filtered off and recrystallized from ethanol.
4-Methoxy-5-oxo-5H-furo[3,2-g][1]-6-(p-chlorophenyliminomethyl)benzo
pyran (3b). Yield 95%, mp 118–120◦C; IR (KBr): 3162.7 (CH, aromatic), 2939.0,
2883.9 (CH, aliphatic), 1650.0 (C O, γ -pyrone), 1618.8(C N), 1592.7, 1560.4(C C,
aromatic) cm−1. Anal. Calcd. (%) for C19H12ClNO4 (353.76): C, 64.51, H, 3.42, Cl, 10.02,

ORGANOPHOSPHORUS CHEMISTRY, PART 37
2283
N, 3.96; Found (%): C, 64.34, H, 3.65, Cl, 10.22; N, 3.86; MS: m/z (%) 353.20 (M+,
20.50), 355.20 (M+, 7.98).
4-Methoxy-5-oxo-5H-furo[3,2-g][1]-6-(p-bromophenyliminomethyl)benz
opyran (3c). Yield 92%, mp 144–146◦C. 13C NMR (DMSO, δ ppm): 180.54 (C O),
144.74 (C N) and 60.76 (OCH3). Anal. Calcd. (%) for C19H12BrNO4 (398.21): C, 57.31;
H, 3.04; Br, 20.07; N, 3.52; Found (%): C, 57.11; H, 3.12; Br, 19.91; N, 3.47.
4-Methoxy-5-oxo-5H-furo[3,2-g][1]-6-(p-fluorophenyliminomethyl)benzo
pyran (3d). Yield 95%, mp 170–171◦C; IR (KBr): 3158.1 (CH, aromatic), 2973.3,
2942.8 (CH, aliphatic), 1649.6(C O, γ -pyrone), 1616.3 (C N), 1590.2, 1564.0(C C,
aromatic) cm−1. Anal. Calcd. (%) for C19H12FNO4 (337.31): C, 67.66, H, 3.59, F, 5.63, N,
4.15; Found (%): C, 67.45, H, 3.79, F, 5.73, N, 3.95; MS m/z (%): 337.00 (M+, 22.90).
4,9-Dimethoxy-5-oxo-5H-furo[3,2-g][1]-6-(p-chlorophenyliminomethyl)
benzopyran (3f). Yield 95%, mp 162–164◦C; IR (KBr): 3136.4 (CH, aromatic), 2968.5,
2927.4 (CH, aliphatic), 1646.8(C O, γ -pyrone), 1611.9(C N), 1592.9, 1477.8 (C C,
aromatic) cm−1; Anal. Calcd. (%) for C20H14ClNO5 (383.79): C, 62.59, H, 3.68, Cl, 9.24,
N, 3.65; Found (%): C, 62.69, H, 3.42, Cl, 9.34, N, 3.45; MS m/z (%): 383.40 (M+, 2.05),
385.40 (M+, 0.58).
4,9-Dimethoxy-5-oxo-5H-furo[3,2-g][1]-6-(p-bromophenyliminomethyl)
benzopyran (3g). Yield 90%, mp 172–174◦C; IR (KBr): 3303.8 (CH, aromatic),
2970.2, 2934.5 (CH, aliphatic), 1650.5(C O, γ -pyrone), 1609.1(C N), 1583.1, 1557.7
(C C, aromatic) cm−1; Anal. Calcd. (%) for C20H14BrNO5 (428.24): C, 56.09, H, 3.30,
Br, 18.66, N, 3.27; Found (%): C, 56.29, H, 3.45, Br, 18.50, N, 3.07; MS m/z (%) : 427.21
(M+, 12.81).
4,9-Dimethoxy-5-oxo-5H-furo[3,2-g][1]-6-(p-fluorophenyliminomethyl)
benzopyran (3h). Yield 90%, mp 168–170◦C; IR (KBr): 3125.9 (CH, aromatic), 2970.8,
2940.0 (CH, aliphatic), 1651.8 (C O, γ -pyrone), 1605.9 (C N), 1594.9, 1565.4 (C C,
aromatic) cm−1. Anal. Calcd. (%) for C20H14FNO5 (367.33): C, 65.40, H, 3.84, F, 5.17, N,
3.81; Found (%): C, 65.63, H, 3.94, F, 4.98, N, 3.62; MS: m/z (%) 366.91 (M+, 81.08).
Reaction of 3a–h with Dialkyl Phosphites 4a–c
A mixture of 3a (or 3b–h) (0.005 mol) and DAP 4a (4b or 4c) was heated in the
absence of solvent at 100◦C until no more of the reactants could be detected (TLC).
After removing the volatile materials in vacuo, the residual substance was collected and
recrystallized from the appropriate solvent to give the respective phosphonates (5a–t). As an
example, the characterization of 5a is presented here. (5b–5t are given in the Supplemental
Materials, available online.)
4-Methoxy-5-oxo-5H-furo[3,2-g][1]-6-[(α-diethoxyphosphoryl-α-anilino)
methyl]benzopyran (5a). Yield 90%, mp 160–162◦C (ethanol, dark yellow); IR
1
(KBr): 3318.9 (NH), 1643.0 (C O), 1228.4 (P O), 1036.5 (P O Et) cm−1. H NMR
(DMSO-d6) 1.13, 1.23[6H, P (O C CH3)2, 2t], 3.95–4.10[4H, P-(O CH2 C)2, m],
2
4.15[3H, OCH3,s], 5.28–5.32[1H, P-C-H, dd JHP = 23.43], 6.14[1H, P C NH, bs
D2O-exchangeable], 6.76–7.10[5H, aromatics, m], 7.29[1H for γ -pyrone ring, s], 7.53[1H,
benzene ring, s], 8.05, 8.38 ppm [2H, for furan ring, 2d, JHH = 2.18]; 31P NMR(DMSO)
24.6 ppm; Anal. Calcd. (%) for C23H24NO7P (457.42) : C, 60.39, H, 5.29, N, 3.06, P, 6.77.
Found (%): C, 60.12, H, 5.28, N, 2.96, P, 6.51; MS: m/z (%) 457(M+, 5.13), 320 (M+-
•P(O)(OC2H5)2, 100).

2284
T. S. HAFEZ ET AL.
Degradation Experiment: Thermolysis of Phosphonate 5n
The phosphonate adduct 5n (0.2 g), taken as a representative example, was heated in
a cold finger sublimator at 200◦C (bath temperature) under reduced pressure (1 mm/Hg)
for 1 h. The reaction vessel was left to cool, and the compound that sublimed was collected
and recrystallized from ethanol to give yellow crystals, mp 162–164◦C, and was proved to
be 3f (mp, mixed mps, and comparative IR spectra). The drops that collected at 40◦C gave
the violet color reaction described for diethyl phosphite with 3,5-dinitrobenzoic acid in the
presence of an alkali.45
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