Isomerization of diethyl 1-alkynylphosphonates to 1,3-dienylphosphonates followed by diels-alder reaction with dead, maleic anhydride and maleimide

Article abstract of DOI:10.3987/COM-10-S(E)12

Isomerization of diethyl 1-alkynylphosphonates, 1, with Pd[(PPh) ₃]₄ in refluxing 1,4-dioxane provides 1,3- dienylphosphonates, 2, in satisfactory to excellent isolated yield (45-83%). The reaction is tolerant of chlorides and cyclic

Full text of DOI:10.3987/COM-10-S(E)12

HETEROCYCLES, Vol. 82, No. 1, 2010
417
HETEROCYCLES, Vol. 82, No. 1, 2010, pp. 417 - 429. © The Japan Institute of Heterocyclic Chemistry
Received, 10th March, 2010, Accepted, 15th April, 2010, Published online, 16th April, 2010
DOI: 10.3987/COM-10-S(E)12
ISOMERIZATION OF DIETHYL 1-ALKYNYLPHOSPHONATES TO
1,3-DIENYLPHOSPHONATES
FOLLOWED
BY
DIELS-ALDER
REACTION WITH DEAD, MALEIC ANHYDRIDE AND MALEIMIDE†
Abdullatif Azab,a Abed Al Aziz Quntar,a,b Tamar Antebi,a and Morris
Srebnika*
a) Institute of Drug Research, School of Pharmacy, Hebrew University in
Jerusalem, Jerusalem, 91120, Israel
b) Department of Material Engineering, Faculty of Engineering, Al-Quds
University, Jerusalem, Palestinian Authority
* Corresponding author: Tel. 972-2-657-7301, fax. 972-2-657-8201
email: morris.srebnik@ekmd.huji.ac.il
† Dedicated to Prof. Dr. Albert Eschenmoser on occasion of his 85th birthday.
Abstract – Isomerization of diethyl 1-alkynylphosphonates, 1, with Pd[(PPh)3]4
in refluxing 1,4-dioxane provides 1,3-dienylphosphonates, 2, in satisfactory to
excellent isolated yield (45-83%). The reaction is tolerant of chlorides and cyclic
substituents.
Cycloaddition reaction of 2 with DEAD provided the
corresponding diethyl 3-(diethoxyphosphoryl)-6-alkyl-3,6-dihydropyridazine-
1,2-dicarboxylates, 3, in 85% isolated yield. The cycloaddition products can be
obtained in
a
one-pot reaction directly from the isomerized
1-alkynylphosphonates with no loss in yields. Similarly, 1,3-dioxo-1,3,3a,4,7,7a-
hexahydroisobenzofuran-4-ylphosphonate,
and
1,3-dioxo-2,3,3a,4,7,7a-
hexahydro-1H-isoindol-4-ylphosphonate
4
were obtained by reacting
1,3-dienylphosphonates with maleic anhydride and maleimide respectively.
INTRODUCTION
1,3-Dienylphosphonates are interesting compounds that undergo a variety of reactions including

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HETEROCYCLES, Vol. 82, No. 1, 2010
1,3-additions,1 cycloaddition with CH2N2,2 [2 + 2] cycloadditions,3 and enolate alkylations.4 We have
previously prepared 1,3-dienylphosphonates by alkyne insertion into zirconacyclopropenes.5 They have
also been prepared by reaction of unsaturated cyanophosphonates with N-tosylsulfonylimines,6 by
nickel-catalyzed addition of P(O)-H bonds to propargyl alcohols,7 by Knoevenagel reaction,3 and by
procedures similar to the preparation of vinylphosphonates.8
1-Alkynylphosphonates are a readily available group of compounds.9 Isomerization of alkynes to
1,3-dienes by metal catalysis is a known process.10,11 Isomerization of 1-alkynylphosphonates to
1,3-dienylphosphonates is essentially unknown. In this paper we discuss our results on the isomerization of
1-alkynylphosphonates to 1,3-dienylphosphonates under a variety of conditions. We also explored a
one-pot isomerization/Diels-Alder reaction of 1-alkynylphosphonates with DEAD to give diethyl
3-(diethoxyphosphoryl)-6-alkyl-3,6-dihydropyridazine-1,2-dicarboxylates.12
RESULTS AND DISCUSSION
Isomerization
When 1a was heated in refluxing dioxane in the presence of a Pd[(PPh3)]4, 2a was isolated in very good
yield (eq. 1).
[(C6H5)3P]4Pd
n-C4H9
P(O)(OEt)2
P(O)(OEt)2
79%
(1)
dioxane / 100-135 oC
1a
2a
Equation 1. Isomerization of 1a to 2a
Various palladium and other metal catalysts in different solvents were investigated but in all cases either no
reaction occurred or a complex reaction mixture was obtained as shown in Table 1. Even under similar
conditions, except for using different palladium catalysts, Pd[(PPh)3]4 was most successful (entries 2, 5).
In addition, attempts to activate catalysts containing carbonyl ligands such as (Ru3(CO)12, Mo(CO)6) by
activation with (CH3)3NO (TMANO) were also unsuccessful.

HETEROCYCLES, Vol. 82, No. 1, 2010
419
Table 1. Yields of 2a using different catalysts and solvents
Run
1
Catalyst
Pd[(PPh)3]4
Solventa/ Temp.
Yield %
83
79
f0
dioxane/reflux
toluene/reflux
MeCN/reflux
dioxane/reflux
toluene/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
xylene /reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
MeCN/reflux
dioxane/reflux
2
Pd[(PPh)3]4
3
Pd2(dba)3
4
Pd2(dba)3
bPd2(dba)3
f0
5
30
f0
6
Pd(acac)2
7
Pd(acac)2
f0
8
palladium 5% carbon
palladium 5% carbon
palladium 5% Ca(CO3)2
palladium 5% Ca(CO3)2
gPd(OAc)2 / 4PPh3 /allyl acetate
cAPC
f0
9
f0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
f0
f0
80
f0
cAPC
f0
PdCl2
f0
PdCl2
f0
Ru3(CO)12
f0
Ru3(CO)12
f0
Ru3(CO)12 + TMANOd
Ru3(CO)12 + TMANOd
Nickel(II) (acac)2
Nickel(II) (acac)2
Mo(CO)6 + TMANOd
Mo(CO)6 + TMANOe
rhodium 5% on alumina
rhodium 5% on alumina
e0
e0
f0
f0
e0
e0
f0
f0
aConditions:1-hexynylphosphonate (1mmol.), catalyst (0.1 mmol.) solvent (1 mL) at reflux for
1.5-3.5 h. bAlkynylphosphonate (1 mmol.), acetic acid (1 mL), (i-Pr)3P (0.2 mmol.),
Pd2(dba)3CHCl3 (0.05 mmol.), toluene (5 mL) 110 °C for 3 h according to reference 12.
d
callylpalladium(II) chloride dimer [C3H5PdCl]2). eTMANO (trimethylamine N-oxide) (0.1 eq).
eStarting alkyne consumed to give complex reaction mixture with no trace of 2a. fStarting alkyne
recovered intact. gAccording to: H. Yasui, H. Yorimitsu, and K. Oshima, Synlett, 2006, 1783.
The optimized conditions were then applied to a series of 1-alkynylphosphonates 1 (Table 2). The
reaction proceeds in satisfactory yields (45-85%) and is tolerant of halogenated (1d), cyclic 1h-i, short
and long chain alkynylphosphontes. All the reactions were carried out in dioxane at (100 - 135 C) except

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HETEROCYCLES, Vol. 82, No. 1, 2010
2d which was carried out in toluene. The reaction time was variable from 1.5 h (2d) to 5 h (2a) (see
experimental).
The stereochemistry of the products 2a-i was determined by NMR coupling constants. The 3JPC of the C3
3
carbon (26.4-29.2 Hz) and JPH of the hydrogen on C2 (21.2-35.4) are indicatives that C3 is trans to
3
phosphorous and that the hydrogen on C2 is cis. Moreover, the hydrogens on (26.4-29.2 Hz) and JPH of
the hydrogen on C2 (21.2-35.4) are indicatives that C3 is trans to phosphorous and that the hydrogen on
C2 is cis. Moreover, the hydrogens on C3 and C4 are trans, and consequently C3-C4 double bond has E
stereochemistry. Thus, the 1,3-dienylphosphonates 2 have E, E stereochemistry.5
Table 2. Isomerization of 1-alkynylphosphonates to 1,3-butadienylphosphonates , 2, with Pd[(PPh3)]4 in
dioxane
R3
[(C6H5)3P]4Pd
R1
P(O)(OEt)2
4
2
3
1
P(O)(OEt)2
dioxane / 100-135 oC
R4
1
R2
2
Entry R1
R2
R4
R3
Isolated yielda %
2a
2b
2c
2d
2e
2f
n-butyl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
ethyl
83
83
85
79
81
72
70
45
68
n-propyl
methy
decyl
dodecyl
4-Cl-n-butyl
n-pentyl
2-Cl-ethyl
n-propyl
dodecyl
tetradecyl
H
tetradecyl
hexadecyl
cyclohexyl
2g
2h
2i
tetramethylene
(cyclohexyl)methyl
H
cyclohexylidene
aConditions: 1-alkynylphosphonate (1mmol), catalyst (0.1 mmol), solvent (1 mL) at reflux for 1.5-3.5
h (see experimental).
Diels-Alder reaction of 2 with DEAD
The 1,3-dienylphosphonates 2 were further utilized by investigating their reactivity with diethyl
azodicarboxylate (DEAD). Cycloaddition products 3a and 3b were obtained by reacting 2b and 2a with
DEAD respectively. Starting either from pure or in situ prepared 1,3-dienylphosphonates 2a-b, the cyclic
products 3 were successfully obtained in 85% yield (Scheme 1).

HETEROCYCLES, Vol. 82, No. 1, 2010
421
EtO2C
CO2Et
dioxane
P(O)(OEt)2
+
H N N H
R3
EtO2C N N CO2Et
80-100 C
O
EtO
EtO
R3
H
P
2
H
3a,b
2a R3 = Et; 2b R3 = Me
Scheme 1. Cyclization of 2 and DEAD to give 3a,b
1
The structure and the stereochemistry of the cycloaddition products were confirmed by 2D-COSY, H,
and 13C NMR. The cyclohexene-like nature of the six-membered ring system tetrahydropyridazines is
generally regarded to have a half chair configuration based on the relationship between vicinal coupling
constants and dihedral angles.13 According to 2D-COSY NMR no coupling between the hydrogen on C4
at ~ 4 ppm and the neighboring vinylic hydrogen at 5.84 ppm was observed (this numbering is just to be
consistent with 1,3-dienylphosphonates numbering). Thus, based on the Karplus relation, the ~ 0 Hz
coupling constant corresponds to a dihedral angle of ~ 90 º between the hydrogens on C4 and C3. On the
other hand, the doublet of doublet in the region 5.07 ppm corresponds to the allylic hydrogen on C1 split
by phosphorus and hydrogen of C2 at 5.99 ppm with a coupling constant 3JHH of 4.2 Hz that corresponds
to a dihedral angle of ~ 45 º between the hydrogen on C1 and the adjacent vinylic hydrogen on C2.13,14
Thus, the methyl group is in a quasi equatorial configuration, whilst the phosphorus group is in a quasi axial
configuration as shown in Figure 1.
CO2Et
N
H
H
Me
H
N
H
(EtO)2OP
CO2Et
Figure 1. Conformation of compound 3a
Regarding the ethyl carboxylate groups on the nitrogen atoms, we suggest that they are trans axial due to
steric factors and energetic stability. This proposed stereochemistry of the cycloaddition compounds is
consistent with the literature.15 A Newman's projection conformation for compound 3a is presented in
Figure 2.
CO2Et
H
H
Me
(EtO)2(O)P
EtO2C
Figure 2. Partial Newman projection of 3a.

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HETEROCYCLES, Vol. 82, No. 1, 2010
In a similar manner, various other Diels Alder products were obtained in good yields (Table 3) as a result
of reacting 1,3-dienylphosphonates 2 with maleic anhydride and maleimide as shown in scheme 2.
R3
P(O)(OR5)2
dioxane
P(O)(OR5)2
+
R3
H
O
H
O
O
80-100 C
X
O
2
X
4
Scheme 2. Diels-Alder reaction between 2 and dienophiles
Table 3. Yiels of Diels-Alder adducts of Maleic anhydride
and Maleimide
Entry
R3
R5
X
Isolated yield
Mass (mgr), %
4a
4b
4c
Et
Me
dodecyl
Et
Et
Et
O
O
O
262 , 83
242 , 80
306 , 67
4d
4e
4f
decyl
Me
Et
Et
Et
Ph
O
NH
NH
O
300 , 70
244 , 81
282 , 62
301 , 73
dodecyl
Et
4g
CONCLUSIONS
Various 1,3-butadienylphosphontates have been obtained by isomerization of 1-alkynylphosphonates in
good isolated yields. This reaction was studied under many different catalysts and conditions, but it
proceeded only when [(C6H5)3P]4Pd is used in dioxane at reflux. Interestingly, the products
1,3-butadienylphosphontates reacted efficiently either pure or in a one-pot reaction with DEAD to
produce diethyl 3-(diethoxyphosphoryl)-6-alkyl-3,6-dihydropyridazine-1,2-dicarboxylates. Reactions of
some of the 1,3-dienes was also satisfactory, in terms of reaction times and yields, with two other
dienophiles: maleic anhydride and maleimide.
EXPERIMENTAL
Typical procedure for the synthesis of diethyl (1E,3E)-hexa-1,3-dienylphosphonate (2a). To (0.116 g,
0.1 mmol) of [(C6H5)3P]4Pd dissolved in dioxane (1 mL) in a screw caped vial were added (1mmol) of 1
under nitrogen atmosphere. After reflux for the required amount of time, the solvent was evaporated and
the product was isolated by silica gel column chromatography using (30% EtOAc: 70% petroleum ether)
and was analyzed by GCMS, elemental analysis, and NMR spectroscopy.

HETEROCYCLES, Vol. 82, No. 1, 2010
423
Diethyl (1E,3E)-hexa-1,3-dienylphosphonate (2a). 1H NMR (300 MHz, CDCl3, Me4Si): 1.01 (3H,
CH3CH2CH tJHH = 7.5 Hz), 1.29 (6H, OCH2CH3, t, JHH = 7.2 Hz), 2.15 (2H, CH3CH2CH, m), 4.04 (4H,
OCH2CH3, qn), 5.51 (1H, CH-P, dd, 2JPH = 19.5 Hz, JHH = 16.8 Hz), 6.00-6.12 (2H, CH2-CH=CH-CH, m),
3
31
7.04 (1H, CH-CH=CH-P, ddd, JPH = 21.4 Hz, JHH = 17.4 Hz). P NMR (125 MHz, CDCl3, Me4Si):
21.06. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.6 (d, 3JPC = 6.6 Hz), 26.0, 61.8 (d, 3JPC = 5.1 Hz),
1
3
2
114.5 (d, JPC = 191.7 Hz), 128.6 (d, JPC = 26.7 Hz), 145.5, 149.6 (d, JPC = 6.3 Hz). MS (EI): m/z (%)
109.0 (76.9), 111.0 (70.0), 137.0 (76.9), 161.1 (56.5), 189.1 (59.3), 190.2 (49.1), 191.1 (39.8), 218.2 (100).
Anal. Calcd for C10H19O3P: C, 54.54; H, 8.64; P, 14.22. Found: C, 54.51; H, 8.55; P, 14.18.
Diethyl (1E,3E)-penta-1,3-dienylphosphonate (2b). Synthesis identical to procedure 2a except refluxed
for 3.5 h. 1H NMR (300 MHz, CDCl3, Me4Si): 1.26 (6H, OCH2CH3, t, JHH = 7.2 Hz), 1.80 (3H,
CH3-CH=CH, d, JHH = 6.0 Hz), 4.03 (4H, OCH2CH3, qn), 5.51 (1H, CH-P, dd, 2JPH = 16.8 Hz, JHH = 16.2
Hz), 6.00-6.12 (2H, CH3-CH=CH, m), 7.04 (1H, CH-CH=CH-P, ddd, 3JPH = 21.2 Hz, JHH = 17.2 Hz); 31P
NMR (125 MHz, CDCl3, Me4Si): 21.20. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.6 (d, 3JPC = 6.6 Hz),
18.7, 61.8 (d, 3JPC = 5.2 Hz), 114.4 (d, 1JPC = 191.5 Hz), 131.0 (d, 3JPC = 26.4 Hz), 138.8, 149.4 (d, 2JPC = 6.0
Hz). MS (EI): m/z (%) 110.9 (32.4), 130.7 (38.5), 132.7 (58.3), 148.0 (55.6), 158.8 (21.3), 175.8 (39.8),
189.0 (14.8), 204.0 (100). Anal. Calcd for C9H17O3P: C, 52.94; H, 8.33; P, 15.20. Found: C, 52.88; H, 8.28;
P, 15.16.
1
Diethyl (1E,3E)-tetradeca-1,3-dienylphosphonate (2c). Synthesis identical to procedure 2b. H NMR
(300 MHz, CDCl3, Me4Si): 0.85CH3-CH2-CH2tJHH = 7.2 Hz), 1.29 (6H, OCH2CH3, t, JHH = 6.9
Hz), 1.20-1.40 (16H, CH3-(CH2)8-CH2, overlap), 2.10 (2H, CH2-CH2-CH, q, JHH = 6.9 Hz), 4.04 (4H,
OCH2CH3, qn), 5.52 (1H, CH-P, dd, 2JPH = 19.5 Hz, JHH = 17.1 Hz), 6.00-6.10 (2H, CH2-CH=CH, m), 7.04
(1H, CH-CH=CH-P, ddd, 3JPH = 27.9 Hz, JHH = 9.6 Hz, JHH = 4.2 Hz). 31P NMR (125 MHz, CDCl3, Me4Si):
21.03. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.3 (d, 3JPC = 6.3 Hz), 22.9, 28.9, 29.4, 29.5, 29.6,
29.8, 29.9, 32.1, 33.0, 61.5 (d, 3JPC = 5.4 Hz), 114.1 (d, 1JPC = 192.0 Hz), 129.3 (d, 3JPC = 26.7 Hz), 144.0,
2
149.4 (d, JPC = 6.3 Hz). MS (EI): m/z (%) 124.9 (27.8), 137.8 (45.6), 151.9 (99.5), 160.9 (62.9), 189.0
(70.4), 204.1 (59.3), 217.0 (100), 231.1 (25.0), 259.2 (24.7), 273.2 (21.3), 287.2 (13.7), 301.3 (11.1), 330.3
(50.9). Anal. Calcd for C18H35O3P: C, 65.45; H, 10.61, 9.39. Found: C, 65.40; H, 10.55; P, 9.33.
Diethyl (1E,3E)-6-chlorohexa-1,3-dienylphosphonate (2d). Synthesis identical to procedure 2a except
refluxed in toluene for 1.5 h. 1H NMR (300 MHz, CDCl3, Me4Si):  OCH2CH3tJHH = 7.2 Hz),
2.62 (2H, ClCH2-CH2-CH, q, JHH = 6.9 Hz), 3.56 (2H, ClCH2, t, JHH = 6.9 Hz), 4.06 (4H, OCH2CH3, qn),
2
5.63 (1H, CH-P, dd, JPH = 19.2 Hz, JHH = 17.1 Hz), 6.05-6.23 (2H, CH2-CH=CH, m), 7.05 (1H,

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HETEROCYCLES, Vol. 82, No. 1, 2010
CH-CH=CH-P, ddd, JHH = 10.5 Hz, JHH = 3.9 Hz 3JPH = 27.3 Hz). 31P NMR (125 MHz, CDCl3, Me4Si):
20.17. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.3 (d, 3JPC = 6.6 Hz), 35.6, 43.1, 61.7 (d, 3JPC = 5.4 Hz),
116.4 (d, 1JPC = 191.5 Hz), 132.0 (d, 3JPC = 27.0 Hz), 138.0, 148.2 (d, 2JPC = 6.0 Hz). MS (EI): MS (EI): m/z
(%) 128.8 (16.7), 132.8 (57.4), 146.8 (25.9), 160.9 (100), 189.0 (85.2), 217.0 (94.4), 252.1 (21.3), 254.2
(16.9). Anal. Calcd for C10H18ClO3P: C, 47.52; H, 7.13; Cl, 14.06; P, 12.28. Found: C, 47.47; H, 7.09; Cl,
14.01 P, 12.25.
Diethyl (1E,3E)-hepta-1,3-dienylphosphonate (2e). Synthesis identical to procedure 2a except refluxed
1
for 3 h. H NMR (300 MHz, CDCl3, Me4Si): CH3-CH2-CH2tJHH = 7.5 Hz), 1.32 (6H,
OCH2CH3, t, JHH = 6.9 Hz), 1.45 (2H, CH3-CH2-CH2, m), 2.12 (2H, CH2-CH2-CH, q, JHH = 7.2 Hz), 4.07
2
(4H, OCH2CH3, qn), 5.51 (1H, CH-P, dd, JPH = 19.5 Hz, JHH = 17.1 Hz), 6.00-6.18 (2H, CH2-CH=CH,
3
31
m), 7.04 (1H, CH-CH=CH-P, ddd, JPH = 28.0 Hz, JHH = 9.6 Hz, JHH = 4.2 Hz). P NMR (125 MHz,
CDCl3, Me4Si): 21.05. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.3 (d, 3JPC = 6.6 Hz), 21.9, 34.8,
61.6 (d, 3JPC = 5.2 Hz), 114.3 (d, 1JPC = 191.8 Hz), 129.5 (d, 3JPC = 26.7 Hz), 143.8, 149.4 (d, 2JPC = 6.0
Hz). MS (EI): m/z (%) 110.9 (40.4.9), 132.8 (57.8), 160.9 (78.0), 175.0 (43.1), 189.0 (54.1), 203.0 (41.8),
204.1 (27.9), 232.1 (100). Anal. Calcd for C11H21O3P: C, 56.90; H, 9.05; P, 13.36. Found: C, 56.85; H,
8.99; P, 13.29.
Diethyl (1E,3E)-hexadeca-1,3-dienylphosphonate (2f). Synthesis identical to procedure 2a except
1
refluxed for 2 h. H NMR (300 MHz, CDCl3, Me4Si): 0.83  CH3-CH2-CH2tJHH = 7.2 Hz), 1.28
(OCH2CH3, 6 H, t, JHH = 7.2 Hz), 1.15-1.42 (20H, CH3-(CH2)10-CH2, overlap), 2.09 (2H, CH2-CH2-CH, q,
JHH = 6.9 Hz), 4.03 (4H, OCH2CH3, qn, JHH = 3.9 Hz), 5.52 (1H, CH-P, dd, 2JPH = 19.5 Hz, JHH = 16.5 Hz),
6.07-6.14 (2H, CH2-CH=CH, m), 7.04 (1H, CH-CH=CH-P, ddd, 3JPH = 35.4 Hz, JHH = 9.6 Hz, JHH = 4.2
Hz). 31P NMR (125 MHz, CDCl3, Me4Si): 21.11. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.6 (d,
3JPC = 6.3 Hz), 22.6, 28.1, 28.6, 29.1, 29.2, 29.3, 29.4, 29.5, 29.6, 29.7, 31.8, 61.5 (d, 3JPC = 5.4 Hz), 114.1
1
3
2
(d, JPC = 192.0 Hz), 129.2 (d, JPC = 26.7 Hz), 144.1, 149.3 (d, JPC = 6.3 Hz). MS (EI): m/z (%) 110.9
(21.1), 135.0 (32.1), 138.0 (38.5), 151.9 (100), 160.9 (42.2), 189.0 (40.4), 204.2 (36.7), 217.1 (62.4), 259.3
(18.3), 273.3 (16.5), 287.3 (11.9), 315.3 (9.2), 329.5 (9.2),358.5 (39.4). Anal. Calcd for C20H39O3P: C,
67.04; H, 10.89; P, 8.66. Found: C, 66.99.51; H, 10.87; P, 8.63.
1
Diethyl (1E,3E)-octadeca-1,3-dienylphosphonate (2g). Synthesis identical to procedure 2a. H NMR
(300 MHz, CDCl3, Me4Si): 0.87  CH3-CH2-CH2tJHH = 7.2 Hz), 1.29 (6H, OCH2CH3, t, JHH = 7.2
Hz), 1.05-1.46 (24H, CH3-(CH2)12-CH2, m, overlap), 2.11 (2H, CH2-CH2-CH, q, JHH = 6.6 Hz), 4.03 (4H,
OCH2CH3, qn), 5.34 (1H, CH-P, dd, 2JPH = 19.5 Hz, JHH = 17.1 Hz), 6.07-6.14 (2H, CH2-CH=CH, m), 7.04

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(1H, CH-CH=CH-P, ddd, 3JPH = 27.9 Hz, JHH = 9.6 Hz, JHH = 3.9 Hz). 31P NMR (125 MHz, CDCl3, Me4Si):
21.08. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.6 (d, 3JPC = 6.3 Hz), 22.9, 28.9, 29.4, 29.6, 29.7,
29.8, 29.9, 32.1, 33.0, 61.8 (d, 3JPC = 5.7 Hz), 114.4 (d, 1JPC = 191.7 Hz), 129.5 (d, 3JPC = 26.7 Hz), 144.4,
2
149.7 (d, JPC = 6.0 Hz). MS (EI): m/z (%) 111.0 (23.6), 125.0 (30.9), 138.0 (36.4), 152.0 (100), 153.1
(31.8), 189.1 (33.6), 204.2 (40.0), 217.2 (60.0), 231.2 (17.3), 259.3 (14.5), 273.3 (14.5), 301.4 (6.4), 341.6
(6.2), 357.7 (6.4) 386.8 (38.2). Anal. Calcd for C22H43O3P: C, 68.39; H, 11.14; P, 8.03. Found: C, 68.31; H,
11.10; P, 7.99.
1
(E)-Diethyl cyclohex-2-enylidenemethylphosphonate (2h). Synthesis identical to procedure 2a. H
NMR (300 MHz, CDCl3, Me4Si): 1.32 (6H, OCH2CH3, t, JHH = 6.9 Hz), 1.60-1.72 (4H,
CH2-CH2-CH2-CH2, overlap), 2.12 (2H, CH2-CH2-C, broad t), 2.19 (2H, CH2-CH2-CH, m), 4.07 (4H,
OCH2CH3, qn), 5.34 (1H, CH-P, dd, 2JPH = 19.0 Hz, JHH = 18.0 Hz), 6.02 (1H, CH2-CH-C, dd, JHH = 7.4 Hz,
JHH = 7.9 Hz ), 6.96 (1H, C-CH=CH, ddd, 3JPH = 22.5 Hz, JHH = 17.4 Hz). 31P NMR (125 MHz, CDCl3 ,
Me4Si): 20.03. 13C NMR (75.5 MHz, CDCl3, Me4Si): 16.4 (d, 3JPC = 6.6 Hz), 22.0, 23.8, 26.3, 30.1, 61.6
(d, 3JPC = 5.1 Hz), 109.3 (d, 1JPC = 191.7 Hz), 131.6 (d, 3JPC = 29.2 Hz), 138.3, 152.4 (d, 2JPC = 6.6 Hz); MS
(EI): m/z (%) 106.0 (44.4), 135.1 (25.9), 151.0 (9.3), 169.0 (21.8), 187.0 (50.1), 188.1 (94.4), 215.2 (23.1),
216.2 (47.2), 244.2 (100). Anal. Calcd for C12H21O3P: C, 59.02; H, 8.61; P, 12.70. Found: C, 58.97; H,
8.59; P, 12.66.
1
(E)-Diethyl 3-cyclohexylideneprop-1-enylphosphonate (2i). Synthesis identical to procedure 2a. H
NMR (300 MHz, CDCl3, Me4Si): 1.27 (6H, OCH2CH3, t, JHH = 6.9 Hz), 1.53-1.58 (6H, CH2-(CH2)3-CH2,
overlap), 2.18 (2H, CH2-CH2-C, broad t), 2.37 (2H, C-CH2-CH2, broad t), 4.07 (4H, OCH2CH3, qn), 5.54
2
(1H, CH-P, dd, JPH = 20.4 Hz, JHH = 16.8 Hz), 5.90 (1H,C-CH=CH, d, JHH = 11.4 Hz), 6.96 (1H,
3
31
CH-CH-CH, ddd, JPH = 26.4 Hz, JHH = 11.4 Hz, JHH = 4.5 Hz). P NMR (125 MHz, CDCl3, Me4Si):
21.66. 13C NMR (75.5 MHz, CDCl3 , Me4Si): 16.2 (d, 3JPC = 6.4 Hz), 26.3, 27.5, 29.1, 29.9, 37.5, 61.5
(d, 3JPC = 5.1 Hz), 113.8 (d, 1JPC = 191.2 Hz), 121.8 (d, 3JPC = 27.8 Hz), 145.1, 153.6 (d, 2JPC = 6.2 Hz). MS
(EI): m/z (%) 120.0 (100), 121.1 (19.1), 122.0 (5.9), 183.0 (4.5), 201.0 (10.0), 229.1 (9.1), 257.3 (31.8),
258.2 (30.0). Anal. Calcd For C13H23O3P: C, 60.47; H, 8.91; P, 12.02. Found: C, 60.42; H, 8.87; P, 11.99.
Synthesis of diethyl 3-(diethoxyphosphoryl)-6-ethylpyridazine-1,2(3H,6H)-dicarboxylate (3a).
Method A: To 0.218 g (1mmol) of 2a dissolved in dioxane (1 mL), was added 0.174 g (1 mmol) of diethyl
azodicarboxylate (DEAD). After reflux of the reaction mixture for 12 h, the solvent was evaporated and the
product was isolated by silica gel column chromatography using a gradient eluent starting from (50%
EtOAc: 50% petroleum ether) to pure EtOAc, and was analyzed by GCMS, elemental analysis, and NMR

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spectroscopy.
Method B: After synthesis of 2a as presented above, 0.174 g (1 mmol) of diethyl azodicarboxylate was in
situ added to the reaction mixture. The mixture was refluxed for 12 h, then the solvent was evaporated and
the product was isolated by silica gel column chromatography using a gradient eluent starting from (50%
EtOAc: 50% petroleum ether) to pure EtOAc, and was analyzed by GCMS, elemental analysis, and NMR
spectroscopy.
1
Diethyl 3-(diethoxyphosphoryl)-6-ethylpyridazine-1,2(3H,6H)-dicarboxylate (3a). H NMR (300
MHz, CD3OD, Me4Si): CH3-CH2-CHt, JHH = 7.5 Hz), 1.13-1.41 (12H, OCH2CH3,
COOCH2CH3, overlap), 1.93 (2H, CH3-CH2-CH, m), 3.95-4.60 (9H, CH3-CH2-CH, OCH2CH3,
COOCH2CH3, overlap), 5.07 (1H, CH-P, dd, 2JPH = 25.2 Hz, JHH = 4.2 Hz), 5.84 (1H, CH2-CH-CH=CH,
31
13
m), 5.99 (1H, CH=CH-CH-P, m). P NMR (125 MHz, CDCl3, Me4Si): 19.04. C NMR (75.5 MHz,
CDCl3, Me4Si): 14.3, 16.2 (d, 3JPC = 6.4 Hz), 25.7, 51.9 (d, 1JPC = 119.5 Hz), 56.6, 62.4 (d, 3JPC
=
3
2
6.2 Hz), 63.2, 128.8 (d, JPC = 12.1 Hz), 131.9 (d, JPC = 12.1 Hz). MS (EI): m/z (%) 66.9 (9.2), 80.8
(83.5), 94.0 (11.3), 108.9 (38.5), 111.0 (17.4), 136.9 (80.7), 153.0 (33.9), 155.0 (9.2), 183.0 (100), 184.2
(11.9), 211.1 (11.9), 255.2 (47.7), 256.3 (5.5), 392.5 (1.8). Anal. Calcd For C16H29N2O7P: C, 48.98; H,
7.40; N, 7.14 P, 7.91. Found: C, 48.88; H, 7.36; N, 7.11 P, 7.87; Isolated yield: 333 mgr, 85%.
Diethyl 3-(diethoxyphosphoryl)-6-methylpyridazine-1,2(3H,6H)-dicarboxylate (3b). Synthesis
identical to procedure 3a. 1H NMR (300 MHz, CD3OD, Me4Si): 1.13-1.41 (12H, OCH2CH3,
COOCH2CH3, overlap), 1.59 (3H, CH3-CH, d, JHH = 6.9 Hz), 3.95-4.40 (9H, CH3-CH, OCH2CH3,
COOCH2CH3, overlap), 5.33 (1H, CH-P, dd, 2JPH = 20.4 Hz, JHH = 4.2 Hz), 5.75 (1H, CH2-CH-CH=CH, m),
5.95 (1H, CH=CH-CH-P, m). 31P NMR (125 MHz, CDCl3, Me4Si): 19.06. 13C NMR (75.5 MHz, CDCl3,
Me4Si): 14.4, 16.3 (d, 3JPC = 6.4 Hz), 20.4, 51.0, 52.3 (d, 1JPC = 119.5 Hz), 62.5 (d, 3JPC = 6.2 Hz), 63.2,
128.4 (d, 3JPC = 12.0 Hz), 132.0 (d, 2JPC = 10.0 Hz). MS (EI): m/z (%) 53.0 (10.9), 81.0 (51.5), 95.0 (21.8),
123.0 (59.4), 153.0 (16.3), 169.0 (100), 197.0 (5.9), 207.0 (15.8), 241.0 (26.7), 378.0 (1.1). Anal. Calcd For
C15H27N2O7P: C, 47.62; H, 7.14; N, 7.41 P, 8.20. Found: C, 47.57; H, 7.12; N, 7.37 P, 8.17. Isolated yield:
321 mgr, 85%.
Diethyl 7-ethyl-1,3-dioxo-1,3,3a,4,7,7a-hexahydroisobenzofuran-4-ylphosphonate (4a). Identical to
1
3a except the addition of maleic anhydride and refluxing for 6 hrs. H NMR (300 MHz, CDCl3, Me4Si):
CH3CH2CHtJHH =7.1 Hz), 1.26 (6H, OCH2CH3, t, JHH =7.5 Hz),  CH3CH2CHm),
2.24 (1H, CH2CHCHCO, dd, JHH = 7.5 Hz, JHH = 4.5 Hz), 2.51 (1H, CH3CH2CH, m), 3.39 (1H, COCHCHP,
m), 3.47 (1H, CHP, m), 4.10 (4H, OCH2CH3, m), 5.66 (1H, CH2CH-CH=CH, dd, JHH = 6.4 Hz, JHH = 4.5

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13
3
Hz), 5.81 (m, CH=CH-CHP, 1H). C NMR (75.5 MHz, CDCl3, Me4Si): (d, JPC = 4.9 Hz),
21.5,  (d, 2JPC = 7.9 Hz), 42.2,43.1 (d, 1JPC = 160.0 Hz),60.9 (d, 2JPC = 8.1 Hz), 129.0, 136.2 (d,
2JPC = 8.0 Hz), 176.7, 177.4. 31P NMR (125 MHz, CDCl3, Me4Si): 31.55. MS (EI): m/z (%) 79.0 (36.0),
91.0 (100), 105.0 (85.0), 125.0 (94.0), 152.0 (59.0), 173.0 (31.0), 187.0 (22.0), 201.0 (28.0), 229.0 (69.0),
316.0 (11.0). Anal. Calcd for C14H21O6P: C, 53.16; H, 6.69; P, 9.79. Found: C, 53.11; H, 6.68; P, 9.78.
Diethyl 7-methyl-1,3-dioxo-1,3,3a,4,7,7a-hexahydroisobenzofuran-4-ylphosphonate (4b). Identical to
4a. 1H NMR (300 MHz, CDCl3 , Me4Si): CH3CHdJHH = 7.3 Hz), 1.28 (6H, OCH2CH3, t, JHH
= 7.3 Hz), 2.25 (1H, CH3CHCHCO, dd, JHH = 7.6 Hz, JHH = 4.9 Hz), 2.52 (1H, CH3CH, m), 3.43 (1H,
COCHCHP, m), 3.50 (1H, CHP, m), 4.07 (4H, OCH2CH3, m), 5.64 (1H, CH3CH-CH=CH, dd, JHH = 6.8 Hz,
J
HH = 4.6 Hz), 5.83 (CH=CH-CHP, H2 m). 13C NMR (75.5 MHz, CDCl3 , Me4Si): (d, 3JPC = 5.6
Hz), (d, 2JPC = 8.6 Hz), 40.1,40.7 (d, 1JPC = 145.9 Hz),62.2 (d, 2JPC = 8.6 Hz), 128.2, 133.1 (d,
2JPC = 7.1 Hz), 172.3, 173.4. 31P NMR (125 MHz, CDCl3, Me4Si): 29.20. MS (EI): m/z (%) 51.0 (14.9),
77.0 (63.3), 91.0 (100), 109.0 (97.0), 119.0 (33.7), 138.0 (92.1), 155.0 (19.8), 173.0 (11.9), 302.0 (10.9).
Anal. Calcd for C13H19O6P: C, 51.66; H, 6.34; P, 10.25. Found: C, 51.61; H, 6.33; P, 10.24.
Diethyl 7-dodecyl-1,3-dioxo-1,3,3a,4,7,7a-hexahydroisobenzofuran-4-ylphosphonate (4c). Identical to
4a. 1H NMR (300 MHz, CDCl3, Me4Si): CH3CHtJHH = 7.4 Hz), 1.24 (6H, OCH2CH3, t, JHH
= 7.7 Hz), 1.26-1.36 (20H, CH3(CH2)10CH2, overlap), 1.31 (2H, CH2CH2CH, m) 2.26 (1H, CH2CHCHCO,
dd, JHH = 8.1 Hz, JHH = 4.7 Hz), 2.50 (1H, CH2CH, m), 3.36 (1H, COCHCHP, m), 3.44 (1H, CHP, m), 4.08
(4H, OCH2CH3, m), 5.63 (1H, CH2CH-CH=CH, dd, JHH = 6.4 Hz, JHH = 5.0 Hz), 5.82 (1H, CH=CH-CHP,
m). 13C NMR (75.5 MHz, CDCl3, Me4Si): (d, 3JPC = 5.1 Hz), 21.3, 21.4, 
 (d, 2JPC = 8.0 Hz), 36.6, 44.4,45.1 (d, 1JPC = 159.9 Hz),61.6 (d, 2JPC = 8.7 Hz), 128.7,
2
31
136.8 (d, JPC = 8.4 Hz), 171.5, 171.8. P NMR (125 MHz, CDCl3, Me4Si): 30.83. MS (EI): m/z (%)
163.0 (75.2), 178.1 (59.6), 191.1 (100), 205.1 (35.8), 219.1 (45.0), 233.2 (42.2), 247.2 (31.2), 261.2 (27.5),
275.3 (23.9), 303.4 (20.2), 331.5 (23.9), 360.7 (43.1), 411.4 (2.1), 456.2 (0.1). Anal. Calcd for C24H41O6P:
C, 63.14; H, 9.05; P, 6.78. Found: C, 63.05; H, 9.04; P, 6.77.
Diethyl 7-decyl-1,3-dioxo-1,3,3a,4,7,7a-hexahydroisobenzofuran-4-ylphosphonate (4d). Identical to
1
4a. H NMR (300 MHz, CDCl3, Me4Si):  CH3CHtJHH = 8.4 Hz), 1.23-1.34 (16H,
CH3(CH2)8CH2, overlap), 1.27 (6H, OCH2CH3, t, JHH = 8.2 Hz), 1.30 (2H, CH2CH2CH, m) 2.26 (1H,
CH2CHCHCO, dd, JHH = 8.2 Hz, JHH = 5.0 Hz), 2.52 (1H, CH2CH, m), 3.33 (1H, COCHCHP, m), 3.44 (1H,
CHP, m), 4.08 (4H, OCH2CH3, m), 5.63 (1H, CH2CH-CH=CH, dd, JHH = 6.3 Hz, JHH = 5.1 Hz), 5.78 (1H,
CH=CH-CHP, m). 13C NMR (75.5 MHz, CDCl3, Me4Si): (d, 3JPC = 5.2 Hz), 22.5, 

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2
1
2
 (d, JPC = 8.8 Hz), 39.9, 43.6,46.1 (d, JPC = 161.0 Hz),64.2 (d, JPC
=
10.0 Hz), 131.2, 139.0 (d, 2JPC = 8.7 Hz), 170.6, 171.9. 31P NMR (125 MHz, CDCl3, Me4Si): 30.73. MS
(EI): m/z (%) 55.0 (16.3), 91.0 (84.8), 105.0 (43.3), 108.0 (25.2), 111.0 (34.4), 125.0 (90.4), 138.0 (33.9),
152.0 (100), 173.0 (34.3), 199.0 (17.0), 207.0 (19.5), 229.0 (54.6), 301.0 (27.8), 428.2 (4.8). Anal. Calcd
for C22H37O6P: C, 61.67; H, 8.30; P, 7.23. Found: C, 61.61; H, 8.70; P, 7.22.
Diethyl 7-methyl-1,3-dioxo-2,3,3a,4,7,7a-hexahydro-1H-isoindol-4-ylphosphonate (4e). Identical to 4a
except using maliemide (1H-pyrrole-2,5-dione). 1H NMR (300 MHz, CDCl3, Me4Si): CH3CH
dJHH = 8.1 Hz), 1.26 (6H, OCH2CH3, t, JHH = 7.9 Hz), 2.27 (1H, CH3CHCHCO, dd, JHH = 7.9 Hz, JHH
=
4.7 Hz), 2.54 (1H, CH3CH, m), 3.41 (1H, COCHCHP, m), 3.49 (1H, CHP, m), 4.09 (4H, OCH2CH3, m),
5.65 (1H, CH3CH-CH=CH, dd, JHH = 6.9 Hz, JHH = 4.7 Hz), 5.82 (1H, CH=CH-CHP, m), 8.95 (1H, NH s,
broad). 13C NMR (75.5 MHz, CDCl3, Me4Si): (d, 3JPC = 4.9 Hz), (d, 2JPC = 9.2 Hz),
44.3,46.3 (d, 1JPC = 150.1 Hz),66.1 (d, 2JPC = 9.5 Hz), 130.1, 133.4 (d, 2JPC = 8.9 Hz), 177.7, 178.6. 31P
NMR (125 MHz, CDCl3, Me4Si): 31.45. MS (EI): m/z (%) 18.0 (65.9), 28.1 (70.2), 29.1 (25.9), 65.0
(36.4), 77.0 (29.7), 83.0 (30.0), 91.0 (96.5), 92.0 (34.0), 93.0 (38.3), 97.0 (45.0), 111.0 (100), 125.4 (65.4),
138.0 (57.0), 152.0 (66.1), 164.0 (13.5), 256.0 (10.3), 301.1 (35.5). Anal. Calcd for C13H20NO5P: C, 51.83;
H, 6.69; N, 4.65; P, 10.28. Found: C, 51.76; H, 6.68; N, 4.64; P, 10.27.
Diethyl 7-dodecyl-1,3-dioxo-2,3,3a,4,7,7a-hexahydro-1H-isoindol-4-ylphosphonate (4f). 1H NMR
(300 MHz, CDCl3, Me4Si): CH3CH2CH2tJHH = 7.5 Hz),  CH2CH2CHm), 1.25-
1.35 (20H, CH3(CH2)10CH2, overlap), 1.23 (6H, OCH2CH3, t, JHH = 7.9 Hz), 2.25 (1H, CH2CHCHCO, dd,
JHH = 7.9 Hz, JHH = 4.6 Hz), 2.51 (1H, CH2CH, m), 3.35 (1H, COCHCHP, m), 3.45 (1H, CHP, m), 4.11 (4H,
OCH2CH3, m), 5.67 (1H, CH2CH-CH=CH, dd, JHH = 6.3 Hz, JHH = 4.2 Hz), 5.81 (1H, CH=CH-CHP, m),
3
9.13 (1H, NH s, broad). C NMR (75.5 MHz, CDCl3, Me4Si): (d, 3JPC = 4.6 Hz), 21.4, 23.9,
 (d, 2JPC = 7.8 Hz), 36.9, 44.9,45.8 (d, 1JPC = 166.9 Hz),63.1 (d,
2JPC = 9.9 Hz), 128.1, 135.9 (d, 2JPC = 8.9 Hz), 177.6, 178.5. 31P NMR (125 MHz, CDCl3, Me4Si): 31.47.
MS (EI): m/z (%) 163.0 (56.9), 178.1 (55.0), 191.1 (100), 205.1 (34.9), 219.1 (43.1), 233.2 (40.4), 247.2
(33.0), 261.2 (27.5), 275.3 (22.9), 289.3 (20.2), 303.4 (18.3), 317.4 (20.2), 331.5 (18.3), 345.5 (10.1), 360.7
(28.4.1), 410.5 (2.9), 455.2 (0.2). Anal. Calcd for C24H42NO5P: C, 63.27; H, 9.29; N, 3.07; P, 6.80. Found:
C, 63.21; H, 9.28; N, 3.07; P, 6.79.
Diphenyl 7-ethyl-1,3-dioxo-1,3,3a,4,7,7a-hexahydroisobenzofuran-4-ylphosphonate (4g). Identical to
4a. 1H NMR (300 MHz, CDCl3, Me4Si): CH3CH2CHtJHH = 7.5 Hz), 
CH3CH2CHm), 2.22 (1H, CH2CHCHCO, dd, JHH = 8.1 Hz, JHH = 5.1 Hz), 2.53 (1H, CH2CH, m), 3.35

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(1H, COCHCHP, m), 3.45 (1H, CHP, m), 5.61 (1H, CH2CH-CH=CH, dd, JHH = 6.1 Hz, JHH = 4.3 Hz), 5.79
(1H, CH=CH-CHP, m), 7.12-7.31 (10H, C6H5 Aromatic, overlap); 13C NMR (75.5 MHz, CDCl3, Me4Si):
 (d, 2JPC = 8.8 Hz), 41.0,43.2 (d, 1JPC = 171.0 Hz),120.4 (d, 3JPC = 10.1 Hz),
2
31
120.5, 125.8, 132.1, 134.2 (d, JPC = 9.1 Hz), 150.1, 178.2, 178.8; P NMR (125 MHz, CDCl3, Me4Si):
28.41. MS (EI): m/z (%) 28.0 (31.9), 77.0 (30.8), 92.0 (35.2), 95.0 (53.8), 105.0 (100), 133.0 (6.6), 207.0
(8.8), 263.0 (25.3), 291.0 (6.6), 319.0 (46.2), 412.0 (2.2). Anal. Calcd for C22H21O6P: C, 64.08; H, 5.13; P,
7.51. Found: C, 64.04; H, 5.13; P, 7.50.
ACKNOWLEDGEMENTS
AA and AAAQ thank the School of Pharmacy for fellowships. This work was partially funded by the
Israel Science Foundation and by a grant from Applied Grants of the Hebrew University.
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