Catalyst-free Diels-Alder reactions of vinylphosphonates with cyclopentadienones

Article abstract of DOI:10.1139/cjc-2017-0267

The unprecedented thermal Diels-Alder reaction of the diethyl vinylphosphonate and diethyl styrylphosphonate with various cyclopentadienones is described. In these Diels-Alder reactions, catalysis was not required and the corresponding cycloadducts deriva

Full text of DOI:10.1139/cjc-2017-0267

Page 1 of 27
Catalyst Free Diels-Alder reactions of
vinylphosphonates with cyclopentadienones
Benmeddah Amel,a,b Villemin Didier,a
Nathalie,a and Legay Remi.a
*
Mostefa-Kara Bachir,b Bar
________________________________________________________________
aNormandie Université, France, ENSICAEN, LCMT, UMR CNRS 6507, INC3M, FR 3038,
Labex EMC3, LabexSynOrg, 14050 Caen, France.
b Laboratoire de Catalyse et Synthèse en Chimie Organique, Faculté des Sciences, Université
de Tlemcen, BP 119, 13000 Tlemcen, Algeria
*Corresponding author : Tel : +231452840; fax :+231452877 ; eꢀmail address:
villemin@ensicaen.fr

Page 2 of 27
Abstract: The unprecedented thermal DielsꢀAlder reaction of the diethyl vinylphosphonate and
diethyl styrylphosphonate with various cyclopentadienones is described. In these DielsꢀAlder
reactions, catalysis was not required and the corresponding cycloadducts derivatives were obtained.
The tetraethyl vinylideneꢀ1,1ꢀbisꢀphosphonate was found to be less reactive than monophosphonates
with the same cyclopentadienones.
Keywords: cycloaddition, cyclopentadienones, DielsꢀAlder reaction, vinylphosphonate,
styrylphosphonate, vinylideneꢀ1,1ꢀbisphosphonate.
Résumé : Pour la première fois, la réaction thermique de DielsꢀAlder du vinylphosphonate de
diéthyle et du styrylphosphonate de diéthyle avec diverses cyclopentadiénones est décrite.
Dans ces réactions de DielsꢀAlder, aucun catalyseur n’est nécessaire et les produits de cycloꢀ
addition ont été obtenus. Le vinylidèneꢀ1,1ꢀbisꢀphosphonate de tétraéthyle s’est révélé être
moins réactif que les monophosphonates avec les mêmes cyclopentadiénones.
Mots clés: cycloꢀaddition, cyclopentadiénones, réactions de DielsꢀAlder, vinylphosphonate,
styrylphosphonate, vinylidèneꢀ1,1ꢀbisꢀphosphonate

Page 3 of 27
Introduction
The chemistry of cyclopentadienones is old but well documented, as witnessed
by the review made by Ogliaruso et al.1 Although not frequently used,
cyclopentadienones remain interesting molecules, owing to their dual role of
diene and dienophile in the DielsꢀAlder cycloadditions (Figure 1). An example
of this dual role is the selfꢀdimerization of cyclopentadienone.2
Figure 1. Dual role of cyclopentadienone in DielsꢀAlder reactions.
Selfꢀdimerisation of cyclopentadienone.
In contrast to nonꢀsubstituted cyclopentadienones, which tend to dimerize,
tetrasubstituted cyclopentadienones are stable and were extensively studied in
the past by Dilthey et al.3 They usually react as dienes with electron poor olefins
in DielsꢀAlder reactions, and the initial product can subsequently be
decarbonylated then oxidized, thus leading to a stable aromatic compound
(Scheme 1).
Scheme 1. Reaction of tetrasubstituted cyclopentadienones with dienophile
olefins followed by decarbonylation and oxidation reactions.
R
R
R
R
R
R
O
CO
R'
R'
Z
R'
R'
Z
R'
R'
Z
Z
oxidation
R
R
O
+
R'
R'

Page 4 of 27
The result of the reaction of tetrasubstituted cyclopentadienones with
dienophiles is sensitive to reaction conditions. Generally, the temperature for the
decarbonylation reaction is higher than the temperature needed for the Dielsꢀ
Alder reaction, and the aromatization step takes place under oxidative conditions
such as air or an oxidizing agent. Cyclopentadienones are important because
their thermal [4+2] DielsꢀAlder reactions furnish polyaromatic materials which
can be of interest for electronic and photovoltaic applications.4 Although few
examples of dienophiles with electron donating groups like vinylidene carbonate
have been reported,5 most of the DielsꢀAlder reactions of cyclopentadienones
described in literature involve olefins bearing electronꢀwithdrawing groups such
as COR, COOR, CN, SOR, SO2R.
To our knowledge, the DielsꢀAlder cycloaddition of alkenylphosphonate esters
with substituted cyclopentadienones has not been reported. Thus, in the context
of synthesizing new polyaromatic phosphonated compounds, we are reporting
herein the thermal catalystꢀfree DielsꢀAlder reaction of various tetrasubstituted
cyclopentadienones with diethyl vinylꢀ and styrylꢀ phosphonates. The
phosphonate group is subsequently interesting for the immobilization of organic
compounds on the surface of inorganic solids6 like titanium dioxide for
photovoltaic applications.
Experimental
General information
Melting points were determined on Kofler Bank apparatus type WME 50ꢀ260°C
and are uncorrected. Analytical thinꢀlayer chromatography (TLC) was
performed on Merck silica gel 60 plates, 40ꢀ63 µm thick with Fꢀ254 indicator
aluminium sheets. Visualization was accomplished by UV light. IR spectra were
recorded with PerkinꢀElmer spectrophotometer equipped with ATR accessory.
31P NMR spectra were recorded at 161.97 MHz on a Bruker AC 400
spectrometer with CDCl3 as solvent and phosphoric acid as external reference.
1
NMR spectra were recorded at 400 or 500 MHz for H NMR and 100.6 or 125

Page 5 of 27
13
MHz for C NMR with a Bruker AC 400 or Bruker AC 500 spectrometer with
CDCl3 as solvent and TMS as an internal standard; Chemical shifts (δ) are
expressed in ppm and are reported as follows: multiplicity (s = singlet, d =
doublet, t = triplet, q = quartet, dd = doublet of doublet, m = multiplet, b =
broad).
Mass spectra were recorded on a QTOF Micro (Waters) spectrometer with
electrospray ionization (ESI, positive mode), lockspray PEG, infusion
introduction at 5µL/min, a source temperature of 80°C and desolvation
temperature of 120°C.
Reagents
Cyclopentadienones (tetracyclone 1a,7 phencyclone 1b,8 acecyclone 1c,9 2,5ꢀ
dimethoxycarbonylꢀ3,4ꢀdiphenylcyclopentadienone 1d,10 2,3ꢀdimethylꢀ3,4ꢀ
diphenylcyclopentadienone 1e11 and 2ꢀmethylꢀ3,4,5ꢀtriphenylcyclopentadienone
1f12 were prepared by Knoevenagel condensation using potassium hydroxide as
base. Diethyl vinylphosphonate 2α, diethyl 2ꢀEꢀphenyl vinylphosphonate 2β13
and tetraethyl vinylideneꢀ1,1ꢀbisphosphonate 2γ14 were synthesized according to
the literature.
Experimental part
Synthesis of diethyl (7-oxo-1,4,5,6-tetraphenylbicyclo[2.2.1]hepta-5-en-2-yl)
phosphonate 3aα
A solution of tetraphenylcyclopentadienone 1a (0.5 g; 1.3 mmol) was added to
diethyl vinylphosphonate 2α (0.23 g; 1.4 mmol) in 5 mL of toluene. The
mixture was refluxed at 110°C for 38 h. The solvent was removed under vacuum
and the residue was crystallized from methanol giving a purple solid (0.34 g,
48%), mp=180°C.
15
14
18
13
19
17
16
O
P
12
8
2
O
O
7
3
10
9
1CO
21
11
6
20
4
22
5
24
23
25
26
3aα
27
1
31P NMR (162 MHz) δ 28.4. H NMR (500 MHz) δ 7.42 (d, 2H, H25, J=7.3 Hz);
7.38ꢀ7.22 (m, 8H, H13, H14, H15, H26, H27); 7.12 (t, 1H, H23, J=7.0 Hz); 7.08ꢀ7.02

Page 6 of 27
(m, 4H, H22, H17); 7.00ꢀ6.89 (m, 5H, H19, H18, H21); 4.33ꢀ4.17 (m, 3H, H8a, H9);
4.04 (dq, H8b, 3JHP= 16.5 Hz, 3JH8ꢀH10 =7.0 Hz); 3.51 (ddd, 1H, H7, 2JHP=16.5 Hz,
2
3
3JH7ꢀH6a=10.0 Hz, 3JH7ꢀH6b =7.0 Hz); 2.83 (ddd, 1H, H6a, JH6ꢀH6=12.0 Hz, JH6aꢀ
3
3
2
H7=10.0 Hz JHP=10.0 Hz); 2.69 (ddd, 1H, H6b, JHP=22.9 Hz, JH6ꢀH6=12.0 Hz,
3JH6bꢀH7 = 7.0 Hz); 1.40 (t, 3H, H11, 3JHH=7.0 Hz); 1.19 (t, 3H, H10, 3JHH=7.0 Hz).
13C NMR (100 MHz) δ 199.7 (d, C1, J=19.2 Hz); 143.8 (C4); 140.1 (d, C3,
J=4.7 Hz); 135.1 (C12); 134.8 (C20); 133.3 (C16); 133.2 (C24); 130.9 (C17);
130.1 (C13); 129.9 (C21); 129.3 (C25); 128.0 (C26); 127.7 (C14); 127.6 (C22);
127.5 (C27); 127.4 (C23); 127.2 (C15); 127.0 (C18); 126.7 (C19); 64.9 (d, C2,
J=2.7 Hz); 62.4 (d, C8, JCP=7.0 Hz); 62.3 (d, C9, JCP=7.7 Hz); 60.3 (d, C5,
JCP=2.7 Hz); 34.0 (d, C7, JCP=144.2 Hz); 32.1 (d, C6, JCP=3.4 Hz); 16.5 (d, C10,
JCP=5.8 Hz); 16.2 (d, C11, JCP=5.8 Hz). IR νmax (neat/cmꢀ1): 2980 (CꢀH); 1778
(C=O); 1441 (C=C); 1231 (P=O intense); 1050 (PꢀOꢀC). ESIꢀTOF MS m/z (%
relative abundance): 521 (M+1, 40). HRMSꢀESI calculated for C34H34O3P
521.2246; found 521.2238.
Synthesis of diethyl (13-oxo- 1,4-diphenyl-1,2,3,4-tetrahydro-1,4-methano-
triphenylen-2-yl)phosphonate 3bα
A solution of phencyclone 1b (0.38 g; 1 mmol) in 10 mL bromobenzene was
added to diethyl vinylphosphonate 2α (0.25 g; 1.5 mmol) in 10 mL of
bromobenzene. The mixture was refluxed for 24 h. The solvent was removed
under vacuum and the residue was crystallized from ethanol to give a colorless
powder (0.22 g, 41%), mp 228°C.
27
26
25
28
29
14
12
24
15
16
13
O
8
2
O
O
7
P
3
10
9
17
23
1CO
11
6
4
22
21
5
18
30
19
35
34
31
32
20
3bα
33
1
31P NMR (162 MHz) δ 26.5. H NMR (500 MHz) δ 8.76 (bd, 1H, H22, J = 8.4
Hz); 8.73 (bd, 1H, H16, J = 8.4 Hz); 8.09 (bd, 1H, H25, J = 7.6 Hz); 7.70 (dt, 1H,
H31, J = 7.7 Hz and 1.4 Hz); 7.65 (td, 1H, H32, J = 7.6 Hz and J = 1.5 Hz); 7.64
(td, 1H, H26, J = 7.7 Hz and J = 1.4 Hz); 7.57ꢀ7.53 (m, 2H, H15,21); 7.50 (tt, 1H,
H33, J = 7.5 Hz and J = 1.4 Hz); 7.46 (tt, 1H, H27, J = 7.6 Hz and J = 1.3 Hz);
7.45 (dd, 1H, H13, J = 8.1 Hz and J = 1.3 Hz); 7.43 (td, 1H, H34, J = 7.7 Hz and J
= 1.5 Hz); 7.38 (td, 1H, H28, J = 7.6 Hz and J = 1.5 Hz); 7.29 (m, 1H, H35); 7.28

Page 7 of 27
(m, 1H, H14); 7.22 (ddd, 1H, H20, J = 8.3 Hz, 7.1 Hz and J = 1.3 Hz); 7.15 (dt,
1H, H29, J = 7.8 Hz and J = 1.4 Hz); 7.08 (dd, 1H, H19, J = 8.4 Hz and J = 1.1
Hz); 3.79ꢀ3.71 (m, 2H, H8); 3.67 (ddd, 1H, H7, JHꢀP = 14.8 Hz, JH7ꢀH6 = 10.5 Hz
and JH7ꢀH6 = 5.5 Hz); 3.41 (dqd, 1H, H9, JH9aꢀH9b = 10.1 Hz, JH9aꢀH11 = 7.1 Hz and
JHꢀP = 6.5 Hz); 3.26 (ddd, 1H, H6a, JH6aꢀH6b = 11.8 Hz, JH6aꢀH7 = 10.5 Hz and JHꢀP
= 10.5 Hz); 3.07 (ddq, 1H, H9b, JH9bꢀH9a = 9.9 Hz, JHꢀP = 8.6 Hz and JH9aꢀH11 = 7.1
Hz); 2.60 (ddd, 1H, H6b, JHꢀP = 22.7 Hz, JH6bꢀH6a = 11.9 Hz and JH6bꢀH7 = 5.5 Hz);
0.89 (t, 3H, H10, J = 7.1 Hz); 0.54 (t, 3H, H11, J = 7.1 Hz). 13C NMR (100 MHz)
δ: 200.1 (d, C1, 3JCP=19.1 Hz); 136.7 (C4); 135.8 (C30); 134.8 (d, C3, 3JCP = 7.4
Hz); 134.4(C24); 131.5 (C29); 131.4 (C23); 131.3 (C35); 130.8 (C17); 129.1
(C32); 128.8 (C34); 128.6 (C26); 128.4 (C25); 128.0 (C33); 127.9 (C28); 127.7
(C27); 127.6 (C31); 127.5 (C12); 127.1 (C13); 126.4 (C18); 126.3 (C21); 126.3
(C15); 126.1 (C20); 125.9 (C14); 125.0 (C19); 123.4 (C22); 122.8 (C16); 62.54
2
2
2
(d, C2, JCP=3.3 Hz); 62.54 (d, C8, JCP=3.3 Hz); 61.7 (d, C9, JCP= 6.9 Hz);
3
1
2
59.1 (d, C5, JCP= 2.3 Hz); 35.6 (d, C7, JCP= 157.3 Hz); 30.5 (d, C6, JCP= 3.9
Hz); 15.9 (d, C10, 3JCP= 6.1 Hz); 15.4 (d, C11, 3JCP= 6.5 Hz). IR νmax (neat/cmꢀ
1): 2979 (CꢀH); 1780 (bridged C=O); 1447 (C=C); 1234 (P=O intense); 1025 (Pꢀ
OꢀC intense). ESIꢀTOF MS m/z (% relative abundance): 547 (M+H, 100).
HRMSꢀESI calculated for C33H32O4P 547.2038; found 547.2032.
Synthesis of diethyl (7,10-diphenylfluoranthen-8-yl)phosphonate 5cα
A solution of acecyclone 1c (0.35 g; 1.0 mmol) in 10 mL bromobenzene was
added to diethyl vinylphosphonate 2α (0.25 g; 1.5 mmol) in 10 mL of
bromobenzene. The mixture was refluxed for 24 h. The solvent was removed
under vacuum and the residue was flashꢀchromatographed on silica gel column
using (AcOEt/Cyclohexane: 15/85) as eluent to give an orange viscous liquid
(0.16 g, 32%).
27
26
25
O
24
14
13
12
8
2
O
O
9
15
16
21
7 P
3
4
17
6
5
18
20 19
31
32
5cα
33
31P NMR (162 MHz) δ 18.5. 1H NMR (500 MHz) δ 8.04 (d, 1H, H6, 3JHP = 14.5
Hz); 7.81 (d, 1H, H21, J = 7.5 Hz); 7.75 (d, 1H, H15, J = 8.0 Hz); 7.68 (bd, 2H,

Page 8 of 27
H25, J = 6.5 Hz); 7.61ꢀ7.54 (m, 8H, H26, H27, H31, H32, H33); 7.41 (t, 1H, H20, J=
7.5 Hz); 7.35 (d, 1H, H19, J = 7.5 Hz); 7.31 (dd, 1H, H14, J =8.0 Hz and J = 7.0
Hz); 6.40 (d, 1H, H13, J = 7.0 Hz); 4.05ꢀ3.89 (m, 4H, H8); 1.23 (t, 6H, H9, J=7.5
13
3
Hz). C NMR (125 MHz) δ 140.2 (d, C24, JCP=8.3 Hz); 140.1 (C30); 140.0
3
3
(C4); 139.2 (d, C3, JCP=18.5 Hz); 138.8 (d, C5, JCP=4.3 Hz); 137.4 (d, C2,
2JCP=16.3 Hz); 135.8 (d, C12, JCP=2.4 Hz); 135.0 (C18); 134.7 (d, C6,
4
2JCP=11.2 Hz); 133.1 (C17); 129.8 (C31); 129.7 (C16); 129.1 (C25); 128.8ꢀ
128.2 (C26/C32); 128.14ꢀ128.09 (C27/C33); 127.9 (C14); 127.8 (C21); 127.6
1
(C20); 127.0 (C15); 126.1 (d, C7, JCP=188.2 Hz); 124.2 (C19); 124.0 (C13);
62.0 (d, C8, 2JCP=5.5 Hz); 16.4 (d, C9, 3JCP=6.3 Hz). IR νmax (neat/cmꢀ1): 3053;
2979 (CꢀH); 1442 (C=C); 1225 (P=O intense); 1020 (PꢀOꢀC intense). ESIꢀTOF
MS m/z (% relative abundance): 491 (M+H, 100). HRMSꢀESI calculated for
C32H28O3P 491.1776; found 491.1762.
Synthesis of dimethyl 4’-(diethoxyphosphoryl)-4’,5’-dihydro-(1,1’:2’1”-
terphenyl)-3’,6’-dicarboxylate 4dα
A solution of 3,4ꢀdimethoxycarbonylꢀ2,5ꢀdiphenylcyclopentadienone 1d
(0.2 g, 5.7 mmol) in 10 mL of bromobenzene was added to diethyl
vinylphosphonate 2α (0.1 g, 6.1 mmol) in 10 mL of bromobenzene. The mixture
was then refluxed during 24 h. The solvent was removed under vacuum to give a
brown viscous liquid. The residue was flashꢀchromatographed on silica gel
column using (AcOEt/Cyclohexane: 15/85) as eluent to give an orange viscous
liquid (0.24 g, 89%).
16
O
O
O
P
13
8
2
14
O
O
10
11
7
3
9
15
6
4
5
12
O
O
4dα
17
1
31P NMR (162 MHz) δ 26.3. H NMR (500 MHz) δ 6.97 (m, 6H, Harom, J = 6.9
Hz); 6.68 (m, 4H, Harom); 4.15ꢀ4.06 (m, 4H, H8, H9); 3.59 (ddd, 1H, H7,
3
2JHP=26.2 Hz, 3JH7ꢀH6b = 9.5 Hz, JH7ꢀH6a=1.5 Hz); 3.37 (s, 3H, H17); 3.33 (s, 3H,
2
3
3
H16); 3.26 (ddd, 1H, H6a, JH6aꢀH6b =18.0 Hz, JHP =17.0 Hz, JH6aꢀH7 =1.5 Hz);
3.01 (ddd, 1H, H6b, JHP =52.5 Hz, 2JH6bꢀH6a=18.0 Hz and JH6bꢀH7= 9.5 Hz); 1.28
(t, 3H, H11, J = 7.2 Hz); 1.25 (t, 3H, H10, J =7.1 Hz). C NMR (125 MHz) δ
3
3
13

Page 9 of 27
4
3
167.8 (d, C12, JCP=1.5 Hz); 167.4 (d, C13, JCP=3.2 Hz); 147.1 (d, C3,
3JCP=11.4 Hz); 144.6 (d, C4, JCP= 5.4 Hz); 137.7 (d, C14, 4JCP=3.6 Hz); 137.6
4
3
(C15); 128.8 (CHarom); 128.6 (CHarom); 127.2 (d, C5, JCP=10.3 Hz); 127.1
(CHarom); 127.0 (CHarom); 126.8 (CHarom); 126.7 (CHarom); 125.4 (d, C2, 2JCP=9.8
2
2
Hz); 62.4 (d, C8, JCP=1.4 Hz); 62.3 (d, C9, JCP=1.4 Hz); 51.7 (C16); 51.0
(C17); 33.0 (d, C7, JCP= 136.4 Hz); 25.1 (d, C6, JCP= 5.5 Hz); 16.6 (d, C10,
3JCP= 5.5 Hz); 16.4 (d, C11, JCP=6.0 Hz). IR νmax (neat/cmꢀ1): 2985 (CꢀH);
1
2
3
1705 (C=O ester intense); 1432 (C=C); 1212 (P=O intense); 1018 (PꢀOꢀC
intense). ESIꢀTOF MS m/z (% relative abundance): 485 (M+1, 100); 507
(M+Na, 35). HRMSꢀESI calculated for C26H30O7P 485.1729; found 485.1722.
Synthesis of diethyl (1,4-dimethyl-7-oxo-5,6-diphenylbicyclo[2.2.1]hept-5-
en-2-yl)phosphonate 3eα and diethyl (3,6-dimethyl-4,5-dihydro[1,1’:2’,1”]-
phosphonate 4eα.
A solution of 2,5ꢀdimethylꢀ3,4ꢀdiphenylcyclopentadienone 1e dimer (0.4g; 0.77
mmol) in 10 mL of bromobenzene was added to diethyl vinylphosphonate
2α (0.25 g; 1.6 mmol) in 10 mL of bromobenzene. The mixture was refluxed for
24 h and the solvent was then distilled under vacuum to give a brown viscous
liquid. The residue was flashꢀchromatographed on silica gel column using
(AcOEt/Cyclohexane: 15/85) as eluent to give an orange viscous liquid (0.5 g,
global yield: 81% which turned to be a mixture of 3eα and 4eα in the ratio
45/55 (determined by 1H NMR).
12
CH3
12'
CH3
O
P
O
P
8
8'
O
O
O
O
3
4
3'
4'
7
10
7'
10'
13
14
13'
14'
9
1
CO
9'
11
11'
6
6'
5
5'
CH3
15
CH3
15'
3eα
4eα
1
31P NMR (162 MHz) δ 28.4; 29.5. H NMR (500 MHz) δ 7.24ꢀ6.85 (m, 16H,
H
arom); 6.83 (t, 2H, Harom, J=7.0 Hz); 6.74 (t, 2H, Harom, J=7.0 Hz) ; 4.21ꢀ3.94
(m, 8H, H8, H9', H8', H9); 2.85 (ddd, 1H, H6a', 3JHP= 54.6 Hz, 2JH6a’ꢀH6’b= 17.3 Hz,
3JH6’aꢀH7’ =9.7 Hz); 2.66 (dd, 1H, H7', JHP=24.6 Hz, JH7’ꢀH6’a= 9.5 Hz); 2.53 (t,
1H, H6'b, JH6’bꢀH6’a =2JHP=17.0 Hz); 2.31 (ddd, 1H, H7, JHP= 17.2 Hz, JH7ꢀH6a
2
3
2
2
2
=
3
3
10.1 Hz, JH7ꢀH6b =7.4 Hz); 2.13ꢀ1.96 (m, 2H, H6); 1.75 (d, 3H, H12’ , JHP= 4.7
Hz); 1.65 (s, 3H, H15’); 1.41 (s, 3H, H12); 1.35ꢀ1.11 (m, 12H, H10, H11, H10’,
13
3
H11’); 1.20 (s, 3H, H15). C NMR (125 MHz) δ 203.9 (d, C1, JCP=20.1 Hz),
143.2 (C4); 140.9 (d, C3, 3JCP =4.7 Hz); 140.4 (C13); 140.3 (C14); 140.2 (C14’);

Page 10 of 27
3
140.1 (C13’); 137.8 (d, C3', JCP=12.8 Hz); 134.3 (C4'); 131.7 (CHarom); 130.5
(CHarom); 130.2 (CHarom); 130.1 (CHarom); 129.5 (CHarom); 128.2 (CHarom); 127.6
3
(CHarom); 127.5 (CHarom); 127.4 (d, C5', JCP=7.0 Hz); 127.3 (CHarom); 127.2
2
(CHarom); 125.8 (CHarom);125.6 (CHarom); 123.8 (d, C2', JCP=11.5 Hz); 62.1 (d,
C8, 2JCP=6.9 Hz); 62.1 (d, C9, 2JCP=5.6 Hz); 62.0 (d, C9', 2JCP=6.8 Hz); 61.9 (d,
C8', 2JCP=7.0 Hz); 54.8 (d, C2, 2JCP=3.1 Hz); 52.2 (d, C5, 3JCP=3.2 Hz); 39.6 (d,
1
1
3
C7’, JCP=130.2 Hz); 38.7 (d, C7, JCP=155.5 Hz); 33.6 (d, C6, JCP=2.7 Hz);
2
3
4
30.5 (d, C6’, JCP=5.9 Hz); 21.3 (d, C12', JCP=3.1 Hz); 21.1 (d, C15’, JCP=1.3
3
3
Hz); 16.8 (d, C11', JCP=5.9 Hz); 16.5 (d, C11, JCP=5.8 Hz); 16.5 (d, C10',
3JCP=6.5 Hz); 16.4 (d, C10, 3JCP=5.8 Hz), 12.4 (C12); 12.2 (C15). ESIꢀTOF MS
m/z (% relative abundance): 425 3eα (M+1; 30); 397 4eα (M+1; 21). HRMSꢀ
ESI calculated for C24H28O3P 395.1776; found 395.1778.
Synthesis of diethyl ( 5’-methyl-6’-phenyl-3’,4’-dihydro [1,1’:2’,1”-
terphenyl]-4’yl)3,4,5)phosphonate 4fα1 and diethyl ( 5’-methyl-6’-phenyl-
3’,4’-dihydro [1,1’:2’,1’’-terphenyl]-3’yl)3,4,5)phosphonate 4fα2.
A solution of 2ꢀmethylꢀ3,4,5ꢀtriphenylcyclopentadienone 1f (0.2 g, 0.62 mmol)
in 10 mL bromobenzene was added to diethyl vinylphosphonate 2α (0.1 g, 0.62
mmol) in 10 mL bromobenzene. The mixture was refluxed for 24 hours. The
solvent was distilled under vacuum giving a brown viscous liquid. The residue
was flashꢀchromatographed on silica gel column using (AcOEt/Cyclohexane:
15/85) as eluent to give an orange viscous liquid (0.21 g, 74%) which is a
mixture of 4fα1 and 4fα2 (60:40).
12
CH3
O
P
O
P
8
12'
8'
O
O
O
O
3'
4'
7
10
11
3
4
7'
10'
13
14
13'
14'
9
9'
11'
6
6'
5
15
5'
CH3
15'
4fα1
4fα2
31
1
NMR P (162 MHz) δ 28.8; 29.3. NMR H (500 MHz) δ 7.42 (d, 4H, Harom
,
J=8.5 Hz); 7.24ꢀ7.14 (m, 4H, Harom); 7.07ꢀ6.92 (m, 10H, Harom); 6.83ꢀ6.73 (m,
8H, Harom); 6.62ꢀ6.57 (m, 4H, Harom); 4.20ꢀ3.89 (m, 8H, H8, H9, H8',H9'); 3.28
3
(ddd, 1H, H6a, JHP=54.9 Hz, 2JH6aꢀH6b =16.8 Hz, 3JH6aꢀH7 =8.9 Hz); 3.16 (dd, 1H,
H7', 2JHP=25.2 Hz , 3JH7’ꢀH6’a =9.1 Hz); 3.02 (dddq, 1H, H6’a, 3JHP =54.5 Hz, 2JH6’aꢀ
3
4
3
H6’b =16.6 Hz, JH6’aꢀH7’ =8.9 Hz, JH6’aꢀH15’ =1.7 Hz); 2.94 (ddd, 1H, H6b, JHP
=16.7 Hz, 2JH6bꢀH6a =16.7 Hz, 3JH6bꢀH7 =1.7 Hz); 2.77 (ddd, 1H, H7, 2JHP= 26.5 Hz,
3JH7ꢀH6a =9.1 Hz, JH7ꢀH6b =1.7 Hz); 2.72 (dd, 1H, H6’b, JHP =17.4 Hz, 2JH6’bꢀH6’a
3
3

Page 11 of 27
=16.7 Hz); 1.83 (d, 3H, H12, 4JHP = 4.7 Hz); 1.68 (t, 3H, H15’, JH15’ꢀH6’a =1.4 Hz);
4
3
3
1.27 (t, 6H, H11, 10', JHH=7.5 Hz); 1.23 (t, 3H, H10, JHH =7.5 Hz); 1.03 (t, 3H,
H11’, JHH= 7.5 Hz). NMR C (125 MHz) δ 142.3 (d, C15, 4JCP=1.7 Hz); 141.8
(d, C13’, JCP=3.1 Hz); 139.9 (d, C12’, JCP=4.0 Hz); 139.8 (C14); 139.7
(C14’); 139.7 (d, C3’, JCP=12.1 Hz); 139.6 (d, C13, JCP=3.9 Hz); 138.4 (d,
C3, JCP=13.3 Hz); 136.0 (d, C4, JCP=6.3 Hz); 135.1 (d, C4’, JCP=5.8 Hz);
3
13
4
3
3
4
3
4
4
3
3
130.6 (d, C5, JCP=6.7 Hz) ; 130.1 (d, C5’, JCP=7.2 Hz) ; 128.2 (d, C2’,
2JCP=10.8 Hz) ; 126.3 (d, C2, JCP=11.2 Hz); 131.6 (CHarom); 131.6
2
(CHarom); 131.6 (CHarom); 130.9(CHarom); 130.9 (CHarom); 130.2 (CHarom); 130.1
(CHarom); 130.1(CHarom); 130.1 (CHarom); 130.0 (CHarom); 128.8 (CHarom); 127.5
(CHarom); 127.4 (CHarom); 127.4 (CHarom); 127.3 (CHarom); 126.9 (CHarom); 126.9
2
2
(CHarom); 126.8 (CHarom); 62.2 (d, C8, JCP=7.2 Hz); 61.8 (d, C9, JCP=6.6 Hz);
2
2
1
61.7 (d, C8’, JCP=7.0 Hz); 61.6 (d, C9’, JCP=6.5 Hz); 39.8 (d, C7, JCP=131.4
1
3
Hz); 39.2 (d, C7', JCP=130.1 Hz); 31.3 (d, C6', JCP=6.2 Hz); 30.8 (d, C6,
3JCP=6.2 Hz); 21.5 (d, C12, JCP=3.0 Hz); 21.2 (d, C15’, JCP=1.3 Hz); 16.7 (d,
3
4
3
3
3
C10, JCP=5.7 Hz); 16.6 (d, C11, C10’, JCP=5.7 Hz); 16.3 (d, C11’, JCP=6.0
Hz). IR νmax (neat/cmꢀ1) : 2982 (CꢀH); 1443 (C=C); 1228 (P=O intense); 1019
(PꢀOꢀC intense). ESIꢀTOF MS m/z (% relative abundance): 459 (M+1, 100).
HRMSꢀESI calculated for C29H32O3P 459.2089, found 459.2079.
Synthesis of diethyl (4’,5’,6’-triphenyl-2’,3’-dihydro[1,1’,:2’,1”-terphenyl]-
3-yl) phosphonate 4aβ.
A solution of tetracyclone 1a (1 g, 2.6 mmol) and diethyl 2ꢀEꢀphenyl
vinylphosphonate 2β (0.78 g, 2.6 mmol) in 2 mL bromobenzene was refluxed
for 96 h. The solvent was removed under vacuum and the residue was
crystallized from ethanol to give colourless solid. The precipitate was collected
and recrystallized in ethanol giving colorless crystals (0.47 g, 31 %), mp 152°C.
18
17
20
9
16
19
12
21
O
11
3
8
O
O
2
P
8
7
22
4
6
15
13
10
30
23
24
5
14
28
25
26
29
4aβ
27
31
1
3
NMR P (162 MHz) δ 26.7. NMR H (500 MHz) δ 7.68 (d, 2H, H28, J = 7.9
3
3
Hz); 7.46 (t, 2H, H29, J = 7.9 Hz); 7.36 (t, 1H, H30, J = 7.9 Hz); 7.10 (d, 2H,
H25, 3J = 6.5 Hz); 7.04ꢀ6.90 (m, 14H, H26, H27, H23, H21, H18, H17, H20, H22); 6.75

Page 12 of 27
(m, 2H, H19); 6.67 (m, 2H, H16); 4.60 (bd, 1H, H6, 3JHP = 16.5 Hz); 4.24ꢀ4.16 (m,
2H, H8a, H8’a); 4.13 (ddq, 1H, H8b, 2JH8bꢀH8a = 10.2 Hz, 3JHP = 7.1 Hz, 3JH8bꢀH9 = 7.0
2
Hz); 3.89 (ddq, 1H, H8’b, JH8’bꢀH8’a = 10.1 Hz, 3JHP = 7.9 Hz, 3JH8’bꢀH10 = 7.3 Hz);
2
3
3.47 (dd, 1H, H7, JHP = 26.5 Hz, JH7ꢀH6 = 1.5 Hz); 1.34 (t, 3H, H9, J = 7.0 Hz);
1.15 (t, 3H, H10, J = 7.0 Hz). NMR 13C (125 MHz) δ 141.5 (C14); 141.4 (d, 3JCP
3
3
= 5.3 Hz C11); 140.8 (d, C15, JCP = 25.5 Hz); 140.1 (d, C3, JCP= 12.0 Hz);
139.2 (C13); 139.1 (d, C4/C12, 4JCP = 6.2 Hz); 139.0 (d, C4/C12, 4JCP = 3.9 Hz);
134.6 (d, C5, JCP = 5.6 Hz); 131.1 (C22); 130.9 (d, C19, JCP = 4.3 Hz); 129.4
3
5
4
(C25); 129.3 (d, C16, JCP = 2.6 Hz); 128.9 (C29); 128.1 (C28); 127.9 (d, C2,
2JCP = 10.8 Hz); 127.5 (C26); 127.4 (C17); 127.3 (C30); 127.1 (C23); 127.0
2
(C20); 126.1 (C27); 126.3 (C18); 125.9 (C21); 62.2 (d, C8, JCP=7.0 Hz); 49.0
(d, C7, JCP = 128.9 Hz); 45.8 (d, C6, JCP=3.3 Hz); 16.7 (d, C9, JCP = 5.9 Hz);
1
2
3
3
16.4 (d, C10, JCP = 5.9 Hz). IR νmax (neat/cmꢀ1): 2978 (CꢀH); 1442 (C=C);
1245 (P=O intense); 1018 (PꢀOꢀC). ESIꢀTOF MS m/z (% relative abundance):
597 (M+H, 100); 619 (M+Na, 57). ESIꢀTOF: calculated for C40H38O3P
597.2559; found 597.565.
Synthesis
of
diethyl
(13-oxo-1,3,4-triphenyl-1,2,3,4-tetrahydro-1,4-
methanotriphenylen-2-yl) phosphonate 3bβ.
A solution of phencyclone 1b (0.38 g; 1 mmol) in 10 mL bromobenzene was
added to diethyl 2ꢀEꢀphenyl vinylphosphonate 2β (0.36 g, 1.5 mmol) in 10 mL
bromobenzene. The mixture was refluxed for 96 h. The solvent was removed
under vacuum and the residue was crystallized from ethanol to give a colorless
powder (0.27 g, 70 %), mp 204°C.
3
4
O O
2
5
1
6
7
8
9
12
11
10
1H (400 MHz) δ 8.81 (d, 2H, H8, 3J= 8.3 Hz); 7.77 (dd, 4H, H3, 3J=8.0 Hz, 4J =
3
3
4
1.6 Hz); 7.74 (ddd, 2H, H9, J=8.6 Hz, J=6.8 Hz, J = 1.2 Hz); 7.72 (dd, 2H,
H11, 3J =8.4 Hz, 4J =0.8 Hz); 7.56ꢀ7.49 (m, 4H, H5,10); 7.35 (dd, 4H, H4, 3J= 8.4
3
13
Hz, J=8.0 Hz). NMR C (100 MHz) δ 198.4 (C1); 137.8 (C2); 135.5 (C6);
134.0 (C5); 130.7 (C7); 130.3 (C3); 128.7 (C4); 128.6 (C12); 128.1 (C9); 127.6
(C10); 127.4 (C8); 123.2 (C11). IR νmax (neat/cmꢀ1): 3055 (CꢀH); 1665; 1593
(C=O); 1446 (C=C). ESIꢀTOF MS m/z (% relative abundance): 387 (M+1, 92);

Page 13 of 27
409 (M+23, 100). HRMSꢀESI calculated for C28H19O2 387.1385, found
387.1371.
The filtrate, a viscous liquid (<4%) constitution was assigned on the basis of
mass spectroscopy to be the bridge carbonyl phosphonated compound 3bβ :
31
NMR P (162 MHz) δ 25.14. ESIꢀTOF MS m/z (% relative abundance): 623
(M+1, 16); 687 (M+23, 4).
Diels-Alder reaction of acecyclone 1c with diethyl 2-E-phenyl
vinylphosphonate 2β.
A solution of acecyclone 1c (0.35 g; 1 mmol) in 10 mL bromobenzene was
added to diethyl 2ꢀEꢀphenyl vinylphosphonate 2β (0.36 g; 1.5 mmol) in 10 mL
of bromobenzene. The mixture was refluxed for 96 h. The solvent was removed
under vacuum and the residue was crystallized from ethanol to give a green
1
powder (0.17 g), mp > 260°C. The H NMR was conform with the structure of
the reactants, however the mass spectrum showed clearly the presence of the
corresponding lactone.
Ph
O
O
Ph
ESIꢀTOF MS m/z (% relative abundance): 373 (M+1; 80); 395 (M+23; 20).
HRMSꢀESI: calculated for C27H17O2 373.1229; found 373.1235.
Synthesis of dimethyl 4’-(diethoxyphosphoryl)-4’5’-dihydro-[1,1’:2”-
terphenyl]-3’6’- dicarboxylate 4dβ.

Page 14 of 27
A solution of 2,5ꢀdimethoxycarbonylꢀ3,4ꢀdiphenylcyclopentadienone 1d
(0.20 g; 0.57 mmol) in 10 mL bromobenzene was added to diethyl 2ꢀEꢀphenyl
vinylphosphonate 2β (0.14g; 0.57 mmol) in 10 mL bromobenzene. The mixture
was refluxed for 4 days then the solvent was distilled under reduced vacuum to
give a brown viscous liquid (0.23 g, 72%).
17
O
O
O
P
13
8
14
O
O
7
10
11
2
3
9
6
15
4
5
12
16
4dβ
O
O
18
NMR 31P (400 MHz) δ 24.92. NMR 1H (500 MHz) δ 7.43 (td, 2Harom, J=4.0 Hz,
J’=1.0 Hz); 7.38 (d, 2Harom, J=9.0 Hz); 7.31 (dd, 4Harom, J=6.5 Hz, J’=2.0 Hz);
7.24 (t, 2Harom, J=7.0 Hz); 7.04ꢀ6.93 (m, 5Harom); 4.68 (d, 1H, H6, 3JHP=19.5 Hz);
1
3
4.09ꢀ4.02 (m, 4H, H9, H8); 3.81 (dd, 1H, H7, JHP= 27.5 Hz, JH7ꢀH6=1.0 Hz);
3.24 (s, 3H, H17); 3.20 (s, 3H, H18); 1.28 (td, 6H, H11, H10, 3JHH=7.0 Hz, 3JHP= 1.5
13
3
Hz). NMR C (125 MHz) δ 167.4ꢀ167.1 (C12/C13); 148.8 (d, C16, JCP=6.7
3
3
Hz); 146.7 (d, C3, JCP=11.4 Hz); 145.7 (d, C4, JCP=5.4 Hz); 137.4 (d, C14,
3JCP=3.4 Hz); 133.1 (C15); 130.3 (C5); 129.3 (CHarom); 129.1 (CHarom); 128.9
(CHarom); 128.7 (CHarom); 128.6 (CHarom); 128.5 (CHarom); 128.2 (CHarom); 127.9
(CHarom); 127.7 (CHarom); 126.9 (d, C2, 2JCP=4.6 Hz); 62.6 (d, C8, 2JCP=7.0 Hz);
2
61.9 (d, C9, JCP=5.4 Hz); 51.7 (C18); 51.6 (C17); 41.8 (d, C7, 1JCP=134.9 Hz);
2
3
3
38.1 (d, C6, JCP=3.0 Hz); 16.6 (d, C10, JCP=5.6 Hz); 16.5 (d, C11, JCP=8.0
Hz). IR νmax (neat/cmꢀ1): 2983 (CꢀH); 1709 (C=O ester); 1434 (C=C); 1229;
1102; 1050 (CꢀO ester intense); 1019 (PꢀOꢀC intense). ESIꢀTOF MS m/z (%
relative abundance): 561 (M+1; 48); 583 (M+23; 15). HRMSꢀESI: calculated for
C32H34O7P 561.2042; found 561.2020.
Synthesis of diethyl (1,4-dimethyl-7-oxo-3,5,6- triphenylbicyclo[2,2,1]hept-
5-en-2-yl) phosphonate 3eβ
A solution of 2,5ꢀ dimethylꢀ3,4ꢀdiphenylcyclopentadienone 1e (0.2 g; 0.76
mmol) in 10 mL bromobenzene was added to diethyl 2ꢀEꢀphenyl
vinylphosphonate 2β (0.24 g; 1 mmol) in 10 mL bromobenzene. The mixture
was refluxed for 96 h. The solvent was removed under vacuum and the residue

Page 15 of 27
was chromatographied on silica gel column using (AcOEt/cyclohexane 20%) as
eluent to give a yellow viscous liquid (0.271 g; yield: 67%).
15
12
CH3
14
16
O
P
8
O
O
7
10
3
4
13
17
9
1
CO
18
6
22
11
19
20
5
CH3
25
23
21
3eβ
24
1
NMR 31P (162 MHz) δ 28.5. NMR H (400 MHz) δ 7.10ꢀ6.98 (m, 9H,
H15,16,19,20,24,25); 7.25ꢀ7.15 (m, 6H, H14,18,23); 3.97ꢀ3.75 (m, 3H, H8,8,9); 3.63ꢀ3.53
(m, 1H, H9); 3.31 (dd, 1H, H6, 3JHP= 21.9 Hz; 3JH6ꢀH7=7.6 Hz); 2.42 (dd, 1H, H7,
3
3
2JHP=18.0 Hz, JH7ꢀH6=7.4 Hz); 1.52 (s, 3H, H12); 1.00 (t, 1H, H10, JH10ꢀH8=6.9
Hz); 0.86 (t, 3H, H11, 3JH11ꢀH9=6.9 Hz); 0.79 (s, 3H, H21). NMR 13C (100 MHz) δ
3
3
204.6 (d, C1, JCP=20.7 Hz); 143.6 (C4); 142.0 (d, C3, JCP=4.7 Hz); 140.2 (d,
3
C22, JCP=3.7 Hz); 134.6 (C13); 134.0 (C17); 130.4 (C14); 129.6 (C18); 128.7
(C15); 128.1 (C19,23); 127.5; (C24); 127.4 (C25); 127.3 (C16); 127.1 (C20);
2
2
61.9 (d, C8, JCP=5.8 Hz); 61.8 (d, C9, JCP=6.2 Hz); 56.4 (d, C5, 3JCP=4.7 Hz);
2
1
54.8 (d, C2, JCP=2.6 Hz); 51.1 (d, C6, 2JCP=0.8 Hz); 48.4 (d, C7, JCP=152.0
3
3
Hz); 16.1 (d, C10, JCP=6.2 Hz); 15.8 (d, C11, JCP=6.4 Hz); 12.4 (C12); 10.1
(C21). IR νmax (neat/cmꢀ1): 2983 (CꢀH); 1770 (C=O); 1443 (C=C); 1240;
1102; 1048 (CꢀO ester intense); 1021 (PꢀOꢀC intense). ESIꢀTOF MS m/z (%
relative abundance): 501 (M+1; 100); 523 (M+23; 90).
Diels-Alder reactions of tetraphenylcyclopentadienone 1a with tetraethyl
vinylidenebisphosphonate 2γ
A solution of tetracyclone 1a (0.14 g; 0.37 mmol) in 10 mL bromobenzene was
added to tetraethyl vinylidenebisphosphonate 2γ (0.11g; 0.37 mmol) in 10 mL
bromobenzene. The mixture was refluxed for 96 h. The solvent was distilled
under vacuum and the residue was crystallized in a brown solid m=0.13 g (92
%).
8
7
6
12
5
2
3
11
9
4
10

Page 16 of 27
1
IR νmax (neat/cmꢀ1): 3055 (CꢀH); 1691; 1598; 1441 (C=C). NMR H (400
MHz) δ 7.54 (s, 2H, H4); 7.22ꢀ7.12 (m, 10H, H7,10,12); 6.97ꢀ6.93 (m, 6H,
H8,11); 6.85ꢀ6.82 (m, 4H, H6). NMR 13C (100 MHz) δ 141.9 (C5); 140.9 (C3);
140.4 (C2); 139.9(C9); 131.6 (C6); 129.9 (C10); 129.4 (C4); 127.5 (C7); 126.9
(C11); 126.2 (C12); 125.6 (C8).
Diels-Alder
reactions
of
phencyclone
1b
with
tetraethyl
vinylidenebisphosphonate 2γ.
A solution of phencyclone 1b (0.38 g; 1 mmol) in 5 mL bromobenzene was
added to tetraethyl vinylidenebisphosphonate 2γ (0.20 g; 1.5 mmol) in 5 mL
bromobenzene. The mixture was refluxed for 96 h. The solvent was distilled
under vacuum to give a residue which was crystallized in methanol, as colorless
crystals (0.18 g, 46%). mp= 204°C which turned out to be the phenanthreneꢀ
9,10ꢀdiylbisphenylcarbonyle.
3
4
O O
2
5
1
6
7
8
9
12
11
10
HRMSꢀESI calculated for C28H19O2 387.1385, found 387.1371.
The filtrate after evaporation of solvent gave a viscous liquid (< 3%). The
constitution was assigned on the basis of mass spectrum analysis to be a
bisphosphonated compound which structure may be:
O
O
O
P
O
P
O
O
4bγ
31
NMR P (162 MHz) δ 21.3. ESIꢀTOF MS m/z (% relative abundance): 655
(M+1, 27).
Results and discussion

Page 17 of 27
We have studied the DielsꢀAlder reaction of diethyl vinylphosphonate 2α,
diethyl 2ꢀstyrylphosphonate 2β and tetraethyl vinylideneꢀbisꢀphosphonate 2γ
with the stable tetrasubstituted cyclopentadienones 1a-f.
Scheme 2. Formation of various cyclic phosphonated compounds 3, 4, 5 from
reaction of tetrasubstituted cyclopentadienones with phosphonated olefins.
The DielsꢀAlder reaction of vinylphosphonates with dienes were described in
particulary for the vinylphosphonates bearing an other electronꢀwithdrawing
groups (CN, COR, COOR…).15 Likewise, tetraalkyl vinylideneꢀ1,1ꢀbisꢀ
phosphonates are also known to react as dienophiles with electron rich diene
systems, but are generally less reactive in cycloadditions probably due to their
steric hindrance.16
In DielsꢀAlder reaction of vinylphosphonates with cyclopentadienones, several
phosphonated products could be generated, such as carbonylated 3,
decarbonylated 4 or aromatic compounds 5 (Scheme 2). The control of the
reaction depends on the reaction temperature, compounds of general structure 3
can be generally isolated through a simple heating. If the temperature is
increased however, compound 3 is converted in compound 4, and eventually in
compound 5 if heating is prolonged under oxidative conditions.
In preliminary experiments, we have used refluxing toluene (110°C), but the
kinetics were oftentimes too slow, thus turning towards the use of
bromobenzene (bp 156°C) as solvent. We have also tested nitrobenzene (bp
210°C) as solvent because its oxidant properties could facilitate the

Page 18 of 27
aromatization step, but it led to many byꢀproducts. Additionally, in some cases,
an extended heating under argon has led to elimination of the phosphonate
group. All isolated products were fully identified using IR, proton, carbon and
phosphorus NMR spectroscopies (especially HMBC and HSQC experiments),
as well as mass spectrometry.
a) Reactions with diethyl vinylphosphonate 2α
The main results of vinylphosphonate 2α with cyclopentadienones 1a-f are
summarized in the Table 1.
Table 1: Cycloadducts synthesis from cyclopentadienones 1a-f and vinyl
phosphonate 2α in refluxing bromobenzene.
Entry Cyclone T(°C) Time (h)
Products
3aα
Yield (%)
Ratio
1
2
3
4
5
6
110
156
156
156
156
156
24
24
24
24
24
24
48*
41
32
89
81
74
1a
1b
1c
1d
1e
1f
3bα
5cα
4dα
45:55**
60:40**
3eα+4eα
4fα1+4fα2
* Reaction was carried out in toluene as solvent. ** determinated by 1H NMR.
When a solution containing tetracyclone 1a and a slight excess of diethyl
vinylphosphonate 2α in bromobenzene was stirred at reflux for 24 hours, the
1,2,3,4ꢀtetraphenylbenzene was obtained as the sole product in a low 34% yield
accompanied by insoluble materials, suggesting that the temperature was too
high. Our suspicions were partly confirmed when refluxing toluene for 38 hours

Page 19 of 27
was used (110°C) instead of bromobenzene (156°C), thus obtaining the 2,3,4,5ꢀ
tetraphenylcyclohexaꢀ2,4ꢀdienylphosphonate 3aα in a 48% yield (Scheme 3).
Ph
Ph
O
Ph
Ph
Ph
P(OEt)2
Ph
Ph
Ph-Br
156°C
O
Ph
Ph
P(OEt)2
Ph
+
Ph
Ph
4aα not isolated
Isolated in 34% yield
O
Toluene
110°C
Ph
O
1a
2α
Ph
Ph
P(OEt)2
O
Ph
3aα Isolated in 48% yield
Scheme 3. Reaction of tetracyclone 1a with diethyl vinylphosphonate 2α in
bromobenzene and toluene.
The structure of 3aα was assigned mainly on the basis of the 13C NMR
spectrum, in which the bridged carbon is at 199.7 ppm. The IR spectrum showed
also a characteristic carbonyl band at 1778 cmꢀ1 suggesting the presence of a
bridged carbonyl group.
The DielsꢀAlder cycloadditions of vinylphosphonate were carried out in
refluxing bromobenzene as solvent for the next reactions. When phencyclone 1b
was refluxed with diethyl vinylphosphonate 2α in bromobenzene, the deep
blackꢀ green color associated with 1b gradually faded to a pale yellow solution
providing the carbonylated bridge product (41%). Likewise, the structure of
13
3bα was mainly determined by C NMR (200.1 ppm) and IR spectrum (1780
cmꢀ1).
In the same conditions, acecyclone 1c reacted with diethyl vinylphosphonate 2α
giving the corresponding aromatic decarbonylated cycloadduct 5cα (32%).
Probably, the fusion of acenaphthylene ring to the bicyclo[2.2.1]ꢀheptenꢀ7ꢀone

Page 20 of 27
system causes a considerable increase in strain energy derived from distortion of
the external angle, thus inducing fast decarbonylation.
When reacting with diethyl vinylphosphonate 2α, cyclopentadienone 1d
produced the decarbonylated cycloadduct 4dα as the sole product in 89% yield,
whereas the cyclone 1e led to a mixture of carbonylated and decarbonylated
products 3eα and 4eα respectively, in 81% overall yield. It is noteworthy that
mass spectrum showed the presence of the corresponding aromatic 5eα whereas
it is not visible in NMR. The conditions of ESIꢀTOF promote probably the
aromatization step during the analysis.
Cyclopentadienone 1f gave a mixture of regioisomers 4fα1 and 4fα2 in a 60/40
ratio, with no carbonylated product however.
The literature reports the DielsꢀAlder reaction of vinylphosphonate with dienes
as being catalyzed by Lewis acids (BF3, GaCl3),17 yet attempts to use boron
trifluoride (hard Lewis acid) or bismuth trichloride (soft Lewis acid) as catalyst
in cycloaddition of vinyl phosphonate 2α with cyclopentadienones 1a or 1d
were unsuccessful, no increase of yield was observed.
1a
1b
1c
1d
1e
1f

Page 21 of 27
3aα
3bα
5cα
4dα
3eα + 4eα
4fα1 + 4fα2
b) Reaction with diethyl 2-E-styrylphosphonate 2β
To our knowledge, the DielsꢀAlder reaction of diethyl 2ꢀEꢀstyrylphosphonate 2β
has never been reported. Only few styrylphosphonates bearing a carbonyl group
have been described.18
The DielsꢀAlder reaction of diethyl 2ꢀEꢀstyrylphosphonate 2β with
cyclopentadienones 1a and 1d afforded, besides some unreacted starting
material, the decarbonylated cycloadducts 4aβ and 4dβ in 31% and 72%
respectively (Table 2). On the other hand, the cyclopentadienone 1e gave the
carbonylated compound 3eβ.

Page 22 of 27
Table 2. Cycloadducts synthesis from cyclopentadienones 1a, 1d and 1e with
vinyl phosphonate 2β in refluxing bromobenzene.
Entry Cyclone T(°C) Time (h)
Products
4aβ
Yield (%)
1
2
3
4
156
156
156
156
24
24
24
24
31
72
67
0
1a
1d
1e
1f
4dβ
3eβ
*: ratio assigned on the basis of NMR analysis
Me
O
O
O
O
Ph
Ph
P(OEt)2
Ph
O
Ph
Ph
P(OEt)2
Ph
Ph
O
Ph
Me
4aβ
4dβ
3eβ
Finally, cyclopentadienone 1f failed to add to diethyl 2ꢀEꢀphenylꢀ
vinylphosphonate 2β, even after extended heating time (6 days) in
bromobenzene.
Cycloaddition of phencyclone 1b with a small excess of diethyl Eꢀ
styrylphosphonate 2β in the same conditions afforded the corresponding bridge
carbonylated cycloadduct 3bβ in only trace, along with the diketonic compound
phenanthreneꢀ9,10ꢀdiylbisphenylcarbonyle 70% (Scheme 4) resulting from an
oxidation process of phencyclone by air.
Scheme 4. Reaction of phencyclone 1b with diethyl 2ꢀEꢀstyrylphosphonate 2β
in refluxing bromobenzene.

Page 23 of 27
O O
Ph
Ph
O
Ph
Ph
O
Ph
Ph
P(OEt)2
P(OEt)2
PhBr, ꢀ
O
+
+
O
Ph
43 h
Ph
2β
1b
3bβ
trace
70 %
Interestingly, the reaction of acecyclone 1c in the same conditions provided a
different compound that turned out to be a lactone instead, after mass spectrum
identification (Scheme 5). Dilthey et al.19 have already described this oxidation
reaction with phencyclone 1b and acecyclone 1c in 1938, but it is only recently
that a mechanism of oxidation was postuled.20 Under argon atmosphere starting
products were recovered.
Scheme 5. Aerobic oxidation of 1c in extended heating in bromobenzene.
1c
c) Tetraethyl vinylidene-1,1-bisphosphonate 2γ.
The DielsꢀAlder cycloaddition of the tetraethyl vinylideneꢀ1,1ꢀbisphosphonate
2γ has been tested with the cyclopentadienones 1a-c in the same conditions as
previously described. Thus, heating of 2γ with tetraphenylcyclopentadienone 1a
in refluxing bromobenzene for 96 hours furnished a brown solid. Unfortunately,
31P NMR spectra displayed no signal at all, while suggesting after further
investigation the formation of the 1,2,3,4ꢀtetraphenylbenzene.
On the other hand, the DielsꢀAlder reaction of phencyclone 1b with an excess of
vinylideneꢀbisꢀphosphonate 2γ upon heating in bromobenzene during 96 hours
led to the formation of a colorless solid which turned out to be the phenanthreneꢀ

Page 24 of 27
9,10ꢀdiylbisphenylcarbonyle, resulting from oxidation process of phencyclone
by air (Scheme 6). However, next to this solid, the analysis of the filtrate by 31P
NMR showed a new phosphorus signal at 21.3 ppm different from the
31
corresponding one in vinylideneꢀbisꢀphosphonate (δ P =13.1 ppm). Further
analysis showed the formation of the diphosphonated compound 4bγ in poor
yield (3 %).
Scheme 6. Reaction of phencyclone 1b with tetraethylvinylidenebisphosphonate
2γ in refluxing bromobenzene.
O
O O
Ph
Ph
O
O
P(OEt)2
P(OEt)2
O
Ph
Ph
PhBr, ꢀ
(EtO)2P
P(OEt)2
O
+
+
Ph
Ph
1b
2γ
4bγ
trace
46 %
Conclusion
The reactions of the cyclopentadienones with unsaturated phosphonates have
never been described. New polycyclic phosphonate compounds were obtained
from cyclopentadienones 1a-f with vinyl and styryl phosphonates 2α and 2β
using thermal DielsꢀAlder reaction. Cycloadditions of tetraethyl
vinylidenebisphosphonate 2γ with cyclopentadienones 1a-c were generally
unsuccessful with poor yield, but opened the field for further investigation.
Thanks to the phosphonate group, the new polycyclic molecules might used for
surface modification,21 immobilization of catalysts, for metal cation
coordination22 or for electronic or photovoltaic applications.23
Acknowledgments

Page 25 of 27
We gratefully acknowledge the CNRS (National Center for Scientific Research),
the "Region Basse Normandie”, the AlgerianꢀFrench cooperation for a BAF
(Bourse AlgéroꢀFrançaise) grant for Benmeddah Amel. The authors
acknowledge the financial support of the french Agence Nationale de la
Recherche (ANR), through the program “Investissements d’Avenir”
(ANRꢀ10ꢀLABXꢀ09ꢀ01), LabEx EMC3 for the project Helios (photovoltaic
application). Also the authors thanks Mrs. Karine Jarsalé for ESIMS and
HRMS analysis.
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