Cycloaddition reactions of 1-alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta- 2,4-dienes

Article abstract of DOI:10.1002/ejoc.200801181

1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-dienes 1, obtained by alkylation of sodium 1,2-diphospha-3,4,5-triphenylcyclopentadienide, exhibit dual reactivity in cycloaddition reactions: as dienes (with maleic anhydride and maleimide) or as dienop

Full text of DOI:10.1002/ejoc.200801181

FULL PAPER
DOI: 10.1002/ejoc.200801181
Cycloaddition Reactions of 1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-
2,4-dienes
Vasili Miluykov,*[a] Ilya Bezkishko,[a] Almaz Zagidullin,[a] Oleg Sinyashin,[a]
Peter Lönnecke,[b] and Evamarie Hey-Hawkins[b]
Keywords: Cycloaddition / Phosphacyclopentadienes / Phosphorus heterocycles / Phosphorus
1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-dienes
1, obtained by alkylation of sodium 1,2-diphospha-3,4,5-tri-
phenylcyclopentadienide, exhibit dual reactivity in cyclo-
addition reactions: as dienes (with maleic anhydride and ma-
leimide) or as dienophiles (with 2,3-dimethylbutadiene).
Thermolysis of 1 occurs with a [1,5] sigmatropic shift to form
a [2+2] cyclodimerization product.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
More reactive are 2H-phospholes containing a reactive
P=C bond formed as a result of a [1,5] sigmatropic
shift.[9,20] For example, 2H-phospholes undergo a [4+2]
cyclodimerization reaction at low temperatures with the for-
mation of endo dimers,[21] which on heating rearrange to
exo isomers.[22] The 2H-phospholes exhibit dual reactivity
in cycloaddition reactions: as powerful dienes towards car-
bon–carbon double or triple bonds or C=O double
bonds[23] and as dienophiles towards conjugated dienes.[24]
However, 2H-phosphole still remains unknown, but can be
stabilized by bulky substituents at the carbon atoms,[25] by
complexation with transition metals[26] or by inclusion in
an aromatic fragment.[27]
Introduction
Cycloaddition reactions of phosphacyclopentadienes
(phospholes) are of significant interest for the preparation
of phosphanorbornenes and phosphanorbornadienes,
which can be employed as weak, bulky ligands in asymmet-
ric Heck reactions,[1] asymmetric hydrogenation,[2] enantio-
selective C- and N-alkylation,[3] and in the rhodium-cata-
lyzed hydroformylation of olefins.[4,5] The thermolysis of
phosphanorbornadienes or their transition-metal com-
plexes is a common method for the generation of phos-
phanylidene species and the synthesis of phosphirenes and
phosphiranes.[6–8]
It has been stated that the diene system of trivalent phos-
pholes is only poorly reactive due to delocalization within
the ring, which diminishes the availability of the four π elec-
trons.[9,10] Thus, head-to-tail [2+2] cyclodimerization of
1,2,5-triphenylphosphole has been observed under UV irra-
diation.[11] Moreover, [2+2] and [4+2] cyclodimerization of
arylphospholes can be realized in the coordination sphere
of transition metals (Cr, Mo, W).[12] The [4+2] cycload-
dition reactions of 1H-phospholes (e.g., 1,2,5-triphenyl- or
1,2,3,4,5-pentaphenylphosphole) with maleic anhydride
proceed at elevated temperatures with low yields (3–
11%).[13,14] Improved yields of the cycloaddition products
were achieved by using N-methyl(aryl)maleimide[15–17] or
fumaronitrile[18] as the dienophile or in the coordination
sphere of transition-metal complexes.[19]
We now report on our investigations of the cycloaddition
reactions of 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes 1,
which represent both 1H- and 2H-phospholes in one mole-
cule.
Results and Discussion
1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-
dienes 1 are readily available by alkylation of sodium 3,4,5-
triphenyl-1,2-diphosphacyclopentadienide with alkyl bro-
mides [Equation (1)].
(1)
[a] A. E. Arbuzov Institute of Organic and Physical Chemistry,
Russian Academy of Sciences,
Arbuzov Str. 8, 420088 Kazan, Russia
Fax: +7-843-273-22-53
E-mail: miluykov@iopc.knc.ru
[b] Institut für Anorganische Chemie, Universität Leipzig,
Johannissallee, 29, 04103 Leipzig, Germany
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
The structures of diphospholes 1 were unambiguously
confirmed by NMR spectroscopy: the 31P NMR spectra of
1 showed two doublets in the range of 70 and 200 ppm,
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V. Miluykov et al.
FULL PAPER
characteristic of sp3- and sp2-hybridized phosphorus atoms, mer formed by weak hydrogen bonds between the NH and
1
with large JPP coupling constants of around 400 Hz.
CO groups of the maleimide fragment of different enantio-
The 1-alkyl-1,2-diphospholes 1 react with maleimide or mers (Figure 2).
maleic anhydride on heating in toluene to give the cycload-
dition products 2 or 3 with high regio- and stereoselectivity
[Equation (2)]. The 31P NMR spectra of the reaction mix-
tures show only two doublets in the range of 85 and
–25 ppm.
(2)
Figure 2. Molecular structure of anti-endo-(PSPRCRCRCS/
PRPSCSCSCR)-10-(2-methylpropyl)-7,8,9-triphenyl-4-aza-1,10-di-
phosphatricyclo[5.2.1.02,6]deca-8-ene-3,5-dione (3b). Hydrogen
atoms of the phenyl and alkyl groups have been omitted for clarity.
Selected bond lengths [Å] and angles [°]: P1–P2 2.1862(5), P1–C3
1.847(1), P1–C4 1.881(1), P2–C26 1.846(1), P2–C1 1.903(1), C3–
P1–C4 92.93(6), C3–P1–P2 86.27(5), C4–P1–P2 91.94(5), C26–P2–
C1 105.38(6), C26–P2–P1 104.35(5), C1–P2–P1 85.16(4).
A crystal structure analysis of 2b showed that only the
endo isomer was obtained with the alkyl group in an anti
orientation to the double bond of the ring. Compound 2b
crystallizes with three independent molecules in the asym-
metric unit that exhibit similar molecular geometry; there-
fore, only one molecule is discussed here (Figure 1, see also
the Supporting Information). Each phosphorus atom has a
typical pyramidal environment. The inner angle at the
bridging phosphorus atom (P2) is very acute (C1–P2–P1
84.87°). For the two carbon atoms of the double bond (C2
and C3), little pyramidalization[28] is observed with ψ =
8.21 and 9.41°, respectively.
1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-
dienes 1 exhibit dual reactivity and can also act as dieno-
philes. Thus, diphospholes 1 react with 2,3-dimethylbutadi-
ene at room temperature over 12 h or on heating in toluene
over 1 h to give 9-alkyl-3,4-dimethyl-6,7,8-triphenyl-1,9-di-
phosphabicyclo[4.3.0]nona-3,7-dienes
[Equation (3)].
4 in high yields
(3)
The structures of compounds 4 were confirmed by NMR
spectroscopy. In the 31P NMR spectra two doublets are ob-
1
served at around +3 and –3 ppm with JPP ≈ 210 Hz. The
13C NMR spectra exhibit a signal corresponding to C6 as
1
2
a doublet of doublets with JCP = 24 and JCP = 3.7 Hz
at around 67 ppm, characteristic of sp3-hybridized carbon
atoms.
Surprisingly, the 1-alkyl-1,2-diphospholes 1 are extremely
stable; no cyclodimerization was observed on heating in tol-
uene or in xylene. Only when decalin was used as the sol-
vent was the cycloaddition product 5 obtained, albeit to-
gether with decomposition products [Equation (4)].
The 31P NMR spectrum of 5 (Figure 3) shows the coup-
Figure 1. ORTEP view of anti-endo-(PSPRCRCRCS)-10-(2-meth-
ylpropyl)-7,8,9-triphenyl-4-oxa-1,10-diphosphatricyclo[5.2.1.02,6]-
deca-8-ene-3,5-dione (2b). Hydrogen atoms other than H4 and H7
have been omitted for clarity. Selected bond lengths [Å] and angles
[°]: P1–C3 1.848(3), P1–C4 1.880(3), P1–P2 2.197(1), P2–C26
1.846(2), P2–C1 1.903(3), C3–P1–C4 93.2(1), C3–P1–P2 86.73(8),
C4–P1–P2 90.46(9), C26–P2–C1 101.0(1), C26–P2–P1 107.05(9),
C1–P2–P1 84.87(8).
The formation of only one diastereomer was clearly ob- ling pattern with 20 lines of an AAЈBBЈ system, characteris-
served for maleimide derivative 3b, which consists of a di- tic of products from [2+2] cycloaddition reactions of 1,2-
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Cycloaddition Reactions 1,2-Diphosphacyclopenta-2,4-dienes
(4)
CrysAlisPro[33] and the program SCALE3 ABSPACK[34] for empir-
ical absorption correction. The structures were solved by direct
methods and all non-hydrogen atoms were refined with
SHELX97.[35] With the exception of H4 and H7 (first molecule),
H33 and H36 (second molecule), and H62 and H65 (third mole-
cule) of 2b all hydrogen atoms were calculated at idealized posi-
tions, whereas for 3b the hydrogen atoms were only calculated for
disordered regions (Table 1). The diagrams of the structures were
generated with ORTEP[36] and DIAMOND-3.[37]
diphospholes[29] formed by a [1,5] shift of alkyl groups.[22]
The chemical shifts and coupling constants were obtained
by simulation of the experimental spectrum.[30]
CCDC-704769 (for 2b) and -704770 (for 3b) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Figure 3. Experimental (bottom) and simulated (top) 31P NMR
spectra of 5.
1-Ethyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-diene (1a):
A
solution of bromoethane (0.80 g, 7.34 mmol, 20% excess) in THF
(10 mL) was added to a solution of sodium 3,4,5-triphenyl-1,2-di-
phosphacyclopentadienide (3.81 g, 6.16 mmol) in THF (40 mL) at
–80 °C and then stirred for 12 h at room temp. Then the solvent
was evaporated under reduced pressure and the residue was ex-
tracted with n-hexane (2ϫ30 mL). The n-hexane extract was evap-
orated in vacuo to leave 1.30 g (59%) of 1-ethyl-3,4,5-triphenyl-1,2-
Conclusions
We have demonstrated that 1-alkyl-3,4,5-triphenyl-1,2-di-
phosphacylopenta-2,4-dienes 1 can act both as dienes and
dienophiles in cycloaddition reactions, similar to 2H-phos-
pholes. However, in contrast to 2H-phospholes the cyclodi-
merization reactions of 1 occur only under harsh reaction
conditions to give a [2+2] cycloaddition product.
1
diphosphacyclopenta-2,4-diene (1a); m.p. 57 °C. H NMR (C6D6):
3
3
δ = 0.94 (dt, JHH = 7.34, JHP = 14.5 Hz, 3 H, Me), 2.13 (m, 2 H,
3
3
CH2), 6.96 (t, JHH = 6.4 Hz, 4 H, Ph), 7.00 (d, JHH = 4.9 Hz, 4
3
3
H, Ph), 7.03 (d, JHH = 5.9 Hz, 2 H, Ph), 7.07 (d, JHH = 7.3 Hz,
2 H, Ph), 7.23 (d, 3JHH = 5.4 Hz, 1 H, Ph), 7.31 (t, JHH = 8.3 Hz,
3
1 H, Ph), 7.34 (d, 3JHH = 7.3 Hz, 1 H, Ph) ppm. 31P NMR (C6D6):
Experimental Section
1
1
δ = 209.5 (d, JPP = 408.9 Hz), 73.1 (d, JPP = 408.9 Hz) ppm. 13C
2
1
General: All reactions and manipulations were carried out under
dry pure N2 in a standard Schlenk apparatus. All solvents were
distilled from sodium/benzophenone and stored under nitrogen be-
fore use. The NMR spectra were recorded with a Bruker MSL-
400 spectrometer (1H: 400 MHz; 31P: 161.7 MHz; 13C: 100.6 MHz).
SiMe4 was used as the internal reference for 1H and 13C NMR
chemical shifts, and 85% H3PO4 as the external reference for 31P
NMR spectroscopy. Sodium 3,4,5-triphenyl-1,2-diphosphacyclo-
pentadienide was obtained according to the literature pro-
cedure.[31,32] Bromoethane, 1-bromo-2-methylpropane, maleic acid
anhydride, maleimide, and 2,3-dimethylbutadiene were purchased
from Aldrich and used without additional purification.
NMR (C6D6): δ = 13.98 (d, JCP = 2.9 Hz, Me), 17.87 (dd, JCP
=
16.1, 2JCP = 5.8 Hz, CH2), 126.37 (s, p-Ph), 126.52 (s, p-Ph), 126.88
(s, p-Ph), 127.52 (s, m-Ph), 128.03 (s, m-Ph), 128.26 (s, m-Ph),
2
3
3
128.65 (dd, JCP = 11.17, JCP = 2.5 Hz, o-Ph), 129.23 (d, JCP
9.3 Hz, o-Ph), 131.38 (t, JCP = 9.1 Hz, o-Ph), 137.34 (d, JCP
5.4 Hz, ipso-Ph), 138.33 (dd, JCP = 10.3, JCP = 4.1 Hz, ipso-Ph),
142.89 (d, JCP = 19.0 Hz, ipso-Ph), 150.28 (pseudo t, JCP
=
=
2
2
2
2
2
2
=
1
2
15.1 Hz, Cring), 164.14 (dd, JCP = 10.8, JCP = 4.6 Hz, Cring),
1
2
191.90 (dd, JCP = 56.9, JCP = 14.3 Hz, Cring) ppm. C23H20P2
(358.36): calcd. C 77.09, H 5.63, P 17.29; found C 76.89, H 5.22,
P 17.89.
1-(2-Methylpropyl)-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-
diene (1b): In a similar manner 1b was obtained from sodium 3,4,5-
triphenyl-1,2-diphosphacyclopentadienide (4.12 g, 6.66 mmol) and
1-bromo-2-methylpropane (1.09 g, 7.95 mmol, 20 % excess) as a
X-ray Analyses: The X-ray data were collected with an Xcalibur-S
diffractometer (Oxford Diffraction) using Mo-Kα radiation (λ =
71.073 pm) with ω and φ scans. Data reduction was performed with
Eur. J. Org. Chem. 2009, 1269–1274
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V. Miluykov et al.
FULL PAPER
Table 1. Crystallographic data for 2b and 3b.
Compound
2b
3b
Empirical formula
Formula weight
Crystal size [mm]
Temperature [K]
Wavelength, λ [pm]
Crystal system
Space group
a [pm]
C29H26O3P2·CHCl3
504.33
0.1ϫ0.1ϫ0.1
130(2)
71.073
monoclinic
P21/n
1788.39(3)
2196.73(3)
1938.03(3)
93.391(1)
7.6004(2)
12
C29H27NO2P2
483.46
0.3ϫ0.2ϫ0.2
130(2)
71.073
monoclinic
P21/n
1021.80(2)
967.46(2)
2550.24(5)
92.044(2)
2.51944(9)
4
b [pm]
c [pm]
β [°]
V [nm3]
Z
ρcalcd. [Mgm–3]
Absorption coefficient [mm–1]
F(000)
1.322
0.254
3164
1.275
0.199
1016
θ range for data collection [°]
Index ranges
2.51–26.37
–22ՅhՅ22
–27ՅkՅ27
–24ՅlՅ24
127657
15528 [R(int) = 0.1251]
6/973
2.64–30.51
–14ՅhՅ14
–13ՅkՅ13
–36ՅlՅ36
49195
7679 [R(int) = 0.0525]
0/396
0.959
R1 = 0.0430
wR2 = 0.0878
R1 = 0.0760, wR2 = 0.0955
0.462 and –0.259
Reflections collected
Independent reflections
Restraints/parameters
Goodness of fit on F2
Final R indices
0.856
R1 = 0.0501
wR2 = 0.0705
R1 = 0.1263, wR2 = 0.0830
0.492 and –0.520
[IϾ2σ(I)]
R indices (all data)
Largest diff. peak and hole [eÅ]–3
1
1
light-yellow oil; yield 1.37 g (55%). H NMR (C6D6): δ = 0.84 (d,
129.73 (s, o-Ph), 130.39 (s, o-Ph), 136.83 (d, JCP = 5.8 Hz, ipso-
3JHH = 6.9 Hz, 6 H), 1.48 (m, 1 H, CH), 1.74 (m, 2 H, CH2), 6.7– Ph), 137.78 (s, ipso-Ph), 138.13 (d, 2JCP = 21.1 Hz, ipso-Ph), 140.91
7.2 (m, 15 H, Ph) ppm. 31P NMR (C6D6): δ = 207.5 (d, JPP
=
(dd, JCP = 27.5, JCP = 18.4 Hz, C=C), 158.13 (dd, JCP = 18.0,
1
1
2
2
420.7 Hz), 62.8 (d, JPP = 420.7 Hz) ppm. 13C NMR (C6D6): δ = 2JCP = 3.9 Hz, C=C), 169.19 (s, CO), 171.55 (s, CO) ppm. IR
1
3
3
23.54 (d, JCP = 7.9 Hz, Me), 23.81 (d, JCP = 7.0 Hz, Me), 27.24
(d, JCP = 5.0 Hz), 33.57 (d, JCP = 17.0 Hz), 126.42 (s, p-Ph),
126.45 (s, p-Ph), 126.78 (s, p-Ph), 127.50 (s, m-Ph), 128.09 (s, m-
(KBr): ν = 442 (m), 494 (m), 507 (m), 544 (m), 579 (m), 621 (m),
648 (m), 697 (s), 726 (m), 740 (sh), 754 (m), 777 (m), 790 (m), 926
(s), 1029 (m), 1054 (sh), 1070 (m), 1108 (w), 1157 (w), 1210 (s),
˜
2
2
Ph), 128.24 (s, m-Ph), 128.59 (s, o-Ph), 129.24 (s, o-Ph), 130.38 (d, 1237 (m), 1380 (w), 1412 (w), 1443 (m), 1493 (m), 1576 (w), 1598
3
3JCP = 1.2 Hz, o-Ph), 137.46 (d, JCP = 6.2 Hz, ipso-Ph), 138.24
(m), 1772 (s, CO), 1850 (s, CO), 1949 (w), 2872 (m), 2928 (m), 2962
(dd, 3JCP = 10.3, 3JCP = 3.7 Hz, ipso-Ph), 142.81 (d, 3JCP = 19.4 Hz, (m), 3024 (m), 3057 (m), 3431 (m, sh) cm–1. C27H22O3P2 (456.42):
ipso-Ph), 149.17 (pseudo t, JCP = 15.5 Hz, Cring), 164.56 (dd, 3JCP
calcd. C 71.05, H 4.86, O 10.52, P 13.57; found C 71.67, H 4.77, P
13.49.
3
3
3
3
= 7.2, JCP = 3.1 Hz, Cring), 188.82 (dd, JCP = 57.1, JCP
=
14.9 Hz, Cring) ppm. C25H24P2 (386.41): calcd. C 77.71, H 6.26, P
16.03; found C 77.82, H 6.04, P 16.14.
10-(2-Methylpropyl)-7,8,9-triphenyl-4-oxa-1,10-diphosphatricyclo-
[5.2.1.02,6]deca-8-ene-3,5-dione (2b): In a similar manner 2b was ob-
tained from 1b (0.37 g, 0.96 mmol) and maleic anhydride (0.1 g,
1.02 mmol); yield 0.37 g (80%). 1H NMR (CDCl3): δ = 0.71 (d,
10-Ethyl-7,8,9-triphenyl-4-oxa-1,10-diphosphatricyclo[5.2.1.02,6]-
deca-8-ene-3,5-dione (2a): Maleic anhydride (0.13 g, 1.33 mmol)
was added to a solution of 1-ethyl-1,2-diphosphacyclopenta-2,4-
diene 1a (0.40 g, 1.22 mmol) in toluene (30 mL) and stirred for 3 h
at 100 °C. After cooling to room temp., the solution was filtered
and the filtrate was evaporated under reduced pressure to give
3
3JHH = 6.9 Hz, 3 H, Me), 0.78 (d, JHH = 6.9 Hz, 3 H, Me), 1.8
3
2
(m, 1 H, CH), 0.95 (m, 2 H, CH2), 4.40 (dd, JHH = 8.8, JHP
=
10.3 Hz, CH), 4.65 (d, 3JHH = 8.8 Hz, CH), 6.68 (d, 3JHH = 6.9 Hz,
3
3
2 H, Ph), 6.82 (t, JHH = 7.1 Hz, 3 H, Ph), 6.87 (d, JHH = 7.3 Hz,
2 H, Ph), 6.93–7.09 (m, 5 H, Ph), 7.15 (d, 3JHH = 9.3 Hz, 2 H, Ph),
7.34 (d, 3JHH = 6.9 Hz, 1 H, Ph) ppm. 31P NMR (CDCl3): δ = 78.3
1
0.46 g (82%) of 2a; m.p. 127–132 °C. H NMR (CDCl3): δ = 0.8
3
3
3
(dt, JHH = 8.0, JHP = 16.0 Hz, 3 H, Me), 1.29 (ddq, JHH = 8.0,
2JHP = 55.0, JHP = 1.3 Hz, 2 H, CH2), 4.36 (dd, JHH = 8.8, JHP
(d, JPP = 198.5 Hz), –19.8 (d, JPP = 198.5 Hz) ppm. 13C NMR
3
3
2
1
1
= 9.3 Hz, 1 H, CH), 4.65 (d, JHH = 8.8 Hz, 1 H, CH), 6.68 (d, (CDCl3): δ = 23.58 (d, 3JCP = 7.0 Hz, Me), 23.79 (d, 3JCP = 9.1 Hz,
3
3JHH = 6.9 Hz, 2 H, Ph), 6.82 (t, JHH = 7.3 Hz, 2 H, Ph), 6.87 (d,
Me), 26.72 (dd, 2JCP = 15.3, JCP = 1.7 Hz, CH2), 34.67 (d, JCP
=
3
3
1
3JHH = 6.9 Hz, 1 H, Ph), 6.99 (m, 3 H, Ph), 7.08 (m, 5 H, Ph), 7.16 37.6 Hz, CH), 49.13 (s, CH), 49.62 (d, JCP = 39.7 Hz, CH), 77.01
1
(d, 3JHH = 5.9 Hz, 1 H, Ph), 7.35 (d, 3JHH = 6.9 Hz, 1 H, Ph) ppm.
(dd, JCP = 26.3, JCP = 4.1 Hz, C-Ph), 126.81 (s, p-Ph), 127.42 (s,
p-Ph), 127.59 (s, p-Ph), 127.69 (s, m-Ph), 128.22 (s, m-Ph), 129.53
1
2
31P NMR (CDCl3): δ = 84.1 (d, JPP = 198.5 Hz), –22.6 (d, JPP
=
1
1
198.5 Hz) ppm. 13C NMR (CDCl3): δ = 10.00 (dd, JCP = 16.8, (s, m-Ph), 129.61 (s, o-Ph), 129.77 (s, o-Ph), 130.41 (s, o-Ph), 136.64
2
3JCP = 3.1 Hz, Me), 18.40 (d, JCP = 34.7 Hz, CH2), 48.96 (s, CH),
(d, JCP = 5.8 Hz, ipso-Ph), 137.79 (d, JCP = 2.1 Hz, ipso-Ph),
1
3
3
1
1
1
3
1
2
49.53 (d, JCP = 39.7 Hz, CH), 76.86 (dd, JCP = 26.5, JCP
4.1 Hz), 126.81 (s, p-Ph), 127.44 (s, p-Ph), 127.58 (s, p-Ph), 127.69 = 18.4 Hz, C=C), 157.99 (dd, JCP = 18.2, JCP = 4.1 Hz, C=C),
(s, m-Ph), 128.21 (s, m-Ph), 129.53 (s, m-Ph), 129.62 (s, o-Ph), 169.23 (s, CO), 171.53 (s, CO) ppm. IR (KBr): ν = 507 (w), 580
=
138.13 (d, JCP = 21.1 Hz, ipso-Ph), 141.48 (dd, JCP = 27.9, JCP
2
2
˜
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Eur. J. Org. Chem. 2009, 1269–1274

Cycloaddition Reactions 1,2-Diphosphacyclopenta-2,4-dienes
(w), 649 (w), 697 (s), 726 (w), 740 (m), 755 (m), 801 (s), 864 (w),
926 (s), 1025 (s), 1070 (s), 1210 (m), 1262 (s), 1367 (w), 1383 (w),
1403 (w), 1443 (m), 1462 (w), 1492 (m), 1597 (m), 1772 (s, CO),
9-Ethyl-3,4-dimethyl-6,7,8-triphenyl-1,9-diphosphabicyclo[4.3.0]-
nona-3,7-diene (4a): 2,3-Dimethylbutadiene (0.12 g, 1.46 mmol) was
added to a solution of 1a (0.52 g, 1.45 mmol) in toluene (30 mL)
1851 (s, CO), 1951 (w), 2869 (m), 2960 (s), 3024 (w), 3057 (w), 3437 and stirred for 12 h at room temp. or heated for 1 h at 100 °C. The
(br. m) cm–1. C29H26O3P2 (484.47): calcd. C 71.90, H 5.41, O 9.91,
P 12.79; found C 71.07, H 5.77, P 12.12.
solvent was evaporated under reduced pressure and the residue was
extracted with n-hexane (2 ϫ20 mL). The n-hexane extract was
evacuated in vacuo to give 0.46 g (72%) of 4a as a white powder;
10-Ethyl-7,8,9-triphenyl-4-aza-1,10-diphosphatricyclo[5.2.1.02,6]-
deca-8-ene-3,5-dione (3a): Maleimide (0.1 g, 1.03 mmol) was added
to a solution of 1a (0.36 g, 1.01 mmol) in toluene (30 mL) and
stirred for 3 h at 100 °C. The solution was filtered and the solvent
was evaporated under reduced pressure to give 0.34 g (75%) of 3a.
1
3
3
m.p. 79 °C. H NMR (CDCl3): δ = 1.05 (dt, JHH = 15.5, JHP
=
7.7 Hz, 3 H, Me), 1.28 (m, 2 H, CH2), 1.61 (s, 3 H, Me), 1.71 (m,
1 H, CH2), 1.93 (s, 3 H, Me), 2.23 (dq, 3JHP = 14.6, 3JHH = 15.5 Hz,
3
1 H), 2.44 (q, JHH = 15.5 Hz, 1 H), 2.58 (m, 1 H, CH2), 6.39 (d,
3
3JHH = 7.3 Hz, 2 H, Ph), 6.76–7.41 (m, 11 H, Ph), 7.49 (d, JHH
=
=
3
3
1H NMR (CDCl3): δ = 0.72 (dt, JHH = 7.8, JHP = 16.4 Hz, 3 H,
1
6.4 Hz, 2 H, Ph) ppm. 31P NMR (CDCl3): δ = 5.9 (d, JPP
Me), 1.32 (ddq, 3JHH = 7.8, 2JHP = 49.2, 3JHP = 1.5 Hz, 2 H, CH2),
4.24 (dd, JHH = 7.4, JHP = 11.0 Hz, 1 H, CH), 4.57 (d, JHH
210.4 Hz), –2.3 (d, JPP = 210.4 Hz) ppm. 13C NMR (CDCl3): δ =
1
3
2
3
2
3
=
11.98 (dd, JCP = 14.5, JCP = 7.4 Hz, C-1), 19.46 (pseudo t, JCP
18.2 Hz), 20.62 (s, C-6), 21.44 (d, JCP = 3.7 Hz), 29.17 (t, JCP
=
=
3
3
7.4 Hz, 1 H, CH), 6.16 (d, JHH = 9.1 Hz, 4 H, Ph), 7.15 (d, JHH
= 7.3 Hz, 4 H, Ph), 7.07 (d, 3JHH = 6.8 Hz, 4 H, Ph), 7.14 (d, 3JHH
21.3 Hz), 38.32 (s, CH2), 67.92 (dd, JCP = 24.0, JCP = 3.3 Hz),
126.16, 126.27, 126.44, 126.91, 127.79, 128.09, 128.3, 128.51,
3
= 6.2 Hz, 2 H, Ph), 7.36 (d, JHH = 6.8 Hz, 1 H, Ph), 9.02 (s, 1 H,
NH) ppm. 31P NMR (CDCl3): δ = 74.2 (d, 1JPP = 192.2 Hz), –26.1
129.83 (d, JCP = 6.6 Hz), 131.16, 138.51 (s), 139.96 (d, JCP
=
(d, JPP = 192.2 Hz) ppm. 13C NMR (CDCl3): δ = 11.12 (dd, JCP
1
2
16.5 Hz), 142.18 (d, JCP = 26.9 Hz), 145.5 (d, JCP = 21.9 Hz),
148.54 (d, JCP = 17.4 Hz), 149.80 (d, JCP = 6.2 Hz) ppm. C29H30P2
(440.50): calcd. C 79.07, H 6.86, P 14.06; found C 79.27, H 681, P
13.92.
3
1
= 15.9, JCP = 3.0 Hz, Me), 18.32 (d, JCP = 35.8 Hz, CH2), 48.71
(s, CH), 51.13 (s, CH), 74.85 (dd, JCP = 24.3, JCP = 2.8 Hz, C-
Ph), 125.89 (s, p-Ph), 126.69 (s, p-Ph), 126.79 (s, p-Ph), 127.09 (s,
1
2
m-Ph), 127.19 (s, m-Ph), 127.66 (s, m-Ph), 127.76 (s, o-Ph), 129.35
2
(s, o-Ph), 130.54 (s, o-Ph), 130.78 (s, ipso-Ph), 138.99 (d, JCP
=
3,4-Dimethyl-9-(2-methylpropyl)-6,7,8-triphenyl-1,9-diphospha-
bicyclo[4.3.0]nona-3,7-diene (4b): In a similar manner 4b was ob-
1
5.3 Hz, ipso-Ph), 139.66 (d, JCP = 20.0 Hz, ipso-Ph), 140.98 (dd,
1JCP = 27.7, JCP = 19.2 Hz, C=C), 157.97 (dd, JCP = 18.3, JCP tained from 1b (0.48 g. 1.24 mmol) and 2,3-dimethylbutadiene
2
2
2
= 4.1 Hz, C=C), 174.89 (s, CO), 177.99 (s, CO) ppm. IR (KBr): ν
= 509 (w), 539 (w), 582 (w), 633 (w), 647 (w), 674 (w), 694 (s), 738
(w), 762 (m), 787 (m), 867 (w), 937 (w), 1029 (w), 1080 (w), 1195
(0.07 g, 1.3 mmol); yield 0.46 g (79%) of 4b as a white powder; m.p.
˜
63 °C. 1H NMR (CDCl3): δ = 0.77 (dd, 3JHH = 13.9, 4JPH = 6.6 Hz,
3
6 H, Me), 1.43 (m, 1 H, CH2), 1.69 (s, 3 H, Me), 1.81 (dt, JHH
=
3
(m), 1265 (w), 1348 (m), 1388 (w), 1461 (m), 1467 (w), 1496 (w), 13.9, JHH = 5.7 Hz, 1 H, CH), 1.97 (m, 1 H, CH2), 2.05 (s, 3 H,
1579 (w), 1591 (w), 1719 (s, CO), 1777 (m, CO), 2349 (w), 2767 (m,
Me), 2.41 (m, 1 H, CH2), 2.5 (m, 2 H, CH2), 2.73 (m, 1 H, CH2),
NH), 2877 (m), 2929 (m), 2967 (m), 3045 (m), 3065 (m), 3146 (m), 6.55 (d, 3JHH = 7.3 Hz, 2 H, Ph), 6.92–7.52 (m, 11 H, Ph), 7.62 (d,
3443 (m) cm–1. C27H23NO2P2 (455.43): calcd. C 71.21, H 5.09, N
3.08, O 7.03, P 13.60; found C 71.67, H 5.22, N 3.13, P 13.44.
3JHH = 7.3 Hz, 2 H, Ph) ppm. 31P NMR (CDCl3): δ = 1.2 (d, JPP
1
1
= 211.9 Hz), –3.8 (d, JPP = 211.9 Hz) ppm. 13C NMR (CDCl3): δ
= 20.64 (s), 21.36 (d, JCP = 2.9 Hz), 23.67 (dd, JCP = 37.0, JCP
9.3 Hz), 27.69 (dd, JCP = 16.5, JCP = 4.1 Hz), 29.46 (t, JCP
=
=
10-(2-Methylpropyl)-7,8,9-triphenyl-4-aza-1,10-diphosphatricyclo-
[5.2.1.02,6]deca-8-ene-3,5-dione (3b): In a similar manner 3b was
prepared from 1b (0.42 g, 1.09 mmol) and maleimide (0.11 g,
21.3 Hz), 36.32 (dd, JCP = 19.2, JCP = 16.8 Hz), 38.32 (s), 67.74
(dd, JCP = 24.0, JCP = 3.7 Hz), 126.15 (s), 126.30 (s), 126.43 (s),
126.94 (s), 127.77 (s), 128.05 (s), 128.32 (s), 128.57 (s), 130.05 (d,
JCP = 6.6 Hz), 131.09 (s), 138.66 (s), 139.93 (d, JCP = 17.0 Hz),
142.19 (d, JCP = 27.7 Hz), 145.77 (d, JCP = 21.9 Hz), 148.59 (d,
JCP = 16.5 Hz), 149.67 (d, JCP = 7.0 Hz) ppm. C31H34P2 (468.56):
calcd. C 79.46, H 7.31, P 13.22; found C 79.12, H 7.01, P 13.87.
1
1.13 mmol); yield 0.42 g (80%) of 3b. H NMR (CDCl3): δ = 0.68
3
3
(d, JHH = 6.9 Hz, 3 H, Me), 0.76 (d, JHH = 6.9 Hz, 3 H, Me),
3
2
1.03 (m, 2 H, CH2), 1.48 (m, 1 H, CH), 4.15 (dd, JHH = 8.3, JHP
3
= 10.3 Hz, 1 H, CH), 4.36 (d, JHH = 8.3 Hz, 1 H, CH), 6.75 (d,
3JHH = 9.3 Hz, 4 H, Ph), 6.99 (d, 3JHH = 7.3 Hz, 4 H, Ph), 7.07 (d,
3JHH = 6.9 Hz, 4 H, Ph), 7.14 (d, 3JHH = 6.4 Hz, 2 H, Ph), 7.36 (d,
3JHH = 6.9 Hz, 1 H, Ph), 9.05 (s, 1 H, NH) ppm. 31P NMR
Thermolysis of 1-Ethyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-
diene (1a): A solution of 1a in decalin (30 mL) was stirred for 3 h
at 187 °C. After cooling to room temp., the solvent was evaporated
and the residue was washed with cold n-hexane to give rac-trans-
1
1
(CDCl3): δ = 74.8 (d, JPP = 195.6 Hz), –27.3 (d, JP P
=
195.6 Hz) ppm. 13C NMR (CDCl3): δ = 23.04 (d, JCP = 8.7 Hz,
3
3
2
3
Me), 23.26 (d, JCP = 8.3 Hz, Me), 25.76 (dd, JCP = 15.9, JCP
=
1
1.9 Hz, CH), 33.55 (d, JCP = 37.6 Hz, CH2), 48.69 (s, CH), 51.06 3,10-diethyl-3,4,5,8,9,10-hexaphenyl-1,2,6,7-tetraphosphatricyclo-
1
2
(s, CH), 74.80 (dd, JCP = 24.4, JCP = 2.9 Hz, C-Ph), 125.73 (s, p-
Ph), 126.51 (s, p-Ph), 126.77 (s, p-Ph), 126.98 (s, m-Ph), 127.10 (s,
[5.3.0.02,6]deca-3,9-diene (5a) as a light-yellow solid; m.p.144–
3
3
149 °C. 1H NMR (CDCl3): δ = 1.07 (dt, JHH = 7.2, JHP
=
m-Ph), 127.53 (s, m-Ph), 127.67 (s, o-Ph), 129.42 (s, o-Ph), 130.30 12.0 Hz, 6 H, Me), 2.13 (m, 4 H, CH2), 7.05–7.33 (m, 30 H,
2
(s, o-Ph), 130.64 (s, ipso-Ph), 138.29 (d, JCP = 5.4 Hz, ipso-Ph),
Ph) ppm. 31P NMR (CDCl3): AAЈBBЈ spin pattern, δA
=
1
1
2
1
1
139.32 (d, JCP = 20.7 Hz, ipso-Ph), 140.86 (dd, JCP = 27.7, JCP
= 19.0 Hz, C=C), 157.91 (dd, JCP = 18.4, JCP = 4.3 Hz, C=C),
174.78 (s, CO), 177.76 (s, CO) ppm. IR (KBr): ν = 507 (w), 543
65.08 ppm, δB = –3.08 ppm, JAB = 180.76 Hz, JBBЈ = 43.75 Hz,
2
2
1
2JABЈ = 32.41 Hz, JAAЈ = 79.65 Hz. 13C NMR (CDCl3): δ = 10.12
(d, 2JCP = 1.9 Hz, Me), 13.44 (dd, 1JCP = 13.0, 2JCP = 3.7 Hz, CH2),
˜
(w), 580 (w), 631 (w), 645 (w), 675 (w), 697 (s), 740 (w), 763 (m), 63.84 (m, 1 C), 125.34 (s, p-Ph), 127.23 (s, p-Ph), 127.88 (s, p-Ph),
790 (m), 865 (w), 940 (w), 1028 (w), 1078 (w), 1185 (m), 1261 (w), 128.55 (s, m-Ph), 129.0 (s, m-Ph), 129.25 (s, m-Ph), 129.37 (s, o-Ph),
1343 (m), 1383 (w), 1443 (m), 1462 (w), 1492 (w), 1576 (w), 1598 131.75 (s, o-Ph), 138.14 (d, JPC = 7.0 Hz, o-Ph), 139.45 (s, ipso-
2
2
(w), 1713 (s, CO), 1773 (m, CO), 1947 (w), 2346 (w), 2758 (m, NH),
Ph), 140.66 (s, ipso-Ph), 141.34 (pseudo t, JPC = 8.9 Hz, ipso-Ph),
2
1
2869 (m), 2928 (m), 2956 (m), 3028 (m), 3057 (m), 3155 (m), 3412 145.89 (pseudo t, JPC = 20.1 Hz, C=C), 152.34 (dd, JPC = 4.2,
(m) cm–1. C29H27NO2P2 (483.49): calcd. C 72.04, H 5.63, N 2.90, 1JPC = 1.2 Hz, C=C) ppm. C46H40P4 (716.7): calcd. C 77.09, H
O 6.62, P 12.81; found C 72.44, H 5.31, N 2.99, P 12.61.
5.63, P 17.28; found C 77.67, H 5.37, P 16.96.
Eur. J. Org. Chem. 2009, 1269–1274
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1273

V. Miluykov et al.
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Received: November 28, 2008
Published Online: January 28, 2009
1274
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 1269–1274