Aryl-2,3-oxaphosphabicyclo[2.2.2]octene derivatives - The precursors of oxoarylphosphine oxides (aryl metaphosphonates)

Article abstract of DOI:10.1016/j.tet.2004.01.069

The Baeyer-Villiger oxidation of 7-phosphanorbornene 7-oxides with sterically demanding substituents on the phosphorus atom (4a-d) by m-chloroperbenzoic acid afforded the title products (5a-d) as a mixture of two regioisomers (A and B). Isomer A, the resu

Full text of DOI:10.1016/j.tet.2004.01.069

Tetrahedron 60 (2004) 2789–2797
Aryl-2,3-oxaphosphabicyclo[2.2.2]octene derivatives—the
precursors of oxoarylphosphine oxides (aryl metaphosphonates)
b
a
c
d
Stefan Jankowski,a Gyorgy Keglevich, Tomasz Nonas, Henrietta Forintos, Marek Głowka
,
,
*
*
´
¨
e,@
´
and Juliusz Rudzinski
aDepartment of Chemistry, Institute of Organic Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
bDepartment of Organic Chemical Technology, Budapest University of Technology and Economics, 1521 Budapest, Hungary
cResearch Group of the Hungarian Academy of Sciences at the Department of Organic Chemical Technology,
Budapest University of Technology and Economics, 1521 Budapest, Hungary
dDepartment of Chemistry, Institute of General and Ecological Chemistry, Technical University of Lodz, Zeromskiego 116,
90-924 Lodz, Poland
eDepartment of Chemistry, Institute of Applied Radiation Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
Received 24 October 2003; revised 18 December 2003; accepted 22 January 2004
We would like to dedicate our paper in memory of Late Professor William E. McEven, distinguished chemist and founder editor of Heteroatom Chemistry
Abstract—The Baeyer–Villiger oxidation of 7-phosphanorbornene 7-oxides with sterically demanding substituents on the phosphorus atom
(4a–d) by m-chloroperbenzoic acid afforded the title products (5a–d) as a mixture of two regioisomers (A and B). Isomer A, the result of
thermodynamic control, was stable, while isomer B, the product of kinetic control, underwent decomposition and/or epoxidation. Single
crystal X-ray analysis of P-(2,4,6-triisopropylphenyl) oxaphosphabicyclooctene (5Ac) was not only useful in the evaluation of its structure,
but, for the first time in the literature, a low-coordinated arylmetaphosphonate (15c) formed by fragmentation on X-ray irradiation could also
be detected. The precursors (5Aa-c) were utilized in the thermoinduced and UV light-mediated fragmentation-related phosphorylations of
alcohols. Beside the well-known elimination-addition mechanism via the metaphosphonate intermediate (15), a novel addition-elimination
route involving a species with a pentavalent pentacoordinated phosphorus atom (16) was also substantiated.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
diphosphene Ar-PvP-Ar (Ar¼2,4,6-tBu3C6H2–) led to a
polymer that was presumably (Ar-PO2)n.6 The meta-
phosphonate Ar-PO2 was formed as an intermediate during
the flash vacuum pyrolysis of a cyclic phosphonite.
Subsequent insertion of the PO2 moiety into the neighboring
methyl group led to a stable cyclic phosphinic acid.7 N-t-
Butyl-P-(2,4,6-tri-t-butylphenyl)phosphonamidic acid was
reported to be an unstable precursor of 2,4,6-tri-t-
butylphenylmetaphosphonate.8
The first synthesis of oxophenylphosphine oxide (phenyl
metaphosphonate) Ph-PO2 and its methyl derivatives MenC6-
H5-n-PO2, (n¼1–3) in the reaction of aryl phosphonic acids
with aryl phosphonic dichloride was reported by Michaelis
over hundred years ago.1 Almost eighty years later it was
shown that the trimers of oxoarylphosphine oxides were
formed rather than monomers.2 The intermediacy of metapho-
sphonate Ph-PO2 was proposed in several reactions on the
basis of the resulting oligometaphoshonates and the trapping
products formed by reaction with the added nucleophiles,3,4 as
well as from kinetic experiments.5
Since 1985, the thermal or photochemical fragmentation of
2,3-oxaphosphabicyclo[2.2.2]octene ring systems has been
widely used as a source of metaphosphoric (RO-PO2) or
metaphosphonic (R-PO2) acid anhydride.4 The inter-
mediacy of meta(thio)phosphates Y-P(X)O (Y¼RO,
R0R0R00N; X¼O, S) in the fragmentation of oxa(thia)phos-
phabicyclooctenes was confirmed by mechanistic studies.9,10
Attempts to decrease the reactivity of phenyl meta-
phosphonate by the introduction of t-butyl groups in ortho
positions of the phenyl ring were unsuccessful. Oxidation of
In this paper, we present the synthesis of P-aryl oxa-
phosphabicyclooctenes that are the precursors of
metaphosphonates ArPO2 with sterically demanding sub-
stituents on the phosphorus atom (Ar¼2,4,6-iPr3C6H2,
2,4,6-Me3C6H2, 4-MeC6H4).
Keywords: Phosphorus heterocycles; Baeyer–Villiger reactions;
Fragmentation
Phosphonylation.
*
reactions;
Metaphosphonate;
Mechanisms;
Corresponding authors. Tel.: þ48-42-631-3152; fax: þ48-42-636-5530; ;
e-mail address: jankowsk@p.lodz.pl
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.01.069

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S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
2. Results and discussion
the 31P NMR chemical shift and coupling constant between
the carbon atom of the vinyl methyl group and the
phosphorus atom. For the regioisomer of type 5B, a
coupling of 4–4.4 Hz with phosphorus was observed,
while a value of 0–2.7 Hz was detected for regioisomers
of type 5A.12–14 From the above data it was concluded that
the isolated products of O-insertion into P-Aryl 7-PNB
system were regioisomers 5Aa-d. To prove this conclusion,
the X-ray analysis of a 5Ac crystal obtained by vapor
diffusion was carried out. A sample dissolved in dichloro-
methane was equilibrated against hexane at 10 8C for
several days. Due to the small size of the crystals obtained, a
synchrotron source had to be used for data collection.
Routine solution and refinement procedures15,16 confirmed
unambiguously the structure of the product from the
O-insertion as 5Ac (Fig. 1).
2.1. O-insertion into the 7-PNB framework
To investigate the effect of the P-substituent on the synthesis
and fragmentation of 2,3-oxaphoshabicyclo[2.2.2]octenes,
we utilized compounds 4a–c that were prepared according
to an earlier protocol (Scheme 1).11
The O-insertion realized by mCPBA led to two regioisomers
5A and 5B (Scheme 2). Additional products were observed
after a certain period of time, which depended on the
substrate. As compared to phenyl derivative 4d, the reaction
was slower when electron donating 4-methylphenyl (4a) or
bulky trialkylphenyl substituents (4b and 4c) were present
on the phosphorus atom. This is consistent with the
associative SN2(P) or addition–elimination (AE) mechan-
isms. The formation of regioisomer 5A (shifted downfield in
the 31P NMR spectrum at dP 41–37) was faster than that of
5B (dP of 35–39). The ratio of regioisomers 5A and 5B also
depended on the space requirement of the substituent and
was constant up to the time shown in Scheme 2; then it was
increasing. Simultaneously, new upfield signals at dP 20–26
appeared.
Though the geometry of 5Ac is consistent with that of
analogous derivatives17,18 and anisotropic thermal par-
ameters do not show any unusual features (Fig. 1), the R
factor remained high (R1¼0.167) and several unexpected
peaks (the highest one of 2.57 e A23 was 1.2 A from
˚
phosphorus) appeared on the final electron density map
(Fig. 2(A)). A detailed analysis of the map suggested,
however, the presence of a metaphosphonate group built of
˚
It is known from earlier work that regioisomers of type 5A
and 5B have different stability, and usually the minor
isomers were lost during the isolation procedures.12,13
However, in the case of the P-ethoxy12 and the P-mesityl-
amino14 derivatives both regioisomers were isolated and
characterized. The regioisomers could be distinguished by
the two highest differential peaks, (Q1 at 1.22 A from P1 and
˚
Q2 at 1.17 A from O2) and the original atom O3. These two
˚
new P–O distances are 1.46 A and the O–P–O angle is
1148 (Fig. 2(B)). The three atoms Q1, Q2 and O3 lie in
a plane parallel to that of P-aryl with a separation of
˚
1.2 A on the opposite side of the phosphonate group in
Scheme 1.
Scheme 2.

S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
2791
Figure 1. The view of molecular structure and selected geometric
parameters of 5Ac in solid state.
5Ac than the vinyl bridge. Hence, there is space for the
planar diene system (14) emerging after the fragmenta-
tion (Scheme 5). It explains the shift of the P-aryl
fragment, allowed by the loose packing in the crystal
(Fig. 2(A)). The distance between the neighboring 2,4,6-
˚
isopropylphenyl groups equals 6.044 A, that is the b
dimension of the unit cell.
Figure 2. Residual peaks comprising metaphosphonate 15c formed by
fragmentation of 5Ac on X-ray irradiation in the crystalline phase. (A)
Viewed parallelly to the 2,4,6-triisopropylphenyl groups and showing their
packing. (B) Viewed perpendicularly to the newly formed metapho-
sphonate moiety.
We suppose that powerful synchrotron X-rays could initiate
the extrusion of metaphosphonate. Both products were
observable in the same crystal by diffraction method due to
their moderate amounts and fairly loose packing, which
enabled the measured monocrystal to remain intact after the
fragmentation. A decomposition degree of 10–15% was
estimated from absolute electron densities of residual peaks
corresponding to new P and O positions.
To investigate this problem, 7-phosphanorbornene 11p
labeled with O-18 in the phosphoryl group was treated
with mCPBA. The product 12p contained the same amount
of heavy oxygen and its 31P NMR spectrum showed the
same 16O/18O splitting as in the substrate. This is an
additional proof that reaction of 7-phosphanorbornenes with
mCPBA follows a similar mechanism as the oxidation of
ketones (Scheme 4).20
This is the first example of metaphosphonate Ar-PO2
structure in the solid state. The X-ray structure was
determined only for a more stable sulphur analogue.19
After the substrate 4a–c was consumed, the excess of
mCPBA and its reduction product m-chlorobenzoic acid
were removed from the solution by complexation on the
surface of anhydrous potassium fluoride. Phosphorus
containing by-products were also adsorbed. We were
successful in isolating the by-product from the synthesis
of 5Ac using the preparative TLC for the reaction
mixture obtained without KF treatment. The major by-
product was probably a product of double O-insertion
13. The epoxidation of the double-bond for the
phosphabicyclooctene system by mCPBA was observed
previously by Kashman21 and for 3,4-dimethyl-1-phenyl-
phosphole oxide by Quin.22
Dithioxo(tri-tert-butylphenyl)phosphorane
Ar-PS2
(Ar¼2,4,6-tBu3C6H2 –) was obtained by reaction of
bis-(trimethylsilyl)(tri-tert-butylphenyl)phosphane with
sulfur dichloride. The CPS2 moiety was planar and
the torsion angle of the aryl group to the PS2 plane was
ca. 808.
The reaction of 7-phosphanorbornenes (7-PNB) with
m-chloroperbenzoic acid (mCPBA) proceeds with retention
of phosphorus configuration.13 mCPBA attacks the phos-
phorus atom with the formation of P(V) intermediates 7-1
and 7-2, possessing one of the P–C bonds in an apical,
while the other in the equatorial position (Scheme 3). The
pseudorotation places the peroxy group into the equatorial
position necessary for the migration of the P–C bond (8-1
and 8-2). According to this mechanism, the phosphoryl
oxygen should remain intact.
The steric hindrance due to the substituents in 7-PNB
system (6, Scheme 3) decreases the rate of O-insertion and
prolongs the time of exposure to mCPBA. The oxygen is

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S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
Scheme 3.
Scheme 4.
inserted easier into the P–C bond placed farther from the
vinyl methyl group, than in the other case (8-2 vs. 8-1). The
epoxidation of the double-bond is facilitated when the vinyl
methyl group and the phosphorus atom are on the same side
(9-2 vs. 9-1). The standard ab initio LCAO-SCF calcu-
lations23 (STO-2G and STO-4G) evidenced that the
unsymmetrical transition state is energetically favorable in
the reaction of peroxy acids with olefins–the peroxyacid
oxygen attacks one of the vinyl carbons.24 Thus, the steric
effect of the substituents at phosphorus is responsible for
the kinetic control of the O-insertion and the consecutive
epoxidation of the double bond.
(Scheme 5). Reaction with methanol is much faster than that
with tert-butyl alcohol. For the thermal or photochemical
fragmentation of 2,3-oxaphosphabicyclo[2.2.2]octene
derivatives, a pure retrocycloaddition process was postu-
lated.9,10 The sensitivity to steric effects suggests the
mixture of EA and SN(2)P (or AE) mechanisms, as for
the EA mechanism no significant effect of the alcohol on the
rate should be observed.25 The pure SN(2)P or AE
mechanism can also be excluded, as the phosphonylation
of the sterically hindered and low nucleophilic tert-butyl
alcohol evidences the intermediacy of 14a–c.26 The
participation of SN2(P) or AE is reduced by the increase
of steric hindrance of the reactants, or even eliminated in the
case of reaction of 5Ac with tert-butyl alcohol. The
participation of 15c was additionally proved by the result
of the reaction with menthol or with a mixture of alcohols.
When menthol was used, the (1:1) mixture of diastereo-
isomers of 20c was found in the reaction mixture after the
methylation of menthol phosphonate (17, R¼menthyl) with
diazomethane. The lack of stereoselectivity evidences the
presence of planar 3-coordinated intermediate.27 Com-
petition experiment with different alcohols was also
performed in order to check the selectivity. We found
that 5Ac reacts three times faster with methanol than with
tert-butyl alcohol in toluene at 110 8C. A somewhat lower
selectivity (2.1) was observed for the reaction of Et-P(S)O
with ethanol and tert-butyl alcohol in chloroform.9 The
2.2. Fragmentation reaction of 2,3-oxaphospha-
bicyclo[2.2.2]octenes 5A in the presence of alcohols
The fragmentation of 2,3-oxaphosphabicyclo[2.2.2]octenes
can be achieved by thermolysis or photolysis.4 The
thermolysis of compounds 5Aa-c in toluene at 110 8C in
the presence of methanol or tert-butyl alcohol or irradiation
at 254 nm in 1,2-dichloroethane in the presence of an
alcohol, followed by reaction with diazomethane led to
the corresponding phosphonates 18a–c and 19a–c, respec-
tively (Scheme 5).
The necessary time for the consumption of the substrate
increases with the steric hindrance of the P-aryl substituent

S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
2793
Scheme 5.
systematic kinetic studies to establish the ratio of EA and
SN2(P) or AE mechanisms will be continued.
gel (0.063–0.2 mm) (Fluka). Eluents: CHCl3 and CHCl3/
MeOH (95/5). Melting point was determined using Boetius
apparatus. Alcohols (Aldrich, Fluka, P. O. Ch. Poland) were
dried over CaH2. L-Menthol (Fluka, pure) was used without
additional purification. Chloroform and dichloromethane (P.
O. Ch., Poland, analytical grade) were dried over P2O5. KF
(Bruxelles-r.c.b. 85078 Belgium) was dried in a dryer at 100–
110 8C. Diazomethane in ethyl ether was generated from
Diazald (Aldrich) directly before use. Water with 79.3%
enrichment of 18O was supplied by Techsnabeksport (USSR).
3. Experimental
3.1. General
NMR spectra were recorded on Bruker Avance DPX 250
spectrometer at 250.13 MHz (1H), 101.20 MHz (31P) and
62.86 MHz (13C) in CDCl3, using tetramethylsilane as
internal and 85% H3PO4 as external standard. Chemical
shifts (d) are indicated in ppm and coupling constants (J) in
Hz. FAB/MS were recorded on a APO Electron (Ukraine)
model MI 12001E mass spectrometer equipped with a FAB
ion source (3-nitrobenzyl alcohol matrix). HRMS spectra
were recorded on a Finnigan MAT 95 (Finnigan MAT
GmbH, Germany) mass spectrometer. Column chromato-
graphy was performed with glass column packed with silica
3.2. 7-Phosphanorbornenes 4a–c and 11
Compounds 4a–d and 11 were prepared following literature
procedures.11,22
3.2.1. 2-Methyl-7-oxo-9-phenyl-7-p-tolyl-9-aza-7-phos-
phabicyclo[5.2.1.02,6]dec-2-ene-8,10-dione (4a). Colorless

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S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
solid, mp 230–232 8C (ethyl acetate); nmax (CCl4) 1704,
1496, 1392, 1192, 1136, 784 cm21; dP (101.3 MHz, CDCl3)
84.2; dH (250.1 MHz, CDCl3) 7.42–7.58 (5H, m, Ph),
7.26–7.29 (2H, m, HAr), 7.12–7.16 (2H, m, HAr), 5.86 (1H,
ddq, J¼11.2 Hz, C3H), 4.15 (2H, bd, J¼1.8 Hz, C5H, C6H),
3.72–3.80 (m, 1H, C4H), 3.57–3.63 (1H, m, C1H), 2.40
the 31P NMR spectra were complex (4a: d (rel. int.)¼36.6
(54), 34.8 (27), 21.2 (9), 12.8 (3), 12.4 (7); 4b: 40.5 (29),
24.6 (65), 23.7 (6); 4c: 40.3 (16), 27.3 (23), 26.2 (14), 23.1
(6), 21.6 (3), 18.9 (6), 14.5 (27), 22.4 (5). Then KF
(202 mg, 3.5 mmol) was added and the mixture was stirred
for 3 h at room temp. The suspension was filtered off (Celite
500) and the solvent evaporated. The crude product was
subjected to column chromatography (CHCl3/MeOH) and
then crystallized from AcOEt to give analytically pure
product in about 15–20% yield.
0
(3H, s, C4 CH3), 1.81 (3H, dd, J¼1.56 Hz, C2CH3); dC
(125.7 MHz, CDCl3) 174.4 (d, J¼13.4 Hz), 174.1 (d,
J¼13.0 Hz), 142.1, 139.8 (d, J¼10.3 Hz), 130.7, 128.5 (d,
J¼11.3 Hz), 128.2, 127.8, 125.5, 121.9 (d, J¼97.0 Hz),
121.4 (d, J¼7.9 Hz), 45.9 (d, J¼64.1 Hz), 44.0 (d,
J¼13.3 Hz), 42.8 (d, J¼11.5 Hz), 42.8 (d, J¼64.7 Hz),
20.6, 18.3; m/z (FAB/NBA) 378 (100, MHþ), 286 (11), 240
(22); HRMS (FAB/NBA): MHþ, found 378.1254.
C22H21NO3P requires 378.1259.
The reaction of 4d with mCPBA was carried out in an NMR
tube (10 mg of substrate) and monitored by 31P NMR to
examine the kinetics of O-insertion only, without isolation
of the product. Attempts to isolate the by-products of
O-insertion by column chromatography were unsuccessful.
However, when preparative TLC chromatography (2 mm
silica gel plates, Merck) was applied to the reaction mixture
after the synthesis of 5Ac, the component at RF¼0.88
(chloroform/methanol 5% as an eluent) was extracted with
acetone to give 13; dP (101.3 MHz, CDCl3) 21.1; HRMS
(ESI): MHþ, found 521.2326. C30H36NO5P requires
521.2322.
3.2.2. 2-Methyl-7-oxo-9-phenyl-7-(2,4,6-trimethyl-
phenyl)-9-aza-7-phosphabicyclo[5.2.1.02,6]dec-2-ene-
8,10-dione (4b). Colorless solid, mp 246–248 8C (ethyl
acetate); nmax (CCl4) 2960, 1712, 1596, 1496, 1448, 1380,
1184, 1040, 880, 660; dP (101.3 MHz, CDCl3) 84.2; dH
(250.1 MHz, CDCl3) 7.45–7.38 (3H, m, HAr), 7.15–7.11
(m, 2H, HAr), 6.88 (2H, d, HAr), 5.85 (ddtq, 1H, J¼10.4, 3.1,
1.6 Hz, C3H), 4.11–4.15 (2H, bd, J¼1.7 Hz, C5H, C6H),
3.94–4.02 (1H, m, C4H), 3.83–3.90 (1H, m, C1H), 2.61
3.3.1. 5-Methyl-8-(4-methylphenyl)-2-phenyl-3a,4,7,7a-
tetrahydro-1H-4,7-(epoxyphosphano)isoindole-1,3-
dione 8-oxide (5Aa). Thick oil; dP (101.3 MHz, CDCl3)
35.2; nmax (neat) 2984, 1716, 1648, 1496, 1448, 1400, 1208,
1144, 792 cm21; dH (250.1 MHz, CDCl3) 7.56–7.43 (5H,
m, Ph) 7.31–7.26 (2H, m, HAr), 7.17–7.13 (2H, m, HAr),
5.95–5.85 (1H, m, C5H), 5.36 (1H, ddd, J¼21.9, 4.2,
2.0 Hz, C4H), 4.18 (1H, dt, J¼7.5, 4.2 Hz, C8H), 4.02 (1H,
dt, J¼7.5, 2.6 Hz, C7H), 3.67 (1H, dt, J¼7.5, 7.3, 2.6 Hz,
0
0
0
(3H, s, C6 CH3), 2.51 (3H, s, C4 CH3), 2.28 (3H, s, C2 CH3),
1.72 (3H, t, J¼1.6 Hz, C2CH3); dC (62.9 MHz, CDCl3) 18.2,
20.1, 21.9 (d, J¼6.4 Hz), 22.2 (d, J¼4.7 Hz), 42.3 (d,
J¼13.8 Hz), 43.7 (d, J¼15.4 Hz), 46.3 (d, J¼63.2 Hz), 48.8
(d, J¼62.9 Hz), 119.6 (d, J¼9.4 Hz), 122.0 (d, J¼94.6 Hz),
125.0, 125.5, 128.0, 128.2, 130.7, 139.6 (d, J¼8.9 Hz),
140.1 (d, J¼9.4 Hz), 140.2 (d, J¼11.5 Hz), 140.7 (d,
J¼2.2 Hz), 174.5 (d, J¼14.0 Hz), 174.7 (d, J¼15.9 Hz);
m/z (FAB/NBA) 406 (100, MHþ), 167 (86, ArPOH); HRMS
(FAB/NBA): MHþ, found 406.1561. C24H25NO3P requires
406.1572.
0
C1H), 2.42 (3H, s, C4 CH3), 1.99 (3H, dd, J¼5.2, 1.75 Hz
C6CH3); dC (62.9 MHz, CDCl3) 175.6 (d, J¼15.1 Hz),
173.0, 143.9, 142.0 (d, J¼10.7 Hz), 132.7 (d, J¼10.7 Hz),
131.3, 129.2, 129.0, 126.1, 125.4 (d, J¼90.0 Hz), 123.5 (d,
J¼8.2 Hz), 76.7 (d, J¼9.4 Hz), 46.1 (d, J¼12.0 Hz), 36.5
(d, J¼79.6 Hz), 36.8 (d, J¼6.8 Hz), 21.6, 19.8 (d,
J¼2.5 Hz); m/z (FAB/NBA) 394 (30, MH]þ), 240 (75,
[MH2ArPO2]þ,), 154 (15); HRMS (FAB/NBA): MHþ,
found 394.1214. C22H21NO4P requires 394.1208.
3.2.3. 2-Methyl-7-oxo-9-phenyl-7-phenyl-9-aza-7-phos-
phabicyclo[5.2.1.02,6]dec-2-ene-8,10-dione (4d). Colorless
solid, mp 239–241 8C (ethyl acetate); dP (101.3 MHz,
CDCl3); nmax (KBr) 1776, 1712, 1496, 1384, 1200, 752,
704 cm21; dH (250.1 MHz, CDCl3) 7.76–7.55 (3H, m,
HAr), 7.55–7.40 (5H, m, Ph), 7.22–7.13 (2H, m, HAr), 5.89
(1H, dddq, J¼11.3, 5.0, 1.8, 1.7 Hz, C3H), 4.20 (2H, ddd,
J¼2.3, 1.7, 04 Hz, C5H, C6H), 3.88–3.80 (1H, m, C4H),
3.70–3.64 (1H, m, C1H), 1.84 (t, 3H, J¼1.8 Hz, C2CH3), dC
(62.9 MHz, CDCl3) 175.2, (d, J¼13.8 Hz), 175.0 (d,
J¼13.6 Hz), 140.9; 140.7, 132.4 (d, J¼2.8 Hz), 131.4 (d,
J¼8.7 Hz), 129.2, 128.9, 128.3 (d, J¼11.8 Hz), 126.5 (d,
J¼91.4 Hz), 126.4, 122.4 (d, J¼8.8 Hz), 46.8 (d,
J¼64.0 Hz), 44.9 (d, J¼14.2 Hz), 43.6 (d, J¼64.2 Hz),
43.7 (d, J¼12.6 Hz), 19.3 (d, J¼3.3 Hz); HRMS (FAB/
NBA): MHþ, found 364.1086. C21H19NPO3 requires
364.1103.
3.3.2. 8-Mesityl-5-methyl-2-phenyl-3a,4,7,7a-tetra-
hydro-1H-4,7-(epoxyphosphano) isoindole-1,3-dione
8-oxide (5Ab). Thick oil; dP (101.3 MHz, CDCl3) 38.97;
nmax (neat) 2976, 1716, 1604, 1380, 1188, 984, 760 cm21
;
dH (250.1 MHz CDCl3) 7.47–7.42 (3H, m, HAr), 7.16–7.12
0
0
(2H, m, HAr), 6.88 (2H, d, J¼5.0 Hz, C3 H, C5 H), 5.85–
5.70 (1H, m, C5H), 5.31 (1H, ddd, J¼20.1, 4.0, 2.0 Hz,
C4H), 4.15 (1H, dt, J¼7.9, 4.0 Hz, C8H), 3.97 (1H, dt,
J¼2.5, 7.9 Hz, C7H), 3.94 (1H, dt, J¼7.5, 2.5 Hz, C1H),
0
0
0
2.58 (6H, s, C2 CH3, C6 CH3), 2.28 (3H, s, C4 CH3), 1.90
(3H, dd, J¼5.15, 1.75 Hz, C6CH3); m/z (FAB/NBA) 422
(60, MHþ), 240 (57, [MH2ArPO2]þ,), 154 (100), 136 (82);
HRMS (FAB/NBA): MHþ, found 422.1514. C24H25NO4P
requires 422.1521.
3.3. Synthesis of 2,3-oxaphosphabicyclo[2.2.2]octenes
(5Aa-c)
A solution of 0.20 mmol of 7-phosphanorbornene derivative
4a–c in dry CHCl3 (1 mL) was added to a solution of
mCPBA/15% mCBA (202 mg, 1.02 mmol) in dry CHCl3
(4 mL). The solution was stirred at room temperature and
monitored by 31P NMR. After the completion of reaction,
3.3.3. 6-Methyl-2-phenyl-9-(2,4,6-triisopropylphenyl)-
3a,4,7,7a-tetrahydro-1H-4,7 (phosphanomethano)iso-
indole-1,3-dione 9-oxide (5Ac). Colorless solid, mp 162–
164 8C; dP (101.3 MHz CDCl3) 39.0; nmax (KBr) 2960,
1712, 1396, 1212, 1184, 1128, 984 cm21; dH (250.1 MHz,

S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
2795
CDCl3) 7.39–7.35 (3H, m, HAr); 7.09–7.05 (2H, m, HAr),
0
When 5Ac was irradiated in the presence of tert-butyl
alcohol, the product of phosphonylation could not be
detected.
0
7.00 (2H, d, J¼5.0 Hz, C3 H, C5 H), 5.70 (1H, dddd,
J¼7.50, 7.25, 2.0, 1.50 Hz, C5H), 5.21 (1H, ddd, J¼22.0,
3
4.50, 2.00 Hz, C4H), 1.17 (d, 12H, JHH¼6.75 Hz,
0
0
(CH3)2CH–C2 , (CH3)2CH–C6 ), 4.07 (1H, ddd, J¼8.25,
7.25, 4.5 Hz, C8H), 3.94 (1H, dt, J¼2.5, 8.25 Hz, C7H), 3.80
(1H, dt, J¼7.25, 2.5 Hz, C1H), 3.62 (2H, ht, J¼6.75 Hz,
3.5.1. Dimethyl 4-methylphenylphosphonate (18a). Thick
oil; dP (101.3 MHz, CDCl3) 22.7; nmax (neat, NaCl) 2952,
1248, 1188, 1032 cm21; dH (250.1 MHz, CDCl3) 2.41 (s,
3
0
0
(CH3)2CHC2 , CH3)2CHC6 ), 2.80 (1H, ht, J¼6.5 Hz,
3H, CH3–C4’), 3.75 (d, 6H, JHP¼11.0 Hz, CH3O), 7.26–
0
(CH3)2CHC4 ), 1.78 (3H, dd, J¼6.75, 1.50 Hz, CH3C6),
7.31 (m, 4H, Ar);); dC (62.9 MHz, CDCl3) 132.0 (d,
J¼10.3 Hz), 129.3 (d, J¼15.1 Hz), 129.2, 124.3 (d,
J¼94.4 Hz), 52.6 (d, J¼5.4 Hz), 21.7; m/z (FAB/NBA)
201 (MHþ, 100), 91 (24), 77 (20); HRMS (EI): Mþ, found
200.0595. C9H13O3P requires 200.0602.
0
1.19 (6H, d, 6.5, (CH3)2CHC4 ), dC (62.9 MHz, CDCl3)
176.0 (d, J¼15.1 Hz), 173.2, 152.9, 152.6 (d, J¼12.6 Hz),
141.4 (d, J¼11.7 Hz), 131.4, 129.3, 129.0, 126.2, 125.5 (d,
93.7 Hz), 122.8 (d, J¼8.2 Hz), 76.1 (d, J¼10.1 Hz), 46.3 (d,
J¼10.2 Hz), 38.9 (d, J¼77.9 Hz), 36.7 (d, J¼5.2 Hz), 34.3,
31.6 (d, J¼4.2 Hz), 26.6, 24.9 (d, J¼25.4 Hz), 20.0; m/z
(FAB/NBA) 506 (22, MHþ), 240 (22, [MH2ArPO2]þ), 154
(100), 136 (71); HRMS (FAB/NBA): MHþ, found
506.2466. C30H37NO4P requires 506.2460.
3.5.2. tert-Butyl methyl 4-methylphenylphosphonate
(19a). Thick oil; dP (101.3 MHz, CDCl3) 16.8; nmax (neat,
NaCl) 2952, 1192, 1128, 1048 cm21; dH (250.1 MHz,
0
CDCl3) 1.51 (s, 9H, (CH3)3–C), 2.40 (s, 3H, CH3–C4 ),
3.65 (d, 3H, 3JHP¼10.0 Hz, CH3O), 7.23–7.28 (m, 4H, Ar);
dC (62.9 MHz, CDCl3) 131.6 (d, J¼10.1 Hz), 129.2, 129.0
(d, J¼15.1 Hz), 124.4 (d, J¼95.0 Hz), 83.2, 52.0, (d,
J¼5.4 Hz), 30.4 (d, J¼3.8 Hz), 21.7; m/z (FAB/NBA)
243 (5, MHþ), 187 ([100), 173 (13), 91 (11), 57 (17);
HRMS (EI): Mþ, found 242.1077.C12H19O3P requires
242.1072.
3.3.4. 5-Methyl-8-phenyl-2-phenyl-3a,4,7,7a-tetrahydro-
1H-4,7-(epoxyphosphano)isoindole-1,3-dione 8-oxide
(5Ad). Colorless solid, mp 132–134 8C; dP (101.3 MHz,
CDCl3) 34.7; nmax (CCl4) 2928, 1712, 1388, 1232, 1192,
984, 936, 784 cm21; dH (250.1 MHz, CDCl3) 7.75–7.46
(8H, m, HAr) 7.17–7.13 (2H, m, HAr), 5.95–5.84 (1H, m,
C5H), 5.37 (1H, ddd, J¼21.3, 4.3, 2.0 Hz, C4H), 4.18 (1H,
dd, J¼7.3, 4.3 Hz, C8H), 4.02 (1H, dt, J¼7.3, 2.5 Hz, C7H),
4.02 (1H, dt, J¼7.3, 7.3, 2.5 Hz, C1H), 2.00 (3H, dd, J¼5.0,
1.75 Hz, C6CH3); dC (62.9 MHz, CDCl3) 175.5 (d, J¼
15.6 Hz), 173.0, 142.1 (d, J¼10.6 Hz), 133.1 (d, J¼2.5 Hz),
132.7 (d, J¼9.4 Hz), 131.3, 129.3, 128.6 (d, J¼10.9 Hz),
126.1, 123.5 (d, J¼7.9 Hz), 46.2 (d, J¼11.3 Hz), 36.8 (d,
J¼6.9 Hz), 36.5 (d, J¼80.5 Hz), 19.8 (d, J¼2.8 Hz); m/z
(FAB/NBA) 380 (30, MHþ), 240 (40, [MH-ArPO2]þ), 154
(75), 137 (90), 109 (100); HRMS (FAB/NBA): MHþ, found
380. 1044, C21H19NO4P requires 380. 1052.
3.5.3. Dimethyl mesitylphosphonate (18b). Thick oil; dP
(101.3 MHz, CDCl3) 23.9; nmax (neat, NaCl) 2952, 1232,
1208, 1184, 1032 cm21; dH (250.1 MHz, CDCl3) 2.27 (s,
0
0
3H, CH3–C4 ), 2.58 (s, 6H, CH3–C2 , CH3–C6 ), 3.73 (d,
0
3
4
6H, JHP¼11.5 Hz, CH3O), 6.91 (d, 2H, JHP¼5.0 Hz,
0
0
H–C3 , H–C5 ); dC (62.9 MHz, CDCl3) 142.2, 129.2 (d,
J¼10.7 Hz), 130.4 (d, J¼16.4 Hz), 120.9 (d, J¼98.4 Hz)
51.7 (d, J¼5.0 Hz), 23.0; m/z (FAB/NBA) 229 (100, MHþ),
197 (8), 119 (18), 91 (15), 77 (14); HRMS (EI): Mþ, found
228.0919.C11H17O3P requires 228.0915.
3.4. Thermolysis of bicyclooctenes 5Aa-c
3.5.4. tert-Butyl methyl mesitylphosphonate (19b). Thick
oil; dP (101.3 MHz, CDCl3) 17.7; nmax (film, NaCl) 2976,
1256, 1212, 1168, 1040 cm21; dH (250.1 MHz, CDCl3) 1.49
A solution (1 mL) of 5Aa-c (0.02 mmol) and an alcohol
(2 mmol) in dry toluene were placed into 5 mm NMR tube
and sealed under argon. Sample was placed in thermostat at
110 8C and the reaction was monitored by 31P NMR. When
the signal of substrate diminished the solvent was
evaporated and the excess of diazomethane in diethyl
ether was added. The solution was again evaporated to
dryness and phosphonate methyl esters 15 were purified by
column chromatography (CHCl3) with 90% yield.
(s, 9H, (CH3)3–C), 2.34 (s, 3H, CH3–C40), 2.59 (s, 6H,
3
0
0
CH3–C2 , CH3–C6 ), 3.62 (d, 3H, JHP¼11.5, CH3O), 6.89
4
0
0
(d, 2H, JHP¼4.5, H–C3 , H–C5 ); dC (62.9 MHz, CDCl3)
142.0, 130.4 (d, J¼15.7 Hz), 129.2 (d, J¼9.4 Hz); 120.6 (d,
J¼97.0 Hz), 77.2 (d, J¼1.8 Hz), 22.7, 21.1; m/z (FAB/
NBA) 271 (5, MHþ), 215 (100), 197 (10), 119 (9); HRMS
(EI): Mþ, found 270.1389.C14H23O3P requires 270.1385.
3.5.5. Dimethyl 2,4,6-triisopropylphenylphosphonate
(18c). Thick oil; dP (101.3 MHz, CDCl3) 24.3; nmax (film,
NaCl) 2960, 1240, 1212, 1188, 1024 cm21; dH (250.1 MHz,
3.5. Photolysis of bicyclooctenes 5Aa-c
3
A solution (1 mL) of 5Aa-c (0.02 mmol) and an alcohol
(2 mmol) in dry 1,2-dichloroethane in 5 mm quartz NMR
tube was placed in the centre of Rayonet reactor fitted with 8
low-pressure mercury lamps (253.7 nm). The reaction was
monitored by 31P NMR. After the completion of reaction the
same protocol as in case of thermolytic reaction was
applied. The reaction of 5Aa and 5Ab with alcohols
proceeded quantitatively and the corresponding methyl
esters 17a and 17b obtained after treatment with diazo-
methane were isolated in about 90% yield. In case of
reaction of 5Ac with methanol the yield was only 29% and
by-products were observed at 53.7, 36.3 and 35.0 ppm.
CDCl3) 1.24 (d, 12H, JH–H4¼5.50 Hz), 1.26 (d, 6H,
3
3JH–H¼5.75 Hz), 2.83 (ht, 1H, JH–H¼5.75 Hz), 3.75 (d,
3
3
6H, JHP¼11.26 Hz), 4.11 (ht, 2H, JH–H¼5.50 Hz), 7.14
4
(d, 2Har, JHar–P¼5.28 Hz); dC (62.9 MHz, CDCl3) 152.8,
155.2 (d, J¼13.8 Hz), 121.6 (d, J¼15.7 Hz), 52.0 (d,
J¼5.6 Hz), 34.3, 30.5 (d, J¼2.5 Hz), 24.9, 23.6; HRMS
(CI, isobutane): MHþ, found 313.1925. C17H30O3P requires
313.1933.
3.5.6. tert-Butyl methyl 2,4,6-triisopropylphenyl-
phosphonate (19c). Thick oil; dP (101.3 MHz, CDCl3)
18.4; nmax (film, NaCl) 2960, 1256, 1240, 1168, 1044 cm21
;

2796
S. Jankowski et al. / Tetrahedron 60 (2004) 2789–2797
3
dH (250.1 MHz, CDCl3) 1.22 (d, 12H, JH–H¼6.75 Hz),
Authors are thankful to Dr. Zdzislaw Wawrzak for X-ray
data collection at the DuPont-Northwestern-Dow
Collaborative Access Team (DND-CAT) Synchrotron
Research Center located at Sector 5 of the Advanced
Photon Source. DND-CAT is supported by the E. I. DuPont
de Nemours and Co., the Dow Chemical Company, the U.S.
National Science Foundation through Grant DMR-9304725
and the State of Illinois through the Department of
Commerce and the Board of Higher Education Grant
IBHE HECA NWU 96. Use of the Advanced Photon
Source was also supported by the U. S. Department of
Energy, Basic Energy Sciences, Office of Energy Research
under Contract No. W-31-102-Eng-38.
3
1.25 (d, 6H, JH–H¼6.75 Hz), 1.56 (s, 9H), 2.88 (ht, 1H,
3JH–H¼6.75 Hz), 3.64 (d, 3H, JH–P¼11.51 Hz), 4.24 (ht,
3
3
4
2H, JH–H¼6.75 Hz), 7.10 (d, 2Har, JH–P¼5.00 Hz);); dC
(62.9 MHz, CDCl3) 151.9, 151.5 (d, J¼13.8 Hz), 122.4 (d,
J¼15.7 Hz), 77.2 (d, J¼1.8 Hz), 51.5 (d, J¼5.7 Hz), 34.3,
30.5 (d, J¼3.8 Hz), 30.1, 25.1; HRMS (CI, isobutane):
MHþ, found 355.2399. C20H35O3P requires 355.2402.
3.6. Synthesis of 12p labeled with O-18
The solution of 11 (30 mg, 0.0796 mmol) and H128O (15 mg,
0.85 mmol) in dry acetonitrile was sealed in glass ampule
under argon and kept at 100 8C for 45 h. Then the solution
was evaporated to dryness under reduced pressure
(0.5 mm Hg), dissolved in CHCl3 and filtered through the
silica gel layer. 31P NMR spectrum showed broad
resonances of 11 at 77.86 ppm and of 11p at 77.82 ppm.
The 18O shift of 0.04 ppm is characteristic for the P¼O
group.28 The isotopic ratios [Mþþ3]/[Mþþ3] were deter-
mined by FAB/MS analysis and equal to 1.982^0.020 and
0.049^0.002 for 11p and 11, respectively. mCPBA (27 mg,
0.135 mmol) was added to the solution of 11p (17 mg,
0.045 mmol) in chloroform (1 mL) and left with stirring for
3 h. Then KF (27 mg) was added and stirring was continued
for next 90 min. After filtration and solvent evaporation the
residue was crystallized from ethyl acetate. Yield of 12p:
10 mg (0.025 mmol) (55.6%). The product showed a pair of
well resolved peaks at 34.66 and 34.62 (1:1.9) and mass
spectrometric analysis gave the isotopic ratios 1.987^0.022
and 0.048^0.005 for 12p and 12, respectively.
References and notes
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3.7. Crystal data of 5Ac
9. Jankowski, S.; Quin, L. D. J. Am. Chem. Soc. 1991, 113,
7011–7017.
Colorless prisms. Crystal size 0.10£0.05£0.03 mm,
´
10. Jankowski, S.; Rudzinski, J. Heteroatom Chem. 1996, 7,
369–374.
˚
C30H36NO4P, M¼505.57, monoclinic, a¼42.105(8) A,
˚
˚
˚
b¼6.044(1) A, c¼20.930(4) A, a¼g¼908, b¼93.36(3)8,
¨
¨
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109–116.
3
V¼5317.17 A , T¼100 K, space group C2/c, Z¼8, m¼
0.14 mm21, l¼0.7 A, D(cal)¼1.263 Mg/m , F(000)¼2160,
3
˚
R1¼0.167, for 4442 observed, wR2¼0.559 for all 4594
reflections. Diffraction data were collected on the 5-ID
beam line of the DND-CAT at the Advanced Photon Source,
Argonne, IL, using a MARCCD detector.
12. Quin, L. D.; Bodalski, R.; Jankowski, S.; Quin, G. S.;
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J. Org. Chem. 1986, 51, 3341–3347.
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre as supplementary
publication number CCDC-226060. Copies of the data can
be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK [fax:þ44(0)-1223-
336033 or e-mail: deposit@ccdc.cam.ac.uk].
14. Quin, L. D.; Bourdieu, C.; Quin, G. S. Phosphorus, Sulfur
Silicon 1991, 63, 349–362.
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¨
Solution; University of Gotingen, Germany, 1997.
16. Sheldrick, G. M. SHELXL: Program for Refinement of Crystal
¨
Structures; University of Gotingen, Germany, 1997.
´
17. Bodalski, R.; Jankowski, S.; Głowka, M. L.; Filipiak, T. J. Org.
Chem. 1994, 59, 5173–5178.
18. Cambridge Structure Database System, ver. 5.24; 2002. Allen,
F. H. Acta Crystallogr. 2002, B58, 380–388.
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This work was carried out within the Scientific and
Technological Cooperation between the Republic of
Hungary and the Republic of Poland (Project Pl-1/2001)
and supported in part by Polish Ministry of Scientific
Research and Information Technology (No 4 T09A 117 24)
and by the Hungarian Scientific Research fund (No T
042479).
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ˇ
ˇ
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