Synthesis of the spiro derivatives of 1,2-oxaphosphetes by [2+2] cycloaddition of cyclic 1-(2,4,6-triisopropylphenyl)phosphine oxides with dimethyl acetylenedicarboxylate

Article abstract of DOI:10.1016/S0040-4020(00)00401-4

Members of a new heterocyclic family, 1,2-oxaphosphetes were prepared by the unexpected [2+2] cycloaddition of the P = O group of 1-(2,4,6- triisopropylphenyl) P-heterocycles with the acetylene moiety of dimethyl acetylenedicarboxylate. The new oxaphosphe

Full text of DOI:10.1016/S0040-4020(00)00401-4

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 4823±4828
Synthesis of the Spiro Derivatives of 1,2-Oxaphosphetes by [212]
Cycloaddition of Cyclic 1-(2,4,6-Triisopropylphenyl)phosphine
Oxides with Dimethyl Acetylenedicarboxylate
²
a,
Gyorgy Keglevich, Henrietta Forintos, Gyorgy Miklos Keseru, Laszlo Hegedus and
a
b
a
*
Â
Í
Â
Â
Í
È
È
c
Â
 Í
Laszlo Toke
aDepartment of Organic Chemical Technology, Budapest University of Technology and Economics, Budapest XI Muegyetem rakpart 3,
1521 Budapest, Hungary
bDepartment of Chemical Information Technology, Budapest University of Technology and Economics,
1521 Budapest XI Muegyetem rakpart 3, 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
Received 6 March 2000; revised 25 April 2000; accepted 11 May 2000
AbstractÐMembers of a new heterocyclic family, 1,2-oxaphosphetes were prepared by the unexpected [212] cycloaddition of the PvO
group of 1-(2,4,6-triisopropylphenyl) P-heterocycles with the acetylene moiety of dimethyl acetylenedicarboxylate. The new oxaphosphetes
are spiro derivatives of the starting heterocycles and exhibit a phosphorus atom with trigonal bipyramidal geometry. PM3 semiempirical
calculations justi®ed the novel reaction path and suggested a stepwise reaction mechanism. q 2000 Elsevier Science Ltd. All rights reserved.
Introduction
dihydrophosphole oxide 3, that is the double-bond isomer
2,3-dihydro derivative 1, also led to product 2. In this case,
the double-bond in the 2,5-dihydrophosphole moiety was
isomerized to give the 2,3-dihydro hetero ring. 2,5-Dihydro-
phosphole oxides are known to undergo double-bond
rearrangement on thermolysis.6,7 Starting from the isomeric
mixture of tetrahydrophosphole oxide 4, obtained by the
catalytic hydrogenation of dihydrophosphole oxide 3
(Scheme 2), the corresponding spiro compound (5) was
also formed as a mixture of diastereomers (5-1 and 5-2).
Tetrahydrophosphole oxide 6, obtained by the hydrogena-
tion of dihydrophosphinine oxide 10, was also used as an
isomeric mixture (6-1, 6-2 and 6-3) (Scheme 3) to afford
product 7 as the mixture of diastereomers (7-1, 7-2 and 7-3).
The reaction of isomer 6-3 separated from the hydrogenated
mixture by repeated column chromatography led to a single
isomer (7-3) of product 7.
The 1,2-oxaphosphetanes are well known intermediates of
the Wittig reaction.1 No examples of the unsaturated
derivatives, oxaphosphetes have, however, been described.
In this paper, we report our surprising ®ndings on the easy
construction of the oxaphosphete ring.
Results and Discussion
Searching for new synthetic methods in P-heterocyclic
chemistry,2±5 we found that the PvO group of cyclic phos-
phine oxides with a 2,4,6-trialkylphenyl substituent on the
phosphorus atom underwent [212] cycloaddition with
dimethyl acetylenedicarboxylate (DMAD) to afford
oxaphosphete derivatives. Thus, the reaction of DMAD
with 2,3-dihydrophosphole oxide 1, tetrahydrophosphole
oxides 4 and 6, or 1,2-dihydrophosphinine oxide 8 at
1508C for 8 days furnished spiro derivatives 2, 5, 7 and 9,
respectively (Scheme 1). The similar reaction of 2,5-
The oxaphosphetes (2, 5, 7 and 9) were obtained in 71±86%
yields after column chromatography and were characterised
by 31P, 1H and 13C NMR, as well as IR data. The 13C NMR
spectral parameters were most useful in showing that the
phosphorus atom in all of the products (2, 5, 7 and 9) must
1
be in the pentavalent pentacoordinated state, i.e. four JPC
²
Â
Preliminary communication: Keglevich, Gy.; Forintos, H.; Szollosy, A.;
Í
Toke, L. Chem. Commun. 1999, 1423±1424.
Í
È
couplings were found in each case. The assignments were
con®rmed by 13C NMR spectra obtained by the Attached
Proton Test technique and, in the case of compounds 2 and
9, by two-dimensional correlation diagrams, such as HMQC
and HMBC spectra. The elemental composition of the
Keywords: p-heterocycles; cycloaddition; mechanism.
* Corresponding author. Tel.: 1361-463-1260; fax: 1361-463-3648;
e-mail: keglevich@oct.bme.hu
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00401-4

4824
G. Keglevich et al. / Tetrahedron 56 (2000) 4823±4828
Scheme 3.
processes. Being small rings, the four- and ®ve-membered
ring may bridge one apical and one equatorial position per
cycle, but the six-membered rings may also tend to prefer
the apical±equatorial position to a diequatorial bridge.
Considering backbonding, the sp2 C(5) atom of products 2
and 9 should occupy the equatorial position, while the corre-
sponding methylene moieties (C(8)H2 and C(9)H2, respec-
tively) are, accordingly, placed in the apical position. It is
noteworthy that, due to the rigid spiro ring system, the phos-
phorus atom of the oxaphosphetes (2, 5, 7 and 9) probably
resists undergoing politopical rearrangements, consequently
the products are racemates. This phenomenon will soon be
explored. Simple pentacoordinated pentavalent P-species
with ®ve different substituents do not display optical activity
due to the pseudorotations.8 Heterocyclic systems contain-
ing the oxaphosphete moiety with a spiro phosphorus atom
have not yet been published. A few examples of spiro-
phosphoranes with the oxaphosphetane ring have, however,
been described.1,9
This is the ®rst case that the PvO group of phosphine
oxides reacted with an acetylene moiety to afford the 1,2-
oxaphosphete ring. As an analogous process, Japanese
authors have recently described the interaction of azaylides
(±PvN±) with DMAD to furnish 1,2-azaphosphetes as
transient species.10 Another valuable observation in this
®eld is that the reaction of a phosphorus ylide with an
isothiocyanate afforded the ®rst example of a 1,2-thia-
phosphete.11
Scheme 1.
products (2, 5, 7 and 9) was supported by elemental analyses
and by HRMS.
In the above structures with trigonal bipyramidal geometry
at phosphorus (2, 5, 7 and 9), the oxygen atom must be in the
apical position due to its electronegativity. The sterically
demanding triisopropylphenyl substituent is preferably
placed in the equatorial position to minimise the number
of interactions with bonds at 908 during the pseudorotation
The ability of the PvO group to react with DMAD is
obviously the consequence of the presence of the electron
releasing triisopropylphenyl substituent at the phosphorus
atom, as the corresponding phenyl derivatives (10, 30, 40,
60 and 80 containing a phenyl group instead of the triiso-
propylphenyl substituent) did not enter into [212] cyclo-
addition reaction with DMAD at 1508C.
We plan to study the mechanism of the new [212] cyclo-
addition by ab initio calculations. Already the PM3 semi-
empirical calculations, particularly well suited to
computation of phosphorus containing systems,12,13 are
promising in suggesting that the oxaphosphete ring is
Scheme 2.

G. Keglevich et al. / Tetrahedron 56 (2000) 4823±4828
4825
why dihydrophosphinine oxide 8 did not react with DMAD
in a [412] (Diels±Alder) fashion in a competitive way. It is
recalled that the P-phenyl analogue (80) easily underwent
Diels±Alder cycloaddition with DMAD to afford phos-
phabicyclo[2.2.2]octadiene 12 (Scheme 4).15 The compara-
tive PM3 study on the [412] cycloaddition of dienes 8 and
80 with DMAD suggested that the P-phenyl compound (80)
is much more reactive as compared to the triisopropyl-
phenyl-derivative (8); the difference in the enthalpy of
activation is as much as 11.93 Kcal/mol in favour of 80. It
can be seen that the results of the PM3 calculations are in all
aspects in accord with the preparative observations. Still, we
wish to re®ne our results by extensive ab initio calculations.
The scope and limitations of the above type [212] cyclo-
addition giving an entry to new oxaphosphetes will also be
explored soon.
Conclusion
Figure 1. Energy pro®le in terms of heat of formation for the 81DMAD!9
transformation calculated by the PM3 method.
The unexpected [212] cycloaddition of the PvO group of
1-(2,4,6-triisopropylphenyl) P-hetereocycles with the
acetylene moiety of DMAD gives an easy access to spiro-
cyclic oxaphosphete derivatives, a completely new family
of P-heterocycles. Theoretical calculations justi®ed the
novel [212] protocol that seems to be of general value for
P-(2,4,6-trialkylphenyl) phosphine oxides.
constructed in a stepwise process through biradical inter-
mediate 11 formed in the rate-determining step from the
interaction of the phosphine oxide (1, 4, 6 and 8) and
DMAD. Species 11 may be stabilised by fast recombination.
The energy pro®le for the 8!9 transformation calculated on
the basis of the values of heat of formation (Hf) for the
starting materials (8 and DMAD), intermediate 11, product
9 and for the transient states leading to 11 and 9 is shown in
Fig. 1. It can be seen that the enthalpy of activation for the
rate-determining step is 47.24 Kcal/mol. The similar value
for the cycloaddition of the phenyl-analogue (80 containing
a phenyl group instead of the triisopropylphenyl substituent)
was found to be 59.79 Kcal/mol, suggesting that the P-tri-
isopropylphenyl compound (8) is more reactive in the [212]
cycloaddition under discussion, than the P-phenyl counter-
part (DDHfˆ12.55 Kcal/mol). A recent study of ours on
1-(triisopropylphenyl)dihydrophosphinine oxide 8 revealed
its unique properties that are the consequence of the
presence of the sterically demanding P-substituent.14
The steric bulk has a signi®cant effect on the molecular
geometry and hence on the electron distribution. The elec-
tron density, especially around the phosphorus atom, is also
affected by the presence of the three electron releasing iso-
propyl groups in the aromatic ring.14 It was also examined,
Experimental
General
1
The 31P, 13C and H NMR spectra were taken on a Bruker
DRX-500 spectrometer operating at 202.4, 125.7 and
500 MHz, respectively. Chemical shifts are down®eld rela-
tive to 85% H3PO4 or TMS. The couplings are given in
Hertz. Mass spectrometry was performed on a ZAB-2SEQ
instrument at 70 eV.
The starting P-heterocycles (3 and 8) were synthesised
according to our earlier procedures.14,16 2,3-Dihydrophos-
phole oxide 1 was obtained by the isomerisation of starting
material 3 (see below). Compounds 4 and 6 were prepared
by the catalytic hydrogenation of unsaturated derivatives 3
and 10 respectively (see below). Column chromatography
was performed on Merck Kieselgel 60 (70±230 mesh).
Composition of the fractions collected was monitored by
31P NMR and/or TLC. The oily products were kept at
408C and 0.05 mmHg for 2 h to give samples suitable for
elemental analysis.
All calculations were performed using mopac 6.017 on a SGI
R8000 workstation. Based on our good experience,16 PM3
semiempirical parametrisation12 was used for geometry
optimisations and for the location of transition states for
the [212] cycloaddition and the Diels±Alder reaction. Full
geometry optimisations have been carried out at the UHF
level. Transition states were located by the linear synchro-
nous transit method and characterised through the correct
number of negative eigenvalues of the energy second deriva-
tive matrix. Transition states having only one negative eigen-
value were ®nally subjected to frequency calculation.
Scheme 4.15

4826
G. Keglevich et al. / Tetrahedron 56 (2000) 4823±4828
152.2 (JPCˆ1.7 Hz, C4 ), 152.5 (JPCˆ10.9 Hz, C2 ); 1H
NMR (CDCl3) d 1.15 (d, Jˆ6.1 Hz, 3H, C3±CH3), 1.26
(d, Jˆ6.9 Hz, 6H, CH(CH3)2), 1.28 (d, Jˆ6.6 Hz, 6H,
CH(CH3)2), 1.31 (d, Jˆ6.6 Hz, 6H, CH(CH3)2), 2.84±2.94
(m, 1H, CHMe2), 3.46±3.56 (m, 2H, CHMe2), 7.08 (s, 2H,
ArH).
0
0
4-Methyl-1-(2,4,6-triisopropylphenyl-)2,3-dihydro-1H-
phosphole 1-oxide 1. A mixture of 2,5-dihydrophophole
oxide 3 (0.70 g, 2.20 mmol) and 6% aqueous sodium
hydroxide (12 mL) was kept at 1308C in a sealed tube for
9 days. After adding the contents of the tube to water
(50 mL), the pH was adjusted to 3 by the addition of
conc. hydrochloric acid and the mixture was extracted
with chloroform (2£40 mL). The organic phase was dried
(Na2SO4) and the solvent evaporated. The residue so
obtained was puri®ed by column chromatography on silica
gel using 3% methanol in chloroform as the eluant to give
product 1 (0.57 g, 81%) as a colourless oil. 31P NMR
(CDCl3) d 61.8; 13C NMR (CDCl3) dC 20.7 (JPCˆ17.0 Hz,
C4-CH3), 23.5 (JPCˆ1.6 Hz, CH(CH3)3), 24.3 (CH(CH3)2),
24.9 (CH(CH3)2), 30.9 (JPCˆ69.4 Hz, C2), 31.8 (JPCˆ
5.1 Hz, CHMe2), 33.6 (JPCˆ8.6 Hz, C3), 34.0 (CHMe2),
3,4-Dimethyl-1-(2,4,6-triisopropylphenyl-)2,3,4,5-tetra-
hydro-1H-phosphole 1-oxides 6-1, 6-2 and 6-3. Dihydro-
phosphole oxide 10 (2.2 g, 6.62 mmol) in methanol (80 mL)
was hydrogenated in the presence of 10% palladium on
carbon (1.2 g ) at 900 kPa and 558C until one equivalent
of hydrogen was consumed. The suspension was ®ltered,
the solvent evaporated and the oily residue puri®ed by
column chromatography on silica gel using 2% methanol
in chloroform as the eluant to afford 1.72 g (78%) of the oily
product as the mixture of isomer 6-1 (51%), isomer 6-2
(27%) and isomer 6-3 (22%). The stereochemistry of
isomers 6-2 and 6-3 was not determined. MS, m/z (rel.
int.) 334 (M1, 73), 319 (M2Me, 100), 291 (M2Pr1H,
46), 250 (ArPO, 16), 203 (Ar, 8); HRMS calcd for
C21H35OP 334.2426, found 334.2409; IR (®lm) 2959,
1602, 1461, 1169, 732 cm21. Repeated column chromato-
graphy of the isomeric mixture (as above) afforded isomer
6-3 in a pure form. The synthesis was repeated several times
to collect 0.19 g of isomer 6-3.
0
122.0 (JPCˆ10.7 Hz, C3 ), 123.4 (JPCˆ98.1 Hz, C5), 129.4
0
0
0
(JPCˆ100.6 Hz, C1 ), 151.2 (JPCˆ10.7 Hz, C2 ), 151.5 (C4 ),
161.3 (JPCˆ25.5 Hz, C4); 1H NMR (CDCl3) (1.24 (d,
Jˆ7.1 Hz, 12H, CH(CH3)2), 1.32 (d, Jˆ6.8 Hz, 6H,
CH(CH3)2), 2.02 (s, 3H, C4±CH3), 2.84±2.93 (m, 1H,
CHMe2), 3.55-3.65 (m, 2H, CHMe2), 6.26 (d, Jˆ24.9 Hz,
1H, C5±H), 7.08 (s, 2H, ArH); MS, m/z (rel. int.) 318 (M1
100), 303 (M±Me, 96), 43 (Pr, 13); HRMS calcd for
C20H31OP 318.2113, found 318.2105. Anal. calcd for
C20H31OP: C, 75.42; H, 9.83. Found: C, 75.63; H, 10.13.
3-Methyl-1-(2,4,6-triisopropylphenyl-)2,3,4,5-tetrahydro-
1H-phosphole 1-oxide 4. Dihydrophosphole oxide 3
(0.82 g, 2.58 mmol) in methanol (30 mL) was hydrogenated
in the presence of 10% palladium on carbon (0.5 g ) at
1000 kPa and 268C until one equivalent of hydrogen was
absorbed (ca 6 h). The suspension was ®ltered, the solvent
evaporated and the residue puri®ed by column chromato-
graphy on silica gel using 2% methanol in chloroform as the
eluant to give 0.67 g (81%) of product 4 as a colourless oil
consisting of 68% of the 4-1 isomer and 32% of the 4-2
isomer. The stereochemistry of isomers 4-1 and 4-2 was
not determined. MS, m/z (rel. int.) 320 (M1, 98), 305
(M2Me, 100), 277 (M2Pr, 28), 250 (ArPO, 12), 203 (Ar,
7); Anal. calcd for C20H33OP: C, 74.95; H, 10.4. Found: C,
75.30; H, 10.71; IR (®lm) 2960, 1603, 1463, 1166,
6-1. 31P NMR (CDCl3) d 52.9; 13C NMR (CDCl3) d 19.0
(JPCˆ17.7 Hz, C3±Mea), 19.1 (JPCˆ13.0 Hz, C4±Mea), 23.7
(CH(CH3)2), 25.4 (CH(CH3)2), 32.3 (JPCˆ5.0 Hz, CHMe2),
34.2 (CHMe2), 39.3 (JPCˆ8.0 Hz, Cb3), 40.0 (JPCˆ5.3 Hz,
Cb4), 43.3 (JPCˆ66.0 Hz, C2c), 43.6 (JPCˆ66.4 Hz, Cc5),
0
0
122.4 (JPCˆ10.6 Hz, C3 ), 128.7 (JPCˆ94.7 Hz, C1 ), 152.1
(C4 ), 152.4 (JPCˆ11.0 Hz, C2 ); a-ctentative assignments.
0
0
6-2. 31P NMR (CDCl3) d 61.0; 13C NMR (CDCl3) d 15.9
(JPCˆ7.5 Hz, C3±Me), 23.7 (CH(CH3)2), 24.6 (CH(CH3)2),
32.5 (JPCˆ5.1 Hz, CHMe2), 34.2 (CHMe2), 36.8 (JPCˆ
7.0 Hz, C3), 40.8 (JPCˆ65.2 Hz, C2), 122.4 (JPCˆ10.6 Hz,
0
C3 ).
6-3. 31P NMR (CDCl3) d 57.9; 13C NMR (CDCl3) d 16.4
(JPCˆ9.0 Hz, C3±Me), 23.8 (CH(CH3)2), 25.2 (CH(CH3)2),
32.6 (JPCˆ5.4 Hz, CHMe2), 34.3 (CHMe2), 35.2 (JPCˆ
7.0 Hz, C3), 40.6 (JPCˆ65.5 Hz, C2), 122.6 (JPCˆ10.8 Hz,
685 cm21
.
4-1. 31P NMR (CDCl3) d 60.6; 13C NMR (CDCl3) (21.2
0
0
0
(JPCˆ10.9 Hz,
C3±Me), 23.8 (CH(CH3)2), 24.8
C3 ), 129.8 (JPCˆ94.4 Hz, C1 ), 152.0 (JPCˆ11.3 Hz, C2 ),
1
0
(CH(CH3)2), 25.4 (JPCˆ2.7 Hz, CH(CH3)2), 32.4 (JPCˆ
4.7 Hz, CHMe2), 32.8 (JPCˆ6.3 Hz, C4), 33.8
(JPCˆ7.1 Hz, C3), 34.3 (CHMe2), 34.9 (JPCˆ65.4 Hz, C5),
152.1 (C4 ); H NMR (CDCl3) d 0.89 (d, Jˆ6.5 Hz, 6H,
C3±CH3), 1.25 (d, Jˆ7.0 Hz, 6H, CH(CH3)2), 1.29 (d,
Jˆ6.5 Hz, 12H, CH(CH3)2), 2.84±2.92 (m, 1H, CHMe2),
3.45±3.55 (m, 2H CHMe2), 7.07 (s, 2H, ArH).
0
42.0 (JPCˆ66.6 Hz, C2), 122.5 (JPCˆ10.7 Hz, C3 ), 128.8
0
0
(JPCˆ93.3 Hz, C1 ), 152.2 (JPCˆ1.7 Hz, C4 ), 152.5
(JPCˆ10.9 Hz, C2 ); 1H NMR (CDCl3)
d 1.21 (d,
0
General method for the preparation of oxaphosphetes 2,
5, 7 and 9
Jˆ5.6 Hz, 3H, C3±CH3), 1.26 (d, Jˆ6.9 Hz, 6H,
CH(CH3)2), 1.28 (d, Jˆ6.6 Hz, 6H, CH(CH3)2), 1.31 (d,
Jˆ6.6 Hz, 6H, CH(CH3)2), 2.84±2.94 (m, 1H, CHMe2),
3.46±3.56 (m, 2H, CHMe2), 7.08 (s, 2H, ArH).
A solution of P-heterocycle 1, 4, 6 or 8 (2.0 mmol) and
DMAD (0.31 mL, 2.50 mmol) in dry 1,4-xylene (5 mL)
was kept at 1508C for 8 days in a sealed tube. The volatile
components were removed in vacuo, ®rst at 20 mmHg and
then at 0.2 mmHg. The residue so obtained was puri®ed by
¯ash chromatography on silica gel using 3% methanol in
chloroform as the eluant. The main fraction was re®ned by a
second chromatography using the same type of absorbent
4-2. 31P NMR (CDCl3) d 59.9; 13C NMR (CDCl3) d 21.3
(JPCˆ15.0 Hz, C3±Me), 23.8 (CH(CH3)2), 24.8 (CH(CH3)2),
25.4 (JPCˆ2.7 Hz, CH(CH3)2), 32.3 (JPCˆ3.7 Hz, CHMe2),
32.6 (JPCˆ5.1 Hz, C4), 33.0 (JPCˆ9.3 Hz, C3), 34.3
(CHMe2), 34.3 (JPCˆ66.4 Hz, C5), 42.5 (JPCˆ64.5 Hz,
0
0
C2), 122.5 (JPCˆ10.7 Hz, C3 ), 128.9 (JPCˆ93.6 Hz, C1 ),

G. Keglevich et al. / Tetrahedron 56 (2000) 4823±4828
4827
and eluant to give the products (2, 5, 7 and 9) as pale brown
oils.
CvO), 167.9 (JPCˆ14.6 Hz, CvO), 183.1 (JPCˆ6.2 Hz,
C4); 1H NMR (CDCl3) d 1.16 (d, Jˆ7.0 Hz, 3H, C6±
CH3), 1.24 (d, Jˆ6.4 Hz, 6H, CH(CH3)2), 1.25 (d,
Jˆ7.1 Hz, 6H, CH(CH3)2), 1.32 (d, Jˆ6.6 Hz, 6H,
CH(CH3)2), 2.84±2.93 (m, 1H, CHMe2), 3.48±3.58 (m,
2H, CHMe2), 3.60 (s, 3H, OCH3), 3.78 (s, 3H, OCH3),
7.10 (s, 2H, ArH).
3,4-Di(methoxycarbonyl)-6-methyl-2-(20,40,60-triisopro-
pylphenyl)-1,2-oxaphosphaspiro[3.4]octa-3,5-diene
2.
Yield: 79%; 31P NMR (CDCl3) d 39.5; 13C NMR (CDCl3)
d
20.7 (JPCˆ18.0 Hz, C6±Me), 23.7 (JPCˆ3.7 Hz,
CH(CH3)2), 23.8 (CH(CH3)2), 25.5 (CH(CH3)2), 26.0
(JPCˆ59.2 Hz, C8), 32.0 (JPCˆ6.3 Hz, CHMe2), 34.3
(CHMe2), 35.7 (JPCˆ6.8 Hz, C7), 50.7 (CH3O), 51.8
(CH3O), 76.1 (JPCˆ103.0 Hz, C3), 116.3 (JPCˆ88.6 Hz,
3,4-Di(methoxycarbonyl)-6,7-dimethyl-2-(20,40,60-triiso-
propylphenyl)-1,2-oxaphosphaspiro(3.4(oct-3-ene
(7).
The starting tetrahydrophosphole oxide (6) was used as a
51-27-22% mixture of three diastereomers (6-1, 6-2 and
6-3). Yield: 71%; isomeric composition: 57% of 7-1, 23%
of 7-2 and 18% of 7-3; HRMS (FAB) calcd for C27H42O5P
477.2770, found 477.2769; IR (®lm) 2957, 1739, 1556,
0
0
C5), 122.8 (JPCˆ93.7 Hz, C1 ), 123.2 (JPCˆ11.3 Hz, C3 ),
0
0
152.7 (C2 ), 152.8 (C4 ), 164.0 (JPCˆ23.0 Hz, C6), 167.0
(JPCˆ14.3 Hz, CvO), 168.1 (JPCˆ15.4 Hz, CvO), 182.5
1
(JPCˆ6.2 Hz, C4); H NMR (CDCl3) d 1.13 (d, Jˆ6.5 Hz,
6H, CH(CH3)2), 1.24 (d, Jˆ7.0 Hz, 6H, CH(CH3)2), 1.34 (d,
Jˆ6.5 Hz, 6H, CH(CH3)2), 2.04 (s, 3H, C6±CH3), 2.27±
2.37 (m, 1H, CH), 2.60±2.71 (m, 1H, CH), 2.83±2.93 (m,
2H, CHMe2, CH), 3.49±3.60 (m) and 3.55 (s) overlapped,
total int. 5H (CHMe2, OCH3), 3.78 (s, 3H, OCH3), 3.85±
3.96 (m, 1H, CH), 6.26 (d, Jˆ27.5 Hz, 1H, C5±H), 7.08 (s,
2H, ArH); HRMS calcd for C26H37O5P 460.2379, found
460.2381. Anal. calcd for C26H37O5P: C, 67.79; H, 8.11.
Found: C, 67.44; H, 8.33; IR (®lm) 2958, 1739, 1559,
1435, 1084, 753 cm21
.
7-1. 31P NMR (CDCl3) d 23.9; 13C NMR (CDCl3) d 18.2
(JPCˆ13.4 Hz, C6±Mea), 18.3 (JPCˆ19.3 Hz, C7±Mea), 24.1
(CH(CH3)2), 25.3 (CH(CH3)2), 31.8 (JPCˆ8.1 Hz, CHMe2),
34.1 (CHMe2), 35.0 (JPCˆ54.6 Hz, Cb5), 40.1 (JPCˆ55.8 Hz,
Cb8), 40.2 (JPCˆ8.5 Hz, C6c), 40.6 (JPCˆ4.3 Hz, C7c), 50.6
(MeO), 51.6 (MeO), 73.3 (JPCˆ98.6 Hz, C4), 120.9
0
0
0
(JPCˆ85.9 Hz, C1 ), 123.3 (JPCˆ(10 C3 ), 152.8 (C4 ),
1436, 1087, 773 cm21
.
153.5 (JPCˆ11.0 Hz, C2 ), 167.2 (JPCˆ14.6 Hz, CvO),
0
167.9 (JPCˆ14.8 Hz, CvO), 183.1 (C4); a±c tentative assign-
The reaction of dihydrophosphole oxide 3 with DMAD
under the conditions provided in the General method also
furnished product 2. Yield: 86%; 31P NMR (CDCl3) d 39.4.
ments.
7-2. 31P NMR (CDCl3) d 32.5; 13C NMR (CDCl3) d 15.0
(JPCˆ7.9 Hz, C6±Me), 23.5 (CH(CH3)2), 24.7 (CH(CH3)2),
31.8 (JPCˆ6.1 Hz, CHMe2), 34.1 (CHMe2), 35.0 (JPCˆ
54.6 Hz, C5), 38.1 (JPCˆ6.1 Hz, C6), 50.6 (MeO), 51.6
3,4-Di(methoxycarbonyl)-6-methyl-2-(20,40,60-triisopro-
pylphenyl)-1,2-oxaphosphaspiro[3.4]oct-3-ene (5). The
starting tetrahydrophosphole oxide (4) was used as a 68±
32% mixture of two diastereomers (4-1 and 4-2). Yield:
83%; isomeric composition: 67% of 5-1 and 33% of 5-2;
HRMS (FAB) calcd for C26H40O5P 463.2613, found
463.2633. Anal. calcd for C26H39O5P: C, 67.50; H, 8.52.
Found: C, 67.17; H, 8.88; IR (®lm) 2957, 1738, 1556,
0
(MeO), 72.8 (JPCˆ98.4 Hz, C4), 121.3 (JPCˆ85.7 Hz, C1 ),
0
0
123.4 (JPCˆ11.7 Hz, C3 ), 152.8 (C4 ), 153.2 (JPCˆ11.1 Hz,
0
C2 ), 167.3 (JPCˆ14.5 Hz, CvO), 167.9 (JPCˆ14.8 Hz,
CvO), 183.0 (C4).
7-3. 31P NMR (CDCl3) d 29.0; 13C NMR (CDCl3) d 16.2
(JPCˆ10.5 Hz, C6±Me), 23.5 (CH(CH3)2), 24.7 (CH(CH3)2),
31.8 (JPCˆ6.1 Hz, CHMe2), 34.1 (CHMe2), 35.0 (JPCˆ
54.6 Hz, C5), 35.6 (JPCˆ6.7 Hz, C6), 50.6 (MeO), 51.6
1434, 1078, 731 cm21
.
5-1. 31P NMR (CDCl3) d 32.7; 13C NMR (CDCl3) d 20.0
(JPCˆ11.7 Hz, C6±Me), 23.6 (CH(CH3)2), 24.2 (CH(CH3)2),
25.2 (CH(CH3)2), 31.9 (JPCˆ54.4 Hz, C8), 31.9 (JPCˆ
5.7 Hz, CHMe2), 33.6 (JPCˆ6.2 Hz, C7), 34.1 (CHMe2),
34.2 (JPCˆ55.5 Hz, C5), 34.6 (JPCˆ6.1 Hz, C6), 50.6
(MeO), 51.6 (MeO), 73.2 (JPCˆ98.1 Hz, C3), 120.9 (JPCˆ
0
(MeO), 72.8 (JPCˆ98.4 Hz, C4), 121.3 (JPCˆ85.7 Hz, C1 ),
0
0
123.4 (JPCˆ11.7 Hz, C3 ), 152.8 (C4 ), 153.3 (JPCˆ11.1 Hz,
0
C2 ), 167.3 (JPCˆ14.5 Hz, CvO), 167.9 (JPCˆ14.8 Hz,
CvO), 183.1 (C4); 1H NMR (CDCl3) d 0.96 (d, Jˆ
6.5 Hz, 6H, C±CH3), 1.25 (d, Jˆ7.0 Hz, 6H, CH(CH3)2),
1.28 (d, Jˆ6.5 Hz, 12H, CH(CH3)2), 2.84±2.94 (m, 1H,
CHMe2), 3.47-3.58 (m, 2H, CHMe2), 3.59 (s, OCH3), 3.77
(s, OCH3), 7.10 (s, 2H, ArH).
0
0
85.6 Hz, C1 ), 123.3 (JPCˆ11.6 Hz, C3 ), 152.8 (JPCˆ2.8 Hz,
0
0
C4 ), 153.5 (JPCˆ11.1 Hz, C2 ), 167.2 (JPCˆ14.0 Hz, CvO),
1
167.9 (JPCˆ14.6 Hz, CvO), 183.1 (JPCˆ6.2 Hz, C4); H
NMR (CDCl3) d 1.22 (d, Jˆ7.1 Hz, 3H, C6±CH3), 1.23
(d, Jˆ6.9 Hz, 6H, CH(CH3)2), 1.25 (d, Jˆ7.1 Hz, 6H,
CH(CH3)2), 1.32 (d, Jˆ6.6 Hz, 6H, CH(CH3)2), 2.84-2.93
(m, 1H, CHMe2), 3.48(3.58 (m, 2H, CHMe2), 3.59 (s, 3H,
OCH3), 3.78 (s, 3H, OCH3), 7.09 (s, 2H, ArH).
7-3 was also prepared from isomer 6-3 separated by
repeated column chromatography in a pure form (31P
NMR (CDCl3) d 29.1).
7-Chloro-3,4-di(methoxycarbonyl)-6-methyl-2-(20,40,60-
triisopropylphenyl)-1,2-oxaphosphaspiro[3.5]nona-
5-2. 31P NMR (CDCl3) d 32.0; 13C NMR (CDCl3) d 20.5
(JPCˆ15.8 Hz, C6±Me), 23.6 (CH(CH3)2), 24.3 (CH(CH3)2),
25.2 (CH(CH3)2), 27.2 (JPCˆ55.2 Hz, C8), 31.8 (JPCˆ
6.5 Hz, CHMe2), 32.5 (JPCˆ3.7 Hz, C7), 33.6 (JPCˆ
10.9 Hz, C6), 34.1 (CHMe2), 38.7 (JPCˆ56.1 Hz, C5), 50.6
(MeO), 51.6 (MeO), 72.9 (JPCˆ98.3 Hz, C3), 120.8
3,5,7,-triene (9). Yield: 84%; 31P NMR (CDCl3) d 24.0; 13
C
NMR (CDCl3) d 16.2 (JPCˆ17.5 Hz, C6(Me), 23.6
(CH(CH3)2), 23.7 (CH(CH3)2), 25.3 (CH(CH3)2), 30.0
(JPCˆ62.8 Hz, C9), 31.8 (JPCˆ6.7 Hz, CHMe2), 34.0
(CHMe2), 50.6 (CH3O), 51.5 (CH3O), 74.4 (JPCˆ
107.4 Hz, C3), 119.3 (JPCˆ13.7 Hz, C8), 121.6 (JPCˆ
0
0
(JPCˆ86.0 Hz, C1 ), 123.4 (JPCˆ11.1 Hz, C3 ), 152.8 (JPCˆ
0
0
0
2.8 Hz, C4 ), 153.5 (JPCˆ11.1 Hz, C2 ), 167.2 (JPCˆ14.3 Hz,
94.3 Hz, C1 ), 122.5 (JPCˆ85.0 Hz, C5), 123.2 (JPCˆ

4828
G. Keglevich et al. / Tetrahedron 56 (2000) 4823±4828
Í
0
5. Keglevich, Gy.; Toke, L. Trends Org. Chem. 1995, 5, 151±155.
6. Hunger, K.; Hasserodt, U.; Korte, F. Tetrahedron 1964, 20,
1593±1604.
11.9 Hz, C3 ), 140.0 (JPCˆ14.1 Hz, C7), 152.7 (JPCˆ
0
0
11.3 Hz, C2 ), 153.0 (C4 ), 155.4 (JPCˆ14.8 Hz, C6), 166.4
(JPCˆ14.8 Hz, CvO), 167.5 (JPCˆ15.6 Hz, CvO), 182.4
1
(JPCˆ6.1 Hz, C4); H NMR (CDCl3) d 1.13 (d, Jˆ6.6 Hz,
7. Quin, L. D.; Gratz, J. P.; Barket, T. P. J. Org. Chem. 1968, 33,
1034±1041.
6H, CH(CH3)2), 1.24 (d, Jˆ6.9 Hz, 6H, CH(CH3)2), 1.39 (d,
Jˆ6.5 Hz, 6H, CH(CH3)2), 2.10 (s, 3H, C6±CH3), 2.84±
2.93 (m, 1H, CHMe2), 3.08 (dd, J1ˆ18.5 Hz, J2ˆ9.0 Hz,
1H, C9±H), 3.51(3.59 (m, 2H, CHMe2), 3.60 (s, 3H,
OCH3), 3.78 (s, 3H, OCH3), 4.93 (dd, J1ˆ17.9 Hz,
J2ˆ14.8 Hz, 1H, C9±H), 6.50 (s, 1H, C8±H), 6.64 (d,
8. Smith, D. J. H. In Comprehensive Organic Chemistry, Barton,
D. H. R., Ollis, W. D., Eds.; Pergamon: Oxford, 1979; Vol. 2
(Sutherland, I. O. Volume Ed., Ch. 10.4, p 1233).
9. Tebby, J. C. In Comprehensive Heterocyclic Chemistry II,
Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds.; Pergamon:
Oxford, 1996; Vol. 8 (Jones, G. Volume Ed., Ch. 8.41, p 1135).
10. Uchiyama, T.; Fujimoto, T.; Kakehi, A.; Yamamoto, I.
J. Chem. Soc., Perkin Trans. 1 1999, 1577±1580.
11. Kawashima, T.; Iijima, T.; Kikuchi, H.; Okazaki, R.
Phosphorus, Sulfur, Silicon 1999, 144±146, 149±152.
12. Stewart, J. J. P. J. Comput. Chem. 1989, 10, 209±220 (see also
pp 221±264).
Jˆ23.3 Hz, 1H, C5±H), 7.09 (s, 2H, ArH); HRMS calcd
35
36
for C27H ClO5P 506.1989, found 506.1941. Anal. calcd
for C27H36ClO5P: C, 63.95; H, 7.17. Found: C, 64.20; H,
7.34; IR (®lm) 2956, 1731, 1556, 1434, 1088, 755 cm21
.
Acknowledgements
Í
13. Keseru, Gy. M.; Keglevich, Gy. J. Organomet. Chem. 1999,
586, 166±170.
This work was supported by FKFP (Grant No. 363/1999)
and OTKA (Grant No. T 029039).
Â
14. Keglevich, Gy.; Keseru, Gy. M.; Forintos, H.; Szollosy, A.;
Í
È Í
Â
Ludanyi, K.; Toke, L. J. Chem. Soc., Perkin Trans. 1 1999, 1801±
Í
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