Organophosphorus Compounds, Part 168;1 1,3-Dipolar Cycloaddition Reactions of 1,3,5-Triphosphinines with Nitrile Oxides

Article abstract of DOI:10.1055/s-2004-44384

Phenylnitrile oxide as well as mesitylnitrile oxide underwent 1,3-dipolar cycloaddition reactions with the 1,3,5-triphosphinines 2 under mild conditions to furnish the condensed heterocyclic compounds 9 and 11, respectively. Oxadiphospholes 14 were accessible by fragmentation reactions of 11.

Full text of DOI:10.1055/s-2004-44384

PAPER
241
Organophosphorus Compounds, Part 168;1 1,3-Dipolar Cycloaddition
Reactions of 1,3,5-Triphosphinines with Nitrile Oxides
1
,3-Dipola
r
Cy
t
c
loadd
e
ition
R
eact
f
ions of
1
f
,3,5-Trip
e
hosphinine
n
s
w
ithNitrile
Oxid
W
es eidner, Jens Renner, Uwe Bergsträßer, Manfred Regitz,* Heinrich Heydt*
Fachbereich Chemie der Universität Kaiserslautern, Erwin-Schrödinger-Straße, 67663 Kaiserslautern, Germany
Fax +49(631)2053921; E-mail: heydt@chemie.uni-kl.de
Received 26 February 2003; revised 26 November 2003
Dedicated to Professor Gerhard Himbert on the ocassion of his 60th birthday.
R
tBuN VCl3
toluene,
-78 °C r.t.
Abstract: Phenylnitrile oxide as well as mesitylnitrile oxide under-
went 1,3-dipolar cycloaddition reactions with the 1,3,5-triphosphin-
ines 2 under mild conditions to furnish the condensed heterocyclic
compounds 9 and 11, respectively. Oxadiphospholes 14 were acces-
sible by fragmentation reactions of 11.
H2C CH2
toluene, r.t.
3
P
P
P
tBu
tBu
3 R
C
P
R = tBu
P
P
R
P
2
R
tBu
4
1
a
c
1, 2
b
HC CH
5
Key words: phosphorus, 1,3-dipolar cycloadditions, nitrile oxides,
1,2,4-oxazaphospholes, 1,2,4-oxadiphospholes
R
tBu tPen MecPen
R = tBu
Me
tPen =
C
Et
Me
P
P
2,4,6-Tri-tert-butyl-1,3,5-triphosphinine (2a) was first
prepared in 1995.2 Shortly thereafter, a simple one-pot
synthesis comprising the cyclotrimerization of the phos-
phaalkynes 1 in the presence of a vanadium catalyst was
developed that also made the isolation of other triphos-
phinines possible.3 Although their physicochemical prop-
erties (NMR spectroscopic data2,3, crystal structure
analysis4) as well as theoretical investigations5 clearly
demonstrated the aromatic character of the 1,3,5-triphos-
phinines 2, the compounds have been exhibiting a surpris-
ingly high reactivity in, for example [4+2] cycloaddition
reactions.6 When ethylene 3 was bubbled into a toluene
solution of 2a, a [4+2] cycloaddition reaction occurred at
room temperature to afford the 7,8-dihydro-1,3,5-triphos-
phabarrelene 4.7 Various monosubstituted alkenes (acryl-
ic acid derivatives, styrene), as well as some selected
disubstituted alkenes (maleic acid derivatives, fumaric
acid derivatives, norbornene, cyclopentadiene) also un-
derwent Diels–Alder reactions with 2 to furnish compara-
ble dihydrotriphosphabarrelenes. Alkynes like acetylene
5 itself reacted with 2a to afford the novel triphospha cage
compound 7 through a Diels–Alder/homo-Diels–Alder
reaction sequence with the 1,3,5-triphosphabicyclo-
[2.2.2]octa-2,5,7-triene 6 as intermediate (Scheme 1).8
tBu
5
tBu
tBu
tBu
2'
Me
MecPen =
1'
5'
P
P
3'
P
P
tBu
tBu
4'
6
7
Scheme 1
ring contraction from a six- to a five-membered ring to af-
ford the heterocycles 11 with a P-acyl substituent.9 Ben-
zonitrile oxide 8a reacted smoothly with 2a,c to give the
trisadducts 9a,b. When the steric overcrowding in the ni-
trile oxide was increased by substituting the phenyl group
1
O
2
R2
C N O , 8
Et2O or toluene,
-78 °C r.t.
N
R2
11
R1
12
P
3
toluene,
∆, 14 d
R2
Ph
12a
8a
P
4a
4
P
2a-c
10N
R1
O 5
N
O
R
R
1 = tBu, tBu
2 = Ph
P
9 R1
O
8
N
7
R2
6
10
(~100%)
9
R1
O
8
a
b
R1
5
Mes
P
5a
9a
4
P
On account to their relatively weakly pronounced aroma-
ticity, 1,3,5-triphosphinines should, in principle, be able
to act as dipolarophiles in [3+2]-cycloaddition reactions.
In order to test this assumption 1,3,5-triphosphinines 2a–
c were allowed to react with 1,3-dipoles, namely phenyl-
and mesitylnitrile oxides (Scheme 2).
Depending on the substituents R1 and R2, reactions of the
1,3,5-triphosphinines 2 with the nitrile oxides 8 in Et2O or
toluene led either to the trisadducts 9 or proceeded with
6
O
R
2 = Mes
R2 Ph Mes
3
N
P
N
7
2
- Mes
C
N
9
O
1
R1
8
Me
Mes
Me
Mes =
11
c
Me
9, 11
R1
a
b
d
e
tBu
tBu MecPen
tPen MecPen
R2
Ph
Ph
Mes Mes Mes
< 5
77
[%] 9
77
-
72
-
< 5
65
39
32
[%] 11
SYNTHESIS 2004, No. 2, pp 0241–0248
x
x
.
x
x
.2
0
0
4
Advanced online publication: 18.12.2004
DOI: 10.1055/s-2004-44384; Art ID: T02103SS
© Georg Thieme Verlag Stuttgart · New York
Scheme 2

242
S. Weidner et al.
PAPER
by a mesityl group (8b), the formation of trisadducts at all 71.0 Hz, confirming the attachment to two phosphorus at-
three P–C bonds of the 1,3,5-triphosphinine was no longer oms. In addition, the chemically equivalent imine carbon
favored.
atoms C-3, C-7, C-11 gave signals at typically low field
between = 156.4 and 159.3 ppm, each with a character-
istic 1JC,P coupling constant ranging from 40.6 to 50.3 Hz,
again demonstrating the direct attachment to a phosphorus
atom and confirming the deduced direction of addition of
the 1,3-dipole to the P–C double bond.
As shown in Figure 1, the reaction path branches presum-
ably at the stage of the monocycloadduct A, because at-
tack of the second nitrile oxide can occur from the C-
5(Si)–P-6(Re) or C-5(Re)–P-6(Si) side of the monoadduct.
Addition of 8 to the double bond C-7–P-8 of A leads to the
same types of intermediates and is therefore not further The cleavage of mesityl nitrile in the formation of the tri-
discussed here.
cyclic compounds 11 was confirmed by correct elemental
analysis results. Moreover, the IR spectrum of 11 revealed
strong absorptions between 1671 cm–1 and 1674 cm–1 that
could be assigned to the carbonyl vibrations of the newly
formed P-acyl group. The phosphorus atoms P-4, P-5, P-
9 of the central 1,2,4-triphospholane appeared as an AMN
spin system in the 31P NMR spectrum at about = 50 (P-
4, P-5) ppm and = 80 (P-9) ppm. Further characteristic
R1
5
N
R2
R2
O
R1
P
attack to the
5Re/6Si-side
R2
4
3
P
8a
P 6
7
P
2
N
N
O
1
P
R1
P
R1
O
R1
R1
8
C
A
1
parameters were the large JP,P coupling constants of be-
ring
contraction
attack to the
5Si/6Re-side
tween 255.8 and 264.1 Hz, demonstrating the direct at-
tachment of P-4 and P-5, as well as typical 2JP,P coupling
constants of 10.7–23.4 Hz between P-4–P-9 on the one
hand and P-5–P-9 on the other hand. Final confirmation of
the structure of 11 was provided by an X-ray crystallo-
graphic analysis of 11c.
O
R1
N
R2
R2
O
R1
R2
P
P
P
P
P
N
R1
R
N
2
+
N
O
O
P
R1
R1
R1
B
D
Figure 1 Plausible intermediates in the 1,3-dipolar cycloaddition
reaction of nitrile oxides towards 1,3,5-triphosphinines
When the C-5(Si)/P-6(Re) side is accessible the reaction
sequence leads to the cycloadduct B and ends at the tetra-
cyclic species 9; when this side is shielded attack at the C-
5(Re)/P-6(Si) side leads to the cycloadduct C with subse-
quent ring contraction under cleavage of the nitrile ( D),
and finally to the formation of product 11. With the 1-me-
thylcyclopentyl and mesityl substituents both reaction
paths are equally possible as an approximately 1:1 mix-
ture of 9e and 11e was obtained.
The constitution of the trisadducts 9 could be deduced un-
ambiguously from their spectroscopic data, which
showed, in particular, that all three equivalents of nitrile
oxides added to the 1,3,5-triphosphinine from the same
side. Thus, all the 31P NMR spectra contained only one
Figure 2 Molecular structure of 11c; selected bond lengths [Å] and
singlet signal confirming the high symmetry of the system bond angles [°]: P4–P5 2.196(2), P4–C3 1.812(5), P5–C5a 1.895(5),
P5–C51 1.888(6), C5a–P9 1.848(5), P9–C9a 1.918(5), P9–C8
1.846(5), C9a–P 4 1.871(5); C9a–P4–P5 101.81(19), C9a–P4–C3
88.5(2), P4–P5–C5a 99.04(17), P4–P5–C51 86.93(18), C5a–P5–C51
104.1(2), P5–C5a–P9 114.2(3), C5a–P9–C9a 102.0(2), C5a–P9–C8
9. The chemical shifts were between = 17.4 and 30.9
ppm thus clearly indicating the loss of three P-C double
bonds. Compounds 9c and 9d were identified as minor
products on the basis of their 31P NMR singlet resonances
86.6(2), C9a–P9–C8 96.7(2), P9–C9a–P4 111.7(3)
of = 28.1 and 29.0 ppm, respectively in the crude reac-
2
tion mixtures. The JP,P coupling constants of 9 were de-
Figure 2 clearly shows that the central 1,2,4-triphos-
termined as simulation parameters of the 13C NMR data
pholane ring possessed a distorted envelope conforma-
and amounted to between 1.8 and 9.4 Hz. The 13C NMR
tion, that the newly formed pivaloyl group on P-5 was
spectra contained only one signal between = 97.6 and
located on the opposite side to the plane of the central
98.3 ppm for the three chemically equivalent atoms C-4a,
five-membered ring as did the two condensed 4,5-dihy-
C-8a, C-12a in agreement with the C3 symmetry. As
drooxazaphosphole rings, and that the oxygen of the car-
shown by a simulation of the AA A X spin system, all the
bonyl group was located below the five-membered ring.
signals of these skeletal carbon atoms possessed two char-
1
acteristic JC,P coupling constants of between 52.0 and
Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York

PAPER
1,3-Dipolar Cycloaddition Reactions of 1,3,5-Triphosphinines with Nitrile Oxides
243
Mes
In order to exclude the subsequent formation of 11 from 9
by cleavage of the nitrile, compound 9a was heated in tol-
uene at 100 °C for 14 days. NMR spectroscopic control
did not reveal any ring contraction, instead a quantitative
[2+2+2]-cycloreversion to the previously known 5-tert-
butyl-3-phenyl-1,2,4-oxazaphosphole (10)10,21 was ob-
served.
tBu
O1
2 8b, toluene
-78 °C r.t., 12 h
toluene
8
9
P
100 °C, 75 min
7
2
N
N
3
9a
14a
13a
(~100%)
5a
O
P
4
6
90%
- "O"
O
Mes
5
tBu
17
Scheme 4
When the tricyclic compounds 11 were subjected to a
comparable thermolysis, an initial [3+2]-cycloreversion
with liberation of mesitylnitrile oxide (8b) and formation
of the bicyclic species 12 occurred with subsequent de-
composition into the oxazaphospholes 13 and the oxa-
diphospholes 14 as indicated in Scheme 3.
The constitutions of the novel oxadiphospholes 14a–c
were confirmed by correct elemental analysis results, the
presence of molecular ion peaks in their EI-mass spectra,
and examination of their spectroscopic data. Hence, each
31P NMR spectra each a signal at low field between
=
Whereas the oxazaphospholes 13 are well known, oxad-
iphospholes 14 have as yet only been poorly
investigated11,12 and this synthetic route has potential for
exploitation as a specific access to this novel class of het-
erodiphospholes. Since control experiments showed that
the oxadiphospholes 14 reacted with mesitylnitrile oxide
under formation of compound 17 (Scheme 4), which re-
duced their yields or prevented their isolation, it seemed
reasonable to remove the inevitably formed 1,3-dipole by
means of a trapping reagent. It is well known that phos-
phaalkenes of the Becker type react with nitrile oxides via
the 4,5-dihydro-1,2,4-oxazaphospholes 16 and cleavage
of hexamethyldisiloxane to afford oxazaphospholes of the
type 13.10,13,20 Thus, when the thermolysis of compounds
11 was performed in the presence of the phosphaalkene
corresponding to the employed compound 11, we could
indeed isolate the oxadiphospholes 14 in good yields of
68–71%. It was even possible to carry out the synthesis of
14 as a one-pot process starting with 2, three equivalents
of 8b, and one equivalent of the respective phospha-
alkene. As shown for the example of 14a it is possible to
obtain this heterocyclic species by this procedure in yields
between 60–65%.
313.9 and 316.4 ppm for the phosphorus atom P-2 directly
attached to the oxygen atom, whereas the signal for P-4
was appreciably shifted to higher field and appeared be-
2
tween = 122.0 and 127.3. ppm The JP,P coupling con-
stants were on average 24.0 Hz. These and all other NMR
data were in complete accord with those of the previously
reported 3,5-dimesityl derivative (14, R = Mes)12 (see also
experimental section). Finally, the selective reaction of
14a with mesitylnitrile oxide should be mentioned. Even
under mild conditions two equivalents of mesitylnitrile
oxide (8b) underwent addition to the two P–C double
bonds of 14a to furnish in high diastereo- and regioselec-
tivity the heterocyclic species 17 which was isolated in the
form of colorless needles in 90% yield. The spectroscopic
data of 17 were closely compatible with those of the al-
ready known analogue in which the oxygen atom in posi-
tion 5 is replaced by sulfur.22 The only significant
differences were observed for P-4 and C-5a, i.e., the at-
oms directly adjacent to the oxygen O-5 or sulfur S-5, re-
spectively. The signals for both atoms in the
corresponding spectra of 17 were markedly shifted to low-
er field (P-4: = 156.7 vs. 78.3 ppm; C-5a: = 140.0 vs.
125.8 ppm). The proposed relative stereochemistry in
R
P
O
toluene, 100 °C,
1-2 d
Mes
P
R
11c-e
Mes
C
N
O
R
+
retro-[3+2]
N
P
8b
O
R
12
C
P
TMS
TMSO
15
Mes
R
4
4
P
TMS
R
Mes
P
3
P
3
+
5
5
13a-c
N
P
N
R
R
2
- TMS2O
2
O
1
O
1
O
TMSO
16
14
13
13 -16
a
b
c
R
tBu tPen MecPen
71 69 68
[%] 14
Scheme 3
Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York

244
S. Weidner et al.
PAPER
(AA A X spin system, 1JC,P = 64.0 Hz, 53.0 Hz, 3JC,P = 0.7 Hz, C-
4a, C-8a, C-12a), 128.3 (s, meta-C-phenyl), 129.1 (s, ortho/para-C-
phenyl), 132.6 (AA A X spin system, 2JC,P = 19.0 Hz, 4JC,P = 0.0 Hz,
which both equivalents of 8b added from the same side to
14a is plausible under consideration of the known angle-
2
dependency of the JC,P coupling constants.14 They were
1
0.0 Hz, ipso-C-phenyl), 159.3 (AA A X spin system, JC,P = 40.6
23.5 and 24.8 Hz for the quaternary carbon atoms of the
tert-butyl groups bonded to C-5a and C-9a, respectively,
thus supporting the cis-orientation of these groups to the
free electron pairs on the phosphorus atoms P-4 and P-9.
Hz, 3JC,P = 0.7 Hz, 0.7 Hz, C-3, C-7, C-11); simulation parameter of
AA A X spin systems: 2JP,P = 1.8 Hz.
31P{1H} NMR (CD2Cl2): = 18.5 (s, P-4, P-8, P-12).
MS (FAB): m/z = 658 [M + H]+.
When 17 was subjected to thermolysis under the same
conditions as employed for compounds 11 above, decom-
position was complete within 75 minutes and the known
compound 13a15 was formed quantitatively. The fate of
the thus liberated oxygen was not followed.
Anal. Calcd for C36H42N3O3P3 (657.67): C, 65.75; H, 6.44; N, 6.39.
Found: C, 65.63; H, 6.44; N, 6.33.
4a,8a,12a-Tris(1-methylcyclopentyl)-3,7,11-triphenyl-bis-
[1,2,4]oxazaphospholo[4 ,5 :3,4;4 ,5 :5,6][1,3,5]triphosphin-
ino[1,2-d][1,2,4]oxazaphosphole (9b); Typical Procedure
To compound 2c (348 mg, 0.92 mmol) and Et3N (279 mg, 2.76
mmol) in Et2O (15 mL), was added dropwise a solution of N-hy-
droxybenzenecarboximidoyl chloride (429 mg, 2.76 mmol) in Et2O
(15 mL) under magnetic stirring at 0 °C. The solution was allowed
to warm to r.t., the reaction mixture was filtered over Celite and the
residue rinsed twice with toluene (15 mL). After removal of the sol-
vent under oil pump vacuum (10–3 mbar/25 °C), the residue was tak-
en up in THF–Et2O (1:1) and crystallization at –25 °C afforded 9b.
Yield: 482 mg (0.66 mmol, 72%); colorless crystals; mp 173 °C (de-
comp).
All reactions were carried out under an Ar atmosphere in oven-dried
1
glassware. The solvents were anhydrous and stored under Ar. H
NMR spectra were measured on Bruker AMX 400 spectrometer and
the chemical shifts are referenced to the solvent as internal stan-
dard.13C NMR spectra were measured on Bruker AMX 400 spec-
trometer and the chemical shifts are referenced to the solvent as
internal standard. 31P NMR spectra were recorded on Bruker AC
200 instrument at 80.8 MHz with 85% H3PO4 as the external stan-
dard. IR spectra were taken on a Perkin-Elmer 1000 series FTIR
spectrometer. MS (EI) was performed on Finnigan MAT 90 instru-
ment. MS (CI) was carried out on Finnigan MAT SSQ 7000 instru-
ment with isobutene as carrier. MS (FAB) data were collected on
Finnigan MAT TSQ 7000 instrument with following settings: Xe:
5–6 keV; 3-nitrobenzyl alcohol matrix, CHCl3. GC–MS was per-
formed on HP 6890 series with MSD and a HP-5MS capillary col-
umn (30 m × 250 m). Elemental analysis was carried out on
Perkin-Elmer 2400 CHN. Analytical TLC was done on plastic
sheets coated with silica gel (Polygram SIL G/UV254, Machery-Na-
gel). Column chromatography was performed with Merck silica gel
(0.063–0.2 mm). Bulb-to-bulb distillation was done with Büchi
GKR 50 apparatus; the temperatures stated are oven temperatures.
Melting points were determined on Mettler FP61 with a heating rate
of 2 °C/min and are uncorrected.
IR (KBr): 3054 (w), 3026 (w), 2960 (vs), 2871 (s), 1598 (w), 1578
(w), 1539 (m), 1490 (m), 1461 (m), 1442 (s), 1380 (s), 1323 (m),
1284 (w), 1268 (m), 1232 (m), 1202 (w), 1178 (w), 1118 (w), 1073
(m), 1049 (w), 1020 (m), 1001 (w), 977 (m), 934 (w), 908 (m), 884
(s), 859 (s), 760 (vs), 695 (vs), 674 (m), 655 (m), 629 (m), 602 (s),
498 (m) cm–1.
1H NMR (CD2Cl2): = 1.28 (s, 9 H, cyclopentyl-CH3), 1.30–1.60
(m, 24 H, H-cyclopentyl), 7.42–7.48 (m, 9 H, H-phenyl), 7.67–7.73
(m, 6 H, H-phenyl).
13C{1H} NMR (CD2Cl2): = 22.7, 23.4 (each s, C-3 -cyclopentyl,
C-4 -cyclopentyl), 23.4 (AA A X spin system, 3JC,P = 15.7 Hz, 15.7
Hz, 5JC,P = 0.9 Hz, 1 -CH3-cyclopentyl), 36.0 (AA A X spin system,
5
3JC,P = 9.5 Hz, 7.3 Hz, JP,C = 0.3 Hz, C-2 - or C-5 -cyclopentyl),
Compounds 2a,3 2b,3 2c,3 8a,16 8b,17 15a,18 15b,19 15c20 were pre-
pared by published methods. All other starting materials were ob-
tained from commercial suppliers and were used without further
purification.
36.4 (AA A X spin system, 3JC,P = 9.8 Hz, 7.4 Hz, 5JC,P = 0.2 Hz, C-
2
2 - or C-5 -cyclopentyl), 54.4 (AA A X spin system, JC,P = 24.2
Hz, 21.8 Hz, 4JC,P = 1.0 Hz, C-1 -cyclopentyl), 98.1 (AA A X spin
system, 1JC,P = 62.9 Hz, 52.0 Hz, 3JC,P = 0.5 Hz, C-4a, C-8a, C-12a),
128.4 (s, meta-C-phenyl), 129.2, 129.3 (each s, ortho/para-C-phe-
nyl), 132.9 (AA A X spin system, 2JC,P = 18.8 Hz, 4JC,P = 0.0 Hz, 0.0
4a,8a,12a-Tri-tert-butyl-3,7,11-triphenyl-4,4a,8,8a,12,12a-bis-
[1,2,4]oxazaphospholo[4 ,5 :3,4;4 ,5 :5,6][1,3,5]triphosphin-
ino[1,2-d][1,2,4]oxazaphosphole (9a); Typical Procedure
To compound 2a (150 mg, 0.50 mmol) and Et3N (152 mg, 1.50
mmol) in Et2O (10 mL), was added dropwise a solution of N-hy-
droxybenzenecarboximidoyl chloride (233 mg, 1.50 mmol) in Et2O
(10 mL) under magnetic stirring at 0 °C. The solution was allowed
to warm to r.t., the reaction mixture was filtered over Celite and the
residue rinsed twice with Et2O (15 mL). After concentration of the
solvent under oil pump vacuum (10–3 mbar/25 °C), 9a crystallized
at –25 °C. Yield: 253 mg (0.38 mmol, 77%); colorless crystals; mp
184 °C (decomp).
1
Hz, ipso-C-phenyl), 159.3 (AA A X spin system, JC,P = 41.1 Hz,
3JC,P = 0.9 Hz, 0.9 Hz, C-3, C-7, C-11); simulation parameter of
AA A X spin systems: 2JP,P = 1.9 Hz.
31P{1H} NMR (CD2Cl2): = 17.4 (s, P-4, P-8, P-12).
MS (FAB): m/z = 736 [M + H]+.
Anal. Calcd for C42H48N3O3P3 (735.78): C, 68.56; H, 6.58; N, 5.71.
Found: C, 68.14; H, 7.02; N, 5.30.
Reaction of 2a–c with Mesitylnitrile Oxide (8b); General Proce-
dure
To a solution of the 1,3,5-triphosphinines 2 in toluene was added
drop by drop a solution of a three-fold amount of mesitylnitrile ox-
ide (8b) in toluene at –78 °C. After warming to r.t., all volatile ma-
terials were removed under oil pump vacuum (10–3 mbar/25 °C)
and the residue was worked up as described for the individual case.
IR (KBr): 3054 (m), 3029 (w), 2960 (vs), 2902 (m), 2867 (m), 1598
(m), 1578 (m), 1538 (m, br), 1490 (m), 1475 (s), 1464 (s), 1443 (s),
1393 (s), 1363 (s), 1267 (m), 1196 (m), 1075 (m), 1028 (w), 1001
(m), 977 (m), 946 (m), 901 (s), 876 (s), 845 (m), 760 (vs), 696 (vs),
659 (m), 626 (m), 603 (s), 487 (m) cm–1.
1H NMR (CD2Cl2): = 1.06 [s, 27 H, C(CH3)3], 7.40–7.47 (m, 9 H,
H-phenyl), 7.64–7.71 (m, 6 H, H-phenyl).
5a,9a-Di-tert-butyl-3,8-dimesityl-5-(2,2-dimethylpropanoyl)-
5,5a-dihydro[1,2,4]oxazaphospholo[4 ,5 :1,5][1,2,4]triphospho-
lo[4,3-d][1,2,4]oxazaphosphole (11c); Typical Procedure
The above-mentioned compound was prepared from 1,3,5-triphos-
phinine 2a (1.55 g, 5.17 mmol) in toluene (10 mL) and 8b (2.50 g,
3
13C{1H} NMR (CD2Cl2): = 27.4 [AA A X spin system, JC,P
=
12.0 Hz, 10.8 Hz, 5JC,P = 0.5 Hz, C(CH3)3], 43.2 [AA A X spin sys-
tem, JC,P = 25.9 Hz, 23.6 Hz, JC,P = 0.8 Hz, C(CH3)3], 98.3
2
4
Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York

PAPER
1,3-Dipolar Cycloaddition Reactions of 1,3,5-Triphosphinines with Nitrile Oxides
245
15.5 mmol) in toluene (10 mL). After bulb-to-bulb distillation was
performed (50–70 °C/10–3 mbar) to remove the formed mesitylni-
trile, the oily crude product was worked up by column chromato-
graphy (silica gel, toluene) and crystallized from toluene–n-pentane
(1:4) at –25 °C. Yield: 2.55 g (3.99 mmol, 77%); colorless to yel-
lowish crystal powder; mp 154 °C (decomp).
13C{1H} NMR (CD2Cl2):
= 8.5, 8.7, 9.2 [each s,
C(CH3)2CH2CH3], 20.8 (d, JC,P = 7.7 Hz, ortho- or para-CH3-mesi-
tyl), 20.9 (s, ortho-CH3-mesityl), 21.0 (s, ortho- or para-CH3-mes-
ityl), 22.4 (s, ortho- or para-CH3-mesityl), 22.5 (broad s,
C(CH3)2CH2CH3], 22.9 (d, JC,P = 22.2 Hz, ortho- or para-CH3-mes-
3
ityl), 23.8 [m, C(CH3)2CH2CH3], 26.3 [d, JC,P = 5.4 Hz,
C(CH3)2CH2CH3], 26.7 [s, C(CH3)2CH2CH3], 31.2 [br m,
C(CH3)2CH2CH3], 31.4 [br s, C(CH3)2CH2CH3], 34.8 [br m,
C(CH3)2CH2CH3], 43.3, 45.9 [each m, C(CH3)2CH2CH3], 54.5 [m,
C(O)C(CH3)2CH2CH3], 117.5 (br m, C-5a or C-9a), 124.3 (br m, C-
IR (KBr): 2957 (s), 2928 (s), 2863 (m), 1671 (s, C=O), 1610 (m),
1474 (s), 1459 (s), 1393 (m), 1364 (s), 1219 (w), 1032 (w), 978 (w),
941 (w), 918 (m), 911 (m), 849 (s), 796 (w), 776 (w), 733 (w) cm–1.
1H NMR (CD2Cl2): = 1.02, 1.12, 1.20 [each s, 9 H, C(CH3)3], 2.28,
2.29 (each s, 3 H, ortho-CH3-mesityl), 2.39 (s, 6 H, ortho-CH3-mes-
ityl), 2.66, 2.68 (each s, 3 H, para-CH3-mesityl), 6.88, 7.00 (each s,
1 H, H-mesityl), 6.91 (s, 2 H, H-mesityl).
2
5a or C-9a), 125.7 (m, ipso-C-mesityl), 126.8 (d, JC,P = 13.8 Hz,
ipso-C-mesityl), 129.1, 129.7, 130.7, 137.5, 138.6, 138.9 (each s, C-
mesityl), 140.0 (d, JC,P = 2.3 Hz, C-mesityl), 155.9 (d, 1JC,P = 34.5
1
Hz, C-3 or C-8), 162.1 (d, JC,P = 46.0 Hz, C-3 or C-8), 223.4 (d,
1JC,P = 52.9 Hz, C=O).
13C{1H} NMR (CD2Cl2): = 20.7 (dd, JC,P = 5.8 Hz, JC,P = 1.9 Hz,
ortho- or para-CH3-mesityl), 20.8 (s, ortho-CH3-mesityl), 20.9 (s,
ortho- or para-CH3-mesityl), 22.3 (s, ortho- or para-CH3-mesityl),
22.9 (d, JC,P = 22.2 Hz, ortho- or para-CH3-mesityl), 26.4 [dd,
31P{1H} NMR (CD2Cl2): = 51.8, 53.8 (AMN spin system, 1JP,P
=
264.1 Hz, 2JP,P = 21.2 Hz, 2JP,P = 12.8 Hz, P-4, P-5), 84.8 (AMN spin
system, 2JP,P = 21.2 Hz, 2JP,P = 12.8 Hz, P-9).
3
3JC,P = 4.8 Hz, 2.9 Hz, C(CH3)3], 27.0 [pseudo t, JC,P = 8.1 Hz,
MS (FAB): m/z = 681 [M + H]+.
3
C(CH3)3], 30.8 [pseudo t, JC,P = 5.6 Hz, C(CH3)3], 40.2 [ddd,
3
2JC,P = 26.6 Hz, 23.2 Hz, JC,P = 2.1 Hz, 9a-C(CH3)3], 42.8 [dd,
Anal. Calcd for C38H55N2O3P3 (680.79): C, 67.04; H, 8.14; N, 4.11.
Found: C, 66.95; H, 8.25; N, 3.96.
2JC,P = 22.6 Hz, 13.4 Hz, 5a-C(CH3)3], 51.0 [d, 2JC,P = 30.3 Hz, 5-
C(O)C(CH3)3], 116.1 (ddd, 1JC,P = 53.0 Hz, 40.9 Hz, 2JC,P = 1.2 Hz,
C-5a or C-9a), 123.2 (ddd, 1JC,P = 59.5 Hz, 49.4 Hz, 2JC,P = 4.9 Hz,
C-5a or C-9a), 125.6 (d, 2JC,P = 15.3 Hz, ipso-C-mesityl), 126.7 (d,
2JC,P = 14.2 Hz, ipso-C-mesityl), 129.0, 129.7, 130.6, 137.4 (each s,
C-mesityl), 137.5 (d, JC,P = 1.5 Hz, C-mesityl), 138.6, 138.9 (each
3,7,11-Trimesityl-4a,8a,12a-tris(1-methylcyclopentyl)-bis-
[1,2,4]oxazaphospholo[4 ,5 :3,4;4 ,5 :5,6][1,3,5]triphosphin-
ino[1,2-d][1,2,4]oxazaphosphole (9e) and 3,8-Dimesityl-5a,9a-
bis(1-methylcyclopentyl)-5-[(1-methylcyclopentyl)carbonyl]-
5,5a-dihydro[1,2,4]oxazaphospholo[4 ,5 :1,5][1,2,4]triphospho-
lo[4,3-d][1,2,4]oxazaphosphole (11e); Typical Procedure
The above-mentioned compound was prepared from 1,3,5-triphos-
phinine 2c (361 mg, 0.95 mmol) in toluene (5 mL) and 8b (462 mg,
2.86 mmol) in toluene (5 mL). The oily crude product was worked
up by column chromatography (silica gel, toluene). After removal
of toluene under oil pump vacuum the residue was several times
subjected to fractional crystallization from toluene–n-pentane (1:2)
at –25 °C yielding 322 mg (0.37 mmol, 39%) 9e as colorless crystal
powder; mp 170 °C (decomp). After further recrystallization from
THF–n-pentane (1:3) 219 mg (0.31 mmol, 32%) 11e was obtained
as a colorless to yellowish crystal powder; mp 159 °C (decomp).
s, C-mesityl), 140.0 (d, JC,P = 2.3 Hz, C-mesityl), 155.7 (dd, 1JC,P
=
42.0 Hz, JC,P = 4.0 Hz, C-3 or C-8), 162.1 (d, 1JC,P = 45.2 Hz, C-3 or
C-8), 223.6 (dd, 1JC,P = 57.3 Hz, JC,P = 4.8 Hz, C = O).
31P{1H}-NMR (CD2Cl2): = 51.2, 55.3 (AMN spin system, 1JP,P
=
260.5 Hz, 2JP,P = 23.4 Hz, 2JP,P = 13.0 Hz, P-4, P-5), 83.2 (AMN spin
system, 2JP,P = 23.4 Hz, 2JP,P = 13.0 Hz, P-9).
MS (CI): m/z = 639 [M + H]+.
Anal. Calcd for C35H49N2O3P3 (638.70): C, 65.82; H, 7.73; N, 4.39.
Found: C, 65.56; H, 7.86; N, 4.13.
3,8-Dimesityl-5-(2,2-dimethylbutanoyl)-5a,9a-bis(1,1-dimethyl-
propyl)-5,5a-dihydro[1,2,4]oxazaphospholo[4 ,5 :1,5][1,2,4]-
triphospholo[4,3-d][1,2,4]oxazaphosphole (11d); Typical
Procedure
The above-mentioned compound was prepared from 1,3,5-triphos-
phinine 2b (284 mg, 0.83 mmol) in toluene (5 mL) and 8b (401 mg,
2.49 mmol) in toluene (5 mL). After bulb-to-bulb distillation was
done (50–70 °C/10–3 mbar) to remove the formed mesitylnitrile, the
oily crude product was worked up by column chromatography (sil-
ica gel, n-pentane–Et2O, 20:1) and crystallized from n-pentane at
–25 °C. Yield: 369 mg (0.54 mmol, 65%); colorless to yellowish
crystal powder; mp 126 °C (decomp).
9e
IR (KBr): 2953 (vs, br), 2869 (s), 1610 (m), 1540 (w), 1457 (m),
1445 (m), 1371 (m), 1324 (w), 1296 (w), 1238 (w), 1162 (w), 1067
(w), 1033 (m), 977 (m), 947 (w), 927 (w), 913 (w), 870 (s), 851 (s),
734 (m), 631 (m), 600 (m), 547 (m) cm–1.
1H NMR (CD2Cl2): = 1.29 (s, 9 H, cyclopentyl-CH3), 1.30–1.80
(m, 24 H, H-cyclopentyl), 2.29, 2.47, 2.50 (each s, 9 H, ortho/para-
CH3-mesityl), 6.85, 6.99 (each s, 3 H, H-mesityl).
13C{1H} NMR (CD2Cl2): = 20.8, 21.6 (each s, ortho- or para-CH3-
mesityl), 21.8 (AA A X spin system, JC,P = 13.8 Hz, JC,P = 0.0 Hz,
0.0 Hz, ortho- or para-CH3-mesityl), 23.6, 24.3 (each s, C-3 - and
C-4 -cyclopentyl), 24.4 (m, 1 -CH3-cyclopentyl), 35.0, 35.7 (each
IR (KBr): 2966 (vs), 2918 (s), 2879 (m), 1674 (s, C=O), 1610 (m),
1460 (s), 1443 (s), 1422 (m), 1389 (m), 1362 (m), 1294 (w), 1248
(w), 1168 (m), 1036 (w), 1016 (w), 978 (w), 935 (m), 918 (m), 890
(m), 863 (m), 851 (s), 840 (s), 803 (m), 791 (m), 733 (m), 623 (w),
614 (m), 607 (m), 549 (m) cm–1.
m, C-2 - and C-5 -cyclopentyl), 55.8 (AA A X spin system, 2JC,P
=
32.0 Hz, 25.9 Hz, 4JC,P = 0.1 Hz, C-1 -cyclopentyl), 97.6 (AA A X
spin system, 1JC,P = 71.0 Hz, 60.4 Hz, 3JC,P = 0.2 Hz, C-4a, C-8a, C-
12a), 127.9 (AA A X spin system, 2JC,P = 13.7 Hz, 4JC,P = 0.0 Hz,
0.0 Hz, ipso-C-mesityl), 128.7, 129.9 (each s, meta-C-mesityl),
137.2, 138.4, 140.2 (each s, ortho/para-C-mesityl), 156.4 (AA A X
spin system, 1JC,P = 50.3 Hz, 3JC,P = 0.4 Hz, 0.4 Hz, C-3, C-7, C-
11); Simulation parameter of AA A X spin systems: 2JP,P = 9.4 Hz.
3
1H NMR (CD2Cl2): = 0.84 [pseudo t, JH,H = 7.4 Hz, 3 H,
3
C(CH3)2CH2CH3], 0.88 [pseudo t, JH,H
=
=
7.1 Hz,
7.7 Hz,
3
3
H,
H,
3
C(CH3)2CH2CH3], 0.95 [pseudo t, JH,H
C(CH3)2CH2CH3], 1.01, 1.07 (each s, 6 H, C(CH3)2CH2CH3], 1.20,
1.23 (each s, 3 H, C(CH3)2CH2CH3], 1.30–1.90 [m, 6 H,
C(CH3)2CH2CH3], 2.33, 2.46 (each s, 6 H, ortho-CH3-mesityl),
2.71, 2.74 (each s, 3 H, para-CH3-mesityl), 6.93, 7.04 (each s, 1 H,
H-mesityl), 6.95 (s, 2 H, H-mesityl).
31P{1H} NMR (CD2Cl2): = 30.9 (s, P-4, P-8, P-12).
MS (FAB): m/z = 862 [M + H]+.
Anal. Calcd for C51H66N3O3P3 (862.02): C, 71.06; H, 7.72; N, 4.87.
Found: C, 71.21; H, 7.83; N, 4.52.
Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York

246
11e
S. Weidner et al.
PAPER
IR (CCl4 solution): 2962 (s), 2926 (m), 2898 (m), 2863 (m), 1478
(m), 1473 (m), 1457 (m), 1392 (w), 1363 (m), 1252 (w), 1236 (w),
1199 (w), 1145 (m), 1105 (m), 1083 (m), 940 (w), 835 (w), 655 (m),
557 (w), 536 (w) cm–1.
IR (KBr): 2958 (vs, br), 2866 (s), 2866 (m), 1673 (s, C=O), 1609
(m), 1442 (m, br), 1420 (w), 1376 (m), 1249 (w), 1036 (w), 977 (m),
952 (m), 909 (w), 858 (w), 849 (m), 733 (m), 624 (w), 550 (w) cm–1.
1H NMR (CD2Cl2): = 1.17, 1.23, 1.26 (each s, 3 H, cyclopentyl-
CH3), 1.27–2.27 (m, 24 H, H-cyclopentyl), 2.30, 2.31 (each s, 3 H,
ortho-CH3-mesityl), 2.42 (s, 6 H, ortho-CH3-mesityl), 2.63, 2.69
(each s, 3 H, para-CH3-mesityl), 6.91 (s, 1 H, H-mesityl), 6.92 (s, 2
H, H-mesityl), 7.01 (s, 1 H, H-mesityl).
13C{1H} NMR (CD2Cl2): = 20.7 (d, JC,P = 7.5 Hz, ortho- or para-
CH3-mesityl), 20.8 (s, ortho-CH3-mesityl), 20.9, 22.2 (each s,
ortho- or para-CH3-mesityl), 22.9, 24.0, 24.7, 25.1, 25.3 (each s, C-
3 - and C-4 -cyclopentyl), 23.0 (d, JC,P = 22.4 Hz, ortho- or para-
CH3-mesityl), 24.1 (m, 1 -CH3-cylopentyl), 25.0 (dd, JC,P = 10.8 Hz,
1H NMR (C6D6): = 1.33 [d, 4JH,P = 1.3 Hz, 9 H, 5-C(CH3)], 1.38
[dd, 4JH,P = 2.0 Hz, 4JH,P = 0.4 Hz, 9 H, 3-C(CH3)].
13C{1H} NMR (C6D6): = 29.9 [d, 3JC,P = 9.3 Hz, 5-C(CH3)3], 34.5
[dd, 3JC,P = 11.9 Hz, 3JC,P = 6.8 Hz, 3-C(CH3)3], 37.0 [dd, 2JC,P = 16.5
Hz, 2JC,P = 14.0 Hz, 3-C(CH3)3], 40.4 [dd, 2JC,P = 14.4 Hz, 3JC,P = 1.7
1
1
Hz, 5-C(CH3)3], 211.2 (dd, JC,P = 69.5 Hz, JC,P = 64.4 Hz, C-3),
223.1 (dd, 1JC,P = 65.3 Hz, 2JC,P = 5.9 Hz, C-5).
31P{1H} NMR (C6D6): = 122.0 (d, 2JP,P = 24.4 Hz, P-4), 313.9 (d,
2JP,P = 24.4 Hz, P-2).
MS (EI, 70 eV): m/z (%) = 216 (33) [M]+, 201 (22) [M – Me]+, 169
(9), 159 (14), 131 (37), 116 (10), 85 (7), 69 (12), 57 (100) [C4H9]+,
55 (8), 43 (5), 41 (86).
J
C,P = 6.6 Hz, 1 -CH3-cyclopentyl), 25.7 (pseudo t, JC,P = 10.4 Hz,
3
1 -CH3-cyclopentyl), 36.7, 36.9 (each pseudo t, JC,P = 3.7 Hz,
3JC,P = 4.1 Hz, respectively, C-2 - or C-5 -cyclopentyl), 37.0 (br m,
C-2 - or C-5 -cyclopentyl), 37.3 (br s, C-2 - or C-5 -cyclopentyl),
38.5 (d, 3JC,P = 5.0 Hz, C-2 - or C-5 -cyclopentyl), 40.7 (br s, C-2 -
or C-5 -cyclopentyl), 51.6 (dd, 2JC,P = 26.1 Hz, 24.5 Hz, C-1 -cyclo-
pentyl), 53.5 (m, C-1 -cyclopentyl), 62.3 (d, 2JC,P = 29.0 Hz, C-1 -
cyclopentyl), 116.1 (br m, C-5a or C-9a), 122.2 (br m, C-5a or C-
9a), 125.7 (d, 2JC,P = 15.8 Hz, ipso-C-mesityl), 126.7 (d, 2JC,P = 14.1
Hz, ipso-C-mesityl), 129.0, 129.7, 130.6, 137.5, 138.7, 138.9 (each
Anal. Calcd for C10H18OP2 (216.20): C, 55.56; H, 8.39. Found: C,
55.49; H, 8.58.
3,5-Bis(1,1-dimethylpropyl)-1,2,4-oxadiphosphole (14b); Typi-
cal Procedure
Prepared according to Variation B (co-thermolysis of 11d with the
phosphaalkene 15b): A pressure-Schlenk tube was charged with a
solution of 11d (302 mg, 0.44 mmol) and phosphaalkene 15b (123
mg, 0.44 mmol) in toluene (5 mL) and heated for 25 h at 100 °C.
The work up was performed as described under Variation A for
14a. Yield: 74.5 mg (0.31 mmol, 69%); colorless oil.
s, C-mesityl), 139.9 (d, JC,P = 2.5 Hz, C-mesityl), 156.2 (d, 1JC,P
=
39.8 Hz, C-3 or C-8), 162.1 (d, 1JC,P = 44.8 Hz, C-3 or C-8), 222.7
(d, 1JC,P = 57.2 Hz, C=O).
31P{1H} NMR (CD2Cl2): = 53.5, 57.9 (AMN spin system, 1JP,P
=
255.8 Hz, 2JP,P = 20.8 Hz, 2JP,P = 10.7 Hz, P-4, P-5), 84.4 (AMN spin
system, 2JP,P = 20.8 Hz, 2JP,P = 10.7 Hz, P-9).
IR (CCl4 solution): 2965 (s), 2921 (m), 2877 (m), 1466 (m), 1461
(m), 1385 (m), 1379 (m), 1362 (m), 1300 (w), 1217 (w), 1172 (w),
1141 (w), 1107 (w), 1051 (w), 1009 (w), 949 (w), 653 (w) cm–1.
MS (FAB): m/z = 717 [M + H]+.
1H NMR (C6D6): = 0.70 [td, 3JH,H = 7.4 Hz, 5JH,P = 0.4 Hz, 3 H,
Anal. Calcd for C41H55N2O3P3 (716.82): C, 68.70; H, 7.73; N, 3.91.
Found: C, 69.01; H, 7.60; N, 3.88.
3
C(CH3)2CH2CH3], 0.77 [t, JH,H = 7.4 Hz, 3 H, C(CH3)2CH2CH3],
4
1.32 [d, JH,P = 1.4 Hz, 6 H, 5-C(CH3)2CH2CH3], 1.34 [dd, 4JH,P
=
=
4
3
2.3 Hz, JH,P = 0.7 Hz, 6 H, 3-C(CH3)2CH2CH3], 1.66 [qd, JH,H
3,5-Di-tert-butyl-1,2,4-oxadiphosphole (14a); Typical Proce-
dure
7.4 Hz, 4JH,P = 1.1 Hz, 2 H, C(CH3)2CH2CH3], 1.68 [qd, 3JH,H = 7.4
Hz, 4JH,P = 0.7 Hz, 2 H, C(CH3)2CH2CH3].
Variation A (thermolysis of 11c): A pressure-Schlenk tube was
charged with a solution of 11c (430 mg, 0.67 mmol) in toluene (5
mL) and heated for 35 h at 100 °C. After cooling to r.t., all volatile
materials were removed under oil pump vacuum (25 °C/5 × 10–1
mbar) and the residue was worked up by column chromatography
(silica gel, n-pentane). Yield: 45.8 mg (0.21 mmol, 32%); colorless
oil; bp 50 °C/5 × 10–1 mbar.
The previously known 1,2,4-oxazaphosphole21,22 13a was identified
on the basis of its 1H and 31P NMR data as obtained from the crude
reaction mixture. Although its isolation by chromatography over
silica gel eluting with a polar eluent (n-pentane–Et2O 40:1) is pos-
sible,22 it was not attempted here.
4
13C{1H} NMR (C6D6):
=
9.2 [d, JC,P
=
1.7 Hz, 5-
4
4
C(CH3)2CH2CH3], 9.3 [dd, JC,P = 1.7 Hz, JC,P = 1.3 Hz, 3-
C(CH3)2CH2CH3], 27.5 [d, JC,P = 10.6 Hz, 5-C(CH3)2CH2CH3],
3
31.7 [dd, 3JC,P = 13.6 Hz,, 3JC,P = 6.8 Hz, 3-C(CH3)2CH2CH3], 35.1
[dd, 3JC,P = 5.7 Hz, 4JC,P = 1.1 Hz, 5-C(CH3)2CH2CH3], 39.2 [pseudo
t, 3JC,P = 7.0 Hz, 3-C(CH3)2CH2CH3], 40.2 [dd, 2JC,P = 15.3 Hz, 2JC,P
= 12.3 Hz, 3-C(CH3)2CH2CH3], 43.8 [dd, 2JC,P = 13.1 Hz, 3JC,P = 1.7
Hz, 5-C(CH3)2CH2CH3], 209.3 (dd, 1JC,P = 69.9 Hz, 1JC,P = 64.8 Hz,
C-3), 222.2 (dd, 1JC,P = 65.3 Hz, 2JC,P = 6.4 Hz, C-5).
31P{1H} NMR (C6D6): = 127.3 (d, 2JP,P = 23.9 Hz, P-4), 316.4 (d,
2JP,P = 23.9 Hz, P-2).
MS (EI, 70 eV): m/z (%) = 244 (48) [M]+, 215 (100) [M – Et]+, 145
(17), 71 (75), 57 (5), 55 (26), 43 (73), 41 (38).
Variation B (co-thermolysis of 11c with the phosphaalkene 15a):
A pressure-Schlenk tube was charged with a solution of 11c (433
mg, 0.68 mmol) and phosphaalkene 15a (178 mg, 0.68 mmol) in
toluene (5 mL) and heated for 35 h at 100 °C. The work up was per-
formed as described under variation A. Yield: 104 mg (0.48 mmol,
71%), colorless oil.
Anal. Calcd for C12H22OP2 (244.25): C, 59.01; H, 9.08. Found: C,
59.01; H, 9.23.
3,5-Bis(1-methylcyclopentyl)-1,2,4-oxadiphosphole (14c)
Prepared according to Variation B (co-thermolysis of 11e with the
phosphaalkene 15c): A pressure-Schlenk tube was charged with a
solution of 11e (192 mg, 0.27 mmol) and phosphaalkene 15c (77.1
mg, 0.27 mmol) in toluene (5 mL) and heated for 23 h at 100 °C.
The work-up was performed as described under Variation A for
14a. Yield: 48.4 mg (0.18 mmol, 68%); colorless oil.
Variation C (one-pot synthesis starting from 2a): In a pressure-
Schlenk tube a solution of 8b (2.04 g, 12.7 mmol) in toluene (7 mL)
was added to a solution of 2a (1.27 g, 4.22 mmol) in toluene (8 mL)
at –78 °C. The mixture was allowed to warm up to r.t. and was then
stirred at this temperature for 1 h. To this mixture the phosphaalkene
15a (1.11 g, 4.22 mmol) was added and the mixture was heated for
35 h at 100 °C. The work up was performed as described under
Variation A. Yield: 566 mg (2.62 mmol, 62% related to 2a), color-
less oil.
IR (CCl4 solution): 2959 (vs), 2869 (s), 1460 (m), 1448 (s), 1377
(sh), 1372 (m), 1133 (w), 1082 (w), 630 (w) cm–1.
Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York

PAPER
1,3-Dipolar Cycloaddition Reactions of 1,3,5-Triphosphinines with Nitrile Oxides
247
1H NMR (C6D6): = 1.39 (d, 4JH,P = 1.2 Hz, 3 H, 5-CH3-cyclopen-
tyl), 1.40 (dd, 4JH,P = 1.7 Hz, 4JH,P = 0.4 Hz, 3 H, 3-CH3-cyclopen-
tyl), 1.49–1.81 (m, 12 H, CH2-cyclopentyl), 1.89–2.08 (m, 2 H,
CH2-cyclopentyl), 2.09–2.32 (m, 2 H, CH2-cyclopentyl).
13C{1H} NMR (C6D6): = 24.4 (dd, 4JC,P = 1.7 Hz, 4JC,P = 0.8 Hz,
5-C-3 - or 5-C-4 -cyclopentyl), 25.2 (d, 4JC,P = 1.3 Hz, 3-C-3 - or 3-
C-4 -cyclopentyl), 27.8 (d, 3JC,P = 9.3 Hz, 5-CH3-cyclopentyl), 32.1
by STOE programs Version 2.75, structure solution by direct meth-
ods (SHELXS-9724) and structure refinement by SHELXL-97,25 hy-
drogen atoms were included in the refinement using riding models.
C35H49N2O3P3; M = 638.67 gmol–1; orthorhombic; space group Pbca
(No. 61); lattice constants a = 9.5560(19), b = 21.160(4), c =
36.096(7) Å, V = 7299(3) Å3; Z = 8; Dcal. = 1.162 Mg/m3; = 1.97
cm–1; T = 293(2) K; crystal size 0.30 × 0.20 × 0.15 mm3; 2.01
25.20°. 39865 reflections collected, 6358 independent reflections
3
3
(dd, JC,P = 10.6 Hz, JC,P = 7.2 Hz, 3-CH3-cyclopentyl), 40.5 (d,
2
(Rint. = 0.2159); 388 parameters; w–1 = [ 2(Fo ) + (0.0085P)2
+
3JC,P = 8.5 Hz, 5-C-2 - or 5-C-5 -cyclopentyl), 44.2 (dd, 3JC,P = 11.2
0.56P] and P = [(Fo ) + 2Fc2]/3; R1 = 0.0706, wR2 = 0.1155 for 2080
reflections with I > 2 (I) and R2 = 0.1848, wR2 = 0.1321 for all data;
residual electron density 226 enm–3 and –196 enm–3, S = GOF (on
F2) = 0.851.
2
Hz, 3JC,P = 6.1 Hz, 3-C-2 - or 3-C-5 -cyclopentyl), 47.6 (dd, 2JC,P
=
15.7 Hz, 2JC,P = 13.1 Hz, 3-C-1 -cylopentyl), 51.8 (dd, 2JC,P = 13.6
3
1
Hz, JC,P = 2.1 Hz, 5-C-1 -cylopentyl), 210.1 (dd, JC,P = 69.1 Hz,
1JC,P = 64.0 Hz, C-3), 222.9 (dd, 1JC,P = 63.8 Hz, 2JC,P = 6.1 Hz, C-5).
31P{1H} NMR (C6D6): = 124.0 (d, 2JP,P = 23.7 Hz, P-4), 315.1 (d,
2JP,P = 23.7 Hz, P-2).
Acknowledgment
MS (EI, 70 eV): m/z (%) = 268 (79) [M]+, 253 (11) [M – Me]+, 221
(24), 185 (18), 157 (61), 142 (43), 119 (10), 117 (10), 11 (6), 95
(28), 93 (21), 91 (11), 83 (79), 81 (11), 79 (12), 77 (8), 69 (8), 67
(29), 55 (94), 53 (22), 47 (11), 41 (100).
We thank the Fonds der Chemischen Industrie for financial support
and a post-graduate grant (to S. W.). We are grateful to the Deutsche
Forschungsgemeinschaft (Graduate College Phosphorus as Con-
necting Link between Various Chemical Disciplines) for generous
financial support.
Anal. Calcd for C14H22OP2 (268.27): C, 62.68; H, 8.27. Found: C,
62.57; H, 8.28.
References
5a,9a-Di-tert-butyl-3,8-dimesityl-[1,2,4]oxazaphospholo-
[4 ,5 :2,3][1,2,4]oxadiphospholo[4,5-d][1,2,4]oxazaphosphole
(17)
(1) Part 167, see: Dietz, J.; Bergsträßer, U.; Binger, P.; Regitz,
M. Eur. J. Org. Chem. 2003, 512.
To a solution of the oxadiphosphole 14a (119 mg, 0.55 mmol) in
toluene (5 mL) was added dropwise a solution of 8b (177 mg, 1.10
mmol) in toluene (5 mL) under magnetic stirring at –78 °C. After
warming to r.t. the solvent was removed under oil-pump vacuum
(25 °C/10–3 mbar), the residue was taken up in Et2O (20 mL) and fil-
tered over Celite. The filtrate was concentrated under oil-pump vac-
uum (25 °C/10–3 mbar) and cooled to –25 °C to induce
crystallization. Yield: 267 mg (0.50 mmol, 90%); colorless needles;
mp 132 °C (decomp).
(2) Binger, P.; Leininger, S.; Stannek, J.; Gabor, B.; Mynott, R.;
Bruckmann, J.; Krüger, C. Angew. Chem., Int. Ed. Engl.
1995, 34, 2227.
(3) (a) Tabellion, F.; Nachbauer, A.; Leininger, S.; Peters, C.;
Regitz, M.; Preuss, F. Angew. Chem. Int. Ed. 1998, 37,
1233. (b) Tabellion, F.; Peters, C.; Fischbeck, U.; Regitz,
M.; Preuss, F. Chem.–Eur. J. 2000, 6, 4558.
(4) Gleiter, R.; Lange, H.; Binger, P.; Stannek, J.; Krüger, C.;
Bruckmann, J.; Zenneck, U.; Kummer, S. Eur. J. Inorg.
Chem. 1998, 1619.
(5) (a) Nyulászi, L.; Veszprémi, T. J. Phys. Chem. 1996, 100,
6456. (b) Hofmann, M.; v. Ragué Schleyer, P.; Regitz, M.
Eur. J. Org. Chem. 1999, 3291.
(6) For a review see: Heydt, H. Top. Curr. Chem. 2003, 223,
215.
IR (KBr): 2953 (vs), 2915 (s), 2864 (s), 1609 (s), 1569 (w), 1545
(m), 1475 (s), 1458 (s), 1421 (m), 1392 (s), 1377 (m), 1363 (s), 1297
(w), 1238 (m), 1224 (m), 1165 (w), 1067 (s), 1039 (m), 1033 (m),
1000 (s), 982 (m), 954 (m), 921 (s), 862 (s), 850 (s), 812 (m), 783
(s), 734 (m), 643 (m), 624 (w), 604 (m), 593 (m), 565 (w), 553 (m),
534 (w), 522 (w) cm–1.
(7) Peters, C.; Disteldorf, H.; Fuchs, E.; Werner, S.; Stutzmann,
S.; Bruckmann, J.; Krüger, C.; Binger, P.; Heydt, H.; Regitz,
M. Eur. J. Org. Chem. 2001, 3425.
(8) Peters, C.; Stutzmann, S.; Disteldorf, H.; Werner, S.;
Bergsträßer, U.; Krüger, C.; Binger, P.; Regitz, M. Synthesis
2000, 529.
(9) Weidner, S. PhD Thesis; University of Kaiserslautern:
Germany, 2002.
(10) Zurmühlen, F.; Rösch, W.; Regitz, M. Z. Naturforsch., B:
Chem. Sci. 1985, 40, 1077.
(11) Mack, A. PhD Thesis; University of Kaiserslautern:
Germany, 1998.
(12) Mack, A.; Bergsträßer, U.; Reiß, G. J.; Regitz, M. Eur. J.
Org. Chem. 1999, 587.
(13) Allspach, T.; Regitz, M.; Becker, G.; Becker, W. Synthesis
1986, 31.
1H NMR (CD2Cl2): = 1.13, 1.14, [each s, 9 H, C(CH3)3], 2.30,
2.32, (each s, 3 H, ortho-CH3-mesityl), 2.34 (s, 6 H, ortho-CH3-
mesityl), 2.55, 2.56 (each s, 3 H, para-CH3-mesityl), 6.94, 6.95
(each s, 2 H, H-mesityl).
4
13C{1H} NMR (CD2Cl2): = 20.7 (d, JC,P = 5.1 Hz, ortho-CH3-
mesityl), 20.9 (s, ortho-CH3-mesityl), 21.0 (s, ortho-CH3-mesityl),
22.0 (s, para-CH3-mesityl), 22.2 (s, para-CH3-mesityl), 25.4 [d,
3
3JC,P = 6.4 Hz, 5a-C(CH3)3], 28.0 [pseudo t, JC,P = 9.5 Hz, 9a-
2
C(CH3)3], 38.5 [pseudo t, JC,P = 23.5 Hz, 9a-C(CH3)3], 40.9 [dd,
2JC,P = 24.8 Hz, 3JC,P = 4.5 Hz, 5a-C(CH3)3], 122.7 (pseudo t, 1JC,P
=
54.0 Hz, C-9a), 126.4 (d, 2JC,P = 16.1 Hz, ipso-C-mesityl), 126.8 (d,
2JC,P = 14.8 Hz, ipso-C-mesityl), 128.9, 129.9, 137.6, 138.0, 138.9,
139.0 (each s, C-mesityl), 140.0 (dd, 1JC,P = 34.5 Hz, 2JC,P = 19.3 Hz,
C-5a), 157.6 (d, 1JC,P = 43.2 Hz, C-3 or C-8), 160.6 (d, 1JC,P = 61.9
Hz, C-3 or C-8).
31P{1H} NMR (CD2Cl2): = 31.3 (d, 2JP,P = 1.5 Hz, P-9), 156.7 (d,
(14) Berger, S.; Braun, S.; Kalinowski, H.-O. NMR-
Spektroskopie von Nichtmetallen, Vol. 3; Georg Thieme
Verlag: Stuttgart, New York, 1993, 140.
(15) Rösch, W.; Regitz, M. Synthesis 1987, 689.
(16) The nitrile oxide was prepared in situ from N-hydroxy-
benzenecarboximidoyl chloride by elimination of HCl with
triethylamine in Et2O: Weiland, H. Ber. Dtsch. Chem. Ges.
1907, 40, 1670.
2JP,P = 1.5 Hz, P-4).
MS (FAB): m/z = 539 [M + H]+.
Anal. Calcd for C30H40N2O3P2 (538.60): C, 66.90; H, 7.49; N, 5.20.
Found: C, 66.68; H, 7.81; N, 5.32.
Crystal Structure Analysis of 11c:23 Crystal Data: C35H49N2O3P3,
STOE Imaging Plate Diffraction System, graphite monochromator,
MoK radiation ( = 0.71073 Å), cell determination and refinement
(17) Grundmann, C.; Dean, J. M. J. Org. Chem. 1965, 30, 2809.
Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York

248
S. Weidner et al.
PAPER
(18) Becker, G. Z. Anorg. Allg. Chem. 1977, 430, 66.
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Germany, 1986.
(20) Rösch, W.; Vogelbacher, U.-J.; Allspach, T.; Regitz, M. J.
Organomet. Chem. 1986, 306, 39.
Crystallographic Data Centre as supplementary publication
no. CCDC-211047. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, U.K. [Fax: +44(1223)336033; E-mail:
deposit@chemcrys.cam.ac.uk].
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(22) Schmidt, T. PhD Thesis; University of Kaiserslautern:
Germany, 2000.
(23) Crystal data (excluding structure factors) for the structure
reported in this paper has been deposited with the Cambridge
(24) Sheldrick, G. M. SHELXS-97, Program for Crystal
Structure Solution; University of Göttingen: Germany,
1990.
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Synthesis 2004, No. 2, 241–248 © Thieme Stuttgart · New York