1,3-Dipolar cycloadditions of 9-diazofluorenes and diphenyldiazomethane to 2-acyl-2H-1,2,3-diazaphospholes

Article abstract of DOI:10.1002/jhet.5570430215

A series of 2-acyl-2H-1,2,3-diazaphospholes 3 underwent ready 1,3-dipolar cycloaddition reactions with 9-diazofluorenes as the 1,3-dipole, yielding the respective bicyclic phosphiranes 5 or trimers 7 depending on the reaction conditions employed. The reac

Full text of DOI:10.1002/jhet.5570430215

Mar-Apr 2006
353
1,3-Dipolar Cycloadditions of 9-Diazofluorenes and
Diphenyldiazomethane to 2-Acyl-2H-1,2,3-diazaphospholes
Xiangyun Guo, Li Feng, Quanrui Wang*, Zhiming Li and Fenggang Tao
Department of Chemistry, Fudan University, Shanghai 200433, P. R. China
Received June 20, 2005
A series of 2-acyl-2H-1,2,3-diazaphospholes 3 underwent ready 1,3-dipolar cycloaddition reactions with
9-diazofluorenes as the 1,3-dipole, yielding the respective bicyclic phosphiranes 5 or trimers 7 depending
on the reaction conditions employed. The reaction is believed to proceed via the formation of the [3+2]-
cycloaddition adducts followed by elimination of nitrogen from the cyclic azo moiety. In the case of 3c, the
phosphatetraazabicyclooctadiene compound 6 has been isolated with no loss of nitrogen. Likewise, the
dipolar cycloaddition reaction of diphenyldiazomethane with the >C=P- moiety as the 1,3-dipolarophile
gave phosphadiazabicyclohexenes 8 in 32-68% yields.
J. Heterocyclic Chem., 43, 353 (2006).
Introduction.
complete regioselectivity has been reported in the DA
reaction of 2-acetyl-2H-1,2,3-diazaphosphole with
isoprene [8]. Aside from phosphaalkenes that are
known to undergo [2+4] cycloadditions under mild
conditions, the similar ability of various heretophos-
pholes to take part in DA reactions with 1,3-dienes
may be attributed to the similarity of their frontier
orbitals. However, such similarities are limited as
phosphaalkenes have energetically closely spaced ꢀ-
and ꢁ orbitals (i.e. HOMO and the next HOMO) [9],
whereas benzoxaphospholes, for instance, have a
10ꢀ-delocalized ring system with all the three
highest occupied MOs being ꢀ-orbitals [10]. On the
other hand, the P atom of anellated heterophospholes
with high ꢀ-electron density tend to act as a
[1+4]cheletropic center and react with heterodienes
such as ꢂ-diketones and ꢂ-diimines to give the
spirocyclic adducts [11,12].
1,3-Dipolar cycloaddition has proved to be an effective
synthetic tool, providing one of the best ways to construct
five-membered heterocyclic compounds with diverse
functionality [1]. In most cases, the reaction proceeds
with controlled stereospecifity and regioselectivity with
respect to the dipolarophiles. Apart from the common
alkenes and alkynes, numerous heteroatom-containing
unsaturated compounds have been developed and applied
successfully as dienophiles, thus widening the scope of
1,3-dipolar cycloadditions considerably.
Two-coordinated trivalent phosphorus compounds,
which appeared about thirty years ago, have earned
ever-increasing research interests from various
perspectives [2,3]. In this context, compounds that
bear a >C=P- functionality, including phosphaalkenes
[4,5], heterophospholes [5], phosphinines [6] and
anellated azaphospholes [7], have received much
attention. It has been shown that many >C=P-
compounds are reactive toward Diels-Alder (DA)
reaction with electron-rich 1,3-dienes. With unsym-
metrical diene like isoprene the reaction occurs
mostly in a high regioselective manner and the sense
of the cycloaddition was governed by the relative
coefficients of the frontier orbitals. For example,
In comparison to the study on the reactivity toward DA
reactions, the exploration of heterophospholes for use as a
dipolarophile in 1,3-dipolar cycloaddition reactions are
seemingly not as plentiful. Exceptions are organic azides
which have been repeatedly examined in the reactions
with compounds containing a >C=P- functionality [3]. It
has been demonstrated that phospha-alkenes including

354
X. Guo, L. Feng, Q. Wang, Z. Li and F. Tao
Vol 43
equivalents of triethylamine giving firstly the 2-acyl-3-chloro-
3,4-dihydro-2H-1,2,3-diazaphospholes 2. Intermediates 2 are
isolated, purified and then treated with another equimolecular
amount of triethylamine to afford the 2H-1,2,3-diaza-
phospholes 3. In the other procedure isolation of the
intermediates 2 is not effected. Both methods have been
tested in the present study. After screening the reaction
conditions, the second one-pot strategy with slight variation
appears to be attractive for synthesizing 3. The trick lies in
that the intermediates 2, generated by reaction of hydrazones
1 with PCl3, filtering off the precipitated salt of NEt3·HCl and
removal of the solvent and the excess PCl3 by vacuum
distillation, were directly taken into dry benzene and treated
1,2,3-diazaphospholes can couple with organic azides
either by the [2+3] cycloaddition reaction or in the
Staudinger mode depending on the structure of substrates
and reaction conditions. Also 1,2,3-diazaphospholes have
been reported by Arbuzov’s group and other researchers
to react with diazoalkanes, giving out mainly the 1:1
cycloadducts via a [2+3]cycloaddition reaction [13].
However, the initial adducts are generally unstable and
decompose under elimination of nitrogen leading to
formation of a mixture of ꢀ3P compounds or cyclic trimer.
In connection with our recent interests on the reactivity
of >C=P- functionality, we initiated a program on the
synthesis of diversely substituted 2H-1,2,3-diazaphos-
pholes and their reactions with 9-diazofluorene or
diphenyldiazomethane as an 1,3-dipole molecule. We
could show that the reaction can proceed in several
directions and that the bicyclic phosphiranes or the cyclic
trimers can be achieved will loss of nitrogen from the
initial adducts. In one case, the “intact” 1,3-dipolar
cycloadduct has been obtained.
Scheme 1
Results and Discussion.
1-3
R1
R2
R3
Yield (%)
a
b
c
d
e
f
H
H
H
Me
Ph
t-Bu
COCH3
COCH3
COCH3
65
56
52
28
36
27
28
26
Our study began with the preparation of 2H-1,2,3-
diazaphospholes 3. A literature survey suggested that methods
for the synthesis of compounds 3 fall into two categories, both
by employment of the acylhydrazones 1 as the starting
material [8,14]. The first one features a two-sep synthesis in
which the hydrazones 1 were allowed to react with two
equivalents of phosphorus trichloride in the presence of two
-(CH2)3-
COCH3
H
H
H
Me
Ph
t-Bu
CO2C2H5
CO2C2H5
CO2C2H5
CO2C2H5
g
h
-(CH2)3-
Scheme 2
5
R1
R2
R3
R4
Yields (%)
a
b
c
d
e
H
H
Me
Ph
-(CH2)3-
H
H
H
Cl
Br
H
H
H
Cl
Br
77
90
83
82
89
H
H
Ph
Ph

Mar-Apr 2006
1,3-Dipolar Cycloadditions of 9-Diazofluorenes and Diphenyldiazomethane
355
Scheme 3
with another equivalent of triethylamine to eliminate the
remaining HCl. Thus, employing this varied procedure, the
diversely substituted 2H-1,2,3-diazaphospholes 3a-h were
obtained in 26-65% yields (Scheme 1).
The reaction of 3a with 9-diazofluorene was used as a
model reaction to investigate the optimal condition. To a
well-stirred solution of 9-diazofluorene 4a in dry
cyclohexane was added an equimolecular amount of 3a.
The reaction proceeded smoothly at room temperature.
TLC analysis indicated that the reaction was successfully
completed upon stirring for approximate 3 hours. Usual
work-up furnished the phosphadiazabicyclohexene 5a as a
pale yellow powder in 77% yield (Scheme 2) with release
of a N2 molecule. Further elongating the reaction time or
elevating the temperature gave inferior results.
Under the optimized conditions, the dipolar cycloaddi-
tion of 9-diazofluorene 4a with 2H-1,2,3-diazophospholes
3b and 3c gave the respective phosphadiazabicyclohexene
5b and tricyclic 5c, respectively. Similarly, from the
dihalogenated 9-diazofluorenes 4d and 4e the correspon-
ding 2ꢀ,7ꢀ-dihalo substituted analogues 5d and 5e were
obtained in high yields (Scheme 2).
However, for the reaction of the 2H-1,2,3-diazophosphole
4a 3c with 9-diazafluorene no elimination of nitrogen
occurred and the respective 3-spiro-substituted 3H-1,2,4-
diazaphospholo fused 1,2,3-diazaphosphole 6 has been
isolated in 65% yield after stirring for five hours at room
temperature as a grayish powder. This may be attributed to
the stabilizing effect exerted by the congested tertiary butyl
substitutent at 7-position of 6 (Scheme 4).
The reaction can also be performed in a polar solvent like
dichloromethane, but the isolated products proved to be cyclic
trimer compounds 7. Thus, 9-diazofluorene 4a reacted with
the 2H-1,2,3-diazaphosphole 3a via a [2+3] cycloaddition
Scheme 4
COCH3
N
P
N
N
But
N
But
Cyclohexane
r.t., 5h
+
COCH3
N
P
N
H
N2
3c
6
4a
reaction to give the cyclic trimer 7a in 95% isolated yield. In a
similar manner, other cyclic trimers were prepared in high to
excellent yields, except for 3c which provided 7c in only 56%
yield due to the steric effect of tertiary butyl group (Scheme 5).
This phenomenon is reminiscent of the observations made by
Appel who reported that the products of 1,3-dilopar cyclo-
addition of phosphaalkenes with azides could eliminate
nitrogen to give the dimer diazadiphosphetidines as final
products [17]. The same thing happens if the reaction is carried
out in dry benzene, affording also the cyclic trimers.
Scheme 3 tries to explain the above reactions. The
initial step is a typical 1,3-dipolar cycloaddition of 9-
diazofluorene as the 1,3-dipole with the 2H-1,2,3-diaza-
phosphole serving as the dipolarophile. The cycloaddition
across the >C=P- double bond provides the primary
adducts I. Intermediates I are characteristic of pyrazolines,
which are labile and prone to eliminating nitrogen to give
the phosphirane-fused heterocycles 5a-e as the final
products. The elimination of nitrogen from cyclic azo
compounds is one of the most widely used procedures,
especially for the synthesis of strained-ring systems [15].
Our results are comparable to those observed for the
reaction between diazo compounds with alkenes [16]. It
has been repeatedly reported that the initially formed
pyrazolines undergo thermal or photochemical loss of
nitrogen to yield various cyclopropanes. Although the
possibility via formation of carbene species (II) cannot be
rigorously excluded, the fact that none of cycloadducts
onto the >C=N- double bonds has been detected from the
product led us prefer route a as the plausible way.
Mechanistically, the formation of the cyclic trimers
7 may be accounted for by a sequence depicted as
follows (Scheme 6). The 2H-1,2,3-diazaphospholes 3
react with 9-diazofluorene 4a by a 1,3-dipolar manner.
The resultant cycloadducts I decompose with loss of
nitrogen to give novel heterocyclic products III
containing a three-coordinate pentavalent P atom,
which resemble a Staudinger product in character [3].
Thus, trimerization of III provided the oligomeric
cyclophosphines 7.

356
X. Guo, L. Feng, Q. Wang, Z. Li and F. Tao
Vol 43
Scheme 5
COCH3
CH2Cl2 or
C6H6
R2
R1
N
P
N
N
R'
+
COCH3
R''
P
N
R2
R4
(H)
R3
r.t., 5h
(H)
3
R1
N2
7
3
4
R3
(H)
R4
(H)
R'-R'' =
Trimers 6
R1
R2
R3
R4
Yields (%)
a
b
c
d
e
H
H
H
Me
Ph
t-Bu
H
H
H
H
Br
H
H
H
H
Br
95
88
56
79
91
-(CH2)3-
H
Ph
Finally, we examined the reactivity of diazaphos-
pholes with diphenyldiazomethane as the 1,3-dipolar
component. In a similar manner, the reaction proceeded
smoothly under comparable conditions, giving out
exclusively the phosphadiazabicyclohexenes 8 by
elimination of nitrogen from the initial [2+3]-cyclo-
addition products in 28-68% yields (Scheme 7).
The structures suggested for all the prepared products
have been verified by analysis of their analytical and
spectroscopic data, which are given in the experimental
part. It is well known that the 31P NMR chemical shifts can
be affected by many factors such as ring members adjacent
to P atom, the anellated ring size, anellation pattern, and
additional heteroatoms in the ring [18]. For each of the
products 5 and also 8 a highly shielded 31P NMR
absorption at ꢀ -92 ~ -45 ppm can be observed, the range
compatible with three-coordinate trivalent P atoms [19]. In
contrast, the precursors 3 give each a highly deshielded 31P
NMR signal at 220-240 ppm. Similar observations are
made for the 13C NMR spectra. Thus, the 13C NMR signals
found in the range of 42-77 ppm with 1JPC = 127~183 Hz
are attributed to the sp3 hybridized carbon atom in the 3,4-
dihydro-2H-1,2,3-diazaphophole ring of compounds 5 and
8. This demonstrated clearly that the original >C=P- bond
in 3 has been saturated after reaction. On the other hand,
the 13C NMR signal for the sp2 hybridized carbon atom
in the 3,4-dihydro-2H-1,2,3-diazaphophole ring of the
products remains nearly unchanged, a result in
expectation. In addition, the –P=CH in the substrates 3
Scheme 6
Scheme 7
1
R2
give each a doublet H NMR signal at 7.8-8.4 ppm with
R1
R2
2JPH 42-44 Hz. In the products 5 and also 8, the respective
>P-CH signal shifted upfield by 4~4.5 ppm, appearing at
3.2~4.5 ppm with 2JPH 20-22 Hz.
N
P
Ph
Ph
n-Pentane
r.t., 3-5h
Ph
Ph
N R3
+
N
N
R3
P
R1
N2
On the other hand, the 31P NMR signal for 6 was
found at –90.4 ppm, locating in the same range as 5
3
8
1
and 8. In the H NMR spectrum of cycloadduct 6, the
m.p. (°C)
8
R1
R2
R3
Yields (%)
2
somewhat upfield doublet at ꢀ 3.15 ppm with JPH 21.0
a
b
c
d
e
f
H
H
H
Me
Ph
t-Bu
COCH3
COCH3
COCH3
132-135
128-132
138-140
124-127
78-80
40-42
99-100
93-95
68
66
32
64
50
52
28
46
Hz can be assigned to C(7a)-H, whilst the respective
signal for –P=CH in the precursor 3c gives a doublet at
ꢀ 8.03 ppm (2JPH ꢁ 43 Hz).
For the cyclic trimer compounds 7, the structures
have been principally ascertained by NMR and IR
spectra along with microelemental analysis. The 31P
-(CH2)3-
COCH3
H
H
H
Me
Ph
t-Bu
CO2C2H5
CO2C2H5
CO2C2H5
CO2C2H5
g
h
-(CH2)3-

Mar-Apr 2006
1,3-Dipolar Cycloadditions of 9-Diazofluorenes and Diphenyldiazomethane
357
This compound was obtained as pale-yellow powders in 90%
1
NMR signal was at approximately 50 ppm, a range
characteristic for three-coordinated P [18]. Furthermore,
each of the trimers show a HRMALDI MASS ion peak
formed by loss of three acetyl residues.
yield. M.p. 160-161°C; H NMR (CDCl3/TMS) ꢀ: 2.60 (s, 3H,
2
COCH3), 4.53 (d, 1H, JP,H = 20.2, P-CH), 7.12-7.95 (m,
13Harom); 31P NMR (CDCl3) ꢀ: -63.66; 13C NMR (CDCl3/TMS)
1
1
ꢀ: 21.94 (COCH3), 33.04 (d, Jc,p = 198.7, C6), 49.65 (d, Jc,p
=
In conclusion, the present work describes the
systematic study on the dipolar cycloaddition reaction
between 2H-1,2,3-diazaphospholes 3 and 9-diazo-
fluorenes 4 or diphenyldiazomethane. Depending on
the reaction conditions employed, the corresponding
bicyclic phosphiranes 5 and 8 or trimers 7 could be
furnished in satisfactory yields. For 3c, the phospha-
tetraazabicyclooctadiene 6 has been isolated with no
loss of nitrogen.
164.2, C5), 120.13-141.44 (m, Carom), 156.80 (C4), 177.36 (d, 2Jc,p
= 44.6, C=O); IR (KBr) ꢁ (cm-1): 1618 (C=N), 1665 (C=O); MS
m/z (%): 368 (M+, 23), 165 (100), 133 (85); HRMS calcd for
C23H17N2OP 368.1079, found 368.1065.
17-Acetyl-17,18-diaza-16-phosphaspiro[fluorene-9,2'-tricyclo-
[4.3.0.01,3]nonane]-18-ene (5c).
This compound was obtained as pale-yellow powders in 83%
1
yield. M.p. 134-136 °C; H NMR (CDCl3/TMS) ꢀ: 2.07-2.21 (m,
4H, 2CH2), 2.46 (s, 3H, COCH3), 2.60 (t, 2H, C3-H2), 6.89-7.84 (m,
8Harom); 31P NMR (CDCl3) ꢀ: -45.16; 13C NMR (CDCl3/TMS) ꢀ:
22.67 (COCH3), 22.74, 26.92, 27.88 (CH2), 36.41 (d, Jc,p = 197.0,
EXPERIMENTAL
1
C13), 61.94 (d, Jc,p = 183.5, C14), 120.11-142.99 (m, Carom), 168.81
(C19), 175.47 (d, 2Jc,p = 44.5, C=O); IR (KBr) ꢁ (cm-1): 1630 (C=N),
1672 (C=O); MS m/z (%):332 (M+, 62), 43 (100), 289 (44); HRMS
calcd for C20H17N2OP 332.1453, found 332.1436.
The melting points are uncorrected. Solvents were dried by
standard methods. The IR spectra were recorded on a Mattson
Alpha-centauri FT-IR spectrometer, using KBr discs. The
2-Acetyl-4-phenyl-spiro[2,3-diaza-1-phospha]bicyclo[3.1.0]hex-
3-ene-6,9'-[9H]-2',7'-dichlorofluorene (5d).
1
absorptions are given in wavenumbers (cm-1). H and 13C NMR
spectra were acquired in DMSO-d6, or CDCl3 as solvents on a
Bruker 500 or Varian 400 spectrometer with TMS as internal
reference. For 31P NMR spectra 85% H3PO4 was used as the
external reference. Coupling constant (J) values are given in Hz.
The mass spectra were performed at 70 eV on a Finnigan MAT
This compound was obtained as pale-yellow powders in 82%
1
yield. M.p. 118-120 °C; H NMR (CDCl3/TMS) ꢀ: 2.28 (s, 3H,
2
COCH3), 3.65 (d, 1H, JP,H = 20.3, P-CH), 7.28-7.96 (m,
11Harom); 31P NMR (CDCl3) ꢀ: -68.32; 13C NMR (CDCl3/TMS)
1
ꢀ: 22.25 (COCH3), 32.81 (d, JC,P = 190.5, C6), 46.99 (d, JC,P
1
=
spectrometer provided with
a data system. Satisfactory
162.5, C5), 119.04-142.86 (m, Carom), 156.36 (C4), 172.30 (d,
2JC,P = 44.2, C=O); IR (KBr) ꢁ (cm-1): 1625 (C=N), 1690 (C=O);
MS m/z (%): 436 (M+, 18), 103 (100), 196 (90); HRMS calcd
for C23H15Cl2N2OP 436.0300, found 436.0321.
microanalysis (C±0.20, H±0.20, N±0.30) was obtained for new
compounds. All the reactions were carried out under a N2
atmosphere with strict exclusion of moisture using oven-dried
apparatus and glassware. Details for preparation of 2H-1,2,3-
diazapholspholes 3 have been described elsewhere [20].
2-Acetyl-4-phenyl-spiro[2,3-diaza-1-phospha]bicyclo[3.1.0]hex-
3-ene-6,9'-[9H]-2',7'-dibromofluorene (5e).
Synthesis of the Heterocycles 5 and 8.
This compound was obtained as yellow powders in 89%
1
A cyclohexane solution of 3 (10 mmole) is added dropwise to
a solution of 9-diazofluorene (1.92 g, 10 mmole) in cyclohexane
under stirring at 20 °C, and the resulting mixture is stirred for
additional 3~6 hours. The red color faded to yellow over about 2
h, the precipitates are collected by filtration and washed with
ether for three times through a porous plate. The product is dried
in vacuum to afford the pure 5 or 8 in 28-90% yields.
yield. M.p. 124-126 °C; H NMR (CDCl3/TMS) ꢀ: 2.01 (s, 3H,
2
COCH3), 3.62 (d, 1H, JP,H = 20.4, P-CH), 7.38-7.76 (m,
11Harom); 31P NMR (CDCl3) ꢀ: -70.56; 13C NMR (CDCl3/TMS)
1
ꢀ: 22.96 (COCH3), 35.22 (d, JC,P = 199.2, C6), 48.23 (d, JC,P
1
=
163.7, C5), 121.36-145.22 (m, Carom), 154.66 (C4), 176.36 (d,
2JC,P = 44.2, C=O); IR (KBr) ꢁ (cm-1): 1621 (C=N), 1682 (C=O);
MS m/z (%): 526 (M+, 20), 163 (100), 243 (61); HRMS calcd
for C23H15Br2N2OP 523.9289, found 523.9272.
2-Acetyl-4-methyl-spiro[2,3-diaza-1-phospha]bicyclo[3.1.0]hex-
3-ene-6,9'-[9H]fluorene (5a).
5-Acetyl-5,7a-dihydro-7-(tert-butyl)-spiro[3H-1,2,4-diazaphos-
pholo][4,3-c][1,2,3]diazaphosphole-3,9ꢀ-[9H]fluorene (6).
This compound was obtained as yellow powders in 77%
1
yield. M.p. 164-166 °C; H NMR (CDCl3/TMS) ꢀ: 2.26 (s, 3H,
This compound was obtained as gray powders in 65% yield.
M.p. 118-120 °C; 1H NMR (CDCl3/TMS) ꢀ: 1.11 (s, 9H,
C(CH3)3), 2.34 (s, 3H, COCH3), 3.15 (d, 1H, 2JP,H = 21.0, P-CH),
7.21-7.68 (m, 8Harom); 31P NMR (CDCl3) ꢀ: -90.35; 13C NMR
(CDCl3/TMS) ꢀ: 21.87 (COCH3), 28.30 (C(CH3)3), 34.6
2
CH3), 2.47 (s, 3H, COCH3), 4.01 (d, 1H, JP,H = 21.0, P-CH),
6.74-7.89 (m, 8Harom); 31P NMR (CDCl3) ꢀ: -75.44; 13C NMR
1
(CDCl3/TMS) ꢀ: 18.65 (CH3), 21.94 (COCH3), 30.20 (d, JC,P
=200, C6), 48.11 (d, 1JC,P = 163.5, C5), 118.36-145.28 (m, Carom),
2
157.03 (C4), 175.16 (d, Jc,p = 44.5, C=O); IR (KBr) ꢁ (cm-1):
1
1
(C(CH3)3), 36.25 (d, Jc,p = 188.2, C3), 46.50 (d, Jc,p = 163.0,
1607 (C=N), 1672 (C=O); MS m/z (%): 306 (M+, 69), 264
(100), 263 (91); HRMS calcd for C18H15N2OP 306.0922, found
306.0932.
2
C7a), 118.82-142.89 (m, Carom), 158.62 (C7), 172.08 (d, Jc,p
=
44.5, C=O); IR (KBr) ꢁ (cm-1): 1560 (N=N), 1630 (C=N), 1700
(C=O); MS m/z (%): 319 (M+- C(CH3)3, 4),165 (100), 261 (29),
318 (M++1-C(CH3)3, 13); HRMS calcd for C21H21N4OP-C4H9
319.0749, found 319.0739.
2-Acetyl-4-phenyl-spiro[2,3-diaza-1-phospha]bicyclo[3.1.0]hex-
3-ene-6,9'-[9H]fluorene (5b).

358
X. Guo, L. Feng, Q. Wang, Z. Li and F. Tao
Vol 43
10Harom); 31P NMR (CDCl3) ꢁ: -92.82; 13C NMR (CDCl3/TMS) ꢁ:
19.27 (CH3), 21.55 (COCH3), 38.44 (d, 1Jc,p = 189.0, C6), 50.40 (d,
1Jc,p = 145.5, C5), 126.15-142.42 (m, Carom), 157.28 (C4), 174.99 (d,
2Jc,p = 41.0, C=O); IR (KBr) ꢀ (cm-1): 1602 (C=N), 1657 (C=O);
MS m/z (%): 308 (M+, 25), 165 (100), 265 (42); HRMS calcd for
C18H17N2OP 308.1079, found 308.1062.
Synthesis of the Trimer 7.
A solution of 3 (5 mmole) and equimolar amount of 9-
diazofluorene in dry CH2Cl2 (5 mmole) or benzene is stirred at
20 °C for 3~5 hours. The solution turned to a thick suspension
upon completion of the reaction. Then, ether or cyclohexane was
added, and the yellow precipitates were collected by suction.
The yellow colored solids were washed with cold ether and
dried at vacuum to give pure 7 in 56-95% yields.
2-Acetyl-4,6,6-triphenyl-2,3-diaza-1-phosphabicyclo[3.1.0]hex-
3-ene (8b).
Cyclic Trimer (7a).
This compound was obtained as white powders in 66% yield.
M.p. 128-132 °C. 1H NMR (CDCl3/TMS) ꢁ: 2.12 (s, 3H,
This compound was obtained as yellow powders in 95%
yield. M.p. 256-258 °C; IR (KBr) ꢀ (cm-1): 739 (s), 1228, 1260
(m), 1335 (s), 1611 (w), 1672 (vs).
Anal. Calcd for C54H45N62O3P3 (%): C, 70.57; H, 4.93; N,
9.14. Found: C, 70.38; H, 4.90; N, 9.29.
2
COCH3), 4.29 (d, 1H, JP,H = 19.7, P-CH), 6.97-7.88 (m,
15Harom); 31P NMR (CDCl3) ꢁ: -90.50; 13C NMR (CDCl3/TMS)
1
ꢁ: 21.55 (COCH3), 39.03 (d, Jc,p = 187.0, C6), 47.02 (d, Jc,p
=
144.0, C5), 126.44-142.48 (m, Carom), 156.32 (C4), 175.40 (d, 2Jc,p
= 39.5, C=O); IR (KBr) ꢀ (cm-1): 1594 (C=N), 1668 (C=O);
MS m/z (%): 370 (M+, 24), 165 (100), 327 (41); HRMS calcd
for C23H19N2OP 370.1235, found 370.1224.
Cyclic Trimer (7b).
This compound was obtained as yellowish brown powders in
88% yield. M.p.186 –188 °C; IR (KBr) ꢀ (cm-1): 739 (s), 1246,
1280 (m), 1347 (s), 1630 (w), 1676 (vs); HRMALDIMS for
C69H51N6O3P3 (M++1-3COCH3): calc 976.1868, found 976.1891.
2-Acetyl-4-(tert-buty)l-6,6-diphenyl-2,3-diaza-1-phosphabicyclo-
[3.1.0]hex-3-ene (8c).
This compound was obtained as white powders in 32% yield.
M.p. 138-140 °C. 1H NMR (CDCl3/TMS) ꢁ: 1.29 (s, 9H,
C(CH3)3), 2.03 (s, 3H, COCH3), 3.98 (d, 1H, 2JP,H = 19.4, P-CH),
6.97-7.34 (m, 10Harom); 31P NMR (CDCl3) ꢁ: -88.69; 13C NMR
(CDCl3/TMS) ꢁ: 21.53 (COCH3), 29.09 (C(CH3)3), 35.92
Cyclic Trimer (7c).
This compound was obtained as grayish brown powders in
56% yield. M.p.80-82 °C; H NMR (CDCl3/TMS) ꢁ: 0.74 (s,
1
2
9H, C(CH3)3), 2.55 (s, 3H, COCH3), 5.43 (d, 1H, JP,H = 31.6,
P=CH), 7.27-8.09 (m, 8Harom); 31P NMR (CDCl3) ꢁ: 51.88; 13C
NMR (CDCl3) ꢁ: 21.86 (COCH3), 27.04 (C(CH3)3), 29.00
1
1
(C(CH3)3), 38.75 (d, Jc,p = 184.5, C6), 47.98 (d, Jc,p = 141.5,
2
C5), 126.52-142.52 (m, Carom), 166.30 (C4), 175.43 (d, Jc,p
=
1
(C(CH3)3), 36.36 (d, JC,P = 187.0, C-P), 120.42-143.82 (m,
41.5, C=O); IR(KBr) ꢀ (cm-1): 1610 (C=N), 1690 (C=O); MS
m/z (%): 350 (M+, 24), 165 (100), 307 (10); HRMS calcd for
C21H23N2OP 350.1548, found 350.1533.
1
2
Carom), 138.70 (d, JC,P =12.0, C=P), 173.38 (d, JC,P = 43.6,
C=O); IR (KBr) ꢀ (cm-1): 741 (s), 1244, 1283 (m), 1350 (s),
1637 (w), 1677 (vs); HRMALDIMS for C63H63N6O3P3 (M++1-
3COCH3): calc 916.2807, found 916.2787.
4-Acetyl-4,5-diaza-2,2-diphenyl-3-phospha-tricyclo[4.3.0.01,3]-
non-5-ene (8d).
Cyclic Trimer (7d).
This compound was obtained as white powders in 64% yield;
M.p. 124-127 °C. 1H NMR (CDCl3/TMS) ꢁ: 1.97 (s, 3H,
COCH3), 2.09-2.69 (m, 6H, 3CH2), 6.78-7.34 (m, 10Harom); 31P
NMR (CDCl3) NMR ꢁ: -64.92; 13C (CDCl3/TMS) ꢀ: 21.67
(COCH3), 25.00, 27.65, 28.31 (CH2), 42.58 (d, 1Jc,p =167.5, C2),
This compound was obtained as yellow powders in 79%
yield. M.p.90-92 °C; IR (KBr) ꢀ (cm-1): 746 (s), 1235, 1266 (m),
1375 (s), 1621 (w), 1665 (vs); HRMALDIMS for C60H51N6O3P3
(M++1-3COCH3): calc 868.1868, found 868.1890.
1
Cyclic Trimer (7e).
64.66 (d, JC,P = 164.5, C1), 126.11-140.71 (m, Carom), 169.62
2
(C6), 175.12 (d, JC,P = 39.5, C=O); IR (KBr) ꢀ (cm-1): 1622
This compound was obtained as yellow powders in 91%
1
(C=N), 1670 (C=O); MS m/z (%): 334 (M+, 50), 165 (100), 215
(70); HRMS calcd for C20H19N2OP 334.1235, found 334.1249.
yield. M.p.163-165 °C; H NMR (CDCl3/TMS) ꢁ: 2.69 (s, 3H,
2
COCH3), 5.50 (d, 1H, JP,H = 32.3, P=CH), 7.30-7.68 (m,
8Harom); 31P NMR (CDCl3) ꢁ: 48.76; 13C NMR (CDCl3/TMS) ꢁ:
2-Ethoxycarbonyl-4-methyl-6,6-diphenyl-2,3-diaza-1-phospha-
bicyclo[3.1.0]hex-3-ene (8e).
1
22.45 (COCH3), 35.81 (d, JC,P = 199.0, C-P), 120.44-146.32
1
2
(m, Carom), 140.75 (d, JC,P = 12.0, C=P), 175.34 (d, JC,P = 43.4,
C=O); IR (KBr) ꢀ (cm-1): 741 (s), 1236, 1270 (m), 1342 (s),
1625 (w), 1690 (vs); HRMALDIMS for C69H45Br6N6O3P3
(M++1-3COCH3): calc 1443.6498, found 1443.6517.
This compound was obtained as white powders in 50% yield.
1
M.p. 78-80 °C. H NMR (CDCl3/TMS) ꢁ: 1.28 (t, 3H, J= 7.0,
2
OCH2CH3), 2.24 (s, CH3), 3.80 (d, 1H, JP,H = 18.4, P-CH),
4.24 (q, 2H, J = 7.0, OCH2CH3), 7.14-7.80 (m, 10Harom); 31P NMR
(CDCl3) ꢁ: -86.68; 13C NMR (CDCl3/TMS) ꢁ: 14.35 (OCH2CH3),
Synthesis of the Heterocycles (8).
1
1
These compounds were prepared as described as for compounds 5
by using diphenyldiazomethane in place of 9-diazofluorene.
18.76 (CH3), 37.26 (d, Jc,p = 188.2, C6), 48.68 (d, Jc,p = 143.5,
C5), 62.56 (OCH2CH3), 127.47-142.99 (m, Carom), 158.76 (C4),
2
172.03 (d, Jc,p = 42.0, C=O); IR (KBr) ꢀ (cm-1): 1598 (C=N),
2-Acetyl-4-methyl-6,6-diphenyl-2,3-diaza-1-phosphabicyclo-
[3.1.0]hex-3-ene (8a).
1695 (C=O); MS m/z (%): 338 (M+, 23), 165 (100), 265 (39);
HRMS calcd for C19H19N2O2P 338.1184, found 338.1199.
This compound was obtained as white powders in 68% yield.
M.p. 132-135 °C. 1H NMR (CDCl3/TMS) ꢁ: 2.00 (s, 3H, CH3), 2.20
(s, 3H, COCH3), 3.76 (d, 1H, JP,H = 20.2, P-CH), 6.84-7.35 (m,
2-Ethoxycarbonyl-4,6,6-triphenyl-2,3-diaza-1-phosphabicyclo-
[3.1.0]hex-3-ene (8f).
2

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1,3-Dipolar Cycloadditions of 9-Diazofluorenes and Diphenyldiazomethane
359
REFERENCES
This compound was obtained as white solids in 52% yield.
1
M.p. 40-42 °C. H NMR (CDCl3/TMS) ꢀ: 1.24 (t, 3H, J = 7.1,
OCH2CH3), 3.22 (d, 1H, 2JP,H = 7.9, P-CH), 4.32 (q, 2H, J = 7.1,
OCH2CH3), 6.93-7.44 (m, 15Harom); 31P NMR (CDCl3) ꢀ: -85.05;
*
Correspondence to: Prof. Quanrui Wang; e-mail: qrwang@
fudan.edu.cn.
[1] Comprehensive review: 1,3-Dipolar Cycloaddition Chemistry,
1
13C NMR (CDCl3/TMS) ꢀ: 14.36 (OCH2CH3), 32.60 (d, Jc,p
=
183.5, C6), 45.80 (d, 1Jc,p =142.0, C5), 62.81 (OCH2CH3), 126.31-
Vols. 1 and 2, ed. Padwa, A., Wiley-Interscience, New York (1984).
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Haddad, J. Barrans, Tetrahedron Lett., 25, 5521 (1984).
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Gupta, Heteroatom Chem., 15, 271 (2004).
2
148.36 (m, Carom), 156.21 (C4), 168.08 (d, Jc,p = 43.0, C=O); IR
(KBr) ꢁ (cm-1): 1608 (C=N), 1702 (C=O); MS m/z (%): 400
(M+, 10), 165 (100), 77 (98); HRMS calcd for C24H21N2O2P
400.1341, found 400.1352.
2-Ethoxycarbonyl-4-(tert-butyl)-6,6-diphenyl-2,3-diaza-1-phos-
phabicyclo[3.1.0]hex-3-ene (8g).
This compound was obtained as white solids in 28% yield.
M.p. 99-100 °C. 1H NMR (CDCl3/TMS) ꢀ: 1.31 (s, 9H,
2
C(CH3)3), 1.47 (t, 3H, J = 7.1, OCH2CH3), 4.05 (d, 1H, JP,H
=
17.6, P-CH), 4.28 (q, 2H, J = 7.1, OCH2CH3), 7.21-7.34 (m,
10Harom); 31P NMR (CDCl3) ꢀ: -82.64; 13C NMR (CDCl3/TMS)
ꢀ: 14.60 (OCH2CH3), 29.14 [(CH3)3C], 36.03 [ (CH3)3C], 40.27
1
1
(d, Jc,p = 187.0, C6), 49.80 (d, Jc,p = 141.8, C5), 63.00
(OCH2CH3), 126.34-142.82 (m, Carom), 157.08 (C4), 166.14 (d,
2Jc,p = 42.5, C=O); IR (KBr) ꢁ (cm-1): 1603 (C=N), 1686
(C=O); MS m/z (%): 380 (M+, 15), 165 (100), 178 (10); HRMS
calcd for C22H25N2O2P 380.1655, found 380.1636.
4-Ethoxylcarbonyl-4,5-diaza-2,2-diphenyl-3-phospha-tricyclo-
[4.3.0.01,3]non-5-ene (8h).
This compound was obtained as white solids in 46% yield.
1
M.p. 93-95 °C. H NMR (CDCl3/TMS) ꢀ: 1.46 (t, 3H, J = 7.1,
OCH2CH3), 2.10-3.10 (m, 6H, 3CH2), 4.25 (q, 2H, J = 7.1,
OCH2CH3), 6.75-7.33 (m, 10Harom); 31P NMR (CDCl3) ꢀ: -58.32;
13C NMR (CDCl3/TMS) ꢀ: 14.60 (OCH2CH3), 23.41, 24.83,
[14] A. F. Vasilev, L. V. Vilkov, N. P. Ignatova, N. N. Melnikov,
V. V. Negrebetskii, N. I Shvetsov-Shilovskii, L. S. Khaikin, J. Prakt.
Chem., 314, 806 (1972).
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Chem. Rev., 80, 99 (1980).
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Ragaini, F. Demartin, S. Cenini, Eur. J. Inorg. Chem.,1452 (2003).
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[19] R. K. Bansal, K. Karaghiosoff, A. Schmidpeter, Tetrahedron,
50, 7675 (1994).
1
1
27.77 (CH2), 45.89 (d, Jc,p = 164.5, C2), 60.89 (d, Jc,p = 162.7,
C1), 62.89 (OCH2CH3), 125.98-138.19 (m, Carom), 158.88 (C6),
2
169.03 (d, Jc,p = 40.5, C=O); IR (KBr) ꢁ (cm-1): 1625 (C=N),
1706 (C=O); MS m/z (%): 364 (M+, 25), 165 (100), 283 (52);
HRMS calcd for C21H21N2O2P 364.1341, found 364.1359.
Acknowledgements.
The authors are grateful for financial support for this work
from the National Natural Science Foundation of China through
grant 20372015. We thank also Ms. Qingqing Meng for
recording some NMR spectra.
[20] X. Y. Guo, Q. R. Wang, F. G. Tao, Chinese J. Chem., 22,
1003 (2004).