Allenylphosphonates useful precursors of pyrazoles and 1,2,3-triazoles

Article abstract of DOI:10.1002/ejoc.200800490

The synthesis of new pyrazoles and triazoles, with or without phosphorus substituents, from allenylphosphonates is described. Thus, Ph3P-promoted reactions of the allenylphosphonates (OCH₂CMe₂CH ₂O)P(O)CH=C=CRR′ [R = H, R′

Full text of DOI:10.1002/ejoc.200800490

FULL PAPER
DOI: 10.1002/ejoc.200800490
Allenylphosphonates Ϫ Useful Precursors of Pyrazoles and 1,2,3-Triazoles
Manab Chakravarty,[a] N. N. Bhuvan Kumar,[a] K. V. Sajna,[a] and K. C. Kumara Swamy*[a]
Keywords: Allenes / Phosphonates / Heterocycles / Pyrazoles / Triazoles
The synthesis of new pyrazoles and triazoles, with or without
at reflux, whereas (β-azidoallyl)phosphonates were obtained
phosphorus substituents, from allenylphosphonates is de- in high yields at room temperature. These latter compounds
scribed. Thus, Ph3P-promoted reactions of the allenylphos-
phonates (OCH2CMe2CH2O)P(O)CH=C=CRRЈ [R = H, RЈ =
Me (1b), R = RЈ = Me (1c)] with DIAD/DEAD lead to phospho-
nopyrazoles by utilizing the –CO2R functionality of DIAD/
DEAD for cyclization. The products derived from allenylpho-
sphonates with an α-phenyl group undergo an unusual but
facile P–C bond cleavage to form tetrasubstituted pyrazoles.
In the second type of reaction, Me3SiN3 reacts with the allen-
ylphosphonates to form phosphono-1,2,3-triazoles in CH3CN
undergo cycloaddition with activated acetylenes to afford
multisubstituted 1,2,3-triazoles. They were subsequently
transformed into diverse N-substituted 1,2,3-triazoles
through the Horner–Wadsworth–Emmons reaction. The
structures of the key compounds were established by X-ray
crystallography.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
Allenes (or 1,2-dienes) are versatile precursors of a vari-
ety of industrially and biologically significant molecules.[1,2]
Allenylphosphonates (phosphorylated allenes) 1a–c can
also be used as important building blocks in organic chem-
istry.[3] Organophosphonates themselves are important
molecules in chemistry and biochemistry.[4,5] As phospho-
rus can impart a different electronic constraint on the inter-
mediates compared with an aryl carbon of aryl-substituted
allenes, the stereochemistry of the products obtained by
using allenylphosphonates and other substituted allenes
(e.g., 2a,b) may be the result of different pathways. As an
example, we have shown recently that in the palladium-cata-
lyzed reactions of 1a–c with iodophenol, a variety of benzo-
furans (e.g., 3–6) can be obtained.[6,7] We have also shown
by using 1a and related allenes that in the nucleophilic ad-
dition of amines to allenylphosphonates, the stereochemis-
try of the β-aminophosphonate products depends upon the
type of amine used (cf. compounds 7–11).[8]
In the above context, we became interested in (i) the
phosphane-promoted addition of dialkyl azodicarboxylates
and (ii) the (non-catalyzed) addition of hydrazoic acid via
trimethylsilyl azide. Whereas the former has the potential
to afford phosphonopyrazoles, the latter could lead to
phosphonotriazoles or -azirines. Pyrazoles find extensive
use in the pharmaceutical industry,[9] but there are only lim-
ited number of routes available for their synthesis.[10] The
1,2,3-triazoles also have a wide range of applications in ag-
rochemicals, corrosion inhibition, the dye industry and as
pharmaceuticals.[11]
Recently, the phosphane-promoted addition of dialkyl
azodicarboxylates RO2CN=NCO2R [R = Et (DEAD) or
iPr (DIAD)] has been elegantly utilized to generate new
pyrazole/pyrazoline derivatives (Scheme 1).[12,13] This ad-
dition reaction occurs via the Morrison–Brunn–Huisgen
(MBH) intermediate Ph3P+N(CO2R)–N––CO2R (12),[14]
which is also the critical component in the Mitsunobu reac-
tion.[15,16] With the readily available and inexpensive allenyl-
phosphonates in our hands,[6,17] we were curious to know
whether phosphono-substituted pyrazoles could similarly
be obtained or not. As regards the addition reaction with
[a] School of Chemistry, University of Hyderabad,
Hyderabad 500 046, A. P. (India)
Fax: +91-40-23012460
E-mail: kckssc@yahoo.com
kckssc@uohyd.ernet.in
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Allenylphosphonates Ϫ Precursors of Pyrazoles and Triazoles
of these two systems, which primarily use inexpensive allen-
ylphosphonates. A hitherto unreported unusual P–C bond-
cleavage reaction is also highlighted.
Results and Discussion
Reaction of Allenylphosphonates with Dialkyl
Azodicarboxylates
With DEAD/DIAD in the absence of triphenylphos-
phane, allene 1a did not react. Allene 1b gave a mixture
and 1c gave stable butadiene products 21 and 22 regio- and
stereospecifically in Ն80% yield (based on 31P NMR spec-
troscopy, Scheme 3). This feature appears to be general for
=CMe2 terminal allenes because we could isolate analogous
butadienes 24 and 25 starting from the allene 23.[6,19] The
E stereochemistry was confirmed by X-ray crystallography
in the case of 22 (Figure 1). Once formed, the butadienes
did not cyclize to form the pyrazoles, even upon prolonged
heating. Interestingly, the formation of similarly substituted
hydrazine derivatives in the reaction of MBH betaine with
ketones has been reported recently by Lee and co-
workers.[13]
Me3SiN3, it was prompted by our desire to investigate the
feasibility of triazole/dihydrotriazole (e.g., 18 and 19) versus
azirine (20) formation (Scheme 2). It should be emphasized
here that Me3SiN3 was used as a source of HN3 in several
reactions.[18] In this paper we address the synthetic aspects
Scheme 3.
Scheme 1.
Figure 1. An ORTEP diagram of 22 [P–C(6): 1.748(2), C(6)–C(7):
1.333(3), C(7)–N(1): 1.408(3), N(1)–N(2): 1.397(2) Å].
We then performed the above reactions of allenes with
DEAD/DIAD in the presence of Ph3P. Compounds 1b,c
readily reacted to afford phosphonopyrazoles 26–29
(Scheme 4), whereas the =CH2 terminal allene 1a re-
Scheme 2.
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K. C. Kumara Swamy et al.
FULL PAPER
was confirmed by X-ray crystallography (Figure 2). These
pyrazole compounds 32–37 are fairly stable. Thus, access
to different aryl-substituted pyrazoles is possible as a large
number of allenes (RO)2P(O)C(Ar)CH=C=CH2 are ac-
cessible via the propargylic alcohols ArCϵCCH2OH.
arranged to the acetylene 30.[6] Of the three solvents (DME,
THF and dichloroethane) studied, THF worked best. Al-
though the isolated yields were moderate, the ease of syn-
thesis makes these reactions quite attractive. The major dif-
ference between this reaction and the one shown in part (a)
of Scheme 1 is the following: for the reaction in Scheme 1
(a), the OEt group on the pyrazole should come from the
allenyl esters, whereas the OiPr substituent at the same posi-
tion in 26–28 arises from the DIAD residue. Compound
28 is analogous to 27, except that the NCO2–iPr group is
hydrolyzed to NH during column chromatography which
can be gainfully employed in further synthetic work. This
type of product also has not been isolated before.
Scheme 5.
Figure 2. The structure of 33 [N(1)–N(2): 1.381(2) Å].
Based on the available literature, the mechanistic path-
way for phosphonopyrazole formation is shown in
Scheme 6.[12a,12b] We note the following: (i) the carbanion is
formed at the carbon atom α to phosphorus (cf. 38) thereby
leading to substituted pyrazoles; (ii) the OR group on the
pyrazole group is derived from the DIAD/DEAD residue
and not from the allene; (iii) the cleavage of the P–C bond
is very facile and subsequent separation of pyrazoles is very
easy. For Ar = Ph and R = iPr, the crystalline compound
33 could be characterized by X-ray crystallography.
Scheme 4.
Perhaps more interesting is the reaction shown in
Scheme 5 in which tetrasubstituted pyrazoles 32–37 were
generated by a facile P–C bond-cleavage reaction via the
phosphonopyrazole intermediate 31.[20,21] Species 31 [R =
iPr, Ar = Ph] was readily identified by H and 31P NMR
1
Triazole Formation by Reaction with Trimethysilyl Azide
spectroscopy. We believe the type of reaction observed here
is unprecedented and provides a novel entry into aryl-sub-
In the straightforward reaction of allenes 1a–c with tri-
stituted pyrazoles. This reaction works for α-aryl allenyl- methylsilyl azide at room temperature, we isolated the hy-
phosphonates and the separation of pyrazoles 32–37 is very drolytically unstable non-cyclized azide products 46–48 re-
easily accomplished.[22] The structure of one of these (33) gioselectively and in good yields (Scheme 7). DMF as sol-
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Allenylphosphonates Ϫ Precursors of Pyrazoles and Triazoles
Scheme 6.
vent was much superior to acetonitrile in this case. Like the
reaction with MBH betaine, here also, the nucleophilic part
–
(N3 ) attaches to the carbon β to the phosphorus. The reac-
tion conducted using the conditions of Huang and co-
workers [NaN3/tBuOH/H2O][23] also gave the azides, but in
the case of 1a, a significant amount of the acetylene 30 was
formed.
Figure 3. An ORTEP diagram of 50 [P–C(6): 1.768(2) Å; hydrogen-
bonding parameters: N(3)–H(3)···O(3Ј): 0.83(3), 1.93(3),
2.749(3) Å, 167(3)°; symmetry code: 2 – x, –0.5 + y, 1 – z].
A possible pathway for the formation of triazoles starting
from the azide addition products 49 and 50 is shown in
Scheme 9. The –N3 group takes a proton from the α carbon
to give 51. Note that the formation of phosphonate carban-
ions at the α carbon in the presence of a base is well known
in Horner–Wadsworth–Emmons (HWE) reactions. Cycliza-
tion followed by aromatization and a proton shift leads to
triazoles 49 and 50. Although the precursor triazole 53
should also be fairly stable, we did not observe this form in
the X-ray structure of the two compounds isolated in this
study. A similar pathway, via the C–N––N+ϵN dipolar
form, is also possible, but is not shown in Scheme 9.
Scheme 7.
The above reaction when conducted in refluxing CH3CN
gave the triazoles 49 and 50 (50–60% yield based on 31P
NMR; 20–40% isolated yield; Scheme 8; Figure 3).[24] Al-
though the isolated yield was not high, it was very easy to
separate these compounds.
Azides undergo 1,3-dipolar cycloaddition reactions with
activated acetylenes to give 1,2,3-triazoles[18,25] and hence
we treated 48 with ethyl propiolate or phenyl acetylene to
obtain the phosphonotriazoles 55 and 56 stereoselectively
Scheme 8.
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K. C. Kumara Swamy et al.
FULL PAPER
Conclusions
The reaction of allenylphosphonates with the MBH beta-
ine formed from PPh3/DEAD or DIAD leads directly to
phosphonopyrazoles without the prerequisite of an ester
group on the allene. In the absence of PPh3, the =CMe2
terminal allenylphosphonates readily afford substituted
phosphono-1,3-butadienes in nearly quantitative yields (31P
NMR evidence) under neat (or MW) conditions. A novel
phosphate elimination reaction leading to tetrasubstituted
pyrazoles has been discovered. The ease of preparation and
the low effective cost of our allenylphosphonates are ad-
ditional assets to this procedure. Stable phosphonotriazoles
are obtained readily through a simple Me3SiN3-mediated
addition of HN3 to allenylphosphonates at reflux tempera-
ture in CH3CN whereas at room temperature (CH3CN or
DMF), β-azido-allylphosphonates are obtained in high
yields. The potential of the β-azido-allylphosphonates is
demonstrated by the high-yielding stereoselective synthesis
of multisubstituted triazoles by 1,3-dipolar cycloaddition
with acetylenes and subsequent HWE reaction, which gives
phosphorus-free triazoles. Any of the three ingredients Ϫ
allene, acetylene or aldehyde Ϫ can be varied in the pro-
duction of this class of triazoles.
Scheme 9.
in high yields. Similarly, 47 and ethyl propiolate led to 54
(Scheme 10, a). In the synthesis of 56, CuI was needed. The
MW-assisted reaction (180 °C, 160 W) in the case of 54 and
55 was also useful and was complete in 10 min. The stereo-
chemistry of 55 was established by X-ray crystallography
(Figure 4). Thus, this route offers functionalized phospho-
notriazoles with activated acetylenes in a very short time.
What is also quite useful is the fact that the phosphonate
group can be readily cleaved by means of the HWE reac-
tion.[26] Thus we could obtain phosphorus-free 1,2,3-tri-
azoles 57–60 very easily in good yields (Scheme 10, b). This
approach opens up a convenient access to diverse phospho-
rus-free triazoles as three variables Ϫ allene, acetylene and
the aldehyde Ϫ are available.
Experimental Section
General: Precursors 1a–c were prepared by following literature pro-
cedures.[6,8] Acetylene 30 was formed normally under basic condi-
tions, even in the presence of Ph3P, as mentioned above. Pure 30
[δ(P) = –12.9 ppm] was prepared by treating 1a with triethyl-
amine.[6,17a]
Allenes (OCH2CMe2CH2O)PC(Ar)=C=CH2 [Ar = Ph (1d), 4-Me-
C6H4 (1e), 4-MeO-C6H4 (1f)] were synthesized by using
(OCH2CMe2CH2O)PCl and the appropriate propargylic alcohol in
80% yield in a manner similar to that for 1a–c.
Compound 1d: M.p. 110–114 °C. IR (KBr): ν = 3059, 2976, 2892,
˜
1962, 1933, 1707, 1489, 1271 cm–1. 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 0.88 and 1.29 (2s, 6 H), 3.92–3.99 (m, 4 H), 5.35
and 5.38 (2s, 2 H), 7.26–7.60 (m, 5 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 20.8, 21.9, 32.6 (d, J = 7.0 Hz), 77.3,
78.7, 78.9, 95.2 (d, J = 181.0 Hz), 127.6, 127.7, 128.0, 128.8, 130.5,
130.6, 212.9 (J = 5.0 Hz) ppm. 31P NMR (80 MHz, CDCl3, 25 °C,
TMS): δ = 6.6 ppm. C14H17O3P (264.3): calcd. C 63.63, H 6.48;
found C 63.68, H 6.42.
Scheme 10.
Compound 1e: M.p. 138–140 °C. IR (KBr): ν = 3059, 2975, 2886,
˜
1
1935, 1715, 1481, 1264 cm–1. H NMR (400 MHz, CDCl3, 25 °C,
TMS): δ = 0.89 and 1.30 (2s, 6 H), 2.34 (s, 3 H), 3.92–4.00 (m, 4
H), 5.33 and 5.36 (m, 2 H), 7.15–7.50 (m, 4 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 20.8, 21.2, 21.9, 32.6 (d, J =
7.0 Hz), 77.3, 77.4, 78.7 (d, J = 14.0 Hz), 95.2 (d, J = 181.0 Hz),
127.4, 127.5, 128.5, 129.5, 137.9, 212.7 (J = 4.0 Hz) ppm. 31P NMR
(160 MHz, CDCl3, 25 °C, TMS): δ = 7.8 ppm. C15H19O3P (278.3):
calcd. C 64.74, H 6.88; found C 64.82, H 6.87.
Compound 1f: M.p. 105–108 °C. IR (KBr): ν = 3061, 2959, 2895,
˜
1937, 1607, 1512, 1458, 1441, 1258, 1057 cm–1. 1H NMR
(400 MHz, CDCl3, 25 °C, TMS): δ = 0.89 and 1.30 (2s, 6 H), 3.80
(s, 3 H), 3.92–3.99 (m, 4 H), 5.33–5.36 (m, 2 H), 6.87–7.54 (m, 4
H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 20.6, 21.8,
Figure 4. An ORTEP drawing of compound 55 [P–C(6):
1.796(2) Å].
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Allenylphosphonates Ϫ Precursors of Pyrazoles and Triazoles
32.5 (d, J = 7.0 Hz), 55.2, 77.27, 77.34, 78.8 (d, J = 14.0 Hz), 94.8
150–153 °C. IR (KBr): ν = 3152, 2975, 1748, 1726, 1595, 1541,
˜
(d, J = 180.0 Hz), 114.2, 122.4, 122.5, 128.8, 128.9, 159.4, 212.3 (J 1474, 1370, 1304, 1273, 1211, 982 cm–1. 1H NMR (400 MHz,
= 4.0 Hz) ppm. 31P NMR (160 MHz, CDCl3, 25 °C, TMS): δ =
7.5 ppm. C15H19O4P (294.3): calcd. C 61.22, H 6.51; found C 61.25,
H 6.52.
CDCl3, 25 °C, TMS): δ = 1.22–1.29 (m, 30 H), 2.08 (s, 3 H), 3.52–
3.59 (br. m, 4 H), 4.20–4.24 (br. m, 4 H), 5.15 and 5.20 (2s, 2 H),
5.88 (br., 1 H), 6.78 (br., 1 H) ppm. 13C NMR (50 MHz, CDCl3,
25 °C, TMS): δ = 14.2, 14.3, 22.7, 23.3, 45.4, 45.5, 61.9, 62.7, 115.5
Reaction of Allene 1c with Dialkyl Azodicarboxylates
(d, J = 146.8 Hz), 117.8, 140.1, 150.0, 150.3, 154.3, 156.1 ppm. 31
P
Synthesis
of
(OCH2CMe2CH2O)P(O)CH=C[N(CO2R)NH-
NMR (160 MHz, CDCl3, 25 °C, TMS):
δ
=
18.7 ppm.
(CO2R)]C(Me)=CH2 [R = Et (21), iPr (22)]: Allene 1c (0.60 g,
2.77 mmol) was heated with DEAD/DIAD (3.33 mmol) at 150 °C
for 30 min. The 31P NMR spectrum showed a single product. Com-
pound 21 or 22 was isolated (≈71%) by using column chromatog-
raphy (EtOAc/hexane, 1:1, silica gel).
C23H45N4O5P (488.6): calcd. C 56.54, H 9.28, N 11.47; found C
56.50, H 9.18, N 11.70.
Compound 25: Prepared by a procedure similar to that used for 21
using the allene 23 (0.20 g, 0.66 mmol). Yield (isolated): 0.29 g
(90%); m.p. 136–138 °C. IR (KBr): ν = 3158, 2980, 1739, 1591,
˜
Alternative MW-Assisted Synthesis of 21 and 22: Allene 1c (0.17 g,
0.77 mmol) and DEAD or DIAD (0.77 mmol) were placed in a
10 mL of conical flask and heated in a microwave reactor for
30 min [180 °C; 160 W]. Compound 21 or 22 was isolated by using
column chromatography (EtOAc/hexane, 2:3, silica gel).
1531, 1472, 1373, 1300, 1269, 1107, 984 cm–1. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 1.21–1.29 (m, 36 H), 2.10 (s, 3 H), 3.50–
3.60 (br. m, 4 H), 4.96–5.02 (br. m, 2 H), 5.18 (s, 2 H), 5.88 (br. d,
J = 8.5 Hz, 1 H), 6.74 (br., 1 H) ppm. 13C NMR (100 MHz, CDCl3,
25 °C, TMS): δ = 21.86, 21.90, 22.8, 23.4, 45.49, 45.54, 70.0, 71.1,
Compound 21: Yield quantitative (31P NMR); isolated yield 0.19 g
115.4 (d,
J = 146.7 Hz), 117.7, 140.6, 150.3, 150.5, 154.0,
155.8 ppm. 31P NMR (160 MHz, CDCl3, 25 °C, TMS): δ =
18.9 ppm. C25H49N4O5P (516.7): calcd. C 58.12, H 9.56, N 10.84;
found C 58.02, H 9.59, N 10.53.
(64%); m.p. 126–128 °C. IR (KBr): ν = 3196, 2990, 1750, 1593,
˜
1
1316, 1238, 1057, 1003 cm–1. H NMR (400 MHz, CDCl3, 25 °C,
TMS): δ = 0.88 and 1.18 (2s, 6 H), 1.28 (t, J = 6.4 Hz, 6 H), 1.99
(s, 3 H), 3.85–3.90 (br. m, 4 H), 4.17–4.24 (m, 4 H), 5.26 (s, 1 H),
5.49 (s, 1 H), 5.53 (d, J ≈ 12.0 Hz, 1 H), 8.13 (br., 1 H) ppm. 13C
NMR (50 MHz, CDCl3, 25 °C, TMS): δ = 14.1, 14.4, 20.8, 21.7,
32.3 (d, J = 6.1 Hz), 61.9, 63.2, 76.2 (br.), 98.3 (d, J = 190.4 Hz),
120.7, 139.1, 153.2, 155.4, 159.2, 159.6 ppm. 31P NMR (160 MHz,
CDCl3, 25 °C, TMS): δ = 14.4 ppm. C16H27N2O7P (390.4): calcd.
C 49.22, H 6.97, N 7.17; found C 49.29, H 6.95, N 7.12.
Preparation
of
(OCH2CMe2CH2O)P(O)[C=C(CH2CH3)N-
(CO2iPr)N=C(OiPr)] (26): DIAD (1.38 g, 1.35 mL, 6.8 mmol) was
added to a stirred solution of allenylphosphonate 1b (1.15 g,
5.7 mmol) in anhydrous THF (10 mL) under N2 and the reaction
mixture was stirred under reflux. Triphenylphosphane (1.79 g,
6.8 mmol) in THF (10 mL) was added to this mixture through an
adding funnel in three portions. The reaction mixture was stirred
under reflux for 24 h, cooled, the solvent removed on a rotary evap-
orator and the residue was purified by column chromatography on
silica gel by using ethyl acetate/hexane (1:3) as eluent to afford the
Compound 22: Yield Ͼ95% (MW route, 31P NMR); isolated yield
0.23 g (80%); m.p. 138–141 °C. IR (KBr): ν = 3150, 2976, 1736,
˜
1595, 1541, 1472, 1279, 1107, 1057, 1005 cm–1. 1H NMR
(400 MHz, CDCl3, 25 °C, TMS): δ = 0.91 and 1.18 (2s, 6 H), 1.28
(d, J = 1.7 Hz, 6 H), 1.29 (d, J = 1.7 Hz, 6 H), 2.00 (s, 3 H), 3.84–
3.96 (br. m, 4 H), 4.95–4.99 (br. m, 2 H), 5.28 (s, 1 H), 5.50 (s, 1
H), 5.61 (d, J = 12.4 Hz, 1 H), 7.38 (br., 1 H) ppm. 13C NMR
(50 MHz, CDCl3, 25 °C, TMS): δ = 20.9, 21.0, 21.7, 21.9, 32.3 (d,
J = 6.1 Hz), 69.9, 71.7, 76.2 (br.), 98.6 (d, J = 194.1 Hz), 120.7,
139.3, 152.8, 155.1, 159.3, 159.7 ppm. 31P NMR (160 MHz, CDCl3,
25 °C, TMS): δ = 13.9 ppm. C18H31N2O7P (418.4): calcd. C 51.67,
H 7.47, N 6.69; found C 51.66, H 7.44, N 6.64. The X-ray structure
of this compound was determined.
product. Yield 1.54 g (70%); m.p. 62–64 °C. IR (KBr): ν = 2976,
˜
1750, 1561, 1509, 1373, 1306, 1231, 1183, 1107, 1049, 995 cm–1. 1H
NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 1.09 and 1.19 (2s, 6
H), 1.23–1.45 (m, 15 H), 3.29 (br. q, J ≈ 7.0 Hz, 2 H), 4.03–4.16
(m, 4 H), 5.13 and 5.23 (2m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 13.9, 20.6, 21.5, 21.7, 22.0, 32.5 (d, J =
6.6 Hz), 72.8, 73.0, 75.9, 76.0, 98.2 (d, J = 216.2 Hz), 148.9, 159.2
(d, J = 26.1 Hz), 162.3, 162.4 ppm. 31P NMR (160 MHz, CDCl3,
25 °C, TMS): δ = 6.3 ppm. C17H29N2O6P (388.4): calcd. C 52.57,
H 7.52, N 7.21; found C 52.64, H 7.54, N 7.17.
Synthesis of the Allene {[(CH3)2CH]2N}2P(O)CH=C=C(CH3)2
(23): This compound was prepared by a procedure similar to that
used for 1a using {[(CH3)2CH]2N}2PCl[27] (3.60 g, 1.35 mmol),
HCϵCC(CH3)2(OH) (1.14 g, 1.31 mL, 1.35 mmol) and NEt3
(1.37 g, 1.88 mL, 1.35 mmol). It was purified by using column
chromatography (EtOAc/hexane, 1:1, silica gel). Yield 3.31 g (80%);
Preparation of (OCH2CMe2CH2O)P(O){C=C[CH(CH3)2]N(CO2-
iPr)N=C(O-iPr)} (27) and (OCH2CMe2CH2O)P(O){C=C-
[CH(CH3)2]N(H)N=C(O-iPr)} (28): In a procedure similar to that
used for 26, allenylphosphonate 1c (0.82 g, 3.8 mmol), DIAD
(0.92 g, 0.90 mL, 4.5 mmol) and triphenylphosphane (1.20 g,
4.5 mmol) were used. Column chromatography afforded 27 (ethyl
acetate/hexane, 1:3) followed by 28 (ethyl acetate/hexane, 1:1).
Crystals of 27 and 28 were obtained from dichloromethane/hexane.
m.p. 52–54 °C. IR (KBr): ν = 2971, 2872, 1966, 1647, 1456, 1401,
˜
1
1366, 1223, 984 cm–1. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 1.19–1.31 (2d, 24 H), 1.70 (d, J ≈ 4. 0 Hz, 3 H), 1.71 (d, J ≈ 3.
0 Hz, 3 H), 3.48–3.56 (m, 4 H), 5.22–5.29 (br. m, 1 H) ppm. 13C
NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 18.70, 18.72, 18.9, 21.9,
22.67, 22.68, 23.05, 23.06, 23.7, 45.4, 45.5, 46.8, 47.3, 86.7 (d, J =
148.8 Hz), 96.0 (d, J = 14.4 Hz), 208.5 ppm. 31P NMR (80 MHz,
CDCl3, 25 °C, TMS): δ = 19.6 ppm. C17H35N2OP (314.5): calcd. C
64.93, H 11.22, N 8.91; found C 64.80, H 11.21, N 8.98.
Compound 27: Yield 0.76 g (50%); m.p. 72–76 °C. IR (KBr): ν =
˜
2976, 2880, 1752, 1566, 1472, 1431, 1375, 1316, 1244, 1183, 1105,
1049, 993 cm–1. 1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ =
1.02 and 1.23 (2s, 6 H), 1.37–1.46 (m, 18 H), 4.00–4.15 (m, 5 H),
5.09–5.12 (m, 1 H), 5.18–5.21 (m, 1 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 19.5, 21.4, 21.7, 22.0, 22.1, 27.0, 32.5 (d,
J ≈ 7.0 Hz), 72.5, 73.1, 76.1, 76.2, 97.0 (d, J ≈ 213.0 Hz), 149.3,
161.9, 162.1, 162.2 ppm. 31P NMR (160 MHz, CDCl3, 25 °C,
TMS): δ = 6.7 ppm. C18H31N2O6P (402.4): calcd. C 53.72, H 7.76,
N 6.96; found C 53.70, H 7.75, N 6.92. The X-ray structure of this
compound was determined.
Synthesis of {[(CH3)2CH]2N}2P(O)CH=C[N(CO2R)NH(CO2R)]-
C(Me)=CH2 [R = Et (24), iPr (25)]
Compound 24: Prepared by a procedure similar to that used for 21
using the allene 23 (0.224 g, 0.72 mmol). Yield 0.31 g (90%); m.p.
Eur. J. Org. Chem. 2008, 4500–4510
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4505

K. C. Kumara Swamy et al.
FULL PAPER
Compound 28: Yield 0.24 g (20%); m.p. 216–218 °C. IR (KBr): ν =
1611, 1591, 1512, 1375, 1314, 1264, 1181, 1109, 1088, 918 cm–1. 1H
˜
3181, 3088, 3046, 1557, 1510, 1470, 1327, 1227, 1186, 1129, 1053,
NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 1.38, 1.46 [2d, 2J(H,H)
1003 cm–1. 1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 1.10, = 6.0 Hz, 12 H], 2.55 (s, 3 H), 5.16, 5.26 (2m, 2 H), 7.33–7.45 (m,
1.21 (2s, 6 H), 1.31 (d, J = 7.0 Hz, 6 H), 1.37 (d, J = 6.1 Hz, 6 H),
3.66–3.69 (br. m, 1 H), 4.00 (t, J = 12.6 Hz, 2 H), 4.23 (t, J =
5 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 13.7,
21.9, 22.1, 71.8, 71.9, 113.2, 127.0, 128.3, 129.6, 130.7, 141.2, 150.3,
10.5 Hz, 2 H), 4.94–4.98 (br. m, 1 H), 10.18 (br., 1 H) ppm. 13C 161.4 ppm. C17H22N2O3 (302.4): calcd. C 67.53, H 7.33, N 9.26;
NMR (50 MHz, CDCl3, 25 °C, TMS): δ = 21.8, 22.2, 25.6, 32.6,
71.9, 75.3, 75.4, 87.1 (d, J = 226.8 Hz), 158.1 (d, J = 26.7 Hz),
163.6 (d, J = 8.5 Hz) ppm. 31P NMR (160 MHz, CDCl3, 25 °C,
TMS): δ = 10.7 ppm. C14H25N2O4P (316.3): calcd. C 53.16, H 7.97,
N 8.86; found C 53.26, H 8.09, N 8.88. The X-ray structure of this
compound was determined.
found C 67.51, H 7.30, N 9.20. X-ray structure of this compound
was determined.
Synthesis of the Pyrazole [C(4-CH3C6H4)=C(CH3)N(CO2Et)-
N=C(OEt)] (34): In a procedure similar to that used for 32, allenyl-
phosphonate 1e (0.46 g, 1.7 mmol), DEAD (0.39 g, 0.35 mL,
2.3 mmol) and triphenylphosphane (0.59 g, 2.3 mmol) were used.
Extraction with diethyl ether and purification by column
chromatography (ethyl acetate/hexane, 2:98) readily gave 34. Yield
Preparation of (OCH2CMe2CH2O)P(O)[C=C(CH2CH3)N(CO2Et)-
N=C(OEt)] (29): In a procedure similar to that used for 26, allenyl-
phosphonate 1b (0.30 g, 1.5 mmol), DEAD (0.31 g, 0.28 mL,
1.8 mmol) and triphenylphosphane (0.47 g, 1.8 mmol) were used.
Column chromatography using 15% ethyl acetate/hexane afforded
0.34 g (68%); m.p. 67–69 °C. IR (KBr): ν = 2984, 2919, 1749, 1603,
˜
1526, 1379, 1344, 1265, 1096, 899 cm–1. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 1.37, 1.45 (2t, J = 7.2 Hz, 6 H), 2.38 (s,
3 H), 2.55 (s, 3 H), 4.38, 4.47 (2q, J ≈ 7.2 Hz, 4 H), 7.21–7.28 (m,
4 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 13.5,
14.4, 14.6, 21.2, 63.7, 64.7, 112.8, 127.3, 129.1, 129.4, 136.9, 141.6,
150.7, 162.3 ppm. C16H20N2O3 (288.4): calcd. C 66.65, H 6.99, N
9.72; found C 66.59, H 6.94, N 9.79.
29. Yield 0.32 g (60%); m.p. 100–102 °C. IR (KBr): ν = 2984, 2936,
˜
1752, 1566, 1509, 1439, 1385, 1314, 1249, 1179, 1053, 995 cm–1. 1H
NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 1.12, 1.15 (2s, 6 H),
1.25 (t, J ≈ 7.4 Hz, 3 H), 1.39–1.46 (m, 6 H), 3.31 (q, J = 7.2 Hz,
2 H), 4.01 (t, J = 11.2 Hz, 2 H), 4.17 (t, J = 10.8 Hz, 2 H), 4.38
(q, J ≈ 7.2 Hz, 2 H), 4.48 (q, J ≈ 7.2 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 13.8, 14.1, 14.5, 20.4, 21.5,
21.9, 32.5 (d, J = 6.5 Hz), 64.1, 65.3, 75.8, 75.9, 96.8 (d, J =
217.2 Hz), 149.4, 160.0 (d, J = 26.0 Hz), 163.1, 163.2 ppm. 31P
NMR (80 MHz, CDCl3, 25 °C, TMS): δ = 5.61 ppm. C15H25N2O6P
(360.4): calcd. C 50.00, H 6.99, N 7.77; found C 50.11, H 7.03, N
7.81.
Synthesis of the Pyrazole [C(4-CH3C6H4)=C(CH3)N(CO2iPr)-
N=C(OiPr)] (35): In a procedure similar to that for 32, allenylphos-
phonate 1e (0.72 g, 2.6 mmol), DIAD (0.71 g, 0.35 mL, 3.5 mmol)
and triphenylphosphane (0.91 g, 3.5 mmol) were used. Yield 0.53 g
(62%); m.p. 57–59 °C. IR (KBr): ν = 2978, 1738, 1607, 1503, 1455,
˜
1379, 1327, 1264, 1200, 1084, 920 cm–1. 1H NMR (400 MHz,
2
CDCl3, 25 °C, TMS): δ = 1.35, 1.44 [2d, J(H,H) = 6.2 Hz, 12 H],
2.38 (s, 3 H), 2.52 (s, 3 H), 5.15, 5.22 (2m, 2 H), 7.20–7.27 (m, 4
H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 13.7, 21.3,
22.0, 22.1, 71.8, 113.3, 127.7, 129.1, 129.5, 136.8, 141.0, 150.4,
161.5 ppm. C18H24N2O3 (316.4): calcd. C 68.33, H 7.65, N 8.85;
found C 68.22, H 7.62, N 8.82.
Synthesis of the Pyrazole [C(Ph)=C(CH3)N(CO2Et)N=C(OEt)]
(32): In a procedure similar to that used for 26, allenylphosphonate
1d (0.40 g, 1.6 mmol), DEAD (0.33 g, 0.30 mL, 1.9 mmol) and tri-
phenylphosphane (0.50 g, 1.9 mmol) were used. The imine
Ph3P=NCO2Et[22] was separated by column chromatography and
the residue was taken up in THF (5 mL) and treated with 6  HCl
(5 mL) for 24 h. Extraction with diethyl ether and purification by
column chromatography (ethyl acetate/hexane, 2:98) gave 32. Yield
Synthesis of the Pyrazole [C(4-CH3OC6H4)=C(CH3)N(CO2Et)-
N=C(OEt)] (36): In a procedure similar to that used for 32, allenyl-
phosphonate 1f (0.33 g, 1.1 mmol), DEAD (0.25 g, 0.23 mL,
1.4 mmol) and triphenylphosphane (0.38 g, 1.4 mmol) were used.
Extraction with diethyl ether and purification by column
chromatography (ethyl acetate/hexane) readily gave 36. Yield 0.22 g
0.31 g (70%); m.p. 61–63 °C. IR (KBr): ν = 2981, 1958, 1898, 1761,
˜
1613, 1593, 1522, 1373, 1325, 1258, 1181, 1063, 1003 cm–1. 1H
NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 1.40, 1.48 (2t, J =
7.1 Hz, 6 H), 2.59 (s, 3 H), 4.42, 4.51 (2q, J ≈ 7.1 Hz, 4 H), 7.34–
7.46 (m, 5 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ
= 13.5, 14.4, 14.6, 63.7, 64.8, 112.9, 127.1, 128.4, 129.5, 130.4,
141.9, 150.7, 162.2 ppm. C15H18N2O3 (274.3): calcd. C 65.68, H
6.61, N 10.21; found C 65.64, H 6.65, N 10.63.
(66%); m.p. 58–60 °C. IR (KBr): ν = 2982, 2935, 1755, 1597, 1528,
˜
1373, 1323, 1258, 1098, 1005 cm–1. 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 1.38, 1.45 (2t, J ≈ 7.0 Hz, 6 H), 3.83 (s, 3 H),
2.55 (s, 3 H), 4.39, 4.47 (2q, J ≈ 7.0 Hz, 4 H), 6.94–7.31 (m, 4
H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 13.6, 14.5,
14.7, 55.4, 63.7, 64.8, 112.7, 114.0, 122.7, 130.7, 141.5, 150.8, 158.9,
162.4 ppm. C16H20N2O4 (304.4): calcd. C 63.14, H 6.62, N 9.20;
found C 63.25, H 6.52, N 9.38.
Synthesis of the Pyrazole [C(Ph)=C(CH3)N(CO2iPr)N=C(OiPr)]
(33): In a procedure similar to that used for 32, allenylphosphonate
1d (1.52 g, 6.0 mmol), DIAD (1.46 g, 1.43 mL, 7.2 mmol) and tri-
phenylphosphane (1.90 g, 7.2 mmol) were used. After separating
Ph3P=NCO2iPr,[22] simple crystallization in air afforded 33 after
separation of the phosphate (OCH2CMe2CH2O)P(O)OH (less sol-
uble).[19] In a separate experiment, the intermediate phosphonate
Synthesis of the Pyrazole [C(4-CH3OC6H4)=C(CH3)N(CO2iPr)-
N=C(OiPr)] (37): In a procedure similar to that for 32, allenylphos-
phonate 1f (0.32 g, 1.1 mmol), DIAD (0.29 g, 0.28 mL, 1.4 mmol)
and triphenylphosphane (0.37 g, 1.4 mmol) was used. Yield 0.24 g
(OCH2CMe2CH2O)P(O)CH(Ph)[CN(CO2iPr)N=C(OiPr)CH=] (65%); m.p. 59–62 °C. IR (KBr): ν = 2980, 2936, 1734, 1599, 1503,
˜
(31; Ͼ93% purity, the rest was 1d) was identified [1H NMR
(400 MHz, CDCl3, 25 °C, TMS): δ = 0.99, 1.17 (2s, 6 H), 1.26–1.42
1455, 1378, 1321, 1262, 1090, 922 cm–1. 1H NMR (400 MHz,
2
CDCl3, 25 °C, TMS): δ = 1.35, 1.44 [2d, J(H,H) = 4.0 Hz, 12 H],
(m, 12 H), 3.97–4.25 (m, 4 H), 5.02 (d, J ≈ 6.0 Hz, 1 H), 5.09– 2.50 (s, 3 H), 3.84 (s, 3 H), 5.15, 5.20 (2m, 2 H), 6.94–7.30 (m, 4
5.19 (m, 2 H), 5.89 (br., 1 H), 7.28–7.69 (m, 5 H) ppm. 31P NMR
(160 MHz, CDCl3, 25 °C, TMS): δ = 9.5 ppm] prior to hydrolysis,
but after separation of Ph3P(O) and Ph3P. This compound could
also be readily prepared by treating the reaction mixture with 6 
H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 13.7, 21.9,
22.1, 55.3, 71.7, 71.8, 112.9, 113.8, 123.0, 129.7, 130.7, 140.7, 150.3,
158.6, 161.5 ppm. LC–MS: m/z = 333 [M + 1]+. C18H24N2O4
(332.4): calcd. C 65.04, H 7.28, N 8.43; found C 65.01, H 7.26, N
8.65.
HCl. Yield 1.12 g (62%); m.p. 61–63 °C. IR (KBr): ν = 2984, 1738,
˜
4506
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 4500–4510

Allenylphosphonates Ϫ Precursors of Pyrazoles and Triazoles
Preparation of (OCH2CMe2CH2O)P(O)CH2C(N3)=CRRЈ [R = RЈ (100 MHz, [D6]DMSO, 25 °C, TMS): δ = 13.5, 16.8, 19.7, 21.3 32.0
= H (46); R = H, RЈ = Me (47); R = RЈ = Me (48)]
(d, J = 7.0 Hz), 76.7 (d, J = 6.0 Hz), 138.0 (br.), 152.0 (br.) ppm.
31P NMR (160 MHz, [D6]DMSO, 25 °C, TMS): δ = 1.5 (s) ppm.
C9H16N3O3P (245.2): calcd. C 44.08, H 6.58, N 17.13; found C
44.09, H 6.59, N 17.02. The X-ray structure of this sample was
determined.
Compound 46: Me3SiN3 (0.132 g, 1.14 mmol) was added to a solu-
tion of allene 1a (0.108 g, 0.57 mmol) in DMF (5 mL) and the mix-
ture was stirred at room temperature for 24 h. Then it was
quenched with water and extracted with diethyl ether (3ϫ10 mL).
The solvent was removed and the product isolated by column
chromatography (EtOAc/hexane, 1:1). Yield 0.105 g (80%); m.p.
Preparation of Phosphono-1,2,3-triazole (OCH2CMe2CH2O)-
P(O)[CN(H)–N=N–C=]CH(CH3)2
(50):
Me3SiN3
(0.32 g,
78–80 °C. IR (KBr): ν = 2101, 1630, 1478, 1314, 1263, 1057,
˜
2.8 mmol) was added to a solution of allene 1c (0.50 g, 2.3 mmol)
in acetonitrile (6 mL) and the mixture was heated at reflux for 16 h.
Then it was quenched with water and extracted with diethyl ether
(3ϫ20 mL). 31P NMR spectrum at this stage showed that there
was around 50% of 50. The product was isolated as a white solid
by column chromatography (EtOAc/hexane, 3:2). Yield (isolated)
1009 cm–1. 1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 1.01 and
1.10 (2s, 6 H), 2.70 (d, J = 21.5 Hz, 2 H), 3.83–3.89 (m, 2 H),
4.18–4.23 (m, 2 H), 4.87–4.97 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 21.4, 21.6, 30.6 (d, J = 136.9 Hz), 32.6
(d, J = 6.3 Hz), 75.5 (d, J = 6.5 Hz), 102.7 (d, J = 10.5 Hz), 137.1
(d, J = 11.6 Hz) ppm. 31P NMR (160 MHz, CDCl3, 25 °C, TMS):
δ = 19.4 ppm. C8H14N3O3P (231.2): calcd. C 41.56, H 6.10, N
18.17; found C 41.60, H 6.16, N 18.50.
0.12 g (20%); m.p. 162–164 °C. IR (KBr): ν = 3090, 1562, 1474,
˜
1
1258, 1175, 1053, 1005 cm–1. H NMR (200 MHz, CDCl3, 25 °C,
TMS): δ = 0.96 and 1.30 (2s, 6 H), 1.34 (s, 6 H), 3.65 (septet, J ≈
8.0 Hz, 1 H), 3.95–4.52 (m, 4 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 20.5, 22.1, 22.2, 24.4, 30.0, 32.7 (d, J =
6.9 Hz), 77.6 (d, J = 6.1 Hz), 131.2 (d, J = 234.2 Hz), 153.2 (d, J
= 30.2 Hz) ppm. 31P NMR (160 MHz, CDCl3, 25 °C, TMS): δ =
2.6 ppm. C10H18N3O3P (259.2): calcd. C 46.33, H 7.00, N 16.21;
found C 46.32, H 7.10, N 16.47. The X-ray structure of this sample
was determined.
Compound 47: Prepared by a procedure similar to that used for
46 by using allene 1b (0.94 g, 4.60 mmol) and Me3SiN3 (0.644 g,
5.60 mmol). A mixture of two geometrical isomers (E/Z ≈ 1:2) was
isolated. Yield 0.57 g (50%); m.p. 84–86 °C. IR (KBr): ν = 2103,
˜
1655, 1476, 1271, 1057, 1007 cm–1. 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 1.07 and 1.13 (2s, 6 H), 1.74–1.80 (m, 3 H), 3.03
and 3.10 [2d, J = 20.8 and 21.7 Hz (for the two isomers)], 3.87–4.26
(m, 4 H), 5.84–5.86 and 5.87–5.92 (2m, 1 H, two isomers) ppm. 13
C
Synthesis of (OCH2CMe2CH2O)P(O)CH2C[NN=NC(CO2Et)-
=CH]=CMeH (54): Compound 47 (0.10 g, 0.41 mmol) and
HCϵCCO2Et (0.048 g, 0.49 mmol) were heated neat at 80 °C (4 h)
or by using a microwave oven (10 min). The product was isolated by
column chromatography (EtOAc/hexane, 1:1). Compound 54 was
isolated as a mixture of two isomers (E/Z ≈ 9:1). Yield 0.105 g
NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 14.6, 21.5, 21.6, 32.6,
31.9, 35.9 (2d, J = 137.8 and 138.5 Hz, two isomers), 75.7 (d, J =
6.7 Hz), 126.1 (d, J = 10.8 Hz), 127.5 (d, J = 11.8 Hz) ppm. 31P
NMR (160 MHz, CDCl3, 25 °C, TMS): δ = 19.8, 19.7 ppm (two
isomers). LC–MS: m/z = 218 [(M – N2) +1]+; the molecular ion
was not observed. C9H16N3O3P (245.2): calcd. C 44.08, H 6.58, N
17.13; found C 44.05, H 6.52, N 17.00.
(75%); m.p. 123–125 °C. IR (KBr): ν = 3140, 1705, 1547, 1472,
˜
1
1271, 1063, 1011 cm–1. H NMR (200 MHz, CDCl3, 25 °C, TMS):
δ = 0.96, 1.02 (2s, 6 H), 1.36–1.42 (m, 3 H), 1.93–1.99 (m, 3 H),
3.18, 3.45 [2d, J = 20.5 Hz each, (two isomers), 2 H], 3.75–4.28 (m,
4 H), 4.38–4.45 (m, 2 H), 6.16–6.23 (m, 1 H), 8.32 (s, 1 H) ppm.
13C NMR (50 MHz, CDCl3, 25 °C, TMS): δ = 13.3, 14.3, 21.2,
21.5, 25.8 (d, J = 136.2 Hz), 32.5 (d, J = 6.0 Hz), 59.2 and 61.4 (2s,
two isomers), 76.0 (d, J = 6.5 Hz), 124.0 (d, J = 10.9 Hz), 126.4,
127.7 (d, J = 13.5 Hz), 140.0, 160.5 ppm. 31P NMR (160 MHz,
CDCl3, 25 °C, TMS): δ = 17.9 and 20.7 ppm (9:1). LC–MS: m/z =
344 [M + 1]+. C14H22N3O5P (343.3): calcd. C 48.97, H 6.46, N
12.23; found C 48.90, H 6.40, N 12.38.
Compound 48: In a procedure similar to that used for 46, allene 1c
(0.40 g, 1.9 mmol) and Me3SiN3 (0.256 g, 2.2 mmol) were used. In
this case, column chromatography was not required to purify the
compound. Yield 0.38 g (80%; after work up); m.p. 102–104 °C. IR
(KBr): ν = 2110, 1661, 1476, 1262, 1173, 1065, 922 cm–1. 1H NMR
˜
(400 MHz, CDCl3, 25 °C, TMS): δ = 0.97 and 1.15 (2s, 6 H), 1.73–
1.76 (m, 6 H), 3.00 (d, J = 20.8 Hz), 3.79–3.87 (m, 2 H), 4.27–4.31
(m, 2 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 19.2
and 20.2 (2d, J ≈ 3.6 Hz), 21.3, 21.4, 25.9 (d, J = 139.5 Hz), 32.6
(d, J = 6.0 Hz), 75.1 (d, J = 139.5 Hz), 118.7 (d, J =13.6 Hz), 124.1
(d, J = 11.4 Hz) ppm. 31P NMR (160 MHz, CDCl3, 25 °C, TMS):
δ = 21.2 ppm. In the presence of adventitious moisture in CDCl3,
the compound is not stable. GC–MS: m/z = 231 [M – (N2)]+; the
molecular ion was not observed. C10H18N3O3P (259.2): calcd. C
46.33, H 7.00, N 16.21; found C 46.23, H 7.04, N 15.94.
Synthesis of (OCH2CMe2CH2O)P(O)CH2C[NN=NC(CO2Et)-
=CH]=CMe2 (55): Compound 48 (0.10 g, 0.39 mmol) and
HCϵCCO2Et (0.045 g, 0.46 mmol) were heated neat in a manner
similar to that in the preparation of 54. The product was isolated
by column chromatography (EtOAc/hexane, 1:1). Yield 0.12 g
Preparation of Phosphono-1,2,3-triazole (OCH2CMe2CH2O)- (88%); m.p. 120–122 °C. IR (KBr): ν = 3160, 1742, 1524, 1451,
˜
P(O)[CN(H)–N=NC=]CH2CH3 (49): Me3SiN3 (0.64 g, 5.60 mmol) 1377, 1285, 1215, 1061, 1007 cm–1. 1H NMR (400 MHz, CDCl3,
was added to a solution of allene 1b (0.94 g, 4.65 mmol) in acetoni-
trile (6 mL), and the mixture was heated at reflux for 16 h. At this
stage, 31P NMR showed around 60% of 49. Then it was quenched
with water and extracted with diethyl ether (3ϫ20 mL). Some in-
soluble material was observed. This, along with ether solubles, was
taken up in diethyl ether and then the solvent was completely re-
moved. The residual solid was washed with dichloromethane and
then crystallized from methanol (3–4 mL). Crystals of compound
49 were obtained after 3 d. Yield 0.45 g (40%); m.p. 206–208 °C
25 °C, TMS): δ = 0.98, 1.00 (2s, 6 H), 1.37–1.40 (m, 3 H), 1.57 and
2.00 (2d, J ≈ 4 Hz each, 6 H), 3.23 (d, J = 20.0 Hz, 2 H), 3.68 (dd
Ǟ t, J ≈ 11.5 Hz each, 2 H), 4.02 (dd Ǟ t, J ≈ 10.6 Hz each, 2 H),
4.37–4.28 (m, 2 H), 8.23 (s, 1 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 14.3, 20.3 and 20.6 (2d, J = 3.0 Hz), 21.2,
21.3, 29.0 (d, J = 135.4 Hz), 32.5 (d, J = 6.1 Hz), 61.3, 75.6 (d, J
= 6.4 Hz), 120.8 (d, J = 13.1 Hz), 130.0, 138.1 (d, J = 11.2 Hz),
139.3, 160.6 ppm. 31P NMR (160 MHz, CDCl3, 25 °C, TMS): δ =
19.5 ppm. LC–MS: m/z = 358 [M + 1]+. C15H24N3O5P (357.3):
calcd. C 50.42, H 6.77, N 11.76; found C 50.47, H 6.70, N 12.02.
(decomp.). IR (KBr): ν = 3146, 3082, 1562, 1470, 1375, 1269, 1231,
˜
1161, 1059, 1001 cm–1. 1H NMR (400 MHz, [D6]DMSO, 25 °C, The X-ray structure of this sample was determined. The other iso-
TMS): δ = 0.87 (s, 3 H), 1.20 (t, J = 7.6 Hz, 3 H), 1.23 (s, 3 H),
mer in which the positions of the H and RЈ groups are reversed
was observed only as a minor product (Ͻ10%, not isolated).
2.83 (q, J = 7.6 Hz, 3 H), 3.99–4.28 (m, 4 H) ppm. 13C NMR
Eur. J. Org. Chem. 2008, 4500–4510
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4507

K. C. Kumara Swamy et al.
FULL PAPER
Preparation of Compound 56: Copper (I) iodide (0.007 g,
0.03 mmol) was added to a 25 mL round-bottomed flask contain-
5.74 (d, J = 15.6 Hz, 1 H), 6.80–7.96 (m, 11 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 20.0, 21.0, 55.4, 114.2, 120.2,
ing a mixture of 48 (0.100 g, 0 40 mmol) and phenyl acetylene 121.8, 125.8, 128.0, 128.3, 129.0, 129.1, 129.3, 130.7, 131.1, 135.7,
(0.040 g, 0.40 mmol) in anhydrous acetonitrile (3 mL). The re-
sulting mixture was stirred for 2 d at room temperature. The solvent
was removed under reduced pressure. Compound 56 was purified
by column chromatography (silica gel, ethyl acetate/hexane, 1:1).
147.3, 159.7 ppm. C21H21N3O (331.4): calcd. C 76.11, H 6.39, N
12.68; found C 76.08, H 6.41, N 12.78.
X-ray Crystallography: Single-crystal X-ray data were collected
with a Bruker AXS-SMART diffractometer using Mo-Kα (λ =
0.71073 Å) radiation. The structures were solved by direct methods
and refined by the full-matrix least-squares method using standard
procedures.[28] Absorption corrections were carried out by using
the SADABS program where applicable. In general all non-hydro-
gen atoms were refined anisotropically; hydrogen atoms were fixed
by geometry or located by a difference Fourier map and refined
isotropically.
Yield 0.112 g (80%); m.p.125–127 °C. IR (KBr): ν = 1628, 1480,
˜
1426, 1373, 1281, 1011, 986 cm–1. 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 0.95, 1.03 (2s, 6 H), 1.64–1.65 (m, 3 H), 2.08–
2.09 (m, 3 H), 3.28 (d, J = 20.0 Hz, 2 H), 3.67 (dd Ǟ t, J ≈ 12.0 Hz
each, 2 H), 3.97 (dd Ǟ t, J ≈ 12.0 Hz each, 2 H), 7.32–7.87 (m, 5
H), 7.98 (s, 1 H) ppm. 13C NMR (50 MHz, CDCl3, 25 °C, TMS):
δ = 20.5, 20.7, 21.3, 21.5, 29.1 (d, J = 133.4 Hz), 32.5 (d, J =
6.0 Hz), 75.8 (d, J = 7.3 Hz), 121.2 (d, J = 12.0 Hz), 122.3, 125.8,
125.8, 128.2, 128.9, 130.5, 137.1 (d, J = 10.9 Hz), 146.9 ppm. 31P
NMR (80 MHz, CDCl3, 25 °C, TMS): δ = 19.3 ppm. LC–MS: m/z
= 362 [M + 1]+. C18H24N3O3P (361.4): calcd. C 59.81, H 6.67, N
11.63; found C 59.88, H 6.69, N 11.73. The X-ray structure of this
sample was determined, but we could not model the solvent (water)
properly. Details are available with the authors.
Crystal Data for 22: C18H31N2O7P, M = 418.42, orthorhombic,
space group Pca21, a = 17.8584(17), b = 10.7633(10), c =
11.6169(11) Å, V = 2232.9(4) Å3, Z = 4, µ = 0.162 mm–1, data/
restraints/parameters: 4720/1/264,
R indices [IϾ2σ(I)]: R1 =
0.0421, wR2 (all data) = 0.1086.
Crystal Data for 27: C18H31N2O6P, M = 402.42, monoclinic, space
group P21/n, a = 6.1082(6), b = 18.912(2), c = 19.611(2) Å, β =
92.129(2)°, V = 2263.9(4) Å3, Z = 4, µ = 0.154 mm–1, data/
Synthesis of 57–60
Typical Procedure for 59: The phosphonate 56 (0.100 g, 0.30 mmol)
was dissolved in dry THF (5 mL) and slowly added to a suspension
of NaH (0.013 g, 0.60 mmol) in THF (5 mL) at 0 °C and the mix-
ture stirred at this temperature for 0.5 h. Then 4-chlorobenzalde-
hyde (0.042 g, 0.30 mmol) in THF (2 mL) was added and the mix-
ture was stirred for 2 h. Water (10 mL) was added and the aqueous
layer was thoroughly extracted with diethyl ether (3ϫ20 mL). The
organic layer was collected, dried (Na2SO4), filtered and the solvent
removed from the filtrate to give a residue that was purified by
column chromatography (silica gel, ethyl acetate/hexane, 1:9) to
give 59. Compounds 57, 58 and 60 were synthesized in a manner
similar to compound 59 using same molar quantities.
restraints/parameters: 3921/1/272,
0.0809, wR2 (all data) = 0.2496.
R indices [IϾ2σ(I)]: R1 =
Crystal Data for 28: C14H25N2O4P, M = 316.33, monoclinic, space
group P21/c, a = 6.9482(6), b = 12.8961(11), c = 19.833(16) Å, β =
99.45(10)°, V = 1753.0(3) Å3, Z = 4, µ = 0.172 mm–1, data/
restraints/parameters: 3093/0/200,
0.0426, wR2 (all data) = 0.1189.
R indices [IϾ2σ(I)]: R1 =
Crystal Data for 33: C17H22N2O3, M = 302.37, triclinic, space
¯
group P1, a = 10.8487(7), b = 11.0447(7), c = 15.7402(10) Å, α =
95.532(10), β = 105.549(10)°, γ = 106.892(10)°, V = 1707.22(19) Å3,
Z = 4, µ = 0.081 mm–1, data/restraints/parameters: 5990/0/407, R
indices [IϾ2σ(I)]: R1 = 0.0484, wR2 (all data) = 0.1321.
Compound 57: Yield 0.063 g (75%); m.p. 118 °C. IR (KBr): ν =
˜
1636, 1483, 1426, 1219, 1019, 949 cm–1. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 1.62 (s, 3 H), 2.15 (s, 3 H), 5.80 (d, J =
16.0 Hz, 1 H), 7.20–7.95 (m, 12 H) ppm. 13C NMR (50 MHz,
CDCl3, 25 °C, TMS): δ = 20.0, 21.0, 121.7, 122.2, 125.9, 126.8,
128.1, 128.4, 128.8, 129.0, 129.6, 130.7, 131.1, 136.6, 137.1,
147.4 ppm. LC–MS: m/z = 302 [M + 1]+. C20H19N3 (301.4): calcd.
C 79.70, H 6.35, N 13.94; found C 79.77, H 6.40, N 14.10.
Crystal Data for 49: C9H16N3O3P, M = 245.22, monoclinic, space
group P21/c, a = 9.7155(16), b = 10.0431(17), c = 12.475(2) Å, β =
100.510(2)°, V = 1196.8(3) Å3, Z = 4, µ = 0.227 mm–1, data/
restraints/parameters: 2359/0/152,
0.0399, wR2 (all data) = 0.1083.
R indices [IϾ2σ(I)]: R1 =
Crystal Data for 50: C10H18N3O3P, M = 259.24, monoclinic, space
group P21, a = 6.1317(9), b = 13.7768(19), c = 8.0675(11) Å, β
= 102.875(2)°, V = 664.37(16) Å3, Z = 2, µ = 0.208 mm–1, Flack
parameter: 0.11(9), data/restraints/parameters: 2607/1/162, R in-
dices [IϾ2σ(I)]: R1 = 0.0380, wR2 (all data) = 0.0609.
Compound 58: Yield 0.069 g (78%); m.p. 121–122 °C. IR (KBr): ν
˜
= 1611, 1510, 1424, 1227, 1020 cm–1. 1H NMR (200 MHz, CDCl3,
25 °C, TMS): δ = 1.62 (s, 3 H), 2.15 (s, 3 H), 2.32 (s, 3 H), 5.77 (d,
J = 16.0 Hz, 1 H), 7.11–7.95 (m, 11 H) ppm. 13C NMR (50 MHz,
CDCl3, 25 °C, TMS): δ = 20.0, 20.9, 21.3, 121.3, 121.8, 125.9,
126.7, 128.3, 129.0, 129.5, 131.1, 133.8, 136.4, 138.1, 147.4 ppm.
LC–MS: m/z = 360 [M + 1]+. C21H21N3 (315.4): calcd. C 79.97, H
6.71, N 13.32; found C 79.90, H 6.51, N 13.48.
Crystal Data for 55: C15H24N3O5P, M = 357.34, triclinic, space
¯
group P1, a = 8.4701(7), b = 9.3757(8), c = 13.0749(11) Å, α =
83.9530(10), β = 89.7080(10), γ = 64.8720(10)°, V = 933.92(14) Å3,
Z = 2, µ = 0.175 mm–1, data/restraints/parameters: 3671/0/222, R
indices [IϾ2σ(I)]: R1 = 0.0538, wR2 (all data) = 0.1368.
CCDC-669797 (for 22), -669798 (for 27), -669799 (for 28), -669800
(for 33), -669801 (for 49), -669802 (for 50), and -669803 (for 55)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Compound 59: Yield 0.070 g (75%); m.p. 60–62 °C. IR (KBr): ν =
˜
1640, 1489, 1424, 1227, 1090, 1020 cm–1. 1H NMR (200 MHz,
CDCl3, 25 °C, TMS): δ = 1.63 (s, 3 H), 2.16 (s, 3 H), 5.73 (d, J =
16.0 Hz, 1 H), 7.17–7.94 (m, 11 H) ppm. 13C NMR (50 MHz,
CDCl3, 25 °C, TMS): δ = 20.0, 21.0, 121.7, 122.7, 125.8, 127.9,
128.2, 128.4, 128.9, 129.0, 130.5, 130.8, 133.7, 135.1, 137.8,
147.5 ppm. C20H18ClN3 (335.8): calcd. C 71.53, H 5.40, N 12.51;
found C 71.52, H 5.39, N 12.47.
Acknowledgments
Compound 60: Yield 0.071 g (76%); m.p. 123–125 °C. IR (KBr): ν
˜
= 1605, 1510, 1424, 1242, 1179, 1032 cm–1. 1H NMR (200 MHz,
We thank the Indian Department of Science and Technology
(DST), New Delhi for financial support and for the single-crystal
CDCl3, 25 °C, TMS): δ = 1.61 (s, 3 H), 2.14 (s, 3 H), 3.79 (s, 3 H),
4508
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 4500–4510

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The phosphate (OCH2CMe2CH2O)P(O)OH [δ(P) = –4.3 ppm]
was characterized as its monohydrate (orthorhombic space
group, which is different to that reported in the literature). De-
tails are available from the authors.
[19]
[20]
[21]
It is important to note that under the conditions employed,
we found that phenylallene 2a did not react (1H NMR
evidence).
Eur. J. Org. Chem. 2008, 4500–4510
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4509

K. C. Kumara Swamy et al.
FULL PAPER
[22] In addition to these compounds, we also isolated 10–15% of
Ph3P=NCO2R {R = Et [δ = 21.2 ppm] and iPr [δ(P) =
21.2 ppm] from the corresponding reactions with DEAD/
DIAD. The compound with R = iPr was isolated and charac-
terized by X-ray crystallography. Details are available with the
authors. This compound was obtained previously by a different
route, see: S. Bittner, Y. Assaf, P. Krief, M. Pomerantz, B. T.
Ziemnicka, C. G. Smith, J. Org. Chem. 1985, 50, 1712–1718.
[24] From this reaction we have also isolated (OCH2CMe2CH2O)
P(O)CH2CN [δ(P) = 21.2 ppm; X-ray evidence] in ca. 15%
yield. As such compounds are known in the literature, we did
not proceed further.
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Received: May 20, 2008
1537.
Published Online: July 31, 2008
4510
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Eur. J. Org. Chem. 2008, 4500–4510