Improved Synthesis of Asymmetrical Substituted 1 H-1,2,4-Diazaphospholes

Article abstract of DOI:10.1080/10426507.2014.919580

The reaction of tris(trimethylsilyl)phosphine and a mixture of two different N,N-dimethylalkylamides (1a,b), followed by the treatment with dry hydrazine in situ, resulted in seven asymmetrical 3,5-disubstituted 1H-1,2,4-diazaphospholes (3a-g). Compounds

Full text of DOI:10.1080/10426507.2014.919580

This article was downloaded by: [University of Calgary]
On: 05 October 2014, At: 12:06
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Phosphorus, Sulfur, and Silicon and the
Related Elements
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gpss20
Improved Synthesis of Asymmetrical
Substituted 1H-1,2,4-Diazaphospholes
Qiaoyun Liuab, Jing Wuab, Junfei Liab, Junwen Wangab, Wenjun
Zhengabc & Herbert W. Roeskyd
a Institute of Organic Chemistry, Shanxi Normal University, Gongyuan
Street 1, Linfen, Shanxi Province 041004, People′s Republic of China
b School of Chemical and Materials Science, Shanxi Normal
University, Gongyuan Street 1, Linfen, Shanxi Province 041004,
People′s Republic of China
c Key Laboratory of Magnetic Molecules and Magnetic Information
Material, Ministry of Education, People′s Republic of China
d Institut für Anorganische Chemie der Universität Göttingen,
Tammannstrasse 4 37077, Göttingen, Germany
Accepted author version posted online: 07 May 2014.Published
online: 25 Sep 2014.
To cite this article: Qiaoyun Liu, Jing Wu, Junfei Li, Junwen Wang, Wenjun Zheng & Herbert
W. Roesky (2014): Improved Synthesis of Asymmetrical Substituted 1H-1,2,4-Diazaphospholes,
Phosphorus, Sulfur, and Silicon and the Related Elements, DOI: 10.1080/10426507.2014.919580
To link to this article: http://dx.doi.org/10.1080/10426507.2014.919580
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Phosphorus, Sulfur, and Silicon, 189:1–12, 2014
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2014.919580
IMPROVED SYNTHESIS OF ASYMMETRICAL
SUBSTITUTED 1H-1,2,4-DIAZAPHOSPHOLES
Qiaoyun Liu,1,2 Jing Wu,1,2 Junfei Li,1,2 Junwen Wang,1,2
Wenjun Zheng,1,2,3 and Herbert W. Roesky4
1Institute of Organic Chemistry, Shanxi Normal University, Gongyuan Street 1,
Linfen, Shanxi Province 041004, Peopleꢁs Republic of China
2School of Chemical and Materials Science, Shanxi Normal University, Gongyuan
Street 1, Linfen, Shanxi Province 041004, Peopleꢁs Republic of China
3Key Laboratory of Magnetic Molecules and Magnetic Information Material,
Ministry of Education, Peopleꢁs Republic of China
4Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4
37077, Go¨ttingen, Germany
GRAPHICAL ABSTRACT
Abstract The reaction of tris(trimethylsilyl)phosphine and a mixture of two different N,N-
dimethylalkylamides (1a,b), followed by the treatment with dry hydrazine in situ, resulted in
seven asymmetrical 3,5-disubstituted 1H-1,2,4-diazaphospholes (3a-g). Compounds 3a-g are
characterized by single crystal X-ray structural analysis. The present protocol provides a
general route to this class of molecules without using phosphaalkynes or phosphaalkenes.
Keywords Asymmetrical 1H-1,2,4-diazaphosphole; hydrogen bonding; X-ray structure;
synthesis
INTRODUCTION
Heterocycles containing a low-coordinate phosphorus center1 have found widespread
applications ranging from ligands in metal complexes,2 devices in materials science3 to fun-
damental importance in theoretical and experimental research.4–7 1H-1,2,4-diazaphosphole
(A) (H[3,5-R2dp]) (Figure 1) exhibits electrochemical and coordinating properties due to
the low-coordinate P and N atoms. Moreover, it represents a class of a unique aromatic
Received 4 December 2013; accepted 27 April 2014.
Address correspondence to Herbert Roesky, Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen,
Tammannstrasse 4, 37077 Go¨ttingen, Germany. E-mail: hroesky@gwdg.de
1

2
Q. LIU ET AL.
Figure 1 Various five-membered rings with the hetero atoms nitrogen and phosphorus.
five-membered heterocyclic system,6,8 and may be viewed as a hybrid molecule of the cor-
responding phosphole (B)9 and pyrazole (C)10 (P-doped pyrazole),5 or as 1H-1,2,4-trizole
analogue in which the 4-nitrogen atom is replaced by a σ2λ3-phosphorus atom (D).
Recently, we reported on two pseudoruthenocenes containing symmetric 1,2,4-
diazaphospholide ligands,11 which play an important role as ligands in efficient palla-
dium catalyzed Heck reactions, where phosphorus-palladium π-backbonding is possible.12
This is consistent with the results that palladium complexes incorporating phospha- and
diphosphaferrocenes with a metallocene backbone and a sp2-hybridized phosphorus atom13
were found to be highly efficient ligands in palladium-catalyzed Suzuki cross-coupling
reactions.14 We became interested in planar-chiral pseudo-1,2,4-diazaphospholide met-
allocenes11,12 due to their properties as potential planar-chiral catalysts with low-valent
late transition metals in asymmetric organic transformations.15–18 Therefore, we set out
to develop a facile and general route to asymmetric 1H-1,2,4-diazaphopholes (Figure 1,
A).19 Herein, we report on an alternative synthesis to a number of asymmetric 1H-1,2,4-
diazaphopholes.
RESULTS AND DISCUSSION
Synthesis of Compounds 3
As shown in Scheme 1, N,N-dimethylimidoyl chlorides 1 were prepared by the
reaction of the corresponding acyl chlorides RCOCl with Me2NH, followed by reaction
with oxalylchloride in anhydrous ether. In the case of commercially available amides
RCONMe2 these were used for the reaction with oxalyl chloride in anhydrous ether.20,21 The
reactions of P(SiMe3)322 with the mixture of 1(R1) and 1(R2) in a ratio of 1:1 in anhydrous
acetonitrile afforded the corresponding 1,3-bis(dimethylamino)-2-phospha- allyl chloride
(2) and two additional known symmetric 1,3-bis(dimethylamino)-2-phospha- allyl chlorides
(2(R1) and 2(R2)) as byproducts (Scheme 1).8,23 Compound 2 was used without further
purification.
Compounds 3a-g were prepared by the reaction of anhydrous hydrazine at ambient
temperature with a mixture of 2, 2(R1) and 2(R2) (Scheme 1), which gives after workup
the target compound 3 and the two byproducts 3(R1) and 3(R2). 3 was isolated by column
chromatography in pretty good yields based on the starting material 1.24 To avoid the
hydrolysis of 2, anhydrous hydrazine was used. Compounds 3 are very soluble in CHCl3
and CH2Cl2 and well soluble in THF and ether, but they are not soluble in n-hexane. They
can also be purified by sublimation in high vacuum. The yield of compounds 3 depends on
the content of 2 in the mixture of the asymmetrical and symmetrical phosphaallylic salts
as well as on the nature of the substituents R1 and R2. To improve the yield of 2 and lower
the quantities of 2(R1) and 2(R2) we alternatively added a solution of 1(R1) in acetonitrile

ASYMMETRICAL SUBSTITUTED 1H-1,2,4-DIAZAPHOSPHOLES
3
Scheme 1
and P(SiMe3)3 simultaneously to 1(R2) in acetonitrile to produce 2 in 50–70% yield based
on the 1H NMR spectra.
NMR Spectroscopy
The 31P NMR data of symmetrical phosphaallylic salts as well as of symmetrical 1H-
1,2,4-diazaphospholes have already been reported in literature.8a,25 The 31P NMR resonance
of the asymmetric phosphaallylic salts 2 is close to those of the corresponding two symmet-
rical phosphaallylic salts 2(R1) and 2(R2).24a Compounds 3 were characterized by spectral
and analytical methods.26 The results of elemental analysis are in complete agreement with
the formula of compounds 3. The 31P NMR chemical shifts of 3 range from δ = 66.7 to
80.4 ppm (Table 1) and are consistent with the electron donor capacity of the substituents.
The physical and spectroscopic data of compounds 3a,b and 3d,e are identical to those
reported previously.19a,b,27 They were prepared by [2+3]-cycloaddition of hydrocarbon-
substituted phosphaalkynes (phosphaalkenes) such as tBuC≡P (ClP C(SiMe3)Ph) with
diazomethanes RCH N2. Our synthetic protocol easily allows tuning the properties of the
3,5-substitutents attached to the 1,2,4-diazaphosphole ring and a variety of asymmetrical
1H-1,2,4-diazaphospholes are now accessible.

4
Q. LIU ET AL.
Table 1 31P NMR chemical shifts and yields of compounds 3
Entry
3
R1
R2
31P NMR, δ (ppm)
Yield (%) based on 1
1
2
3
4
5
6
7
a
b
c
d
e
f
tBu
tBu
tBu
Ph
tBu
tBu
tBu
H
Me
iPr
H
Ph
76.7 (d, 2JPH = 42.5 Hz)
74.5 (d, 3JPH = 9.5 Hz)
66.7 (d, 3JPH = 5.4 Hz)
80.4 (d, 2JPH = 41.3 Hz)
71.3 (s)
24
37
42
20
44
35
30
2-furanyl
2-thienyl
70.7 (s)
70.6 (s)
g
Structure Conformations in the Solid State
The crystal structures of 3a,b and 3d feature cyclic tetramers that present a pseudo-
42m (D2h) internal symmetry, of which only a two-fold axis remains as a crystallo-
graphic element, while those of 3e and 3g form cyclic dimers with a pseudo-two-fold
. . .
axis (Table 2).26,28 All structures exhibit NH N bridges in the solid state and are linked
to oligomers. The intermolecular hydrogen bonds of 3 are shown by the special molecu-
lar orientation in the packing diagram.25,28 No formation of a P−H tautomeric structure
was observed. This is consistent with the recently published theoretical calculations.29 The
small difference between the two nitrogen internal angles of 3 is likely attributable to the
disordered NH protons (Figures 2–4).
Figure 2 Molecular structure of 3a with thermal ellipsoids at the 30% probability level. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): P(1A)−C(7A) 1.719(6),
N(1A)−N(2A) 1.342(6), N(1A)−C(7A) 1.317(6); C(7A)−P(1A)−C(8A) 86.6(6), C(7A)−N(1A)−N(2A)
113.0(4), N(1A)−N(2A)−C(8A) 112.8(4). Structure of 3b is analogous with methyl group in place of hy-
drogen atom: P(1A)−C(1A) 1.760(4), C(1A)−N(1A) 1.336(4), N(1A)−N(2A) 1.363(4); C(1A)−P(1A)−C(6A)
87.42(17), C(6A)−N(2A)−N(1A) 111.0(3), N(2A)−N(1A)−C(1A) 115.6(3).

ASYMMETRICAL SUBSTITUTED 1H-1,2,4-DIAZAPHOSPHOLES
Table 2 Crystal data and data collection parameters of compounds 3a,b,d,e,g
5
Compounds
3a
3b
3d
3e
3g
Formula
fw
Cryst. size (mm) 0.30 × 0.20
C6H11N2P
142.14
C7H13N2P
156.16
0.30 × 0.20
× 0.20
Monoclinic
C2/c
12.260(17)
22.05(3)
14.10(2)
90
C8H7N2P1
162.13
C12H15N2P
218.23
C10H13N2PS
224.25
0.30 × 0.20
0.30 × 0.20
0.21 × 0.16
× 0.20
× 0.20
× 0.20
× 0.12
Cryst. Syst.
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
C2/c
Monoclinic
P2(1)/n
15.1257(8)
11.5748(6)
19.0517(10)
90
Monoclinic
P2(1)
Monoclinic
P2(1)/c
20.785(6)
9.875(3)
18.310(5)
90
117.922(4)
90
3320.5(16)
16
1.137
11.8190(14)
8.5829(9)
24.840(3)
90
103.238(2)
90
2452.8(5)
8
1.182
11.9543(2)
8.8572(2)
12.5222(2)
90
115.9730(10)
90
1191.96(4)
4
1.250
α(deg)
β(deg)
γ (deg)
V (Å3)
Z
94.24(2)
90
3802(9)
16
93.5880(10)
90
3329.0(3)
4
Dc (g cm−3
)
1.091
1.294
Absorption
0.253
0.226
0.262
0.195
0.371
coefficient
(mm−1
F (000)
T (K)
Range (deg)
)
1216
296(2)
2.22–25.04
1344
296(2)
1.85–24.99
9803
1344
296(2)
1.67–25.05
34623
928
296(2)
1.77–25.05
13876
472
296(2)
1.89–25.99
16465
reflns measured 16631
Unique reflns
θmax (deg)
Rint
2946
25.04
0.0509
3336
24.99
0.0346
5885
25.05
0.0360
8157
25.05
0.0653
2340
25.99
0.0203
Max and min
Transmn
R1, wR2 [I >
2σ(I)]a
0.9511 and
0.9280
0.0801, 0.2310
0.9561 and
0.9352
0.0567, 0.1489
0.9494 and
0.9255
0.0409, 0.0998
0.9621 and
0.9439
0.0656, 0.1105
0.9565 and
0.9256
0.0512, 0.1494
R1, wR2 (all
data)b
0.1077, 0.2633
0.0835, 0.1687
0.0630, 0.1149
0.1643, 0.1411
0.0596, 0.1601
GOF
ꢀρ(max)
1.057
0.563
1.075
0.435
1.029
0.238
0.981
0.185
1.022
0.567
(e·Å−3
ꢀρ(min)
(e·Å−3
)
−0.525
−0.255
−0.243
−0.195
−0.304
)
aR1 = ꢁ|Fo| –|Fc|/ꢁ|Fo|. b wR2 = [ꢁw(Fo2– Fc2)2/ꢁw(Fo2)2]0.5
.
In spite of the tendency of compounds 3a,b to show proton disorder, the molecular
structure of 3a exclusively exhibits a conformation with two-fold symmetry in the solid
25
. . .
state (Figure 1), connected by N−H N hydrogen bonds. There are two independent
molecules in the asymmetric unit and the tert-butyl groups show large amplitudes of
internal rotational motion. The bond lengths are slightly longer in 3a,b and the bond angles
are less acute than those found in H[dp] (P(1)−C(3) 1.710(3) Å, N(1)−C(2) 1.305(3) Å,
N(1)−N(2) 1.323(3) Å, C(3)−P(1)−C(2), 85.1(1)◦).23a
As illustrated in Figure 3, the 1H-1,2,4-diazaphosphole rings of four 3d molecules
. . .
in the asymmetric unit are connected by N−H N hydrogen bonds to form cyclic four-
membered oligomers in the solid state. In two of the 1,2,4-diazaphosphole rings it is the
N atom in position 1 that carries the H atom, whereas in the other two rings the N atom

6
Q. LIU ET AL.
Figure 3 Molecular structure of 3g with thermal ellipsoids at the 30% probability level. Selected bond
lengths (Å) and angles (deg): P(1A)−C(2A) 1.728(2), C(1A)−N(2A) 1.335(3), N(2A)−N(1A) 1.358(3);
C(1A)−P(1A)−C(2A) 87.08(12), C(1A)−N(2A)−N(1A) 118.5(2), N(2A)−N(1A)−C(2A) 108.1(2). Structure
of 3e is analogous with phenyl group in place of 2-thienyl group, 3e: P(2)−C(13) 1.725(6), C(13)−N(3) 1.340(6),
N(3)−N(4) 1.345(6); C(13)−P(2)−C(20) 87.3(3), C(13)−N(3)−N(4) 109.2(5), N(3)−N(4)−C(20) 117.0(5).
in position 2 carries the H atom. There are no further short contacts between symmetry-
equivalent oligomers. The average planes formed by phenyl groups and the heterocyclic ring
are not coplanar in 3d. The dihedral angles (25.56◦) are likely caused by an intramolecular
interaction of adjacent groups due to a repulsive interaction between the CH of phenyl
groups and the NH.23b This observation of the two twisted conformations is similar to
those found in H[3,5-Ph2dp].23b The bond lengths and angles of 3d are comparable with
those found in H[3,5-Ph2dp] (P(1)−C(1) 1.7404(18) Å, N(1)−C(1) 1.329(2) Å, N(1)−N(2)
1.341(2) Å, C(3)−P(1)−C(2), 87.16(9)◦).23b
Compounds 3e and 3g crystallize in the monoclinic space group P21/c. Molecular
dimensions are shown in Figure 4. As illustrated in these figures, the planes formed by
the phenyl (thienyl) groups and the heterocycle ring show that they are not coplanar
(the dihedral angle is 27.2◦ for 3e and 24.8(3)◦ for 3g), which is likely caused by an
intramolecular interaction of adjacent groups due to a repulsive interaction between the
CH of phenyl groups and the NH,23b or by steric effects between the thienyl groups and
the heterocycles. Hydrogen bridging has been previously observed in 1,2,4-diazaphosphole
structures in which there are similar H-bond patterns.25 The dimers are held together by four
symmetry related hydrogen bonds. Interestingly, one phenyl ring is at the same orientation
to the other in 3e, while one thienyl group is at the opposite position of the other in 3g. The
bond lengths and angles of 3e and 3g are comparable with those found in H[3,5-tBu2dp]
(P(1)−C(1) 1.737(5) Å, N(1)−C(1) 1.330(5) Å, N(1)−N(2) 1.360(5) Å, C(3)−P(1)−C(2),
87.3(2)◦).23a

ASYMMETRICAL SUBSTITUTED 1H-1,2,4-DIAZAPHOSPHOLES
7
Figure 4 Molecular structure of 3d with thermal ellipsoids at the 30% probability level. Hydrogen atoms are
omitted for clarity. Selected bond lengths (Å) and angles (deg): P(1A)−C(1A) 1.722(2), P(1A)−C(2A) 1.746(2),
N(1A)−N(2A) 1.340(2), N(1A)−C(1A) 1.318(3); C(1A)−P(1A)−C(2A) 86.22(10), C(1A)−N(1A)−N(2A)
113.65(18), N(1A)−N(2A)−C(2A) 112.10(17).
CONCLUSIONS
In summary, we report an improved and general route to asymmetrical 3,5-
substituted 1H-1,2,4-diazaphospholes by condensation reaction of hydrazine and two
different substituted 1,3-bis(amino)-2-phosphaallyl chlorides. The products have been
structurally characterized. Successful preparation of asymmetrically 3,5-substituted 1H-
1,2,4-diazaphospholes as ligands is an important step for the preparation of planar-chiral
pseudo-1,2,4-diazaphospholide complexes. The chemistry is in progress in our laboratory.
EXPERIMENTAL
General Experimental and Physical Measurements
All manipulations were carried out in an argon atmosphere under anaerobic condi-
tions using standard Schlenk, vacuum line and glove box techniques. The solvents were
thoroughly dried, deoxygenated, and distilled in an argon atmosphere prior to use. The 1H,
1
1
13C{ H} and 31P{ H} NMR spectra were recorded with a Bruker DRX-600 spectrometer.
IR measurements were carried out with a NICOLET 360 FT-IR spectrometer from Nujol
mulls prepared in a dry box. Melting points were measured in sealed argon-filled capillaries
without temperature correction with an apparatus XT4-100A (Electronic and Optical In-
struments, Beijing). Elemental analyses were performed on an Elemental Vario EL3 (J&K
Chemicals and Sigma-Aldrich, Germany) elemental analyzer by the Analytical Laboratory
at Shanxi Normal University. Diffraction data of compounds 3a,b,d,e,g were collected

8
Q. LIU ET AL.
on a Stoe-Siemens four-circle diffractometer. Tris(trimethylsilyl)phosphine P(SiMe3)3 was
prepared according to the literature.22
Syntheses
Preparation of Imidoyl Chlorides (1)8a,25,30. To a solution of the corresponding
N,N-dimethylamide (125 mmol) in anhydrous ether (350 mL), oxalyl chloride (32 mL,
375 mmol) was slowly added by a syringe at room temperature under stirring. After gas
evolution ceased the suspension was stirred for further 12 h and then filtered. The white
solid was washed with anhydrous ether (3 × 100 mL) and dried in vacuo to afford N,N-
dimethylimidoyl chloride 1 as pure solid.
Preparation of Asymmetrical 1,3-Bis(amino)-2-phosphaallyl Chlorides
(2)8a,25. To a solution of mixed 1(R1) (15 mmol) and 1(R2) (15 mmol) in anhydrous
acetonitrile (120 mL), tris(trimethylsilyl)phosphine P(SiMe3)3 (11 mL, 35 mmol)22 was
slowly added by a syringe within 1 h. After the solution was stirred for 10 h, the volatile
components were removed in high vacuum (0.01 mm Hg). The resulting residue was washed
with anhydrous ether (3 × 20 mL) to give 2 as dark orange solid, which was used without
further purification.
Synthesis of Asymmetrical 1H-1,2,4-diazaphospholes (3)8a,25. To a so-
lution of 2 (30.0 mmol) in trichloromethane (90 mL), anhydrous hydrazine (5.5 mL,
165 mmol) was slowly added. The color changed immediately from orange to gray. The
reaction mixture was stirred for 24 h at room temperature, and then heated to reflux for
12 h. After the volatile components were removed under reduced pressure, the residue was
extracted with ether (5 × 30 mL). The combined organic layers were washed with water (2
× 100 mL), dried with MgSO4, and filtered. The solvent of the filtrate was removed under
reduced pressure and the resulting white solid was purified by column chromatography on
silica-gel using ethylacetate / petroleum ether (6:9) as an eluent to afford 3 as pure white
solid. The physical and spectroscopic data of compounds 3a,b,19a,b 3d,27 and 3e19a,b are
identical to those reported previously.
1H-3-tert-Butyl-1,2,4-diazaphosphole (3a). The crude product was purified
on silica-gel using ethylacetate/petroleum (10:1) as eluent. Yield: 1.05 g (24.0%). M.p.
75−76◦C. 1H NMR (600 MHz, CDCl3, 23◦C): δ = 11.0 (s, br., 1H, NH), 8.52 (d, 2JPH
=
1
43.2 Hz, 1H, CH), 1.43 (d, 3JPH = 6.0 Hz, 9H, t-Bu); 13C{ H} NMR (150 MHz, CDCl3,
23◦C): δ = 189.8 (d, 1JPC = 63.0 Hz, N CBu), 159.8 (d, 1JPC = 73.5 Hz, P CH), 35.1 (d,
2JPC = 15.0 Hz, C(CH3)3), 31.93 (d, 3JPC = 6.0 Hz, CH3); 31P NMR (243 MHz, CDCl3,
2
23◦C): δ = 76.7 (d, JPH = 42.5 Hz); anal. calcd for C6H11N2P: C, 50.70; H, 7.80; N,
19.71. Found: C, 50.81; H, 7.83; N, 19.65%. Single crystals suitable for X-ray diffraction
analysis were obtained by sublimation of the crude product at 40◦C under high vacuum.
1H-3-tert-Butyl-5-methyl-1,2,4-diazaphosphole (3b). The crude product
was purified through column chromatography (ethylacetate/petroleum, 1:6) as eluent.
1
Yield: 1.74 g (37.0%). M.p. 115−118◦C. H NMR (600 MHz, CDCl3, 23◦C): δ = 10.4
3
4
(s, br., 1H, NH), 2.59 (d, JPH = 9.6 Hz, 3H, CH3), 1.41 (d, JPH = 1.2 Hz, 9H, t-Bu);
13C{ H} NMR (150 MHz, CDCl3, 23◦C): δ = 191.2 (d, 1JPC = 60.0 Hz, N CBu), 173.2
1
1
2
3
(d, JPC = 55.5 Hz, P CCH3), 35.3 (d, JPC = 13.5 Hz, PCCHCH3), 31.8 (d, JPC
= 6.0 Hz, C(CH3)3), 29.7 (s, C(CH3)3), 15.9 (d, JPC = 22.5 Hz, PCCH3); 31P NMR
2
(243 MHz, CDCl3, 23◦C): δ = 74.5 (q, JPH = 9.5 Hz); anal. calcd for C7H13N2P: C,
3

ASYMMETRICAL SUBSTITUTED 1H-1,2,4-DIAZAPHOSPHOLES
9
53.84; H, 8.39; N, 17.94. Found: C, 53.89; H, 8.30; N, 17.99 %. Single crystals suitable
for X-ray diffraction analysis were obtained by sublimation at 70◦C under high vacuum.
1H-3-tert-Butyl-5-isopropyl-1,2,4-diazaphosphole (3c). The crude product
was purified through column chromatography (petroleum/ethylacetate 16:1) as eluent.
1
Yield: 2.34 g (42 %). M.p. 138−139◦C. H NMR (600 MHz, CDCl3, 23◦C): δ = 11.0
4
3
(br., 1H, NH), 3.20 (m, 1H, CHCH3), 1.42 (d, JPH = 3.0 Hz, 9H, t-Bu), 1.37 (d, JHH
= 6.6 Hz, 6H, CHCH3); 13C{ H} NMR (150 MHz, CDCl3, 23◦C): δ = 189.5 (d, 1JPC
=
1
60.0 Hz, N CBu), 182.3 (d, 1JPC = 57.0 Hz, CCH), 31.81 (d, 2JPC = 6.0 Hz, C(CH3)3),
24.4 (d, JPC = 6.0 Hz, CH); 31P NMR (243 MHz, CDCl3, 23◦C): δ = 66.7 (d, JPH
=
2
3
5.4 Hz); anal. calcd for C9H17N2P: C, 58.68; H, 9.30; N, 15.21; P, 16.81. Found: C, 58.84;
H, 9.26; N, 15.31%.
1H-3-Phenyl-1,2,4-diazaphosphole (3d). The residue was purified by column
chromatography (petroleum/ethylacetate 6:1) to yield 3d as white solid (0.98 g, 20 %).
1
2
M.p. 70−71◦C. H NMR (600 MHz, CDCl3, 23◦C): δ = 8.74 (d, JPH = 40.2 Hz, 1H,
P CH), 7.86 (d, JHH = 8.4 Hz, 2H, o-H), 7.38−7.43 (m, 3H, m,p-H); 13C{ H} NMR
3
1
(150 MHz, CDCl3, 23◦C): δ = 207.3 (d, JPC = 60.0 Hz, P CPh), 177.5 (d, JPC
=
1
1
56.0 Hz, P CH), 158.5 (s, CPh), 136.6 (s, Ph), 129.4 (s, Ph), 128.4 (s, Ph), 126.4 (s,
Ph); 31P NMR (243 MHz, CDCl3, 23◦C): δ = 80.3 (d, JPH = 41.3 Hz); anal. calcd
2
for C8H7N2P: C, 59.27; H, 4.35; N, 17.28. Found: C, 59.18; H, 4.28; N, 17.34 %. Sin-
gle crystals suitable for X-ray diffraction analysis were sublimed at 60◦C under high
vacuum.
1H-3-Phenyl-5-tert-butyl-1,2,4-diazaphosphole (3e). The crude product was
purified by column chromatography (petroleum/ethyl acetate 20:1) as eluent. Yield: 2.87 g
(44 %). M.p. 78−79◦C. 1H NMR (600 MHz, CDCl3, 23◦C): δ = 11.5 (br., 1H, NH), 7.80
(d, 3JHH = 8.4 Hz, 2H, o-H) 7.35−7.81 (m, 3H, m,p-H), 1.48 (d, 4JPH = 6.0 Hz, 9H, t-Bu);
1
13C{ H} NMR (150 MHz, CDCl3, 23◦C): δ = 190.0 (d, 1JPC = 61.0 Hz, N CBu), 177.5
(d, 1JPC = 56.0 Hz, P CH), 126.2 (d, 3JPC = 9.0 Hz, Ph), 128.9 (s, Ph), 31.8 (d, 2JPC
=
3
1
6.0 Hz, C(CH3)3), 29.4 (d, JPC = 1.5 Hz, C(CH3)3); 31P{ H} NMR (243 MHz, CDCl3,
23◦C): δ = 71.3; anal. calcd for C12H15N2P: C, 66.04; H, 6.93; N, 12.84. Found: C, 65.88;
H, 7.01; N, 12.95 %. Single crystals suitable for X-ray diffraction analysis were obtained
by crystallization from ether.
1H-3-tert-Butyl-5-furanyl-1,2,4-diazaphosphole (3f). The crude product was
purified on silica-gel using a mixture of n-hexane and EtOAc (1:1) as eluent. Yield: 2.29 g
(35.0 %). M.p. 161◦C. 1H NMR (600 MHz, CDCl3, 23◦C): δ = 11.5 (s, br., 1H, NH), 7.47
3
3
(d, JHH = 3.6 Hz, 1H, CH on the furanyl ring), 7.31 (d, JHH = 4.8 Hz, 1H, CH on the
furanyl ring), 7.08 (dd, 3JHH = 3.6 Hz, 3JHH = 4.8 Hz, 1H, CH on the furanyl ring), 1.51 (d,
4JPH = 0.6 Hz, 9H, C(CH3)3); 13C{ H} NMR (150 MHz, CDCl3, 23◦C): δ = 142.3 (d, 2JPC
1
= 4.5 Hz, P C–C, furyl ring), 110.8 (s, furyl ring), 107.6 (s, furyl ring), 31.8 (s, C(CH3)3),
31.7 (s, C(CH3)3); 31P{ H} NMR (243 MHz, CDCl3, 23◦C): 70.7. Single crystals suitable
1
for X-ray diffraction analysis were obtained by sublimation at 130◦C under high vacuum.31
1H-3-tert-Butyl-5-thienyl-1,2,4-diazaphosphole (3g). The crude product was
purified on silica-gel using a mixture of n-hexane and EtOAc (1:1) as eluent. Yield: 2.02 g
(30 %). M.p. 154◦C. 1H NMR (600 MHz, CDCl3): δ = 7.44 (d, 3JHH = 2.4 Hz, 1H, on the
thienyl ring), 7.26 (d, 3JHH = 4.2 Hz, 1H, on the thienyl ring), 7.03 (dd, 3JHH = 4.0 Hz, 3JHH
= 2.4 Hz, 1H, on the thienyl ring), 1.46 (d, 4JPH = 0.6 Hz, 9H, C(CH3)3). 13C{ H} NMR
1
(150 MHz, CDCl3, 23◦C): δ = 127.6 (d, JPC = 1.5 Hz, P C–C, thienyl ring), 125.4 (s,
3
thienyl ring), 125.3 (s, thienyl ring), 31.7 (s, C(CH3)3), 31.6 (s, C(CH3)3). 31P{ H} NMR
1

10
Q. LIU ET AL.
(243 MHz, CDCl3, 23◦C): δ = 70.6. Single crystals suitable for X-ray diffraction analysis
were obtained by sublimation at 120◦C under high vacuum.
X-ray Crystallography. The single crystal X-ray diffraction data of 3 were col-
lected using a Bruker SMART CCD diffractometer operating at 50 kV and 20 mA using
Mo-Kα radiation (λ = 0.71073 Å). An empirical absorption correction was applied using
the SADABS program. The structures were solved by direct methods, and all nonhydrogen
atoms were subjected to anisotropic refinement by full-matrix least squares on F2 using the
SHELXTL package.28
CCDC 940090(3a), 940091(3b), 940094(3d), 940092(3e), and 940093(3g) contain
the supplementary crystallographic data for compounds 3, respectively. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
+44 1223 336 033; or e-mail: data request@ccdc.cam.ac.uk.
ACKNOWLEDGMENT
Liu thanks Dr. Hongbo Tong (Shanxi University) for the help with X-ray diffraction
analysis.
FUNDING
We gratefully acknowledge financial support from the Program for the Top Young and
Middle-Aged Innovative Talents of Higher Learning Institutions of Shanxi (TYMIT 2011),
the Doctoral Foundation of Chinese Education Ministry (grant no. 20111404110001),
National Natural Science Foundation of China (NSFC; grant no. 21272143), the Program
for Changjiang Scholar and Innovative Research Team in University (IRT1156), State R&D
Program of China (no. 2012BAE06B08), the State Key Laboratory of Advanced Technology
for Comprehensive Utilization of Platinum Metals, Scientific and Technological Innovation
Programs of Higher Education Institutions in Shanxi (STIP 20120016), Natural Science
Foundation of Shanxi (grant no. 2013011011-2), and Natural Science Foundation of Shanxi
Normal University (grant no. 872018).
SUPPLEMENTAL MATERIAL
Supplementary data for this article can be accessed on the publisher’s website,
www.tandfonline.com/gpss.
The X-ray crystallographic data, spectroscopic data, and the crystallographic plots of
3 are deposited in the Supporting Information.
REFERENCES
1. Dillon, K. B.; Mathey, F.; Nixon, J. F. Phosphorus: The Carbon Copy: From Organophosphorus
to Phosphaorganic Chemistry, Wiley & Sons; West Sussex, 1998.
2. Weber, L. Angew. Chem. Int. Ed. 2002, 41, 563-572.
3. Washington, M. P.; Gudimetal, V. B.; Laughlin, F. L.; Deligonul, N.; He, S.; Payton, J. L.;
Simpson, M. C.; Protasiewicz, J. D. J. Am. Chem. Soc. 2010, 132, 4566-4567.

ASYMMETRICAL SUBSTITUTED 1H-1,2,4-DIAZAPHOSPHOLES
11
4. (a) Mathey, F. Angew. Chem. Int. Ed. 2003, 42, 1578-1604 (b) Graule, S.; Rudolph, M.; Shen,
W.; Williams, J. A. G.; Lescop, C.; Autschbach, J.; Crassous, J.; Re´au, R. Chem. Eur. J. 2010,
16, 5976-6005.
5. (a) Romero-Nieto, C.; Durben, S.; Kormos, I. M.; Baumgartner, T. Adv. Funct. Mater. 2009, 19,
3625-3631 (b) Matano, Y.; Saito, A.; Fukushima, T.; Tokudome, Y.; Suzuki, F.; Sakamaki, D.;
Kaji, H.; Ito, A.; Tanaka, K.; Imahori, H. Angew. Chem. Int. Ed. 2011, 50, 8016-8020.
6. Nyula´szi, L.; Veszpre´mi, T.; Re´ffy, J.; Burkhardt, B.; Regitz, M. J. Am. Chem. Soc. 1992, 114,
9080-9084.
7. The replacement of a nitrogen atom by a phosphorus atom may entice a significant electron effect
on molecules and would convert the active form of the species: Visser, S. P. J. Phys. Chem. B.
2006, 110, 20759-20761.
8. (a) Schmidpeter, A.; Willhalm, A. Angew. Chem. Int. Ed. Engl. 1984, 23, 903-904.
9. (a) Mathey, F. Chem. Rev. 1988, 88, 429-453 (b) Schmidpeter, A. In Mathey, F. (Ed.),
Phosphorus-Carbon on Heterocyclic Chemistry: The Rise of a New Domain; p. 363, Amsterdam:
Pergamon, 2001.
10. Elguero, J. In Katritzky, A. R.; Rees, C. W.; Potts, K. T. (Eds.), Comprehensive Heterocyclic
Chemistry; Pergamon Press: Oxford, U.K. 1984; 5, pp. 167-282.
11. Zheng, W.; Zhang, G. Z.; Fan, K. N. Organometallics 2006, 25, 1548-1550.
12. Yorke, J.; Wan, L.; Xia, A. B.; Zheng, W. Tetrahedron Lett. 2007, 48, 8843-8845.
13. (a) Sava, X.; Ricard, L.; Mathey, F.; Floch, P. L. Chem. Eur. J. 2001, 7, 3159-3166 (b) Melaimi,
M.; Ricard, L.; Mathey, F.; Floch, P. L. J. Organomet. Chem. 2003, 684, 189-195.
14. (a) Sava, X.; Ricard, L.; Mathey, F.; Floch, P. L. Organometallics 2000, 19, 4899-4903
(b) Melaimi, M.; Mathey, F.; Floch, P. L. J. Organomet. Chem. 2001, 640, 197-199.
15. Fu, G. C. Acc. Chem. Res. 2006, 39, 853-860.
16. (a) Ruble, J. C.; Fu, G. C. J. Am. Chem. Soc. 1998, 120, 11532-11533 (b) Lee, E. C.; McCauley,
K. M.; Fu, G. C. Angew. Chem. Int. Ed. 2007, 46, 977-979 (c) Dai, X.; Fu, G. C. Angew. Chem.
Int. Ed. 2007, 46, 4367-4369 (d) Son, S.; Fu, G. C. J. Am. Chem. Soc. 2007, 129, 1046-1047
(e) Berlin, J. M.; Fu, G. C. Angew. Chem. Int. Ed. 2008, 47, 7048-7050.
17. Ogasawara, M.; Watanabe, S.; Nakajima, K.; Takahashi, T. J. Am. Chem. Soc. 2010, 132, 2136-
2137.
18. (a) Carmichael, D.; Ricard, L.; Seeboth, N. Organometallics 2007, 26, 2964-2970
(b) Carmichael, D.; Klankermayer, J.; Muller, E.; Pietrusiewicz, K. M.; Ricard, L.;
Seeboth, N.; Sowa, S.; Stankevic, M. Organometallics 2011, 30, 1804-1811.
19. A few asymmetrical 1H-3,5-di-substituented diazaphospholes were prepared by [2+3]-
cycloaddition reaction of hydrocarbon-substituted phosphaalkynes (phospha-alkenes) such
as tBuC P (ClP C(SiMe3)Ph) with diazomethane RCH N2. These routes are exclusively
involved in the cumbersome preparation of low-yield starting material of phosphaalkynes and
phophaalkenes and the substituents on the products are greatly limited by the R group of reactant
RCH N2, see (a) (a) Ro¨sch, W.; Regitz, M. Angew. Chem. Int. Ed. Engl. 1984, 23, 900-901
(b) Ma¨rkl, G.; Tro¨tsch, I. Angew. Chem. Int. Ed. Engl. 1984, 23, 901-903 (c) Ito, S.; Miyake,
H.; Yoshifuji, M. Eur. J. Inorg. Chem. 2007, 3491-3500 (d) Dianous, P.; Himdi-Kabbab, S.;
Hamelin, J. Heteroatom Chem. 1995, 6, 403-406 (e) Grobe, J.; Le Van, D.; Hegemann, M.;
Krebs, B.; La¨ge, M. Chem. Ber. 1992, 125, 411-414 (f) Schnurr, W.; Regitz, M. Synthesis 1989,
511-515 (g) Grandin, C.; About-Jaudet, E.; Collignon, N. Heteroatom Chem. 1992, 3, 337-343
(h) Ma¨rkl, G.; Pflaum, S. Tetrahedron Lett. 1986, 27, 4415-4418.
20. Speziale, A. J.; Freeman, R. C. Org. Synth. 1973, 5, 387-389.
21. (a) Belzecki, C.; Rogalska, E. J. Chem. Soc., Chem. Commun. 1981, 57-58 (b) Grdinic, M.;
Hahn, V. J. J. Org. Chem. 1965, 30, 2381-2384 (c) Haveaux, B.; Dekoker, A.; Rens, M.; Sidani,
A. R.; Toye, J.; Ghosez, L. Org. Synth. 1980, 59, 26-34.
22. Becker, G.; Schmidt, H.; Uhl, G.; Uhl, W. Inorg. Synth. 1990, 27, 243-249.
23. (a) Polborn, K.; Schmidpeter, A.; Ma¨rkl, G.; Willhalm, A. Z. Naturforsch. B 1999, 54, 187-192
(b) Wan, L.; Alkorta, I.; Elguero, J.; Sun, J.; Zheng, W. Tetrahedron 2007, 63, 9129-9133.

12
Q. LIU ET AL.
24. Note: The formation of two additional symmetric 1H-3,5-substituted 1,2,4-diazaphospholes
H[3,5-R1R1dp] and H[3,5-R2R2dp] indicates moderate yields of 3 due to the presence of the
two symmetric 1,3-bis(amino)-2-phosphaallyl chlorides in the system. The 31P NMR data of the
unsymmetrical phosphaallylic salts are not reliable for publication due to incomplete separation.
25. Wang, J.-W.; Ding, L.-Y.; Wang, B.-Q.; He, Y.-Y.; Guo, Y.; Jia, X.-F.; Zheng, W. J. Mol. Struct.
2014, 1058, 62-70.
26. See Supplementary Material for this article supporting information.
27. (a) Ro¨sch, W.; Hees, U.; Regitz, M. Chem. Ber. 1987, 120, 1645-1652 (b) Ro¨sch, W.; Richter,
H.; Regitz, M. Chem. Ber. 1987, 120, 1809-1813.
28. Sheldrick, G. M. SHELXS-97, Program for X-ray Crystal Structure Refinement, University of
Go¨ttingen, Germany 1997.
29. Oziminski, W. P. Comput. Theoret. Chem. 2012, 980, 92-100.
30. Speziale, A. J.; Freeman, R. C. Org. Synth. 1973, 5, 387-388.
31. Note: The quality of the crystallographic data of tetrameric 3f is not warranted for publication
due to the disorder of tBu group, but the structural connections are reliable: C10H13N2OP, Mr =
208.19, tetragonal, space group I4(1)/a, a = 19.6212(4) Å, b = 19.6212(4) Å, c = 11.9224(5)
Å, α = β = γ = 90◦.