A convenient and practical method for the synthesis of N-thiophosphoryl aldimines and ketimines

Article abstract of DOI:10.1002/hc.20412

A convenient and practical method for the preparation of N-thiophosphoryl imines was developed through the thermal condensation of acetals with different thiophosphoramides at 120160°C.

Full text of DOI:10.1002/hc.20412

Heteroatom Chemistry
Volume 19, Number 3, 2008
A Convenient and Practical Method for the
Synthesis of N-Thiophosphoryl Aldimines and
Ketimines
Xinyuan Xu, Chungui Wang, Zhenghong Zhou, Zebing Zeng,
Xinpeng Ma, Guofeng Zhao, and Chuchi Tang
State Key Laboratory of Elemento-Organic Chemistry, Institute of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, People’s Republic of China
Received 11 January 2007; revised 17 October 2007
tions [5]. Because of these advantages, N-phosphoryl
ABSTRACT: A convenient and practical method
imines have recently begun to draw much attention
of synthetic chemists and have been successfully em-
ployed in a variety of asymmetric reactions [4], such
for the preparation of N-thiophosphoryl imines was
developed through the thermal condensation of ac-
etals with different thiophosphoramides at 120–
as hydrogenation, alkylation, the Mannich reaction,
the aza-Henry reaction, and the Strecker reaction.
However, N-phosphoryl imines used in the afore-
mentioned reactions are limited to diphenylphos-
phinoylimines. In fact, the reactivities of phosphoryl
imines may be finely tuned by changing the sub-
stituents on the phosphorus atom. In addition, thio-
phosphoryl compounds generally possess better sta-
bility compared with the corresponding phosphoryl
analogues. Thus, replacement of phosphoryl group
by thiophosphoryl makes the imine synthesis and
purification easier. To date, there is only one re-
port about the synthesis of N-thiophosphoryl imines.
In 1988, Kawashima described a simple procedure
for the preparation of allylphenylphosphinoylimnes
through the condensation of the corresponding al-
lylphenylphosphinamide and aldehyde in the pres-
ence of a dehydrating agent MgSO4 [6]. However,
no data were available, and this methodology was
proved to limit to the preparation of phosphinoylim-
ines and inapplicable for ketimines. Therefore, it is
necessary to develop a versatile protocol for the syn-
thesis of both N-thiophosphory aldimines and ke-
timines. In this paper, a convenient and econom-
ical method for the synthesis of several types of
thiophosphoryl imines is described and that will
promote the wide application of these compounds
◦
ꢀ
C
160 C. 2008 Wiley Periodicals, Inc. Heteroatom Chem
19:238–244, 2008; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20412
INTRODUCTION
Asymmetric addition of imines is an important
approach to the preparation of synthetic valu-
able nitrogen-containing compounds, such as chi-
ral amines, 1,2-diamines, and α- or β-amino acids.
Recently, significant progress has been witnessed
in this area [1]. To increase the electrophilic ac-
tivity of the C N double bond of imines, electron-
withdrawing groups, for example, acyl [2], sulfonyl
[3], and phosphoryl [4], are often introduced on
the nitrogen atom. The introduction of a phospho-
ryl group modulates the reactivity of the imines,
and the phosphoryl group can be easily removed
through acid-catalyzed hydrolysis under mild condi-
Correspondence to: Zhenghong Zhou; e-mail: z.h.zhou@nankai.
edu.cn.
Contract grant sponsor: National Natural Science Foundation
of China.
Contract grant number: 20472033.
2008 Wiley Periodicals, Inc.
c
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238

A Convenient and Practical Method for the Synthesis of N-Thiophosphoryl Aldimines and Ketimines 239
TABLE 1 Experimental Data of the Prepared N-Thio-
phosphoryl Aldimines 1
as electrophiles in organic synthesis, especially in
asymmetric synthesis.
RESULTS AND DISCUSSION
An earlier procedure reported by Kruglyak et al. [7a]
in 1968 for the synthesis of N-phosphoryl imines
involved the treatment of an aldoxime or ketoxime
with a trivalent phosphorus derivative. Then, the re-
arrangement of the initially formed trivalent inter-
mediate, phosphorous oximes, led to N-phosphoryl
imines. This is a general protocol for the synthe-
sis of phosphorylimines with different substituents
on the phosphorus atom. However, because of the
instability of trivalent phosphorus compounds, the
main drawback of this reaction was its harsh reac-
tion conditions. The reaction was most commonly
carried out at ca. −40◦C.
Compound
R1
R2
R3
Yield (%)a
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
1r
Ph
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
90
95
92
94
95
93
83
98
84
71
94
97
91
93
91
91
92
84
88
83
82
80
98
4-MeC6H4
3-MeOC6H4
4-MeOC6H4
2-ClC6H4
3-ClC6H4
4-F3CC6H4
2-Furyl
PhCH CHCH EtO
EtOCH
Ph
EtO
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4-MeC6H4
4-MeOC6H4
2-ClC6H4
3-ClC6H4
4-F3CC6H4
4-O2NC6H4
4-BrC6H4
3-FC6H4
PhCH CHCH
EtOCH
Jennings and Lovely documented a simple
method for the preparation of diphenylphosphi-
noylimines [8]. The direct condensation of an alde-
hyde and P,P-diphenyl phosphinamide catalyzed
by TiCl4/Et3N led to the formation of the desired
diphenylphosphinoylimine. However, the reaction
suffered from a tedious workup, and the yield was
only 35%–58%. Moreover, the substrate aldehyde
was limited to aromatic aldehyde.
1s
1t
1u
1v
1w
Ph
Ph
Ph
Ph
PhO PhO
EtO Ph
Compounds 1a–c, 1e–j, 1u, and 1w were purified via column chro-
matography. Compounds 1d, 1j–t, and 1v were purified through re-
crystallization.
Zwierzak and coworkers reported that ther-
mal condensation of acetals of aromatic aldehy-
des with diethyl phosphoramidate in the absence of
solvent afforded the corresponding phosphorylim-
ines in good yields (68%–88%) [9]. However, the
reaction was unsuccessful with aliphatic acetals,
and only limited to the synthesis of O,O-diethyl N-
benzylidene phosphoramidate.
aIsolated yield.
120–160◦C was investigated. The results are listed
in Table 1.
The aforementioned procedures for the prepara-
tion of phosphoryl (or phosphinoyl) imines may be
helpful in the synthesis of N-thiophosphoryl imines.
Apparently, Kruglyak’s methodology is not suitable
for the synthesis of these compounds because the
rearrangement of the trivalent phosphorous oximes
can only lead to phosphorylimines. Second, it was
found that TiCl4/Et3N-catalyzed direct condensation
of aldehyde with the corresponding amide is not
effective in preparing such imines from thiophos-
phoramides. The reaction was very complicated, and
the isolated yield of thiophosphorylimine was quite
low. Finally, we discovered that Zwierzak’s proce-
dure is more suitable for the preparation of N-
thiophosphoryl imines. Satisfactory results were ob-
tained for the N-thiophosphoryl imines synthesis.
The preliminary result has already been communi-
cated [10].
As shown in Table 1, acetals of aromatic aldehy-
des could react smoothly with different types of thio-
phosphoramide (3a: R2 = R3 = EtO, 3b: R2 = R3 = Ph,
3c: R2 = EtO, R3= Ph, or 3d: R2 = R3 = PhO) to afford
the corresponding imines 1 in good to excellent yield
(83%–98%). The substituents R2 and R3 on phospho-
rus atom have an obvious influence on the reaction.
A substantial decrease in the yield was observed for
those thiophosphoramides in which R2 and R3 are
equal to phenoxy (80%). The reaction of aliphatic ac-
etals without α-hydrogens (nonenolizable), such as
cinnamic aldehyde acetal and triethyl orthoformate,
and 3 also took place smoothly to afford the expected
product with a little decrease in yields (71%–84%).
The reaction of aldehydes containing α-hydrogens
(enolizable), such as propanal and butanal, led to the
predominant formation of compounds 4 rather than
the desired imines. It seems feasible that this type
of compound is produced by further condensation
of the initially formed imines with another molecule
First of all, thermal condensation of a set of
acetals 2 with different thiophosphoramides 3 at
Heteroatom Chemistry DOI 10.1002/hc

240 Xu et al.
TABLE 2 Experimental Data of the Prepared N-Thio-
phosphoryl Ketimines 5
Compound
R1
R2
R3
Yield (%)a
5a
5b
5c
5d
5e
5f
C6H5
Me
Me
Me
Me C6H5
Me C6H5
EtO
EtO
EtO
97
69
72
91
81
76
79
74
4-MeC6H4
4-ClC6H4
C6H5
4-MeC6H4
4-MeOC6H4 Me C6H5
4-ClC6H4
C6H5
In conclusion,
a convenient and practical
method for the synthesis of different types of N-
thiophosphoryl imines was developed through ther-
mal condensation of acetals and the corresponding
thiophosphoramides. This protocol has the advan-
tage of mild reaction conditions, ease of workup and
purification, and readily availability of raw materi-
als. Studies aimed at exploring the application of
these compounds in organic synthesis and asymmet-
ric synthesis are currently ongoing in our laborato-
ries, and examples for the preliminary application of
the thiophosphoryl imines as electrophiles are pre-
sented in [12].
5g
5h
Me C6H5
Et C6H5
Compounds 5a–c were purified via column chromatography. Com-
pounds 5d–h were purified through recrystallization.
aIsolated yield.
of acetal. Acceptable yields were obtained for com-
pounds 4 employing a 2:1 molar ratio of acetals to
thiophosphoramide 3.
EXPERIMENTAL SECTION
General
1H and 31P NMR spectra were recorded in CDCl3
on a Varian 400 instrumental using TMS as an in-
1
ternal standard for H NMR and 85% H3PO4 as an
external standard for 31P NMR. Elemental analyses
were conducted on a Yanaco CHN Corder MT-3 au-
tomatic analyzer. Melting points were determined
on a X-4 melting point apparatus. All temperatures
were uncorrected.
The procedure used for aromatic aldehydes was
proved to be still efficient for the preparation of N-
thiophosphoryl ketimines 5. The results are summa-
rized in Table 2.
As shown in Table 2, generally, there exists an
obvious difference in the reactivity between acetals
and ketals with respect to chemical yield of the corre-
sponding N-thiophosphoryl imines. The reaction of
thiophosphoramide (or thiophosphinamide) 7 and
diethyl acetal of acetophenone successfully resulted
in N-thioketimines 5 in excellent yields (97% and
91% for imine 5a and 5d, respectively). Although a
slight decrease in the yield was noticed in substituted
acetophenones and propiophenone, the correspond-
ing N-thiophosphoryl ketimines were obtained in
good yield (69%–81%).
In addition, this procedure also demonstrated
a great advantage over Jennings’ method and
Kruglyak’s methodology for the preparation of
diphenylphosphinoylimines. For example, imines
8a, 8b, and 9 were obtained in 75%, 80% and 64%
yield, respectively, following this thermal condensa-
tion protocol. The results were obviously better than
those of Jennings’ method (8a, 58%; 8b, 80%) [8]
and Kruglyak’s methodology (9, 42%) [11].
Typical Procedure for the Synthesis of
N-Thiophosphoryl Imines 1, 4, 5, 8
A mixture of acetal and the corresponding phospho-
ramide (with a molar ratio of 1.3:1, in case of 4, a
molar ratio of 2:1 was used) was placed in a round-
bottom flask equipped with a distilling apparatus.
The resulting mixture was gently heated (the bath
temperature was gradually raised to ca. 160◦C) with
stirring. The reaction was completed until ethanol
was distilled off from the reaction mixture (2–6 h).
After removal of the excess acetal, the crude prod-
uct was purified through recrystallization or column
chromatography on silica gel (200–300 meshes, gra-
dient eluted with petroleum ether and ethyl acetate).
N-Benzylidene-O,O-diethylthiophosphoramide
(1a). Pale yellow oil, 90% yield, 31P NMR(δ,
CDCl3): 80.17; 1H NMR(δ, CDCl3): 1.26(t, 6H,
JH−H = 7.2 Hz, 2CH3), 4.05–4.20 (m, 4H, 2OCH2),
Heteroatom Chemistry DOI 10.1002/hc

A Convenient and Practical Method for the Synthesis of N-Thiophosphoryl Aldimines and Ketimines 241
7.37–7.52 (m, 3Harom), 7.87–7.89 (m, 2Harom),
4H, 2CH2), 7.74–7.76 (d, 2Harom, JH−H = 8.0 Hz),
8.08–8.10 (d, 2Harom, JH−H = 8.0 Hz), 9.18 (d,
1H, JP−H = 38.4 Hz, CH N ). Anal. Calcd for
C12H15F3NO2PS: C, 44.31; H, 4.65; N, 4.31; Found:
C, 44.25; H, 4.71; N, 4.55.
9.06 (d, 1H, JP−H = 39.3 Hz, CH N). Anal. Calcd for
C11H16NO2PS: C, 51.35; H, 6.27; N, 5.44; Found: C,
51.25; H, 6.32; N, 5.31.
N-4-Methylbenzylidene-O,O-diethylthiophospho-
ramide (1b). Pale yellow oil, 95% yield; 31P NMR
(δ, CDCl3): 80.58; 1H NMR (δ, CDCl3): 1.33 (t,
6H, JH−H = 7.2 Hz, 2CH3), 2.42 (s, 3H, CH3),
4.12–4.25 (m, 4H, 2OCH2), 7.28 (d, 2Harom,
JH−H = 8.0 Hz), 7.85 (d, 2Harom, JH−H = 8.0 Hz),
9.09 (d, 1H, JP−H = 39.6 Hz, CH N). Anal. Calcd for
C12H18NO2PS: C, 53.12; H, 6.69; N, 5.16; Found: C,
53.07; H, 6.53; N, 5.14.
N-2-Furylmethylidene-O,O-diethylthiophosphora-
mide (1h). Brown oil, 98% yield; 31P NMR (δ,
CDCl3): 79.80; 1H NMR (δ, CDCl3): 1.30 (t, 6H,
JH−H = 7.2 Hz, 2CH3), 4.03–4.22 (m, 4H, 2CH2), 6.60
(m, 1Harom), 7.25 (d, 1Harom, JH−H = 3.2 Hz), 7.69
(s, 1Harom), 8.86 (d, 1H, JP−H = 39.6 Hz, CH N ).
Anal. Calcd for C9H14NO3PS: C, 43.27; H, 5.71; N,
5.66; Found: C, 43.32; H, 5.62; N, 5.61.
N-3-Methoxybenzylidene-O,O-diethylthiophospho-
N-3-Phenyl-2-propenylidene-O,O-diethylthiopho-
ramide (1c). Pale yellow oil, 92% yield; 31P NMR
sphoramide (1i). Pale yellow oil, 84% yield; 31P
1
1
(δ, CDCl3): 80.37; H NMR (δ, CDCl3): 1.33 (t, 6H,
NMR (δ, CDCl3): 79.82; H NMR (δ, CDCl3): 1.32 (t,
JH−H = 7.2 Hz, 2CH3), 3.84 (s, 3H, OCH3), 4.10–4.25
(m, 4H, 2CH2), 7.11–7.13 (m, 1Harom), 7.36–7.50
(m, 3Harom), 9.09 (d, 1H, JP−H = 39.2 Hz, CH N).
Anal. Calcd for C12H18NO3PS: C, 50.16; H, 6.32; N,
4.88; Found: C, 50.06; H, 6.34; N, 4.77.
6H, JH−H = 7.2 Hz, 2CH3), 4.06–4.21 (m, 4H, 2CH2),
6.97–7.04 (m, 1H, CH), 7.39–7.54 (m, 5Harom,
CH), 8.85 (dd, 1H, JH−H = 9.2 Hz, JP−H = 38.4 Hz,
CH N ). Anal. Calcd for C13H18NO2PS: C, 55.11;
H, 6.40; N, 4.94; Found: C, 53.06; H, 6.53; N, 5.01.
N-4-Methoxybenzylidene-O,O-diethylthiophospho-
ramide (1d). White solid, mp 61–62◦C, 94% yield;
31P NMR (δ, CDCl3): 80.82; 1H NMR (δ, CDCl3): 1.33
(t, 6H, JH−H = 7.2 Hz, 2CH3), 3.87 (s, 3H, OCH3),
4.09–4.24 (m, 4H, 2CH2), 6.96–6.98 (d, 2Harom,
JH−H = 8.8 Hz), 7.91–7.93 (d, 2Harom, JH−H = 8.8 Hz),
9.05 (d, 1H, JP−H = 39.2 Hz, CH N). Anal. Calcd for
C12H18NO3PS: C, 50.16; H, 6.32; N, 4.88; Found: C,
49.72; H, 6.30; N, 4.52.
N-Ethoxymethylidene-O,O-diethylthiophosphora-
mide (1j). Pale yellow oil, 71%, yield; 31P NMR
1
(δ, CDCl3): 75.08; H NMR (δ, CDCl3): 1.28 (t, 6H,
JH−H = 7.2 Hz, 2CH3), 1.30 (t, 3H, CH3), 4.02–4.11
(m, 4H, 2CH2), 4.27 (q, 2H, JH−H = 7.2 Hz, CH2),
8.25 (d, 1H, JP−H = 19.2 Hz, CH N ). Anal. Calcd
for C7H16NO3PS: C, 37.32; H, 7.16; N, 6.22; Found:
C, 53.06; H, 6.53; N, 5.01.
N-Benzylidene-diphenylthiophosphinamide (1k).
White solid, 87–89◦C, 94% yield; 31P NMR (δ, CDCl3):
62.08; H NMR (δ, CDCl3): 7.41–7.59 (m, 9Harom),
7.99–8.80 (m, 6Harom), 9.38 (d, 1H, JP−H = 44.0 Hz,
CH N ). Anal. Calcd for C19H16NPS: C, 71.01; H,
5.02; N, 4.36; Found: C, 70.95; H, 4.60; N, 4.68.
N-2-Chlorobenzylidene-O,O-diethylthiophosphora-
1
mide (1e). Pale yellow oil, 95% yield; 31P NMR
1
(δ, CDCl3): 79.57; H NMR (δ, CDCl3): 1.34 (t, 3H,
JH−H = 7.2 Hz, 2CH3), 4.12–4.28 (m, 4H, 2CH2),
7.31–7.50 (m, 4Harom), 9.60 (d, 1H, JP−H = 38.8 Hz,
CH N). Anal. Calcd for C11H15ClNO2PS: C, 45.28;
H, 5.18; N, 4.80; Found: C, 45.09; H, 5.23; N, 4.67.
N-4-Methylbenzylidene-diphenylthiophosphinam-
ide (1l). White solid, 119–120◦C, 97% yield, 31P
1
N-3-Chlorobenzylidene-O,O-diethylthiophosphora-
NMR (δ, CDCl3): 61.82; H NMR (δ, CDCl3): 2.44 (s,
mide (1f). Pale yellow oil, 93% yield; 31P NMR
3H, CH3), 7.32 (d, 2Harom, JH−H = 8.0 Hz), 7.42–
7.46 (m, 6Harom), 7.96 (d, 2Harom, JH−H = 8.0 Hz),
7.98–8.04 (m, 4Harom), 9.35 (d, 1H, JP−H = 39.6 Hz,
CH N ). Anal. Calcd for C20H18NPS: C, 71.62; H,
5.41; N, 4.18; Found: C, 71.53; H, 5.29; N, 3.98.
1
(δ, CDCl3): 79.87; H NMR (δ, CDCl3): 1.33 (t, 3H,
JH−H = 7.2 Hz, 2CH3), 4.15–4.21 (m, 4H, 2CH2),
7.42–7.79 (m, 3Harom), 7.98 (s, 1Harom), 9.07
(d, 1H, JP−H = 38.4 Hz, CH N). Anal. Calcd for
C11H15ClNO2PS: C, 45.28; H, 5.18; N, 4.80; Found:
C, 45.31; H, 5.10; N, 4.82.
N-4-Methoxybenzylidene-diphenylthiophosphina-
mide (1m). White solid, 139–141◦C, 91% yield,
31P NMR (δ, CDCl3): 61.56; 1H NMR (δ, CDCl3):
3.89 (s, 3H, CH3), 7.01 (d, 2Harom, JH−H = 8.8 Hz),
7.40–7.46 (m, 6Harom), 7.98–8.04 (m, 6Harom),
9.29 (d, 1H, JP−H = 39.6 Hz, CH N ). Anal. Calcd
N-4-Trifluoromethylbenzylidene-O,O-diethylthi-
ophosphoramide (1g). Pale yellow oil, 83% yield.
31P NMR (δ, CDCl3): 79.35; 1H NMR (δ, CDCl3):
1.35 (t, 6H, JH−H = 7.2 Hz, 2CH3), 4.15–4.28 (m,
Heteroatom Chemistry DOI 10.1002/hc

242 Xu et al.
for C20H18NOPS: C, 68.36; H, 5.16; N, 3.99; Found:
C, 68.00; H, 5.27; N, 4.00.
N-3-Phenyl-2-propenylidene-diphenylthiophosphi-
namide (1t). White solid, mp 101–102◦C, 83%
yield; 31P NMR (δ, CDCl3): 62.21; 1H NMR (δ,
CDCl3): 7.19–7.24 (m, 1H, CH), 7.41–7.59 (m,
11Harom, CH), 7.94–8.00 (m, 4Harom), 9.15 (dd,
1H, JH−H = 9.2 Hz, JP−H = 38.8 Hz, CH N ). Anal.
Calcd for C21H18NPS: C, 72.60; H, 5.22; N, 4.03;
Found: C, 67.09; H, 4.25; N, 4.19.
N-2-Chlorobenzylidene-diphenylthiophosphinam-
ide (1n). White solid, 115–116◦C, 93% yield,
31P NMR (δ, CDCl3): 62.07; 1H NMR (δ, CDCl3):
7.44–7.48 (m, 9Harom), 7.99–8.06 (m, 4Harom),
8.32 (dd, 1Harom, JH−H = 7.5 and 1.5 Hz), 8.89
(d, 1H, JP−H = 38.7 Hz, CH N ). Anal. Calcd for
C19H15ClNPS: C, 64.13; H, 4.25; N, 3.94; Found: C,
64.17; H, 4.27; N, 3.92.
N-Ethoxymethylidene-diphenylthiophosphinami-
de (1u). White solid, mp 53–55◦C, 82% yield, 31P
1
NMR (δ, CDCl3): 56.04; H NMR (δ, CDCl3): 1.40 (t,
N-3-Chlorobenzylidene-diphenylthiophosphinam-
3H, JH−H = 7.2 Hz, CH3), 4.46 (q, 2H, JH−H = 7.2 Hz,
CH2), 7.39–7.47 (m, 6Harom), 7.91–7.96 (m,
4Harom), 8.45 (d, 1H, JP−H = 20.8 Hz, CH N ).
Anal. Calcd for C15H16NOPS: C, 62.27; H, 5.57; N,
4.84; Found: C, 67.09; H, 4.25; N, 4.19.
ide (1o). White solid, 136–138◦C, 91% yield; 31P
1
NMR (δ, CDCl3): 62.66; H NMR (δ, CDCl3): 7.44–
7.56 (m, 8Harom), 7.66–8.10 (m, 6Harom), 9.35
(d, 1H, JP−H = 40.0 Hz, CH N ). Anal. Calcd for
C19H15ClNPS: C, 64.13; H, 4.25; N, 3.94; Found: C,
64.43; H, 4.60; N, 3.92.
N-Benzylidene-O,O-diphenylthiophosphoramide
(1v). White crystal, mp 80–89◦C, 80% yield; 31P
N-4-Trifluoromethylbenzylidene-diphenylthiopho-
sphinamide (1p). White solid, 145–147◦C, 91%
yield; 31P NMR (δ, CDCl3): 61.96; 1H NMR (δ,
CDCl3): 7.41–7.49 (m, 6Harom), 7.78 (d, 2Harom,
JH−H = 8.1 Hz), 7.98–8.06 (m, 4Harom), 8.18 (d,
2Harom, JH−H = 8.1 Hz), 9.45 (d, 1H, JP−H = 38.7 Hz,
CH N ). Anal. Calcd for C20H15F3NPS: C, 61.69;
H, 3.88; N, 3.60; Found: C, 61.65; H, 4.09; N, 3.55.
1
NMR (δ, CDCl3): 74.18; H NMR (δ, CDCl3): 7.18–
7.65 (m, 15Harom), 9.15–9.25 (d, 1H, JP−H = 40.4 Hz,
CH N ). Anal. Calcd for C19H16NO2PS: C, 64.58;
H, 4.56; N, 3.96; Found: C, 64.62; H, 4.57; N, 3.89.
N-Benzylidene-O-ethyl phenylthiophosphonamide
(1w). Pale yellow oil, 98% yield; 31P NMR
(δ, CDCl3): 87.31; 1H NMR (δ, CDCl3): 1.32
(t, 3H, JH−H = 7.2 Hz, CH3), 4.07–4.13 (m, 2H,
JH−H = 7.2 Hz, CH2), 7.43–7.56 (m, 6Harom), 7.96–
8.13 (m, 4Harom), 9.18–9.28 (d, 1H, JP−H = 38.8 Hz,
CH N ). Anal. Calcd for C15H16NOPS: C, 62.27; H,
5.57; N, 4.84; Found: C, 62.23; H, 5.61; N, 4.92.
N-4-Nitrobenzylidene-diphenylthiophosphinamide
(1q). Golden solid, 216–219◦C, 92% yield; 31P NMR
1
(δ, CDCl3): 62.49; H NMR (δ, CDCl3): 7.44–7.56 (m,
6Harom), 7.98–8.06 (m, 4Harom), 8.23 (d, 2Harom,
JH−H = 8.7 Hz), 8.36 (d, 2Harom, JH−H = 8.7 Hz), 9.49
(d, 1H, JP−H = 39.0 Hz, CH N ). Anal. Calcd for
C19H15N2O2PS: C, 62.29; H, 4.13; N, 7.65; Found: C,
62.27; H, 3.99; N, 7.65.
N-2-Methyl-2-pentenylidene-diphenylphosphina-
mide (4a). Pale yellow oil, 73% yield; 31P NMR
(δ, CDCl3): 60.71; 1H NMR (δ, CDCl3): 1.07 (t,
3H, JH−H = 7.2 Hz, CH3), 2.01 (s, 3H, CH3), 2.35
(quintet, 2H, JH−H = 7.2 Hz, CH2), 6.49 (t, 1H,
JH−H = 7.2 Hz, CH), 7.39–7.43 (m, 6Harom), 7.99–
8.04 (m, 4Harom), 8.89 (d, 1H, JP−H = 39.2 Hz,
CH N ). Anal. Calcd for C18H20NPS: C, 68.98; H,
6.43; N, 4.47; Found: C, 68.74; H, 6.53; N, 4.32.
N-4-Bromobenzylidene-diphenylthiophosphinam-
ide (1r). White solid, 127–128◦C, 84% yield; 31P
1
NMR (δ, CDCl3): 61.55; H NMR (δ, CDCl3): 7.40–
7.51 (m, 6Harom), 7.66 (d, 2Harom, JH−H = 8.4 Hz),
7.93 (d, 2Harom, JH−H = 8.4 Hz), 7.97–8.04 (m,
4Harom), 9.35 (d, 1H, JP−H = 39.0 Hz, CH N ).
Anal. Calcd for C19H15BrNPS: C, 57.01; H, 3.78; N,
3.50; Found: C, 57.02; H, 3.54; N, 3.58.
N-2-Ethyl-2-hexenylidene-diphenylphosphinamide
(4b). Pale yellow oil, 71% yield; 31P NMR (δ,
CDCl3): 60.75; 1H NMR (δ, CDCl3): 0.97 (t, 3H,
JH−H = 7.2 Hz, CH3), 1.08 (t, 3H, JH−H = 7.2 Hz, CH3),
2.33 (quintet, 2H, JH−H = 7.2 Hz, CH2), 2.54 (q, 2H,
JH−H = 7.2 Hz, CH2), 4.20–4.28 (m, 4H, 2CH2), 6.46
(t, 1H, JH−H = 7.2 Hz, CH), 7.39–7.42 (m, 6Harom),
7.96–8.01 (m, 4Harom), 8.82 (d, 1H, JP−H = 40.0 Hz,
CH N ). Anal. Calcd for C20H24NPS: C, 53.12; H,
6.69; N, 5.16; Found: C, 53.06; H, 6.53; N, 5.01.
N-3-Fluorobenzylidene-diphenylthiophosphinam-
ide (1s). White solid, 128–131◦C, 88% yield;
31P NMR (δ, CDCl3): 61.50; 1H NMR (δ, CDCl3):
7.28–7.31 (m, 1Harom), 7.41–7.53 (m, 7Harom),
7.77–7.83 (m, 2Harom), 7.98–8.05 (m, 4Harom),
9.37 (d, 1H, JP−H = 39.0 Hz, CH N ). Anal. Calcd
for C19H15FNPS: C, 67.24; H, 4.46; N, 4.13; Found:
C, 67.09; H, 4.25; N, 4.19.
Heteroatom Chemistry DOI 10.1002/hc

A Convenient and Practical Method for the Synthesis of N-Thiophosphoryl Aldimines and Ketimines 243
yield. 31P NMR (δ, CDCl3): 48.26; 1H NMR (δ, CDCl3):
2.77 (s, 3H, CH3), 7.41–7.47 (m, 6Harom), 8.02–8.08
(m, 6Harom). Anal. Calcd for C20H17ClNPS: C, 64.95;
H, 4.63; N, 3.79; Found: C, 65.02; H, 4.72; N, 3.76.
N-1-Phenylethyliden-O,O-diethylthiophosphora-
mide (5a). Pale yellow oil, 97% yield. 31P NMR
1
(δ, CDCl3): 67.38; H NMR (δ, CDCl3): 1.38 (t, 6H,
JH−H = 7.2 Hz, 2CH3), 2.79 (s, 3H, CH3), 4.20–4.28
(m, 4H, 2CH2), 7.39–7.43 (m, 2Harom), 7.49–7.53
(m, 1Harom), 7.96–7.98 (m, 1Harom). Anal. Calcd
for C12H18NO2PS: C, 53.12; H, 6.69; N, 5.16; Found:
C, 53.06; H, 6.53; N, 5.01.
N-1-Phenylpropylidene-diphenylthiophosphinam-
ide (5h). White solid, 126–128◦C, 74% yield; 31P
1
NMR (δ, CDCl3): 46.67; H NMR (δ, CDCl3): 1.04 (t,
3H, JH−H = 7.6 Hz, CH3), 3.41 (q, 2H, JH−H = 7.6 Hz,
CH2), 7.42–7.55 (m, 9Harom), 7.97–8.09 (m,
6Harom). Anal. Calcd for C21H20NPS: C, 72.18; H,
5.77; N, 4.01; Found: C, 72.09; H, 5.60; N, 3.95.
N-1-(4-Methylphenyl)ethylidene-O,O-diethylthio-
phosphoramide (5b). Pale yellow oil, 69% yield;
31P NMR (δ, CDCl3): 67.49; 1H NMR (δ, CDCl3):
1.37 (t, 6H, JH−H = 7.2 Hz, 2CH3), 2.38 (s, 3H,
CH3), 2.79 (d, 3H, JP−H = 2.0 Hz, CH3), 4.19–4.26
(m, 4H, 2CH2), 7.19 (d, JH−H = 8.0 Hz, 2Harom),
7.85 (d, JH−H = 8.0 Hz, 2Harom). Anal. Calcd for
C13H20NO2PS: C, 54.72; H, 7.07; N, 4.91; Found: C,
54.86; H, 7.35; N, 4.73.
N-Benzylidene-diphenylphosphinamide
(8a).
White solid, 124–126◦C, 75% yield; 31P NMR (δ,
CDCl3): 23.10; 1H NMR (δ, CDCl3): 7.19–7.38
(m, 10Harom), 7.52–7.67 (m, 3Harom), 8.03 (d,
2Harom, JH−H = 8.0 Hz), 9.23 (d, 1H, JP−H = 20.8 Hz,
CH N ).
N-1-(4-Chlorophenyl)ethylidene-O,O-diethylthio-
phosphoramide (5c). Pale yellow oil, 72% yield;
31P NMR (δ, CDCl3): 67.23; 1H NMR (δ, CDCl3):
1.37 (t, 6H, JH−H = 7.2 Hz, 2CH3), 2.76 (s, 3H, CH3),
4.17–4.29 (m, 4H, 2CH2), 7.37 (d, JH−H = 8.2 Hz,
2Harom), 7.90 (d, JH−H = 8.2 Hz, 2Harom). Anal.
Calcd for C12H17ClNO2PS: C, 47.14; H, 5.60; N, 4.58;
Found: C, 46.97; H, 5.53; N, 4.54.
N-4-Methoxybenzylidene-diphenylphosphinamide
(8b). White solid, 146–148◦C, 80% yield, 31P NMR
1
(δ, CDCl3): 25.87; H NMR (δ, CDCl3): 3.88 (s, 3H,
OCH3), 6.99 (d, 2Harom, JH−H = 8.8 Hz), 7.42–7.49
(m, 6Harom), 7.90–7.95 (m, 4Harom), 7.97 (d,
2Harom, JH−H = 8.8 Hz), 9.22 (d, 1H, JP−H = 32.4 Hz,
CH N ).
N-1-Phenylethylidene-diphenylthiophosphinamide
(5d). White solid, 129–131◦C, 91% yield; 31P NMR
(δ, CDCl3): 46.90; 1H NMR (δ, CDCl3): 2.79 (s,
3H, CH3), 7.40–7.55 (m, 9Harom), 8.01–8.08 (m,
6Harom). Anal. Calcd for C20H18NPS: C, 71.62; H,
5.41; N, 4.18; Found: C, 71.65; H, 5.47; N, 4.20.
N-1-Phenylethylidene-diphenylphosphinamide
(9). White solid, 139–140◦C, 64% yield; 31P NMR
(δ, CDCl3): 19.99; 1H NMR (δ, CDCl3): 2.97 (d,
3H, JP−H = 1.2 Hz, CH3), 7.42–7.57 (m, 9Harom),
7.96–8.10 (m, 6Harom).
N-1-(4-Methylphenyl)ethylidene diphenylthiopho-
sphinamide (5e). White solid, 144–147◦C, 81%
yield; 31P NMR (δ, CDCl3): 47.53; 1H NMR (δ,
CDCl3): 2.43 (s, 3H, CH3), 2.77 (d, 3H, JP−H = 1.6 Hz,
CH3), 7.27 (d, JH−H = 8.4 Hz, 2Harom), 7.40–7.44 (m,
6Harom), 7.96 (d, JH−H = 8.4 Hz, 2Harom), 8.01–8.06
(m, 4Harom). Anal. Calcd for C21H20NPS: C, 72.18;
H, 5.77; N, 4.01; Found: C, 72.19; H, 5.90; N, 4.00.
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