Cyclodimerization and cyclotrimerization of isocyanates promoted by one praseodymium benzenethiolate complex [Pr(SPh)3(THF)3]

Article abstract of DOI:10.1016/j.tet.2010.12.069

The cyclotrimerization of aryl isocyanates and the cyclodimerization of alkyl isocyanates initiated by one praseodymium benzenethiolate complex [Pr(SPh)₃(THF)₃] were investigated. Comparative runs with [Pr(SPh)₃(THF)₃] and its precursor Pr[(Me ₃Si)₂N]₃ showed that the former has the advantages of a higher selectivity toward isocyanates, easy preparation, low catalyst loading, high conversion as well as mild reaction conditions.

Full text of DOI:10.1016/j.tet.2010.12.069

Tetrahedron 67 (2011) 1530e1535
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Cyclodimerization and cyclotrimerization of isocyanates promoted by one
praseodymium benzenethiolate complex [Pr(SPh)3(THF)3]
,b,
He-Ming Wang a, Hong-Xi Li a, Xiang-Yang Yu a, Zhi-Gang Ren a, Jian-Ping Lang a
*
a College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 210032, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 October 2010
Received in revised form 16 December 2010
Accepted 24 December 2010
Available online 8 January 2011
The cyclotrimerization of aryl isocyanates and the cyclodimerization of alkyl isocyanates initiated by one
praseodymium benzenethiolate complex [Pr(SPh)3(THF)3] were investigated. Comparative runs with [Pr
(SPh)3(THF)3] and its precursor Pr[(Me3Si)2N]3 showed that the former has the advantages of a higher
selectivity toward isocyanates, easy preparation, low catalyst loading, high conversion as well as mild
reaction conditions.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Praseodymium
Thiolate
Amide
Catalysis
Phenyl isocyanate
1. Introduction
halides and alkoxides,15 copper and nickel halides,10 palladium(0)
complexes,16 and organolanthanide complexes.17e19 Among orga-
Investigation of catalysts that can selectively catalyze the cyclo-
dimerization, cyclotrimerization, or polymerization of isocyanates is
one active topic of organic chemistry.1 Isocyanurates are employed
in the preparation of copolymer resins that requirewater-resistance,
transparency, and impact resistance,2 and a novel optically active
isocyanuratehasbeen usedforchiraldiscriminationofenantiomeric
amino acid units.3 Triaryl isocyanurates are useful activators for
nolanthanide
complexes,
lanthanide
amide
complexes
(MeC5H4)2LnNiPr2(THF) (Ln¼Y, Er, Yb)17 were reported to exhibit
good catalytic performance for phenyl isocyanate polymerization,
while (MeC5H4)2LnCl/n-BuLi18 systems were excellent catalysts for
the cyclotrimerization of phenyl isocyanate. These results showed
that ancillary ligands play an important role on the selectivity of the
catalysts. Recently, we found that lanthanide thiolate complexes20
displayed excellent catalytic performances on the ring-opening
anionic polymerization of e-caprolactams to nylon-6 and are known
to substantially enhance the stability of polyurethane networks and
coating materials with respect to thermal resistance, flame re-
tardation, chemical resistance, and film-forming characteristics.4
The isocyanate cyclodimerized products could readily eliminate
one CO molecule to result in the formation of organic ureas, which
have industrialand academicapplications as agrochemicals, dyes for
cellulose fibers, antioxidants in gasoline, resin precursors, and syn-
thetic intermediates.5 The most common catalysts for the cyclo-
dimerization, cyclotrimerization, or polymerization of isocyanates
include phosphines,6 N-heterocyclic carbenes,7 calcium carbene
complexes,8 amines,9 potassium phthalimide,10 fluoride anions,11
and alkoxyalkenes.12 Metal-containing cyclotrimerization catalysts
include organotin13 and zirconium compounds,14 organozinc
polymerization of e-caprolactone, which may be due to the fact that
the LneSbond disruptionenthalpyis smaller thanthose of LneC and
LneN bonds.21 Do the lanthanide thiolate complexes show the cat-
alytic activity and selectivity for cyclodimerization, cyclo-
trimerization, or polymerization of isocyanates? With this question
in mind, we prepared one praseodymium benzenethiolate complex
[Pr(SPh)3(THF)3] from the protonlysis reactions of its triamide
complex Pr[(Me3Si)2N]3 with benzenthiol and carried out their
catalytic reactions of various isocyanates. [Pr(SPh)3(THF)3] does
show good activity and selectivity for the cyclodimerization and
cyclotrimerization of isocyanates. All these results will be described
in this article.
2. Results and discussion
22
Lanthanide tri(dimethylsilyl)amide complex Ln[(Me3Si)2N]3
* Corresponding author. Tel.: þ86 512 6588 2865; fax: þ86 512 6588 0089;
e-mail address: jplang@suda.edu.cn (J.-P. Lang).
could be used to prepare its corresponding thiolate complex
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.12.069

H.-M. Wang et al. / Tetrahedron 67 (2011) 1530e1535
1531
Table 2
through its protonolysis reaction with a thiol because thiol has an
acidity stronger than that of HN(SiMe3)2 and could protonate the
(Me3Si)2Nꢀ anion to give lanthanide thiolate complex.20,23 There-
fore, treatment of Pr[(Me3Si)2N]3 with 3 equiv of benzenethiol in
toluene followed by a standard workup produced [Pr(SPh)3(THF)3]
in 92% yield. The elemental analysis was consistent with its
chemical formula. Attempts to grow its single crystals for de-
termining its crystal structure always failed. This product was quite
unstable and very sensitive to air and moisture. To examine the
reactivity of this complex toward isocyanates, [Pr(SPh)3(THF)3] was
mixed with phenyl isocyanate (1a) in a 1/100 M ratio and stirred at
20 ꢁC for 12 h. After hydrolysis by water and extraction by diethyl
ether, the filtrate was concentrated to dryness in vacuo. The solid
was re-crystallized with hot toluene/THF to give colorless crystals
of one cyclotrimerized product 1,3,5-trisphenyl-1,3,5-triazinane-
2,4,6-trione (2a) in 54% yield. To our knowledge, it represents the
first example to employ lanthanide thiolate complexes to catalyze
the cyclotrimerization of isocyanates.
Data for the [Pr(SPh)3(THF)3]-catalyzed cyclodimerization or cyclotrimerization of
different isocyanates
O
R = phenyl (2a),
R
O
R
O
4-isopropylphenyl (2b),
4-nitrophenyl (2c),
N
N
4-chlorophenyl (2d),
3-chlorophenyl (2e),
3-methylphenyl (2f)
N
R
Cat.
THF
R
N
C O
R = phenyl (1a),
R = benzyl (3a),
R
O
4-isopropylphenyl (1b),
4-nitrophenyl (1c),
hexyl (3b),
O
N
cyclohexyl (3c),
-CO
4-chlorophenyl (1d),
3-chlorophenyl (1e),
3-methylphenyl (1f),
benzyl (1g), hexyl (1h),
cyclohexyl (1i),
allyl (3d),
N
R
N
H
N
H
R
phenylethyl (3e)
O
R
Cat. = [Pr(SPh) (THF) ]
3
3
allyl (1j), phenylethyl (1k)
Entrya
Isocyanate
Product
Yieldb (%)
O
N
N
To optimize the above reaction conditions, different solvents,
temperatures, and catalyst loading were explored. Table 1 lists the
results for the cyclotrimerization of phenyl isocyanate (1a) cata-
lyzed by [Pr(SPh)3(THF)3]. Four different solvents (toluene, THF, n-
hexane, and MeCN) were used to evaluate their influence on the
catalytic performance for the cyclotrimerization of phenyl iso-
cyanate. We observed a strong solvent dependence of the cyclo-
trimerization. In n-hexane or toluene, [Pr(SPh)3(THF)3] did not
catalyze phenyl isocyanate cyclodimerization, cyclotrimerization,
polymerization at 20 ꢁC. In MeCN, it could catalyze the cyclo-
trimerization of phenyl isocyanate in a low activity. Whereas the
same reaction in THF afforded the product 1,3,5-triphenyl-[1,3,5]
triazinane-2,4,6-trione (2a) in 54% yield within 12 h at 20 ꢁC. As
shown in Table 1, the temperature did exert a great impact on the
catalytic activity of [Pr(SPh)3(THF)3]. The catalytic activity in THF
increased as the temperature was raised. For example, when the
temperature was raised from 20 ꢁC to 40 ꢁC to 60 ꢁC, the cyclo-
trimerization reaction conducted in the presence of 1 mol % catalyst
in THF after 12 h, afforded the cyclotrimerized product in 54%, 87%,
and 99% yields, respectively. In the last example, the amount of
catalyst used to initiate the reaction efficiently was examined. As
shown in Table 1 (entries 4, 7, and 8), increasing the catalyst loading
resulted in an obvious increase of the product yield. For example,
the outputs of the reactions increased dramatically from 54% to 63%
to 98% when the catalyst loading was changed from 1 mol % to
2 mol % to 3 mol % in THF at 20 ꢁC. To this end, the optimal reaction
conditions for the cyclotrimerization of phenyl isocyanate were
achieved by using catalyst loading: 1 mol % of [Pr(SPh)3(THF)3];
solvent: THF; reaction time: 12 h; and reaction temperature: 60 ꢁC.
NCO
O
N
O
1
99
1a
2a
O
N
N
O
N
O
NCO
2
97
1b
2b
O
O2N
NO2
N
N
O
N
O
O2N
NCO
3
4
5
100
1c
NO2
2c
Cl
Cl
O
N
N
N
O
O
Cl
NCO
92
1d
Cl
2d
Cl
O
N
NCO
N
N
Cl
99
O
O
Table 1
Cl
Catalytic activity of [Pr(SPh)3(THF)3] on the cyclotrimerization of phenyl isocyanate
1e
(1a)
Cl
2e
Entrya
Cat./1a (%)
Temp (ꢁC)
Solvent
Yieldb (%)
1
2
3
4
5
6
7
8
1
1
1
1
1
1
2
3
20
20
20
20
40
60
20
20
n-Hexane
Toluene
MeCN
THF
THF
THF
0
0
O
18
54
87
99
63
98
N
N
NCO
6
91
O
N
O
1f
THF
THF
2f
a
Reaction time: 12 h.
Isolated yield.
b
O
97
NCO
The scope of substrates was then investigated by using this cat-
N
H
N
H
7
alytic system under the optimized reaction conditions. The results
are presented in Table 2. It can be seen that this catalyst exhibited
high catalytic activity for the cyclotrimerization of aryl isocyanates,
1g
3a
(continued on next page)

1532
H.-M. Wang et al. / Tetrahedron 67 (2011) 1530e1535
Table 2 (continued )
Table 3
Data for the Pr[(Me3Si)2N]3-catalyzed cyclodimerization or cyclotrimerization of
different isocyanates
Entrya
Isocyanate
Product
Yieldb (%)
R = phenyl (2a),
4-isopropylphenyl (2b),
4-nitrophenyl (2c),
4-chlorophenyl (2d),
3-chlorophenyl (2e),
3-methylphenyl (2f)
benzyl (2g),
O
O
R
O
R
O
NCO
N
N
8
9
94
99
N
H
N
H
1h
N
R
3b
O
allyl (2h),
Cat.
THF
phenylethyl (2i)
R
N
C O
NCO
R = phenyl (1a),
R
O
O
N
H
N
H
4-isopropylphenyl (1b),
4-nitrophenyl (1c),
N
-CO
R = hexyl (3b),
1i
3c
O
cyclohexyl (3c)
R
N
H
N
H
R
4-chlorophenyl (1d),
3-chlorophenyl (1e),
3-methylphenyl (1f),
benzyl (1g), hexyl (1h),
cyclohexyl (1i),
N
O
R
NCO
10
85
93
N
H
N
H
Cat. = Pr[(Me Si) N]
3
2
3
1j
allyl (1j), phenylethyl (1k)
3d
O
Entrya
Isocyanate
Product
Yieldb (%)
NCO
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
2a
2b
2c
2d
2e
2f
99
74
83
81
79
76
11
N
H
N
H
3e
1k
a
Catalyst: [Pr(SPh)3(THF)3], catalyst/isocyanate¼1/100.
b
Isolated yield.
O
such as phenyl isocyanate, 4-isopropylphenyl isocyanate, 4-nitro-
phenyl isocyanate, 4-chlorophenyl isocyanate, 3-chlorophenyl iso-
cyanate, 3-methylphenyl (Table 2, entries 1e6) in nearly quantitative
yields. However, when alkyl isocyanates, such as benzyl isocyanate,
hexyl isocyanate, cyclohexyl isocyanate, allyl isocyanate, and phe-
nylethyl isocyanate were employed under the same conditions, no
cyclotrimerized products were isolated from the HRMS and 1H NMR
results of the reaction products. Instead, the corresponding
substituted ureas, N,N0-dibenzylurea, N,N0-dihexylurea, N,N0-dicy-
clohexylurea, N,N0-diallylurea, and N,N0-diphenylethylurea, were
isolated from the corresponding reactions (Table 2, entries 7e11).
The formation of the substituted ureas is assumed to proceed
through the hydrolysis of the corresponding isocyanate cyclo-
dimerized products. These results are different from those of
(MeC5H4)2LnNiPr2(THF) (Ln¼Y, Er, Yb)17 and (MeC5H4)2LnCl/n-BuLi,18
suggesting that ancillary ligands on lanthanide centers greatly in-
fluence the selectivity of the catalysts. The structure of product 3a
(Fig.1) were determined for the clear identification of their identities.
N
N
O
N
O
7
1g
75
2g
8
9
1h
1i
3b
3c
74
72
O
N
N
10
1j
69
O
N
O
2h
O
N
N
O
N
O
11
1k
75
2i
a
Catalyst: Pr[(Me3Si)2N3], catalyst/isocyanate¼1/100.
b
Isolated yield.
(SPh)3(THF)3] exhibited a relatively higher catalytic activity on the
cyclotrimerization or cyclodimerization of the corresponding iso-
cyanates than Pr[(Me3Si)2N]3. For example, when cyclo-
trimerization of 4-isopropylphenyl isocyanate, a 74% yield of the
cyclotrimerization product catalyzed by Pr[(Me3Si)2N]3 can be
obtained, while the conversion of the 4-isopropylphenyl isocyanate
to cyclotrimer catalyzed by [Pr(SPh)3(THF)3] system can be raised to
97% under the same conditions. As discussed below, the mecha-
nism of [Pr(SPh)3(THF)3] on the cyclotrimerization or cyclo-
dimerization of isocyanate may be the similar to that of Pr
[(Me3Si)2N]3. But their corresponding intermediates are different,
which result in the different catalytic activity and selectivity of [Pr
(SPh)3(THF)3] and Pr[(Me3Si)2N]3 on the cyclotrimerization or
cyclodimerization of isocyanate.
For the above cyclodimerization and cyclotrimerization of iso-
cyanate initiated by [Pr(SPh)3(THF)3], we suggested the following
possible mechanism (Scheme 1). Coordination of the isocyanate to
the central metal atom of [Pr(SPh)3(THF)3] through replacement
of the coordinated THF molecules may form an isocyanate-co-
ordinated intermediate I ‘[Pr(SPh)3(RNCO)n]’, which may be the first
step of the catalytic cycle. Insertion of one isocyanate into the LneS
Fig. 1. View of the molecular structure of 3a.
For comparison, the catalytic activity of the precursor Pr
[(Me3Si)2N]3 on the cyclotrimerization or cyclodimerization of
isocyanate was also studied (Table 3). The results are listed in Table
3. This complex also exhibited a relatively high selectivity on
cyclotrimerization of aryl isocyanates. When it was used to initiate
the cyclotrimerization of alkyl isocyanates, only benzyl isocyanate,
allyl isocyanate, and phenylethyl isocyanate gave rise to the cor-
responding cyclotrimerized products. However, the hexyl iso-
cyanate, cyclohexyl isocyanate produced the substituted ureas,
which might be derived from the corresponding cyclodimerized
products. Comparative runs with Pr[(Me3Si)2N]3 showed that [Pr
(SPh)3(THF)3] initiated a higher selectivity. It is found that [Pr

H.-M. Wang et al. / Tetrahedron 67 (2011) 1530e1535
1533
bond may lead to the formation of the intermediate II, which reacts
with another isocyanate molecule to give the intermediate III. This
intermediate may proceed in two different ways. One is that it may
be converted into the cyclodimerized product, when the alkyl iso-
cyanate is present. The other is that the intermediate III may further
combine one isocyanate molecule, forming the intermediate IV,
when the aryl isocyanate is used. The intermediate IV then con-
verted into the cyclotrimerized product and the intermediate I. The
electronic properties of different isocyanates may lead to different
reactivity of the intermediate III, which may cause its different se-
lectivity. A series of experiments were conducted to understand the
insertion mechanism. Reaction of [Pr(SPh)3(THF)3] with 3 equiv of
PhNCO in THF did not produce the expected insertion product ‘[Pr
(OC(SPh)NPh)3]’ but the cyclotrimerized product 2a. When we di-
rectly added PhNCO to the mixture containing Pr[(Me3Si)2N]3 and
3 equiv of PhSH in THF, a standard workup produced colorless
crystals of phenyl-thiocarbamic acid S-phenyl ester (4) (Fig. 2), in
which the intermediate II should be formed but hydrolyzed by
(Me3Si)2NH released in the reaction system. Although we were
unable to isolate any intermediate complexes, the identification of 4
supported our initial assumption that [Pr(SPh)3(THF)3] was formed
and isocyanate was inserted into the PreS bond.
be prepared to catalyze the above reactions and other organic re-
actions with better catalytic activities. Studies on these respects are
underway in our laboratory.
4. Experimental
4.1. General
All manipulations were carried out under argon using standard
Schlenk-techniques. Solvents were dried by distillation from sodium/
benzophenone (THF, toluene, hexane) or P2O5 (MeCN) under argon
22
prior to use. Pr[(Me3Si)2N]3 was prepared according to the litera-
ture methods. The PhSH ligand and phenyl isocyanate, 4-iso-
propylphenyl isocyanate, 4-nitrophenyl isocyanate, 4-chlorophenyl
isocyanate, 3-chlorophenyl isocyanate, 3-methylphenyl benzyl iso-
cyanate, hexyl isocyanate, cyclohexyl isocyanate, allyl isocyanate,
phenylethyl isocyanate were purchased from Aldrich. 1H NMR and
13C NMR spectra were recorded at ambient temperature on a Varian
UNITYplus-400 spectrometer. 1H NMR and 13C NMR chemical shifts
were referenced to the solvent signal in CDCl3 or DMSO-d6. Elemental
analyses were performed on a Carlo-Erbo CHNOeS microanalyzer.
The IR spectra (KBrdisc) were recorded on a Nicolet MagNa-IR550 FT-
IR spectrometer (4000e400 cmꢀ1). The uncorrected melting points
were measured on a Mel-Temo II apparatus.
S
S
Ph
Ph
R
R
C
C
N
Ph
N
C
O
O
Ph
O
C
RNCO
S
4.2. Preparation of [Pr(SPh)3(THF)3]
Pr
S
Pr
O
N
N
S
S
N
R
Ph
R
To a solution of Pr[(Me3Si)2N]3 (0.728 g, 1.172 mmol) in toluene
(30 mL) was slowly added a solution of PhSH (0.387 g, 3.520 mmol)
in THF (10 mL). A large amount of yellow precipitate was observed
to form within minutes. After the mixture was stirred at room
temperature for 12 h, it was evaporated to remove all the volatile
species under vacuum. The resulting yellow solid was washed with
toluene (2ꢂ10 mL) and dried in vacuum. Yield 0.736 g (92%, based
on Pr). Anal. Calcd for C30H39O3S3Pr: C 52.62, H 5.74, S 14.05; found:
C 52.21, H 6.18, S 14.49. Mp: 59.0e61.0 ꢁC. IR (KBr disk): 3056(w),
2982(s), 2870(m), 1629(m), 1473(w), 1400(m), 1260(m), 1192(w),
Ph
O
R
(III)
(IV)
O
R
O
R
O
N
N
O
R
O
O
C
N
R
O
N
-CO
N
R
R
N
H
N R
H
N
R
R
N
C
O
O
S
S
C
Ph
Ph
[Pr(SPh)3(THF)3]
S
Pr
+
Pr
Ph
N
S
R
N=C=O
Ph
S
S
R
Ph
1082(s), 920(w), 767(m), 689(m), 601(m) cmꢀ1
.
Ph
(I)
(II)
4.3. General procedure for the cyclotrimerization or
cyclodimerization of isocyanates catalyzed by [Pr
(SPh)3(THF)3] (2a as an example)
Scheme 1. Proposed catalytic mechanism.
To a 30 mL Schlenk tube under dried argon were added [Pr
(SPh)3(THF)3] (0.0137 g, 0.02 mmol), THF (10 mL), and phenyl iso-
cyanate (0.216 mL, 2.00 mmol). When the resulting mixture was
stirred at 60 ꢁC for 12 h, it was hydrolyzed by water (1 mL),
extracted with diethyl ether (3ꢂ10 mL), dried over anhydrous
MgSO4, and filtered. After removal of the solvent from the extract
under the reduced pressure, the solid was re-crystallized in THF and
toluene and filtered off. The filtrate was allowed to stand at ꢀ18 ꢁC
for several days, forming colorless crystals of 1,3,5-trisphenyl-1,3,5-
triazinane-2,4,6-trione (2a) in 97% yield.
Fig. 2. View of the molecular structure of 4.
3. Conclutions
In summary, we have demonstrated the preparation of one
praseodymium benzenethiolate complex [Pr(SPh)3(THF)3] from
protonolysis reactions of Pr[(Me3Si)2N]3 with benzenthiol. Com-
parative runs with Pr[(Me3Si)2N]3 showed that [Pr(SPh)3(THF)3]
exhibited a higher catalytic activity and selectivity on cyclo-
trimerization of aryl isocyanates and cyclodimerization of alkyl
isocyanates. In addition, this catalyst has the advantages of easy
preparation, low catalyst loading, high conversion, mild reaction
conditions, and compatibility with different substrates. To our
knowledge, it represents the first example to employ lanthanide
thiolate complexes to catalyze the cyclodimerization of isocyanates.
It is anticipated that other lanthanide thiolate complexes may also
4.3.1. 1,3,5-Trisphenyl-1,3,5-triazinane-2,4,6-trione
(2a). Mp:
280.5e281.6 ꢁC. IR (KBr disk): 3067, 1709, 1593, 1490, 1414, 1219,
1072, 1028, 918, 753, 689, 590, 506 cmꢀ1. 1H NMR (CDCl3, ppm):
d
7.529e7.159 (15H, m, aromatic CH). 13C NMR (CDCl3, ppm)
d 148.9,
133.9, 129.6, 128.7. HRMS (EI) m/z: calcd for C21H15N3O3 357.11;
found: 357.11.
4.3.2. 1,3,5-Tris(4-isopropylphenyl)-1,3,5-triazinane-2,4,6-trione
(2b). White solid. Mp: 287.8e288.3 ꢁC. IR (KBr disk): 3046, 2961,
2929, 2869, 1707, 1605, 1551, 1511, 1409, 1308, 1222, 1183, 1056,
1019, 830, 756, 706, 568, 446 cmꢀ1 1H NMR (CDCl3, ppm):
.
d
7.477e7.254 (12H, m, aromatic CH), 3.132e3.026 (3H, m, CH),

1534
H.-M. Wang et al. / Tetrahedron 67 (2011) 1530e1535
1.397e1.380 (18H, d, CH3). 13C NMR (CDCl3, ppm):
d
150.1, 149.1,
1221, 728, 629, 441 cmꢀ1. 1H NMR (CDCl3, ppm): 5.158 (2H, s, NH),
131.3, 128.3, 127.5, 34.0, 24.0. HRMS (EI) m/z: calcd for C30H33N3O3
483.25; found: 483.25.
2.911e2.867 (4H, t, CH2), 1.294e1.156 (4H, m, CH2), 1.062 (12H, s,
CH2), 0.673e0.636 (6H, t, CH3). 13C NMR (CDCl3, ppm):
d 158.8, 39.8,
31.3, 30.1, 26.4, 22.3, 13.8. HRMS (EI) m/z: calcd for C13H28N2O
4.3.3. 1,3,5-Tris(4-nitrophenyl)-1,3,5-triazinane-2,4,6-trione
(2c). Yellow solid. Mp: 410.5e411.0 ꢁC. IR (KBr disk): 3080, 1728,
1688,1617,1552,1527,1493,1432,1407,1351,1016, 865, 806, 757, 691,
228.22; found:228.22.
4.3.12. 1,3-Dicyclohexylurea (3c). White solid. Mp: 231.8e232.3 ꢁC.
IR (KBr disk): 3326, 2928, 2850, 1629, 1580, 1535, 1436, 1311, 1271,
1244, 1186, 1088, 1045, 892, 641, 454 cmꢀ1. 1H NMR (CDCl3, ppm):
756, 494 cmꢀ1. 1H NMR (DMSO-d6, ppm):
d
8.436e7.766 (12H, m,
aromatic CH). 13C NMR (DMSO-d6, ppm):
d 148.0, 147.6, 139.6, 130.4,
124.6. HRMS (EI) m/z: calcd for C21H12N6O9 492.07; found: 492.07.
d
4.058 (2H, s, NH), 3.496e3.463 (2H, m, CH), 2.007e1.917 (4H, m,
CH2), 1.707e1.613 (8H, m, CH2), 1.403e1.293 (4H, m, CH2),
1.155e1.041 (4H, m, CH2). 13C NMR (CDCl3, ppm):
156.9, 49.5, 34.3,
4.3.4. 1,3,5-Tris(4-chlorophenyl)-1,3,5-triazinane-2,4,6-trione
(2d). White solid. Mp: 342.0e342.5 ꢁC. IR (KBr disk): 3050, 1706,
1605, 1491, 1426, 1234, 1169, 1087, 1014, 812, 758, 519, 426 cmꢀ1. 1H
d
25.9, 25.2. HRMS (EI) m/z: calcd for C13H24N2O 224.19; found:
224.19.
NMR (CDCl3, ppm):
(CDCl3, ppm): 148.3, 135.7, 131.9, 129.9. HRMS (EI) m/z: calcd for
d
7.490e7.314 (12H, m, aromatic CH). 13C NMR
d
4.3.13. 1,3-Diallylurea (3d). White solid. Mp: 91.7e92.2 ꢁC. IR (KBr
C21H12N3O3Cl3 458.9944; found: 458.9944.
disk): 3331, 3082, 2913, 2864, 1627, 1586, 1460, 1419, 1384, 1252,
1060, 991, 917, 672, 435 cmꢀ1. 1H NMR (CDCl3, ppm):
d 5.871e5.779
4.3.5. 1,3,5-Tris(3-chlorophenyl)-1,3,5-triazinane-2,4,6-trione
(2e). White solid. Mp: 229.8e230.3 ꢁC. IR (KBr disk): 3087, 1721,
1694,1591,1476,1409,1224,1075,1034,1003, 880, 782, 760, 694, 595,
(2H, m, C]CeH), 5.582 (2H, s, NH), 5.186e5.143 (2H, d, C]CeH),
5.079e5.054 (2H, d, C]CeH), 3.756 (4H, s, CH2). 13C NMR (CDCl3,
ppm): d 159.1, 135.8, 115.5, 43.0. HRMS (EI) m/z: calcd for C7H12N2O
140.10; found: 140.10.
557 cmꢀ1
CH). 13C NMR (CDCl3, ppm):
126.9. HRMS (EI) m/z: calcd for C21H12N3O3Cl3 458.99; found: 459.00.
.
1H NMR (CDCl3, ppm):
d
7.481e7.296 (12H, m, aromatic
d
148.1, 135.1, 134.3, 130.6, 130.1, 129.0,
4.3.14. 1,3-Diphenethylurea (3e). White solid. Mp: 140.0e140.5 ꢁC.
IR (KBr disk): 3337, 3061, 3026, 2933, 2879, 1616, 1575, 1503, 1475,
1449, 1384, 1305, 1237, 1081, 1034, 911, 746, 700, 486 cmꢀ1. 1H NMR
4.3.6. 1,3,5-Trim-tolyl-1,3,5-triazinane-2,4,6-trione
(2f). White
solid. Mp: 280.8e281.3 ꢁC. IR (KBr disk): 3033, 2956, 2921, 2867,
(CDCl3, ppm):
NH), 3.406e3.360 (4H, t, CH2), 2.791e2.745 (4H, t, CH2). 13C NMR
(CDCl3, ppm): 158.3, 139.4, 129.1, 128.8, 126.7, 41.9, 36.7. HRMS (EI)
d 7.3 16e7.154 (10H, m, aromatic CH), 4.484 (2H, s,
1708, 1609, 1490, 1409, 1409, 1251, 1188, 1089, 1054, 1003, 876, 785,
738, 692, 602, 553 cmꢀ1. 1H NMR (DMSO-d6, ppm):
d
7.411e7.252
(12H, m, aromatic CH), 2.367 (9H, s, CH3). 13C NMR (DMSO-d6,
ppm): 148.9, 138.4, 134.7, 129.4, 129.2, 128.7, 125.9. HRMS (EI) m/z:
d
m/z: calcd for C17H20N2O 268.16; found: 268.16.
d
calcd for C24H21N3O3 399.16; found: 399.16.
4.4. Synthesisof phenyl-thiocarbamic acid S-phenyl ester (4)
4.3.7. 1,3,5-Tribenzyl-1,3,5-triazinane-2,4,6-trione (2g). White solid.
Mp: 160.3e160.8 ꢁC. IR (KBr disk): 3036, 2980, 2969, 1686, 1586,
1495, 1452, 1364, 1325, 1205, 1075, 1030, 885, 822, 748, 697, 599,
ToasolutionofHSPh(0.3104 mL, 2.82 mmol)wasaddedasolution
of Pr[(Me3Si)2N]3 (0.5732 g, 0.924 mmol) inTHF (15 mL). The reaction
mixture was stirred overnight. At ambient temperature, PhNCO
(0.345 g, 2.901 mmol) in THF (10 mL) solution was added into the
mixture. The resulting mixture was stirred for 12 h and then was
concentrated to dryness in vacuo. The resulting solid was extracted
with toluene (20 mL) and then filtered. The filtrate was kept at ꢀ18 ꢁC
for several days and colorless crystals of 4 were formed. Yield: 0.477 g
(74%). Mp:125.0e125.5 ꢁC. IR(KBrdisk):3253, 3052,1661,1596,1536,
1499, 1441, 1306, 1240, 1164, 1088,1024, 918, 880, 756, 689, 642, 575,
516 cmꢀ1. 1H NMR (CDCl3, ppm):
d
7.454e7.225 (15H, m, aromatic
CH), 5.018 (6H, s, CH2). 13C NMR (CDCl3, ppm):
d
149.3, 136.0, 129.3,
128.9, 128.4, 46.5. HRMS (EI) m/z: calcd for C24H21N3O3 399.16;
found: 399.16.
4.3.8. 1,3,5-Triallyl-1,3,5-triazinane-2,4,6-trione (2h). White solid.
Mp: 24.5e25.0 ꢁC. IR (KBr disk): 3070, 2932, 2856, 1710, 1645, 1462,
1392, 1346, 1318, 1090, 993, 918, 669, 582 cmꢀ1
.
1H NMR (CDCl3,
580, 506, 452 cmꢀ1. 1H NMR (CDCl3, ppm):
d 7.635e7.616 (2H, m, ar-
ppm):
CeH), 5.080e5.055 (3H, d, C]CeH), 4.411 (6H, s, CH2). 13C NMR
(CDCl3, ppm): 149.8, 132.6, 117.7, 45.5. HRMS (EI) m/z: calcd for
d
5.872e5.778 (3H, m, C]CeH), 5.187e5.144 (3H, d, C]
omatic CH), 7.484e7.471 (3H, m, aromatic CH), 7.387e7.376 (2H, d,
aromatic CH), 7.327e7.288 (2H, t, aromatic CH), 7.135e7.098 (1H, t,
d
aromatic CH), 7.056(1H, s, NH). 13C NMR (CDCl3, ppm):
d 164.8, 137.7,
C12H15N3O3 249.11; found: 249.11.
135.8, 130.1, 129.7, 129.3, 128.2, 124.8, 119.8. HRMS (EI) m/z: calcd for
C13H11NOS 229.06; found: 229.06.
4.3.9. 1,3,5-Triphenethyl-1,3,5-triazinane-2,4,6-trione
(2i). White
solid. Mp: 133.0e133.5 ꢁC. IR (KBr disk): 3061, 3026, 2968, 2933,
Acknowledgements
2878, 1689, 1615, 1576, 1461, 1371, 1337, 1236, 1133, 1078, 1029, 952,
825, 748, 700, 608, 488 cmꢀ1. 1H NMR (CDCl3, ppm):
d
7.308e7.155
(15H, m, aromatic CH), 3.406e3.372 (6H, t, CH2), 2.786e2.751(6H, t,
CH2). 13C NMR (CDCl3, ppm):
158.3, 139.4, 129.1, 128.9, 126.7, 41.9,
This work was supported by the National Nature Science
Foundation of China (Nos. 20871088, 20871038, and 90922018), the
Nature Science Key Basic Research of Jiangsu Province for Higher
Education (09KJA150002), the NSF of the Education Committee of
Jiangsu Province (No. 07KJD150182), the State Key Laboratory of
Organometallic Chemistry of Shanghai Institute of Organic Chem-
istry (08-25), the Qin-Lan Project of Jiangsu Province, and the
SooChow Scholar Program and Program for Innovative Research
Team of Suzhou University.
d
36.6. HRMS (EI) m/z: calcd for C27H27N3O3 441.21; found: 441.21.
4.3.10. 1,3-Dibenzylurea (3a). White solid. Mp: 167.8e168.3 ꢁC. IR
(KBr disk): 3321, 3030, 2919, 2873, 1627, 1572, 1492, 1453, 1246,
1062, 1026, 909, 751, 696, 591, 490 cmꢀ1 1H NMR (CDCl3, ppm)
.
d
7.319e7.227 (10H, m, aromatic CH); 4.873 (2H, s, NH); 4.338 (4H, s,
CH2). 13C NMR (CDCl3, ppm)
d 158.7, 139.3, 128.9, 127.7, 127.6, 44.8.
HRMS (EI) m/z: calcd for C15H16N2O 240.13; found: 240.13.
Supplementary data
4.3.11. 1,3-Dihexylurea (3b). White solid. Mp: 74.5e75.2 ꢁC. IR (KBr
disk): 3334, 2956, 2931, 2856, 1616, 1578, 1468, 1384, 1299, 1251,
Crystal data and refinement parameters for 3a (CCDC No.
789447) and 4 (CCDC No. 789448). The 1H and 13C NMR spectra for

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