Heterobimetallic dianionic guanidinate complexes of lanthanide and lithium: Highly efficient precatalysts for catalytic addition of amines to carbodiimides to synthesize guanidines

Article abstract of DOI:10.1016/j.tet.2011.08.072

A series of heterobimetallic dianionic guanidinate complexes of lanthanide and lithium, [Li(THF)(DME)]₃Ln[μ- η²η¹(ⁱPrN)₂C(NC ₆H₄p-R)]₃ [R=Cl, Ln=Nd (I), Y (II), La (III); R=H, Ln=Nd (IV)] were synthesized and fully characterized. These complexes were found to be highly efficient precatalysts for the addition of various primary and secondary amines, and aromatic and aliphatic diamines to carbodiimides to give the corresponding monoguanidine and biguanidine derivatives under mild condition (at 25-60 °C), which provides an efficient way for the synthesis of biguanidines compounds. The activity depends on the central metals and ligands: La>Nd>Y for the metals and [(ⁱPrN) ₂C(NC₆H₄p-Cl)]^2->[( ⁱPrN)₂C(NC₆H₅)]^2- for the ligands were observed.

Full text of DOI:10.1016/j.tet.2011.08.072

Tetrahedron 67 (2011) 8790e8799
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Heterobimetallic dianionic guanidinate complexes of lanthanide and lithium:
highly efficient precatalysts for catalytic addition of amines to carbodiimides to
synthesize guanidines
,b,
Xingmin Zhang a, Chuanyong Wang a, Cunwei Qian a, Fubin Han a, Fan Xu a, Qi Shen a
*
a College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s Republic of China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 24 June 2011
Received in revised form 19 August 2011
Accepted 26 August 2011
Available online 30 August 2011
A
series of heterobimetallic dianionic guanidinate complexes of lanthanide and lithium, [Li(TH-
F)(DME)]3Ln[
m
-
h2h1(iPrN)2C(NC6H4p-R)]3 [R¼Cl, Ln¼Nd (I), Y (II), La (III); R¼H, Ln¼Nd (IV)] were syn-
thesized and fully characterized. These complexes were found to be highly efficient precatalysts for the
addition of various primary and secondary amines, and aromatic and aliphatic diamines to carbodiimides
to give the corresponding monoguanidine and biguanidine derivatives under mild condition (at
25e60 ꢀC), which provides an efficient way for the synthesis of biguanidines compounds. The activity
Keywords:
Heterobimetallic complexes
Catalysis
depends on the central metals and ligands: La>Nd>Y for the metals and [(iPrN)2C(NC6H4p-Cl)]2ꢁ
>
[(iPrN)2C(NC6H5)]2ꢁ for the ligands were observed.
Ó 2011 Elsevier Ltd. All rights reserved.
Addition
Guanidines
1. Introduction
addition of primary and secondary amines to carbodiimides. Nev-
ertheless, the guanylation reactions with secondary aliphatic
amines catalyzed by all these catalysts reported still need to elevate
reaction temperature and/or prolong reaction time.7e12 Because
secondary amines are generally less active than primary amines
toward carbodiimides.
The synthesis of guanidines is of significant importance in or-
ganic synthesis because guanidines are important structural motifs
found in many biologically and pharmaceutically active com-
pounds1 and can serve as base catalysts in organic synthesis.2 Be-
sides, guanidines can also be used as ancillary ligands in the
preparation of a variety of metal complexes, including those of the
main, transition and lanthanides metals.3 An addition of amine to
carbodiimide provides a convenient and atom-economical ap-
proach to multisubstituted guanidines. However, the addition re-
action without a catalyst requires harsh condition.4 Recently, imido
complexes of titanium and vanadium,3k,5 were reported to be
highly active catalysts for the addition of primary aromatic amines
to carbodiimides, but not for that with secondary amines, as the
active species in that process is an imido intermediate. Amide
complexes of metals including LiN(SiMe3)2,6 lanthanide amides7
and titanacarborane amide,8 and alkyl complexes of metals, such
as half-sandwich lanthanide alkyl complexes,9 and commercial
Biguanidines could serve as useful templates for the construc-
tion of further larger molecules, or as ligands for the synthesis of
metal complexes with constrained geometry.13 However, the cat-
alytic reaction of diamines with carbodiimides to multisubstituted
biguanidines has been limited. Only a few examples were found in
the literatures till now.7b,8,9,13 The reaction of 1,3-diaminobenzene
i
with 2 equiv of PrN]C]NiPr was reported to give quantitatively
the corresponding biguanidine compound with 1 mol % of a half-
sandwich yttrium alkyl complex at 80 ꢀC for 1 h.9 The catalytic
addition of 1,4-diaminobenzene to iPrN]C]NiPr catalyzed by
3e5 mol % of half-sandwich titanacarborane amide complex at
110 ꢀC for 6 h8 and by 1 mol % of lanthanide amide complex at 60 ꢀC
for 4 h,7b respectively, afforded the 1,4-diguanidinobenzene in ex-
available alkyl metal complexes ZnEt2, MgBu2, n-BuLi,10a AlR3,10b
cellent yield. Ethylenediamine could react with PrN]C]NiPr at
i
10c
and Zn(OTf)2
were explored to be the efficient catalysts with
100 ꢀC in the absence of a catalyst, however, only 60% of the
biguanidine was obtained after 18 h.13 Thus, the design of efficient
catalysts capable of promoting addition of secondary aliphatic
amines and diamines including aromatic and aliphatic diamines to
carbodiimides under mild conditions is still required. Recently, we
have reported that the heterobimetallic lanthanide and lithium
a wide scope of amines including primary aromatic amines and
aliphatic secondary amines. Divalent lanthanide complexes11 and
ytterbium triflate12 are also found to be the efficient catalysts for
* Corresponding author. E-mail address: qshen@suda.edu.cn (Q. Shen).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.08.072

X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
8791
(Table 1, entries 4e6). The reaction with these precatalysts could
still proceed smoothly even when the catalyst loading decreased to
0.1 mol % (Table 1, entries 7e10). However, the differences in ac-
tivity among them were observed. The active sequence is Y<Nd<La
for the center metals (Table 1, entries 7e9), which is consistent with
the order of the ionic radius, and [(iPrN)2C(NC6H5)]2ꢁ
<[(iPrN)2C(NC6H4p-Cl)]2ꢁ for the ligands (Table 1, entries 7 and 10).
In comparison, the same reaction with monometallic trisguanidi-
nate lanthanum complex was tested. As shown in Table 1 (entry 11),
V could serve as a precatalyst to afford 1 in 75% yield after 30 min,
when the catalyst loading increased to 2 mol %. Obviously, the ac-
tivity of monometallic guanidinate complex is much lower than
those of heterobimetallic complexes.
Fig. 1. Lanthanide complexes IeVI.
Complex III was then chosen as a precatalyst for the addition
reaction of various aromatic primary amines to carbodiimides.
Representative results are summarized in Table 2. As shown in
Table 2, III is a very robust and efficient precatalyst, which showed
good functional group tolerance. The reaction was not influenced
by either electron-withdrawing or electron-donating substituents
or the position of the substituents at the phenyl ring (Table 2, en-
tries 1e14). Aromatic CeF and CeCl bond at the phenyl ring
remained unchanged in the present reactions (Table 2, entries 3e6
and 12). The reaction with a steric bulky amine also went smoothly
at 25 ꢀC. For example, in the presence of 0.5 mol % of III, the ad-
dition reaction of 2,6-diisopropylaniline to iPrN]C]NiPr gave the
guanidine compound 14 in 85% yield at 25 ꢀC and in 97% yield at
50 ꢀC for 5 h (Table 2, entry 14). Even the less reactive n-BuNH2
complexes supported by dianionic guanidinate ligands are highly
efficient catalysts for addition of amines to aldehydes under mild
conditions,14 and the activity is much higher than that of the cor-
responding monometallic triguanidinate lanthanide complexes.15
In continuation of our study on the reactivity of these hetero-
bimetallic complexes, we have found that the complexes are ex-
tremely high active precatalysts for addition of amines to
carbodiimides. The reactions with secondary amines can be carried
out at 25 ꢀC even with 0.5% catalyst loading. The catalytic double
addition of aromatic diamines to carbodiimides afforded the cor-
responding biguanidines in almost quantitative yield at 25 ꢀC, and
the reactions with aliphatic diamines can proceed at 40e60 ꢀC to
give the corresponding biguanidines in excellent yield. Here we
report the results.
i
could also add to PrN]C]NiPr using 0.5 mol % of III to yield the
desired product 15 in good yield at 25 ꢀC for 5 h and in excellent
yield at 50 ꢀC for 5 h (Table 2, entry 15).
2. Results and discussion
Secondary amines are well-known to be less reactive than pri-
mary amines toward carbodiimides. However, in the presence of
0.5 mol % of III, various cyclic secondary amines could react with
iPrN]C]NiPr and CyN]C]NCy at 25 ꢀC affording the corre-
sponding tetrasubstituted guanidines in good to excellent yields
after 2 h, depending on the amines (Table 2, entries 16e18 and
20e22). The yields can be improved when the same addition re-
actions were carried out at 50 ꢀC (Table 2, entries 16, 17, 20, and 22).
The addition reaction of methylbenzylamine to iPrN]C]NiPr
could also give the guanidine compound 22 in 89% yield at 25 ꢀC
and in 97% yield at 50 ꢀC for 2 h (Table 2, entry 23). In comparison,
the addition reaction of piperidine to iPrN]C]NiPr with ytterbium
amide complex VI was conducted and the reaction went sluggishly
under the same conditions (Table 2, entry 19) indicating the activity
of bimetallic complex III is much higher than that of the mono-
metallic lanthanide amide complex VI.
Complexes IeVI (Fig. 1) were synthesized by the reported pro-
cedure.14,15 New complexes III and IV were fully characterized in-
cluding single-crystal structure analysis. Their molecular structures
were quite similar to that of the analogous I reported previously.14
With these complexes in hand the reaction of PhNH2 with
iPr2N]C]NiPr2 was examined as model reaction at 25 ꢀC under
solvent-free condition. We were pleased to see that an addition of
i
0.5 mol % of I led to rapid addition of aniline to PrN]C]NiPr to
give 1 quantitatively after 30 min (Table 1, entry 3). In contrast, the
same addition reaction did not occur without the presence of
a catalyst (Table 1, entry 12). The other heterobimetallic complexes
IIeIV were also effective in this reaction to give 1 quantitatively
Table 1
Catalytic addition of aniline to N,N0-diisopropylcarbodiimide by complexes IeVa
A double catalytic addition reaction of diamines to 2 equiv of
carbodiimides is a direct method to biguanidines. To explore the
application of the present complexes in the synthesis of biguani-
dines compounds, the addition of 1,4-diaminobenzene with 2 equiv
of iPrN]C]NiPr was then tried using 0.5 mol % of III at 25 ꢀC, as the
same reaction was reported to proceed under heating condition (at
0.5 mol% cat.
HN
N
C N
+
C N
NH2
solvent free, 25 o
C
HN
Yieldb (%)
60 ꢀC using 1 mol % of lanthanide amide [(Me3Si)2N]3Yb(
m-Cl)
Entry
Cat.
Catalyst loading (mol %)
Time (min)
7b
Li(THF)3 and at 110 ꢀC with 3e5 mol % of half-sandwich titana-
carborane amide complex).8 The reaction went smoothly and was
completed for 2 h to afford quantitatively the corresponding
biguanidine compound 23 (Table 3, entry 1). The result promoted us
to examine the scope of diamines. As shown in Table 3 various ar-
omatic diamines can be applied in the double addition reaction. The
activity is not influenced by the position of the two amino groups on
the phenyl ring. For example, all the addition reactions of dia-
minobenzene to iPrN]C]NiPr, including 1,4-diaminobenzene, 1,3-
diaminobenzene, and 1,2-diaminobenzene, could be carried out at
25 ꢀC and was completed within 2 h to afford the corresponding
biguanidines compounds 23, 25, and 27 in almost quantitativeyields
with a catalyst loading of 0.5 mol % (Table 3, entries 1, 3, and 5).
1
2
3
4
5
6
7
8
I
I
I
2
1
30
30
30
30
30
30
10
10
10
10
30
30
>99
>99
>99
>99
>99
98
0.5
0.5
0.5
0.5
0.1
0.1
0.1
0.1
2
II
III
IV
I
II
III
IV
V
d
90
85
93
70
9
10
11
12
75
d
d
a
The reaction was performed by treating 1 equiv of amine with 1 equiv of
carbodiimide.
b
Isolated yields.

8792
X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
Table 2
Catalytic addition of amines to carbodiimides by IIIa
R
NH
R
R
NH
NH
R1
R2
1,3-H shift
R2 = H
0.5 mol % III
R
25 oC
N
R1
+
C N
R1R2NH
R
N
C
N
R
N
Entry
1
R
R1R2NH
Time (h)
0.5
Product
Yieldb (%)
iPr
Cy
iPr
Cy
iPr
Cy
iPr
Cy
1
>99
NH2
2
3
4
5
6
7
8
0.5
0.5
0.5
0.5
0.5
0.5
0.5
2
3
4
5
6
7
8
99
>99
99
95
94
90
91
F
NH2
Cl
NH2
NH2
iPr
Cy
0.5
0.5
9
98
92
OMe
NH2
9
10
10
11
12
iPr
iPr
2
11
12
90
95
O2N
H2N
NH2
0.5
Cl
NH2
13
iPr
0.5
13
95
NH2
14
15
16
iPr
iPr
iPr
5
5
2
14
15
16
85 (97d)
80 (96d)
91 (98d)
n-BuNH2
NH
17
18
19
20
21
Cy
iPr
iPr
Cy
iPr
2
2
2
2
2
17
18
18
19
20
88 (96d)
93
25c
NH
NH
84 (96d)
95
O
22
Cy
iPr
2
2
21
22
90 (98d)
N
H
23
89 (97d)
a
The reaction was performed by treating 1 equiv of amine with 1 equiv of carbodiimide at 25 ꢀC.
Isolated yields.
b
c
Catalyzed by [(Me3Si)2N]3Yb(
m-Cl)Li(THF)3.
d
At 50 ꢀC.

X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
8793
Table 3
Catalytic addition of diamines to carbodiimidesa
R
NH
NH
HN
HN
R
R
0.5 mol % III
N
R3 N
H2N R3 NH2
+
R
N
C
N
R
2
R
Entry
Diamines
R
T (ꢀC)
Time (h)
Product
Yieldb (%)
i
i
Pr
Pr
Pr NH
HN
NH
i
Pr
N
N
1
iPr
25
2
98
H2N
NH2
HN
i
23
(
)
Cy
Cy NH
N
HN
HN
NH
Cy
N
2
3
Cy
50
25
5
2
95
99
H2N
NH2
Cy
(24)
i
i
Pr
Pr
NH2
HN
N
N
NH
iPr
HN
NH
i
i
Pr
(
Pr
NH2
25
)
Cy
HN
Cy
NH2
N
N
NH
4
Cy
50
5
97
HN
NH
Cy
Pr
Cy
NH2
(26)
i
i
Pr
HN
HN
NH
NH
NH2
NH2
N
N
5
6
7
iPr
iPr
Cy
25
25
50
2
2
5
98
98
97
i
i
Pr
Pr
(27)
H
H
N
NH2
NH2
N
N
N
i
i
Pr
Pr
NH
HN
i
i
Pr
Pr
NH2
NH2
(28)
H
N
H
N
N
N
Cy
Cy
NH
HN
Cy
Cy
(29)
H
N
H
N
N
N
N
i
i
Pr
Pr
8
iPr
25
2
96
NH
HN
i
i
Pr
Pr
H2N
N
NH2
(30)
i
Pr
HN
NH2
NH
Pr
95
i
N
9
iPr
25
2
i
Pr
HN
N
NH
NH2
(continued on next page)
i
(31)
Pr

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X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
Table 3 (continued )
Entry
Diamines
R
T (ꢀC)
Time (h)
Product
Yieldb (%)
Cy
HN
N
NH2
NH
Cy
10
Cy
50
5
98
Cy
HN
N
NH2
NH
(32)
Cy
H
H
N
N
i
i
Pr
Pr
NH2
N
N
i
i
Pr
Pr
11
iPr
60
3
98
N
HN
NH
N
H2N
N
NH2
HN
N
N
NH
(33)
i
i
Pr
Pr
i
Pr
NH
i
Pr
N
N
H
NH2
NH2
12
iPr
40
12
90
N
i
Pr
HN
N
H
i
Pr
(34)
i
Pr
i
Pr NH
NH
H2N
N
N
N
N
13
iPr
40
6
96 (85c91d)
NH2
i
HN
HN Pr
i
Pr
35
(
)
Cy
Cy NH
HN
NH
H2N
14
15
Cy
50
40
6
6
98
96
NH2
HN Cy
Cy
(36)
i
Pr
i
Pr
NH
NH
HN
iPr
H2N
NH2
i
N
N
Pr
i
Pr
HN
(37)
i
Pr
NH
i
Pr
H
N
NH
i
Pr
i
NH2
iPr
40
6
98
Pr
16
N
H
H2N
N
N
38
)
(
i
Pr
NH
H
i
N
Pr
i
Pr
NH
i
N
Pr
95
N
N
H
17
iPr
40
6
NH2
H2N
(39)

X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
8795
Table 3 (continued )
Entry
Diamines
R
T (ꢀC)
Time (h)
Product
Yieldb (%)
i
i
Pr
Pr
Pr
HN
HN
NH
NH
N
N
iPr
25
2
(Tracee)
H2N
18
NH2
i
i
Pr
(27)
i
Pr
i
Pr NH
NH
25e (70f)
19
iPr
25
6
H2N
N
N
NH2
i
HN
HN Pr
i
Pr
35
(
)
a
The reaction was performed by treating 1 equiv of amine with 2 equiv of carbodiimides.
b
c
d
e
f
Isolated yields.
At 25 ꢀC.
For 24 h at 25 ꢀC.
Catalyzed by [(Me3Si)2N]3Yb(m-Cl)Li(THF)3.
2% [(Me3Si)2N]3Yb( -Cl)Li(THF)3 (2%) loading.
m
The reaction was also not influenced by the presence of a sub-
imino-nitrogen atom (C]N) (Fig. 2 and Table 3, entry 15). This is in
agreement with its 1H and 13C NMR spectrum in a solution.
It is worth noting that the reaction of 1,2-diaminoethane with
iPrN]C]NiPr was carried out even at 25 ꢀC, compound 35 could
still be obtained in 85% yield after 6 h and in 91% yield after 24 h
(Table 3, entry 13). For comparison, the addition reactions of 1,2-
diaminoethane and 1,2-diaminobenzene to iPrN]C]NiPr were
also conducted by use of lanthanide amide VI as a precatalyst under
the same conditions. As shown in Table 3, only 25% of 35 and trace
of 27, respectively, were isolated (Table 3, entries 18 and 19). Even
the catalyst loading of VI was increased to 2 mol %, the yield of 35
was still much lower than that obtained with III (Table 3, entry 19)
indicating that the activity of III is much higher than that of VI in
the catalytic double addition reaction. It was noticed that in the
case of 2-aminobenzylamine, the reaction with iPrN]C]NiPr
proceeded also fluently at 40 ꢀC yielding the corresponding
biguanidine 34 in 90% yield for 12 h and no selective monoguani-
dine compound 1-guanidinobenzylamine could be isolated (Table
3, entry 12).
stituent at the phenyl ring or by the presence of heteroatom at the
ring skeleton. For example, the reactions of 2,4-diaminotoluene
i
with PrN]C]NiPr and CyN]C]NCy went smoothly to give the
corresponding biguanidines compounds 28 and 29 in excellent
yields (Table 3, entries 6 and 7). Both 2,6-diaminopyridine and
1,3,5-triaminopyrimidine could add to iPrN]C]NiPr affording the
corresponding biguanidine compound 30 and triguanidine com-
pound 33 both in excellent yields (Table 3, entries 8 and 11).
However, it is needed to elevate the reaction temperature to 50 ꢀC
or 60 ꢀC for all the addition reactions to CyN]C]NCy in order to
get the biguanidines in excellent yields (Table 3, entries 2, 4, 7, 10,
and 14), because CyN]C]NCy is a solid.
Aliphatic diamines are less reactive than aromatic diamines to
carbodiimides in the double addition reaction. However, with the
present precatalyst various aliphatic diamines could be applied. In
the presence of 0.5 mol % of III, all the aliphatic diamines tested,
such
as
1,2-diaminoethane,
1,3-diaminopropane,
1,4-
i
diaminobutane, and 1,6-diaminohexane, could add to PrN]C]
NiPr in a 1:2 molar ratio at 40 ꢀC to afford the corresponding
biguanidines compounds 35, 37, 38, and 39 in excellent yields
(95e98%) for 6 h (Table 3, entries 13, 15, 16, and 17).
An X-ray structure analysis of 37 revealed that all the four iso-
propylamino groups bear a proton on their nitrogen atoms,
whereas the aliphatic substituent CH2CH2CH2 is bonded to the
Fig. 2. ORTEP drawing of 37 with 30% probability thermal ellipsoids. Hydrogen atoms,
except those on the nitrogen atoms, are omitted for clarity.
Scheme 1. Supposed mechanism of catalytic addition of diamines to carbodiimides.

8796
X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
We believe that the much high reactivity of bimetallic complex III
should be contributed to the cooperation effect by lanthanide and
lithium metals. An attempt to isolate the active species by the re-
actions of III with amine or with carbodiimide was not in success
yet. The proposed reaction mechanism was presented in Scheme 1,
although the detailed reaction pathway is not clear yet.
1,4-diaminobenzene (0.216 g, 2 mol) under dried argon. The
resulting mixture was stirred at 25 ꢀC for 2 h. The reaction mixture
was extracted with ether and filtered to give a clean solution. After
removing the solvent under vacuum, the residue was recrystallized
in ether to provide a white solid 25 in 99% yield.9b 1H NMR
(300 MHz, CDCl3):
J¼7.7 Hz, 2H), 6.38 (s, 1H), 3.73 (m, 4H), 1.15e1.13 (d, J¼6.4 Hz, 24H).
d
¼7.15e7.10 (t, J¼7.8 Hz, 1H), 6.46e6.43 (d,
3. Conclusion
13C NMR (75 MHz, CDCl3):
23.4.
d
¼151.4, 150.1, 129.9, 118.8, 117.3, 43.3,
In conclusion, heterobimetallic dianionic guanidinate lanthanide
and lithium complexes [Li(THF)(DME)]3Ln[
m
-
h2h1(iPrN)2C(NC6H4p-
4.4. Procedure 3: synthesis and characterization of
[Li(THF)(DME)]3La[
h2h1(iPrN)2C(NC6H4p-Cl)]3 (III)
R)]3 [R¼Cl, Ln¼Nd (I), Y (II), La (III); R¼H, Ln¼Nd (IV)] were found to
be excellent precatalyst for catalytic addition of various mono-
amines to carbodiimides, leading to efficient formation of a series of
monoguanidine derivatives with a wide range of substituents on the
nitrogen atoms. These complexes can also serve as extremely active
precatalysts for catalytic double addition of diamines to carbodii-
mides affording the corresponding biguanidine compounds in ex-
cellent yields under mild conditions. The present catalytic system
has a wide scope of diamines including various aromatic and ali-
phatic diamines.
m-
A Schlenk tube was charged with [iPrNHCNiPr(NC6H4p-Cl)]3La
(THF) (2.92 g, 3.0 mmol),2 THF (30 mL), and a stir bar. The solution
was cooled to 0 ꢀC, and n-BuLi (5.1 mL, 9.0 mmol, 1.75 M in hexane)
was added, then slowly warmed to room temperature and stirred
for 24 h. The resulting solution was then evaporated to dryness in
vacuo. DME (15 mL) and toluene (5 mL) were added to the residue
and then heated until to the solution being clear. The solution was
cooled to room temperature for crystallization and the colorless
crystals III was isolated. Yield: 2.78 g (54%). Mp: 243e245 ꢀC. Anal.
Calcd for C86H149Cl3Li3N9O11La (1751.22): C, 58.98; H, 7.20; N, 8.58;
La, 7.93. Found: C, 58.64; H, 7.04; N, 8.32; La, 7.79%. IR (KBr pellet):
3067(s) cmꢁ1, 2943 (s), 2908 (s), 2869 (s), 1641 (s), 1599 (s),1571 (s),
1538 (s), 1513 (s), 1485 (s), 1364 (m), 1176 (m), 1113 (m), 1063 (m),
4. Experimental section
4.1. General
All manipulations and reactions were performed under a puri-
fied argon atmosphere using standard Schlenk techniques or under
a nitrogen atmosphere in a glovebox. Solvents were degassed and
distilled from sodium benzophenone ketyl under argon prior to
use. These heterobimetallic complexes of lanthanide and lithium
959 (m), 843(m). 1H NMR (400 MHz, C4D8O)
HePh), 6.71e6.61 (m, 3H, p-HePh), 6.55e6.46 (m, 6H, o-HePh),
3.66e3.58 (m, 36H, -HeTHF), 3.33e3.30 (m, 6H, HeC(N)Me2),
1.77e1.70 (m, 36H, -H, THF), 1.10e0.97 (d, 36H, CH3).
d
¼7.17e6.76 (d, 6H, m-
a
b
supported by dianionic guanidinate ligands [Li(THF)(DME)]3Ln[
m
-
4.5. Procedure 4: synthesis and characterization of
[Li(THF)(DME)]3Nd[
h2h1(iPrN)2C(NC6H5)]3 (IV)
h2h1(iPrN)2C(NC6H4p-R)]3 [R¼Cl, Ln¼Nd (I), Y (II), La (III); R¼H,
Ln¼Nd (IV)] were prepared according to the literature procedure.14
The structure of III and IV was confirmed by X-ray structural
analysis. The corresponding monometallic trisguanidinate lantha-
nide complex V and lanthanide amides VI were prepared according
to literatures.15,16
m-
A Schlenk tube was charged with [iPrNHCNiPr(NC6H4p-Cl)]3Nd
(THF) (2.8 g, 3.0 mmol),2 THF (30 mL), and a stir bar. The solution
was cooled to 0 ꢀC, and n-BuLi (5.1 mL, 9.0 mmol, 1.75 M in hexane)
was added, then slowly warmed to room temperature and stirred
for 24 h. The resulting solution was then evaporated to dryness in
vacuo. DME (15 mL) and toluene (5 mL) were added to the residue
and then heated until to the solution being clear. The solution was
cooled to room temperature for crystallization and the blue crystals
IV were isolated. Yield: 3.21 g (75%). Mp: 206e208 ꢀC. Anal. Calcd
for C73H121Li3N11O7Nd (1429.87): C, 61.32; H, 8.53; N, 10.78; Nd,
10.09. Found: C, 61.25; H, 8.44; N, 10.20; Nd, 10.01%. IR (KBr pellet):
3071 (s) cmꢁ1, 2983 (s), 2924 (s), 2866 (s), 1634 (s), 1602 (s), 1590
(s),1532 (s),1505 (s),1484 (s),1361 (m),1158 (m),1011 (m), 932 (m),
877(m).
All carbodiimides and amines were pre-dried, sublimed,
recrystallized or redistilled before use. Melting points were de-
termined in capillary tube, and uncorrected. 1H and 13C NMR
spectra were recorded on a 300 MHz or 400 MHz spectrometer.
Chemical shifts (d) were reported in parts per million. HRMS were
recorded on a GCT-TOF instrument.
4.2. General procedure 1: synthesis of guanidines by reaction
of aromatic amines and secondary amines with carbodiimides
catalyzed by III (product 1 as an example)
A
10 mL Schlenk tube was charged with III (0.0128 g,
4.5.1. N-Phenyl-N0,N00-dicyclohexylguanidine (2)8. Product
2 was
0.0075 mmol), N,N0-diisopropylcarbodiimide (0.189 g, 1.5 mmol),
and aniline (0.140 g, 1.5 mmol) under dried argon. The resulting
mixture was stirred at 25 ꢀC for 30 min. The reaction mixture was
extracted with ether and filtered to give a clean solution. After re-
moving the solvent under vacuum, the residue was recrystallized in
ether to provide a white solid 1 in >99% yield.8 1H NMR (400 MHz,
obtained following the procedure 1 catalyzed by catalysts III and
isolated as a white solid in 99% yield. 1H NMR (400 MHz, CDCl3):
d
¼7.25e7.23 (m, 2H), 6.95e6.91 (m,1H), 6.88e6.86 (d, 2H), 3.64 (br,
2H), 3.42 (br, 2H), 2.03e1.05 (m, 20H). 13C NMR (100 MHz, CDCl3):
¼150.7, 150.7, 129.5, 123.9, 121.6, 50.5, 34.1, 26.0, 25.2.
d
CDCl3):
d
¼7.22 (m, 2H), 6.95e6.91 (m, 1H), 6.86 (d, J¼7.6 Hz, 2H),
4.5.2. N-p-Flurophenyl-N0,N00-diisopropylguanidine (3)11. Product 3
was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in >99% yields. 1H NMR (400 MHz,
3.77 (br, 2H), 3.61(br, 2H), 1.17 (d, J¼6.4 Hz, 12H). 13C NMR
(100 MHz, CDCl3):
d¼150.5, 150.4, 129.4, 123.7, 121.4, 43.4, 23.5.
CDCl3):
d
¼6.95e6.91 (m, 2H), 6.79e6.75 (m, 2H), 3.74 (br, 2H), 3.52
4.3. General procedure 2: synthesis of biguanidines from
reaction of diamines with carbodiimides catalyzed by III
(product 25 as an example)
(br, 2H), 1.16 (d, 12H). 13C NMR (100 MHz, CDCl3):
141.8, 123.4, 122.5, 28.3, 24.2.
d
¼148.0, 144.6,
4.5.3. N-p-Flurophenyl-N0,N00-dicyclohexylguanidine (4)11. Product 4
was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 99% yield. 1H NMR (400 MHz,
A
10 mL Schlenk tube was charged with III (0.0174 g,
0.01 mmol), N,N0-diisopropylcarbodiimide (0.504 g, 4 mmol), and

X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
8797
CDCl3):
d
¼6.92 (m, 2H), 6.77 (m, 2H), 3.59 (br, 2H), 3.38 (br, 2H),
CDCl3):
4H), 6.93 (d, 1H), 3.88 (br, 2H), 3.63 (br, 2H), 1.19e1.17 (d, 12H). 13C
NMR (100 MHz, CDCl3):
d
¼8.08e8.06 (d, 1H), 7.80e7.78 (d, Hz, 1H), 7.47e7.35 (m,
1.99e1.03(m, 20H). 13C NMR (100 MHz, CDCl3):
d¼150.6, 124.9,
124.8, 116.1, 115.9, 50.4, 34.0, 25.9, 25.2.
d¼150.2, 147.1, 135.1, 129.9, 128.1, 126.8,
126.1, 125.0, 124.7, 121.7, 118.1, 43.6, 23.7.
4.5.4. N-o-Chlorophenyl-N0,N00-diisopropylguanidine (5)11. Product 5
was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 95% yield. 1H NMR (400 MHz,
CDCl3):
3.79 (br, 2H), 3.48 (br, 2H), 1.19e1.17 (12H). 13C NMR (100 MHz,
CDCl3):
¼150.1, 147.2, 130.1, 128.5, 127.8, 125.5, 122.7, 43.6, 23.6.
4.5.13. N,N00-Diisopropyl-N0-2,6-diisopropylphenylguanidine (14)7b
.
Product 14 was obtained following the procedure 1 catalyzed by
d
¼7.35e7.33 (m, 1H), 7.15e7.11(m, 1H), 6.91e6.85 (m, 2H),
catalysts III and isolated as a white solid in 97% yield. 1H NMR
(400 MHz, CDCl3):
d
¼7.07e7.05 (d, 2H), 6.98e6.94 (m, 1H), 4.19 (br,
d
1H), 3.43e3.19 (br, 3H), 3.11e3.04 (m, 2H), 1.25e1.04 (m, 24H). 13C
NMR (100 MHz, CDCl3):
42.7, 28.0, 23.9.
d
¼147.7, 144.3, 141.6, 123.2, 122.3, 43.5,
4.5.5. N-o-Chlorophenyl-N0,N00-dicyclohexylguanidine (6)11. Product
6 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 94% yield. 1H NMR (400 MHz,
CDCl3):
3.56 (br, 2H), 3.42 (br, 2H), 2.05e1.06 (m, 20H). 13C NMR (100 MHz,
CDCl3):
4.5.14. N-Butyl-N0,N00-diisopropylguanidine (15)11. Product 15 was
obtained following the procedure 2 catalyzed by catalysts III
d
¼7.34e7.33 (m, 1H), 7.15e7.11 (m, 1H), 6.92e6.85 (m, 2H),
and isolated as
(400 MHz, CDCl3):
a
colorless liquid in 96% yield. 1H NMR
d
¼150.1, 147.6, 130.1, 128.7, 127.8, 125.6, 122.6, 50.5, 34.1,
d
¼3.57e3.48 (m, 2H), 3.05e2.98 (m, 2H),
26.0, 25.2.
1.53e1.48 (m, 2H), 1.42e1.34 (m, 2H), 1.15e1.07 (d, 12H), 0.93 (t,
3H). 13C NMR (100 MHz, CDCl3):
21.2, 14.7.
d
¼151.8, 44.7, 34.0, 33.7, 24.6,
4.5.6. N-o-Methylphenyl-N0,N00-diisopropylguanidine (7)7b. Product
7 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 90% yield. 1H NMR (400 MHz,
4.5.15. N,N0-Diisopropylpyrrolidine-1-carboximidamide (16)11. Pro-
duct 16 was obtained following the procedure 1 catalyzed by cat-
alysts III and isolated as a colorless liquid in 98% yield. 1H NMR
CDCl3):
d
¼7.15 (d, 1H), 7.09 (m, 1H), 6.90e6.86(m, 1H), 6.78 (d, 1H),
3.76 (br, 2H), 3.46 (br, 2H), 2.14 (s, 3H), 1.17 (d, 12H). 13C NMR
(100 MHz, CDCl3):
43.4, 23.7, 18.4.
d
¼149.1, 148.6, 131.8, 130.6, 126.8, 123.4, 121.9,
(400 MHz, CDCl3):
d
¼3.38 (m, 2H), 3.26 (m, 4H), 1.80 (m, 4H),
1.11 (d, 12H). 13C NMR (100 MHz, CDCl3):
26.3, 24.8.
d
¼153.7, 47.9, 46.8,
4.5.7. N-o-Methylphenyl-N0,N00-dicyclohexylguanidine (8)7b. Product
8 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 91% yield. 1H NMR (400 MHz,
4.5.16. N,N0-Dicyclohexylpyrrolidine-1-carboximidamide (17)11. Pro-
duct 17 was obtained following the procedure 1 catalyzed by cat-
alysts III and isolated as a white solid in 96% yield. 1H NMR
CDCl3):
d
¼6.93 (m, 2H), 6.78 (m, 2H), 3.62 (br, 2H), 3.40 (br, 2H),
2.00(s, 3H), 1.97e1.03 (m, 20H). 13C NMR (100 MHz, CDCl3):
(400 MHz, CDCl3):
d
¼3.21(m, 4H), 2.89 (m, 2H), 1.75e1.08 (m, 24H).
d
¼148.9, 148.7, 131.9, 130.6, 126.8, 123.5, 121.9, 50.4, 34.2, 25.9, 25.2,
13C NMR (100 MHz, CDCl3):
25.5.
d¼154.0, 55.3, 48.3, 35.4, 26.0, 25.9,
18.4.
4.5.8. N-o-Methoxyphenyl-N0,N00-diisopropylguanidine (9)9b. Product
9 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 98% yield. 1H NMR (400 MHz, CDCl3):
4.5.17. N,N0-Diisopropylpiperidine-1-carboximidamide (18)11. Product
18 was obtained following the procedure 2 catalyzed by catalysts I
and isolated as a colorless liquid in 93% yield. 1H NMR (400 MHz,
d
¼6.94e6.86(m, 4H), 3.78 (m, 5H), 3.56 (br, 2H), 1.17e1.15 (d, 12H).
CDCl3):
d
¼3.40e3.30 (m, 2H), 3.03 (s, 4H), 1.53 (s, 6H), 1.10 (d,
13C NMR (100 MHz, CDCl3):
111.8, 55.6, 43.3, 23.4.
d
¼152.4, 150.7, 139.2, 124.7, 122.2, 121.3,
12H). 13C NMR (100 MHz, CDCl3):
24.8, 24.0.
d
¼156.3, 49.2, 46.6, 45.7, 26.3,
4.5.9. N-o-Methoxyphenyl-N0,N00-dicyclohexylguanidine (10)11. Product
10 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 92% yield. 1H NMR (400 MHz, CDCl3):
4.5.18. N,N0-Dicyclohexylpiperidine-1-carboximidamide (19)11. Product
19 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 96% yield. 1H NMR (400 MHz, CDCl3):
d
¼6.96e6.85 (m, 4H), 3.79 (s, 3H), 3.60 (br, 2H), 3.45 (br, 2H),
d
¼3.02 (s, 4H), 2.87 (br, 2H), 1.90e1.05 (m, 26H). 13C NMR (100 MHz,
2.04e1.04(m, 20H). 13C NMR (100 MHz, CDCl3):
d
¼152.6, 150.5, 139.3,
CDCl3):
d¼156.0, 55.9, 53.7, 49.2, 34.9, 34.9, 26.3, 26.0, 25.7, 25.4.
125.0, 122.4, 121.4, 111.9, 55.7, 50.4, 34.0, 25.9, 25.1.
4.5.19. N,N0-Diisopropylmorpholine-4-carboximidamide (20)11. Product
20 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 95% yield. 1H NMR (400 MHz, CDCl3):
4.5.10. N-p-Nitrophenyl-N0,N00-diisopropylguanidine (11)8. Product
11 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a yellow solid in 90% yield. 1H NMR (400 MHz,
d
¼3.69e3.67 (m, 4H), 3.42e3.39 (m, 1H), 3.32e3.29 (m, 1H),
3.08e3.06 (m, 4H), 1.14e1.06(m, 12H). 13C NMR (100 MHz, CDCl3):
¼155.5, 67.3, 48.9, 47.4, 46.6, 23.9, 23.8.
CDCl3):
d
¼8.11e8.09 (m, 2H), 6.90e6.88 (m, 2H), 3.83e3.78 (br, 4H),
1.19e1.18 (d, 12H). 13C NMR (100 MHz, CDCl3):
d
¼158.6, 150.8, 141.1,
d
125.9, 123.1, 43.7, 23.6.
4.5.20. N,N0-Dicyclohexylmorpholine-4-carboximidamide (21)8. Product
21 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 98% yield. 1H NMR (400 MHz, CDCl3):
4.5.11. N-p-Chlorophenyl-N0,N00-diisopropylguanidine (12)3k. Product
12 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 95% yield. 1H NMR (400 MHz, CDCl3):
d
¼3.66 (m, 4H), 3.06 (m, 4H), 2.97e2.88 (m, 2H), 1.90e1.02 (m, 20H).
d
¼7.20e7.18 (d, 2H), 6.79e6.77 (d, 2H), 3.75 (br, 2H), 3.60 (br, 2H),
13C NMR (100 MHz, CDCl3):
26.3,26.1, 25.9.
d
¼155.2, 67.5, 56.7, 54.0, 49.1, 35.6, 34.9,
1.17e1.15(d, 12H). 13C NMR (100 MHz, CDCl3):
d
¼150.5, 149.2, 129.4,
126.4, 125.1, 43.5, 23.6.
4.5.21. N-Benzyl-N-methyl-N0,N00-diisopropylguanidine (22)11. Product
22 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a colorless liquid in 97% yield. 1H NMR (400 MHz,
4.5.12. N-(1-Naphthyl)-N0,N00-diisopropylguanidine (13)8. Product
13 was obtained following the procedure 1 catalyzed by catalysts III
and isolated as a white solid in 95% yield. 1H NMR (400 MHz,
CDCl3):
d¼7.32e7.29 (m, 3H), 7.24e7.20 (m, 2H), 4.30 (s, 2H), 3.50 (br,

8798
X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
2H), 3.60 (br,1H), 2.61 (s, 3H),1.12 (s,12H). 13C NMR (100 MHz, CDCl3):
¼155.9, 139.7, 128.5, 128.0, 126.9, 55.4, 37.1, 24.9.
4H), 1.17e1.15 (d, 24H). 13C NMR (75 MHz, CDCl3):
131.1, 125.5, 118.4, 43.6, 23.7. HRMS (ESI): m/z calcd for C24H38N6:
410.3158, found: 410.3157.
d¼150.3, 146.9,
d
4.5.22. N00,N000-1,4-Phenylenebis (N,N0-diisopropylguanidine) (23)7b
.
Product 23 was obtained following the procedure 2 catalyzed by
4.5.30. N00,N000-1,5-Naphthalenebis (N,N0-dicyclohexylguanidine) (32).
Product 32 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a yellow solid in 98% yield. 1H NMR
catalysts III and isolated as a white solid in 98% yield. 1H NMR
(300 MHz, CDCl3):
NMR (75 MHz, CDCl3):
d
¼6.76 (s, 4H), 3.75 (br, 4H), 1.15e1.13 (d, 24H). 13
C
d
¼151.2, 143.9, 124.7, 43.4, 23.5.
(300 MHz, CDCl3):
d
¼7.67e7.64 (d, 2H), 7.31e7.28 (m, 2H), 6.90e6.98
(d, 2H), 3.74e3.20 (br, 8H), 2.00e1.04 (m, 40H). 13C NMR (75 MHz,
4.5.23. N00,N000-1,4-Phenylenebis (N,N0-dicyclohexylguanidine) (24)7b
.
CDCl3):
d
¼150.1, 146.7, 130.9, 125.9, 118.5, 68.2, 50.4, 34.1, 25.9, 25.1.
Product 24 was obtained following the procedure 2 catalyzed by
Mp: 249e251 ꢀC. HRMS (ESI): m/z calcd for C36H54N6: 570.4410,
catalysts III and isolated as a white solid in 95% yield. 1H NMR
found: 570.4412.
(300 MHz, CDCl3):
d
¼6.83 (s, 4H), 3.55e3.18 (br, 4H), 1.99e1.06 (m,
40H). 13C NMR (75 MHz, CDCl3):
33.9, 25.8, 24.9.
d
¼150.1,144.2,124.6, 55.8, 50.1, 35.0,
4.5.31. {(iPrNH)2C]N}3(2,4,6-C4HN2) (33)9b. Product 33 was
obtained following the procedure 2 catalyzed by catalysts III and
isolated as a yellow solid in 98% yield. 1H NMR (300 MHz, CDCl3):
4.5.24. N00,N000-1,3-Phenylenebis (N,N0-dicyclohexylguanidine) (26).
Product 26 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 97% yield. Mp:
d
¼5.82 (s, 1H), 3.89e3.83 (m, 6H), 1.20e1.11 (m, 36H). 13C NMR
(75 MHz, CDCl3):
23.5.
d¼168.7, 163.5, 154.3, 153.8, 99.9, 45.2, 42.9, 24.8,
61e64 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼7.12e7.10 (t, 1H),
6.43e6.40 (m, 3H), 3.73e3.18 (br, 4H), 1.98e1.07 (m, 40H). 13C
NMR (75 MHz, CDCl3):
4.5.32. N00,N000-2-Aminobenzylaminebis (N,N0-diisopropylguanidine)
(34). Product 34 was obtained following the procedure 2 cata-
lyzed by catalysts III and isolated as a yellow tacky solid in 90%
d
¼151.4, 150.0, 129.9, 119.1, 117.3, 50.3, 35.1,
33.9, 25.9, 25.1. HRMS (ESI): m/z calcd for C32H52N6: 520.4253,
found: 520.4253.
yield. 1H NMR (400 MHz, CDCl3):
d
¼7.32e7.30 (d, 1H), 7.04e7.02 (t,
1H), 7.00e6.81 (t, 1H), 6.79e6.64 (d, 1H), 4.08 (s, 2H), 3.66e3.60
(m, 4H), 1.01e0.97 (m, 24H). 13C NMR (100 MHz, CDCl3):
4.5.25. N00,N000-1,2-Phenylenebis (N,N0-diisopropylguanidine) (27).
Product 27 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 98% yield. Mp:
d
¼153.7,
150.5, 147.6, 132.9, 129.8, 128.1, 122.8, 122.4, 44.5, 43.2, 42.2, 23.5,
23.1. HRMS (ESI): m/z calcd for C21H38N6: 374.3158, found:
374.3163.
107e109 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼7.22e7.20 (m, 2H),
6.96e6.94 (m, 2H), 6.90 (br, 4H), 3.75 (m, 4H), 1.14e1.12 (d, 24H). 13C
NMR (100 MHz, CDCl3):
d¼155.6,149.6,124.5,122.9,119.6,111.9, 44.4,
4.5.33. N00,N000-1,2-Ethylanebis (N,N0-diisopropylguanidine) (35)13
.
43.3, 23.6, 23.2. HRMS (ESI): m/z calcd for C20H36N6: 360.3001, found:
360.3001.
Product 35 was obtained following the procedure 2 catalyzed
by catalysts III and isolated as a white solid in 96% yield. 1H
NMR (300 MHz, CDCl3):
d
¼3.59e3.54 (m, 4H), 3.13 (br, 4H),
4.5.26. N00,N000-2,4-Toluenebis
(N,N0-diisopropylguanidine)
(28).
1.10e1.08 (d, 24H). 13C NMR (75 MHz, CDCl3):
d
¼153.8, 46.2,
Product 28 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 98% yield. Mp:
43.9, 23.3.
148e150 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼7.00e6.98 (d, 1H),
6.37e6.35 (d, 1H), 6.30 (s, 1H), 3.72e3.51 (br, 8H), 1.98 (s, 3H),
1.19e1.12 (br, 24H). 13C NMR (75 MHz, CDCl3):
4.5.34. N00,N000-1,2-Ethylanebis (N,N0-dicyclohexylguanidine) (36).
Product 36 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 98% yield. Mp:
d¼150.3, 149.2, 148.9,
131.2, 124.7, 118.7, 117.6, 43.3, 23.6, 17.6. HRMS (ESI): m/z calcd for
C21H38N6: 374.3158, found: 374.3157.
55e57 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼3.63e3.12 (br, 8H),
1.97e1.21 (m, 40H). 13C NMR (75 MHz, CDCl3):
d
¼153.8, 51.1, 46.8,
46.4, 33.9, 24.9. HRMS (ESI): m/z calcd for C28H52N6: 472.4253,
found: 472.4254.
4.5.27. N00,N000-2,4-Toluenebis
(N,N0-dicyclohexylguanidine)
(29). Product 29 was obtained following the procedure 2 cat-
alyzed by catalysts III and isolated as a yellow solid in 97%
4.5.35. N00,N000-1,3-Propanebis
(N,N0-diisopropylguanidine)
(37).
yield. Mp: 45e47 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼6.93e6.91
(d, 1H), 6.31e6.28 (d, 1H), 6.25 (s, 1H), 3.67e3.12 (br, 8H),
1.98e0.97 (m, 43H). 13C NMR (75 MHz, CDCl3):
Product 37 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 96% yield. Mp: 52e54 ꢀC.
d
¼150.1, 149.2,
1H NMR (300 MHz, CDCl3):
d
¼3.66e3.58 (m, 4H), 3.12e3.08 (m, 4H),
148.9, 148.7, 130.9, 124.5, 118.2, 117.4, 55.7, 50.3, 34.9, 34.1, 25.8,
25.1, 17.5. HRMS (ESI): m/z calcd for C33H54N6: 534.4410, found:
534.4410.
1.72e1.68 (m, 2H), 1.11e1.09 (d, 24H). 13C NMR (75 MHz, CDCl3):
d
¼153.8, 44.7, 40.7, 30.9, 23.1. HRMS (ESI): m/z calcd for C17H38N6:
326.3158, found: 326.3155.
4.5.28. N00,N000-2,6-Pyridinebis
(N,N0-diisopropylguanidine)
(30).
4.5.36. N00,N000-1,4-Butanebis
(N,N0-diisopropylguanidine)
(38).
Product 30 was obtained following the procedure 2 catalyzed by
Product 38 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 98% yield. Mp:
catalysts III and isolated as a white solid in 96% yield. Mp: 89e90 ꢀC.
1H NMR (300 MHz, CDCl3):
d
¼7.38e7.33 (t, 1H), 6.35e6.32 (d, 2H),
107e109 ꢀC ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼3.73e3.67 (m, 4H),
3.21 (m, 4H), 1.94 (m, 4H), 1.65 (br, 4H), 1.26e1.24 (d, 24H). 13C NMR
(75 MHz, CDCl3):
¼151.9, 44.6, 31.2, 27.4, 24.0. HRMS (ESI): m/z
calcd for C18H40N6: 340.3314, found: 340.3313.
3.88e3.56 (m, 4H), 1.20e1.18 (d, 24H). 13C NMR (75 MHz, CDCl3):
d
¼160.9, 152.4, 138.7, 110.6, 49.4, 42.9, 24.8, 23.6. HRMS (ESI): m/z
d
calcd for C19H35N7: 361.2954, found: 361.2954.
4.5.29. N00,N000-1,5-Naphthalenebis (N,N0-diisopropylguanidine) (31).
Product 31 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a white solid in 95% yield. Mp:
4.5.37. N00,N000-1,6-Hexanebis (N,N0-diisopropylguanidine)
(39).
Product 39 was obtained following the procedure 2 catalyzed by
catalysts III and isolated as a colorless tacky oil in 95% yields. 1H
226e228 ꢀC. 1H NMR (300 MHz, CDCl3):
d¼7.69e7.66 (d, 2H),
NMR (300 MHz, CDCl3):
d
¼3.50 (br, 4H), 2.99e2.97 (m, 4H), 1.53 (br,
7.31e7.28 (m, 2H), 6.89e6.87 (d, 2H), 3.84 (br, 4H), 3.58e3.54 (m,
4H), 1.36 (br, 4H), 1.12e1.10 (d, 24H). 13C NMR (75 MHz, CDCl3):

X. Zhang et al. / Tetrahedron 67 (2011) 8790e8799
8799
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Acknowledgements
We are grateful to the National Natural Science Foundation of
China (Grant Nos. 20972107 and 20872106) and Specialized Re-
search Fund for the Doctoral Program of Higher Education
(200802850003).
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2011.08.072.
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