Aza-crown compounds synthesised by the self-condensation of 2-amino-benzyl alcohol over a pincer ruthenium catalyst and applied in the transfer hydrogenation of ketones

Article abstract of DOI:10.1039/d0dt03257c

A well-defined PNN-Ru catalyst was revisited to self-condense 2-aminobenzyl alcohol in forming a series of novel aza-crown compounds [aza-12-crown-3 (1), aza-16-crown-4 (2) and aza-20-crown-5 (3)]. All aza-crown compounds are separated and determined by NMR, IR, and ESI-MS spectroscopy as well as X-ray crystallography, indicating the saddle structure of 1 and the twisted 1,3-alternate conformation structure of 3. These aza-crown compounds have been explored to study ferric initiation of transfer hydrogenation (TH) of ketones into their corresponding secondary alcohols in the presence of 2-propanol with a basic t-BuOK solution, achieving a high conversion (up to 95%) by a ferric complex with 2 in a low loading (0.05 mol%). This journal is

Full text of DOI:10.1039/d0dt03257c

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DOI: 10.1039/D0DT03257C
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ARTICLE
Aza‐crown Compounds by the Self‐condensation of 2‐Amino‐
benzyl alcohol over a Pincer‐Ruthenium Catalyst and Applied in
Transfer Hydrogenation of Ketones§
Received 00th January 20xx,
Accepted 00th January 20xx
Shanshan Zhang,a,# Zheng Wang,a,b,c,# Qianrong Cao,a,d,# Erlin Yue,b Qingbin Liu,a,*,Yanping Ma,b
DOI: 10.1039/x0xx00000x
Tongling Liang,b and Wen‐Hua Sunb,*
www.rsc.org/
Abstract: A well‐defined PNN‐Ru catalyst was revisited to self‐condense 2‐aminobenzyl alcohol in forming a series of novel
aza‐crown compounds [aza‐12‐crown‐3 (1), aza‐16‐crown‐4 (2) and aza‐20‐crown‐5 (3)]. All aza‐crown compounds are
separated and determined by NMR, IR, ESI‐MS spectra as well as the X‐ray crystallography indicating the saddle structure
of 1 and twisted 1,3‐alternate conformation structure of 3. These aza‐crown compounds have been explored to steady
ferric initiation of transfer hydrogenation (TH) of ketones into their corresponding secondary alcohols in the presence of 2‐
propanol with basic t‐BuOK solution, achieving a high conversion (up to 95%) by ferric complex with 2 in a low loading
(0.05 mol%).
Introduction
Previously work
The macrocyclic compounds1 including crown ethers,2 cryptands,3
spherands,4 cyclodextrins5, and calix[n]arenes1b,1f,6 have been
applied in exploring of the non‐covalent bond interactions,7
molecular recognition,1,2b and self‐assembly8 and as ligands in
catalysis.9 With respect to catalysis, the transfer hydrogenation (TH)
by macrocyclic iron (II) catalysts10 has been attracted and pioneered
by Gao,9a,11 Mezzetti,12 and Morris,13 and developed as both chiral
and achiral catalytic platforms.9a,10,12,13 In the progress of catalysts
using macrocyclic molecules9,10 and supramolecular chemistry,7,14
the challenge has remained with the issues of convenient syntheses
and available numbers of macrocyclic compounds. Moreover, there
is a few of aza‐crown compounds available.1b,15 Recently we
developed a pincer‐ruthenium(II) catalyst for the dehydrogenative
coupling‐cyclization of γ‐amino alcohols with secondary alcohols
(Scheme 1),16 in which substance containing both functional groups
of amine and secondary alcohol commonly proceed the coupling‐
cyclization. Certainly the substance containing both functional
N
N
Ru-Cat =
PPh2
H
Ru
Ph3P
CO
NH2
N
OH
Ru-Cat.
0.025%
+
-H2O, -H2
OH
This work
NH
OH
NH2
Ru-Cat.
-H2O
HN
N
H
n = 1, 2, 3
Scheme 1. Formation of N‐heteroaromatics16 or aza‐crown compounds via
dehydrogenative coupling of alcohols and amines catalyzed by a pincer‐
ruthenium catalyst (Ru‐Cat)
a
Hebei Key Laboratory of Organic Functional Molecules, College of Chemistry and
groups of amine and primary alcohol, 2‐aminobenzyl alcohol, is
investigated for the the dehydrogenative coupling‐cyclization over
the pincer‐ruthenium(II) catalyst, interestingly the self‐condensation
of 2‐aminobenzylalcohol is achieved to form a series of aza‐crown
compounds (aza‐12‐crown‐3 (1), aza‐16‐crown‐4 (2) and aza‐20‐
crown‐5 (3), Scheme 1). These aza‐crown compounds can be
interesting of both novel macrocycles and ligands in coordination
chemistry, being similar to the medium‐sized multi‐anthranilides.17
Subsequently the aza‐crown compounds (1, 2 and 3) have been
used in coordinating with ferric chloride and resultant iron
complexes are explored for transfer hydrogenation of ketones.9a,10
The aza‐16‐crown‐4 (2) efficiently catalyze transfer hydrogenation of
Material Science, Hebei Normal University, Shijiazhuang 050024, China
bKey Laboratory of Engineering Plastics and Beijing National Laboratory for
Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing
100190, China
c College of Science, Hebei Agricultural University, Baoding 071001, China
dHebei Research Institute of Microbiology, Baoding 071051, China
#Shanshan Zhang, Zheng Wang, Qianrong Cao made equal contributions in this
work.
†Corresponding Authors: whsun@iccas.ac.cn; liuqingbin@hebtu.edu.cn
§Dedicated to Prof. Dr. Shiyong Yang on his 60th birthday.
Electronic Supplementary Information (ESI) available: Figures, tables, and giving
NMR spectra of the new compounds; CCDC 2008494 for 1, CCDC 2008495 for 3. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/x0xx00000x
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various alkyl‐ and aryl‐containing ketones to the corresponding single crystals of aza‐crown compounds 1 and 3 are isolated and
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DOI: 10.1039/D0DT03257C
secondary alcohols.
subjected for the X‐ray diffraction to obtain their absolute
structures as aza‐12‐crown‐3 (1) and aza‐20‐crown‐5 (3). With
regard to the molecular weights of three aza crown compounds, the
second compound is aza‐16‐crown‐4 (2).20
Results and discussion
X‐ray crystallographic study
Synthesis of flexible CH2NH‐bridged aza‐crown compounds (1, 2
The single crystals of the new aza‐crown compounds 1 and 3
suitable for the single crystal X‐ray diffraction were obtained by the
slow diffusion of n‐hexane into a dichloromethane solution of 1 and
3, respectively. As shown in Figure 1, a saddle structure of 1 was
clearly demonstrated, as in the case of triaza‐[1.1.1]cyclophane.21
Three hydrogens on amino group lay inside of the internal 12‐
membered ring, and the closest interatomic distance is observed
between HN1(1) and HN3(3) as ca. 2.331 Å. In connection with the
distorted structure of 1 due to the strong NH∙∙∙N hydrogen bond
(2.593 and 2.722 Å, See Figure 2) formed between the intra
molecule.1a,1f,21b In the same reason, it is noteworthy that the
presence of CH2NH group as linker, 1 showed a much more flexible
cavity, and the nitrogen atoms in 1 as donor atoms can be
coordinated with metal ion to form complexes, which could be
applied for ion and molecular recognition and the non‐covalent
bond interactions. In contrast to the crystal structures of
silacalix[3]arenes.21b It can be concluded that the bridging CH2NH
group effectively reduces the internal 12‐membered ring strain.
and 3)
N
x
N
Ru-Cat. (0.025 mol%) ,
1 eq. t-BuOK
p-xylene,160 oC, 24h
OH
NH2
N
H
N
H
NH
NH
HN
NH
HN
+
+
HN
H
NH
HN
N
H
N
1
3
2
Scheme 2. One‐pot synthetic routes to new aza‐crown compounds (1, 2
and 3) by 2‐aminobenzyl alcohol via Ru‐Cat
The self‐coupling cyclization of 1‐(2‐aminophenyl)ethanol over the
pincer‐ruthenium catalyst (Ru‐Cat) was observed to form 2‐(4‐
methylquinolin‐2‐yl)benzenamine.16 Instead of secondary alcohol,
the primary alcohol analog 2‐aminobenzyl alcohol is explored to
form azacyclo compounds (1, 2 and 3, Scheme 2) without observing
the expected product (5Z,11Z)‐dibenzo[b,f][1,5] diazocine. The
mechanism of aza‐crown compounds formation is essentially the
formation of a series of C‐N bond involved borrowing hydrogen (BH)
strategy.18 The catalytic cycle includes dehydrogenation of alcohols,
followed by formation of imines with the release of water molecules
and finally in‐situ hydrogenation of the imines produced the desired
N‐alkylated amines. In this work, one of 2‐aminobenzyl alcohol is
first dehydrogenation by a ruthenium catalyst to the corresponding
aldehyde, similar to our work on the dehydrogenation of secondary
alcohols to ketones.19 It undergoes condensation reaction with
another molecule 2‐aminobenzyl alcohol forming imine, then
followed by a reduction step with the hydrogen equivalents from
dehydrogention of the following 2‐aminobenzyl alcohol stepwisely.
Finally, the aza‐12‐crown‐3 (1), aza‐16‐crown‐4 (2) and aza‐20‐
crown‐5 (3) were obtained. In the presence of t‐BuOK and Ru‐Cat as
catalyst, 2‐aminobenzyl alcohol is refluxed in p‐xylene at 160 oC for
24h to produce aza crown compounds 1, 2 and 3 in isolated 10%,
19%, and 17% yields, respectively.
Figure 1 ORTEP representations of 1. Thermal ellipsoids are shown at
30% probability, and hydrogen atoms have been omitted for clarity.
Selected bond lengths [Å] and angles [deg]: N1–C1 1.407(2), N1–C21
1.457(2), N3–C15 1.391(3), N3–C14 1.463(3), N2–C8 1.401(3), N2–C7
1.463(3); C21–N1–C1 121.33(17), C2–C1–N1 123.35(18), C6–C1–N1
117.38(17), C14–N3–C15 121.76(16), C7–N2–C8 119.57(17), C20–C21–
N1 112.51(15), C13–C14–N3 110.19(16), C13–C8–N2 120.68(19), C9–
C8–N2 120.68(19), C6–C7–N2 109.12(17).
1
All the aza‐crown compounds, 1 – 3 are characterized by H and
13C NMR spectroscopy (Figures S1 – S6, SI), high performance liquid
chromatography (HPLC) (Figures S7 – S9, SI), MS‐ESI (Figure S10)
and IR spectra (Figures S13 – S15, SI). It is noticeable the solely
individual signal of the 1H and 13C NMR spectra for all the aza‐crown
compounds (Figures S1 – S6), and also a strong absorption around
3250 cm‐1 consistent with the bond of NH of their IR spectra
(Figures S13 – S15).12 The data of their elemental analyses are
theoretically same with the fact of obtained data within acceptable
errors, their retention times in HPLC significantly indicate at around
7.17, 24.88 and 26.28 mins for 1, 2, and 3, respectively.
Furthermore, the HPLC‐MS spectra show compounds 1, 2, and 3
with the [m+1]+ peak signals at 316.3, 421.2 and 526.3, respectively.
Therefore it could be rationalised as aza crown compounds with the
presence of the CH2NH‐bridges (n = 3, 4 and 5). Fortunately, the
Figure 2 NH⋯N hydrogen‐bonding interactions in molecules of 1.
Hydrogen bond lengths [Å] and angles [deg]: N(1)⋯H(3) 2.593,
N(2)⋯H(1) 2.722; N(1)⋯H(3)–N(3) 102.40, N(2)⋯H(1)–N(1) 104.50.
2 | J. Name., 2012, 00, 1‐3
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Subsequently we tried to use the aza‐crown compoVuienwdsAr(ti1cl,e2Onalninde
3) as macrocyclic ligands coordinatedDOwI:it1h0.10f3e9r/rDic0DTs0a3lt257aCs
homogeneous transfer hydrogenation catalysts. The three aza‐
crown compounds (1, 2, and 3) reacted with an equivalent of
FeCl3•6H2O in a mixture of dichloromethane and ethanol at room
temperature for 24h, respectively, on work‐up, obtained Fe1, Fe2
and Fe3. The IR spectra (Figure S16 – S18) of Fe1 – Fe3 displayed
strong absorption bands around 1035 cm‐1 consistent with the
coordination of the Fe‐N bond11 and telescopic vibration of the O‐H
bond around 3430 cm‐1.
Figure 3. ORTEP representations of 3. Thermal ellipsoids are shown at
30% probability, and hydrogen atoms have been omitted for clarity.
Selected bond lengths [Å] and angles [deg]: N2–C7 1.453(3), N2–C8
1.366(3), N5–C29 1.396(3), N5–C28 1.461(3), N1–C35 1.457(3), N1–C1
1.396(3), N3–C14 1.279(3), N3–C15 1.423(3), N4–C21 1.456(3); C8–
N2–C7 124.63(19), C28–N5–C29 123 45(18), C34–C29–N5 118.5(2),
C30–C29–N5 123.0(2), C1–N1–C35120.93(19), C6–C7–N12 114.17(18),
C15–N3–C14 119.3(2), N1–C35–C34 111.24(18), C13–C14–N3
124.6(2), C13–C8–N2 120.1(2), C9–C8–N2 122.1(2), C27–C22–N4
120.1(2), C23–C22–N4 120.8(2), C21–N4–C2 123.3(2), C20–C21–N4
109.44(19), C6–C1–N1 119.4(2), C2–C1–N1 121.8(2), C20–C15–N3
117.3(2), C16–C15–N3 122.4(2), C27–C28–N5 113.47(18).
Catalytic evaluation in transfer hydrogenation of ketones to
alcohols
Based on reported for iron complexes,11‐13 the current investigation
explored the potential of Fe1, Fe2 and Fe3 to serve as catalysts for
the transfer hydrogenation of ketones. Using 2‐propano (i‐PrOH) as
solvent, acetophenone as the template substrate, the loading of
catalyst as well as the type of bases were screened, and
identification of robust conditions for the transfer hydrogenation of
acetophenone to 1‐phenylethanol were listed in Tables 1 and 2.
Table 1.Catalyst screening and identification of robust conditions
for the transfer hydrogenation of acetophenone.a
Entry
1
2
[Fe]
Fe1
Fe2
Fe3
none
Fe2
FeCl3
Fe2
Fe2
Fe2
Fe2
μmol of [Fe]
Conv. (%)b
2.5
2.5
2.5
‐‐
2.5
2.5
1
2
5
10
5
60
41
34
2
35
38
54
61
62
3
4c
5d
6
Figure 4 NH⋯N hydrogen‐bonding interactions in molecules of 3.
Hydrogen bond lengths [Å] and angles [deg]: N(1)⋯H(5) 2.505,
N(2)⋯H(1) 2.438, N(3)⋯H(2) 2.043; N(1)⋯H(5)–N(5) 111.21,
N(2)⋯H(1)–N(1) 115.54, N(3)⋯H(2)–N(2) 133.70.
7
8
9
10
aConditions: 5 mmol acetophenone, 5 mmol t‐BuOK, 10 mL i‐
PrOH, 82°C, 3h; bDetermined by GC: based on acetophenone
As shown in Figure 3, similar to 1, a saddle structure of 3 was
clearly demonstrated, as in the case of aza‐20‐crown‐5, 3 adopted a
excessively twisted 1,3‐alternate conformation. Due to the
presence of CH2NH group as linker and the strong NH∙∙∙N
intramolecular hydrogen bond (2.043, 2.438 and 2.505 Å, See
Figure 4) formed among them. There is a remakable different from
the nearly regular pentagonal cavities of corona[5]arenes adopted
1,2,4‐alternate conformational structures,22 3 exhibited a heavily
twisted cavity of the 20‐membered ring due to affect of the strong
intra molecular NH∙∙∙N hydrogen bond, and Five bridging nitrogen
atoms lay on the 20‐membered ring, and the closest interatomic
distance is observed between N(2) and N(3) as 2.727 Å and furthest
interatomic distance is observed between N (3) and N(5) as 4.990 Å.
Similar to 1, 3 could be a N5‐type ligand to form complexes with
metal ions. Moreover, The two planes were made of the N3‐C15‐
C20‐C21 and N5‐C29‐C34‐C35 in the structure are almost face‐to‐
face parallel but with a dihedral angle of 14.13o. There are no inter
molecular contacts of note in either structure. Also it can be a good
model for study of the non‐covalent bond interactions, ion and
molecular recognition.
c
consumption with dodecane as the internal standard; In the
absence of iron complexes; d In the absence of t‐BuOK.
Table 2. The effect of base on the transfer hydrogenation a
Entry
Time (h)
Base (5 mmol)
t‐BuOK
t‐BuONa
NaOH
KOH
Ca(OH)2
LiOH
t‐BuOK
t‐BuOK
t‐BuOK
Conv. (%)b
1
2
3
4
5
6
7
8
9
3
3
3
3
3
3
6
12
24
60
49
45
43
11
8
74
96
97
aConditions: 5 mmol acetophenone, 2.5 μmol Fe2, 5 mmol base
b
(1 eq.), 10 mL i‐PrOH, 82 °C 3 ~ 24 h; Determined by GC: based
on acetophenone consumption with dodecane as the internal
standard.
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The reactions were typically performed with freshly distilled and to 1‐phenylethanol. Moreover, it was also fouVniedw AtrthicaletOntlhinee
DOI: 10.1039/D0DT03257C
degassed 2‐propanol at 82 °C over 3 hours under an atmosphere of FeCl3•6H2O has no catalytic activity (35%, entry 6, Table 1)
nitrogen. Firstly, a selection of iron catalysts (2.5 μmol), Fe1, Fe2 exhibited similar conversion to blank control (34%, entry 4, Table 1).
and Fe3, was investigated with the loading of base set at an With the amount of t‐BuOK now fixed at 5 mmol, and the amount
equimolar ratio of t‐BuOK to the acetophenone as a template of Fe2 catalyst was changed between 1μmol and 10 μmol resulting
substrate (5 mmol), respectively (entries 1‐3, Table 1). It was found in conversions of 38% (1μmol), 54% (2 μmol), 60% (2.5 μmol), 61%
that only the Fe2 catalyst has activity with the 60% conversion to 1‐ (5 μmol) and 62% (10 μmol) (entries 2 and 7‐10, Table 1),
phenylethanol (entry 2, Table 1), Fe1 has only 5% conversion less respectively.
than blank control 34% (entries 1 and 4, Table 1), and 41% for Fe3 is
Secondly, in order to investigate the effect of base on the
similar to blank control (entries 3 and 4, Table 1). Meanwhile transfer hydrogenation of acetophenone, six different bases, t‐
without t‐BuOK (entry 5, Table 1), Fe2 showed only 2% conversion BuOK, t‐BuONa, NaOH, KOH, Ca(OH)2, LiOH, were screened with the
Table 3. Exploring substrate scope in the transfer hydrogenation of ketones by Fe2 under the optimal condition a
Entry
1
Substrates
Products
t(h)
12
Conv.(%)b
96
2
24
97
3
4
24
6
93
97
5
6
7
24
24
24
84
79
94
O
8
48
60
9
24
24
24
95
56
69
10
11
OH
12
13
3
99
95
24
aConditions: 5 mmol subustrate, 5 mmol t-BuOK, 2.5 umol Fe2, 10 mL i-PrOH, 82℃; b Determined by GC: based on ketones consumption with dodecane as
the internal standard.
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loading of base set at an equimolar ratio of acetophenone and the group as linker and the strong inter molecular NH‐‐H hydrogen bond
loading of Fe2 fixed at 0.05 mol% (entries 1‐6, Table 2). It was found formed between them, the titled compounds displayed unique
that in the six bases, t‐BuOK was found to achieve the best spatial configurations and formed NH‐‐‐N H‐bond macroporous
conversion of 60%. To explore the effect of reaction time on the caves which can be suitable for study of ion and molecular
transfer hydrogenation of acetophenone, t‐BuOK as the co‐catalyst, recognition and the non‐covalent bond interactions. Also,
the tests were conducted over different reaction times from 3 to 24 macrocyclic N3 ~ N5 (1, 2 and 3) as donor ligands for iron complexes
hours (entries 1 and 7 – 9, Table 3) with the S/C ratio set at 2000 (Fe1, Fe2 and Fe3) has been independently assessed as a catalyst in
and the reaction temperature at 82oC, which resulted in the transfer hydrogenation of ketones to secondary alcohols, only
conversions of 60% (3h), 74% (6h), 96 % (12h) and 97 % (24h)
Fe2 could catalyze the transfer hydrogenation of ketone, and more
Finally, to examine the capability of Fe2 as a tolerant robust than thirteen of ketones was transformed into their corresponding
catalyst, a wide of ketone substrates were screened (entries 1‐13, alcohol in high yields.
Table 3). Typically, the catalytic tests were conducted under the
optimal conditions established of 5 mmol ketone, 0.05 mol% Fe2, Experimental section
5mmol t‐BuOK at 82 °C over 3 ‐ 48 hours with bench 2‐propanol.
The transfer hydrogenation of polar bonds of thirteen ketones was
achieved using Fe2 with good to high conversions range from 56%
General information.
All experiments with metal complexes were carried out under
nitrogen. All solvents were reagent grade or better and used after
being distilled under nitrogen. Most of the chemicals used in the
catalytic reactions were repurified according to standard
to 99% (entries 1‐13, Table 5). Aryl ketones contained electron‐
withdrawing groups such as halides (F, Cl, Br, entries 2‐6, Table 3)
displayed higher conversions than the electron‐donating
acetophenones with methyl or methoxy substituents (entries 7‐8,
Table 3). It is easy to understand that the number of electron‐
withdrawing groups on the benzene ring has increased the rate of
transfer hydrogenation due to the increasing of polarity of carbonyl
group. Such as, the dichloro‐substitution on acetophenone (entry 4,
Table 3) demonstrated higher rate than that monochloro‐
substitution on acetophenone (entries 2‐3, Table 3). On the other
hand, 1‐phenyl‐1‐propanone produced 95% of 1‐phenyl‐1‐propanol
(entry 9, Table 3). Similarly, the electron‐donating group methyl
substitution on the aryl ring of 1‐phenyl‐1‐propanone have reduced
the transfer rate, only producing 56% of 1‐(4‐methylphenyl)‐1‐
propanol (entry 10, Table 3). Meanwhile, benzophenone containing
the strong electron‐donating group phenyl obtained lower
conversion, only 66%. In contrast, 2,2‐diethoxyacetophenone
containing the diethoxy group produced 99% of 2,2‐diethoxy‐1‐
phenylethan‐1‐ol. In addition, 4‐phenyl‐2‐butanone also obtained
95% conversion over 24 hours. So Fe2 can be a wide adaptable
catalyst for transfer hydrogenation.
1
procedures (vacuum distillation). All H NMR and 13C NMR were
recorded on a Bruker AVⅢ–500 NMR spectrometer. GC analyses
were carried out on an Agilent 6820 instrument. HPLC analysis were
carried out on Waters 600 instrument using a column BDS HYPERSIL
C18 (250 x 4.6 mm x 5.0 um), acetonitrile: water (PH = 4, Aqueous
KH2PO4 (0.05 mol/L) solution) = 70:30, flow rate = 1 mL/min, wave
length = 254 nm; ESI‐MS analysis were carried out on 3200 QTRAP
1200 infinity series instrument using a column C18, acetonitrile :
water = 70:30, flow:1 mL/min, electronic energy = + 40eV, Q1MS
scan range = 50 ~ 600
Synthesis of aza‐crown compounds
Under an atmosphere of nitrogen, a 100 mL Schlenk tube, equipped
with a stir bar under N2, was loaded with 2‐aminobenzyl alcohol
(1.2 g, 10 mmol), t‐BuOK (1.1 g, 10 mmol) and Ru‐Cat. (1.9 mg, 2.5
umol) in p‐xylene (15 mL). The mixture was stirred at 160 oC for 24
hours. On cooling to room temperature, the mixture was diluted
with water and extracted with ethyl acetate (10 mL) for three times.
The organic layer was dried with anhydrous Na2SO4 and
concentrated in vacuum to afford the yellow liquid product. The
residue was purified by silica gel column chromatography to afford
three yellow products. Eluent component is petroleum ether/ethyl
acetate = 400/1, obtained 0.10 g 1 (10%); Eluent component is
petroleum ether/ethyl acetate = 30/1, obtained 0.19 g 2 (19%);
Eluent component is petroleum ether/ethyl acetate = 10/1,
obtained 0.17 g 3 (17%).
Conclusions
We have developed a novel route to prepare three novel aza‐crown
compounds [aza‐12‐crown‐3 (1), aza‐16‐crown‐4 (2) and aza‐20‐
crown‐5 (3)] via a ruthenium catalyzed the self‐condensation of 2‐
aminobenzyl alcohol. All the azacyclo compounds were separated
and identified by NMR, ESI‐MS, elemental analysis as well as X‐ray
crystallography for 1 and 3. With regard to the presence of CH2NH
Aza‐12‐crown‐3 (1): Mp: 161‐163 oC, 1H NMR (DMSO‐d, 500 MHz) δ
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7.15‐7.14 (d, J = 5 Hz, 3H), 7.03‐7.00 (m, 3H), 6.69‐6.68 (d, J= 5 Hz, of 2‐propanol precooled to room temperature, dodecane
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3H), 6.53‐6.50 (m, 3H), 5.43 (s, 3H, NH), 4.28 (s, 6H);13C NMR introduced, before being analyzed by GC. The composition of the
DOI: 10.1039/D0DT03257C
(DMSO‐d, 125 MHz) δ 146.76, 131.37, 128.66, 124.34, 116.34, reaction mixture was confirmed by running GC of a mixture of pure
113.40, 65.38, 46.58. ESI‐MS: [M+1]/z = 316.3; FT‐IR (KBr, cm‐1): ketone, alcohol and dodecane.
3250 (s, νNH), 3022 (w), 1623(w), 1506 (w), 1459 (m,νCH2 ), 1396 (m),
X‐ray Structure Determination
1076 (w), 755 (s).
A single‐crystal X‐ray diffraction study of 1 and 3 were conducted on
a Rigaku Sealed Tube CCD (Saturn 724+) diffractometer with
graphite‐monochromated Mo‐Kα radiation (λ = 0.71073 Å) at 173(2)
K. Cell parameters were obtained by global refinement of the
o
Aza‐16‐crown‐4 (2)20: Mp: 240‐244 C, 1H NMR (CDCl3, 500 MHz) δ
7.23‐7.19 (m, 8H), 6.84‐6.82 (d, J=10 Hz, 4H), 4.33 (s, 8H); 13CNMR
(DMSO‐d, 125 MHz) δ 146.76, 131.37, 128.66, 124.34, 116.34,
113.40, 65.38, 46.58. ESI‐MS: [M+1]/z = 421.2; FT‐IR (KBr, cm‐1):
positions of all collected reflections (Table S1, see SI). Intensities
3250 (m, vNH), 3040 (w), 2966 (w), 2849 (w), 1617 (s), 1567 (s, νCH2),
1508 (s), 1450 (s), 1333 (w), 1299 (w), 905 (w), 880 (w), 805 (w), 739
(m).
were corrected for Lorentz and polarization effects and empirical
absorption. The structures were solved by direct methods and
refined by full‐matrix least squares on F2. All non‐hydrogen atoms
were refined anisotropically and all hydrogen atoms were placed in
calculated positions. Using the SHELXL‐2015 package, structural
o
1
Aza‐20‐crown‐5 (3): Mp: 217‐219 C, H NMR (CDCl3, 500 MHz) δ
7.13‐7.10 (m, 10H), 6.74‐6.69 (m, 10H), 4.92 (s, 5H, NH), 4.06 (s,
10H); 13CNMR (DMSO‐d, 125 MHz) δ 146.76, 131.37, 128.66, 124.34, solution and refinement were performed.23
116.34, 113.40, 65.38, 46.58; ESI‐MS: [M+1]/z = 526.3; FT‐IR (KBr,
cm‐1): 3396 (m), 3308 (s, vNH), 2854 (m), 1608 (m), 1586 (m), 1562 (s,
Conflicts of interest
νCH2), 1506 (w), 1455 (w), 1331 (w), 1309 (w), 1250 (w), 1125 (w),
1044 (w), 743 (s).
The authors declare no competing financial interest.
Synthesis of iron(Ⅲ) complexes (Fe1 ‐ Fe3)
Synthesis of Fe1
A small Schlenk tube, equipped with a stir bar, was evacuated and
Acknowledgements
back‐filled with nitrogen. Under an atmosphere of nitrogen, the We acknowledge the support from the National Natural Science
tube was charged with 1 (0.16 g, 0.5 mmol) in dichloromethane (15 Foundation of China (21871275), the Nature Science Foundation of
mL). Under N2, FeCl3•6H2O (0.13 g, 0.5 mmol) and ethanol (10 mL) Hebei Province (B2019205149) and Talent Introduction Foundation
were introduced to the tube and the reaction mixture stirred at of Hebei Agricultural University (YJ201931).
room temperature for 24 h. The resulting precipitate was filtered
and washed with ethanol (3 × 10 mL), then washed with
Notes and references
dichloromethane (3 × 10 mL). The titled complex Fe1 was obtained
as brown solid (0.12 g, 47%). FT‐IR (KBr, cm‐1): 3432 (m, vOH), 1602
(m, vNH), 1510 (m), 1454 (s, vCH2), 1301 (w), 1254 (m), 1045 (m, Fe‐
N), 751 (s), Anal. Calcd for Fe1 [C21N3H21FeCl3(H2O)4]: N, 7.64, C,
45.88, H, 5.31; Found: N, 7.66, C, 45.98, H, 5.28.
[1] (a) P. A. Gale, P. Anzenbacher, J. L. Sessler, Coord. Chem. Rev
2001, 222, 57‐102; (b) M. X. Wang, Acc Chem Res 2012, 45,
182‐195; (c) T. K. Khan, M. Bröring, S. Mathur, M. Ravikanth,
Coord. Chem. Rev 2013, 257, 2348‐2387; (d) A. Swidan, C. L.
Macdonald, Chem Soc Rev 2016, 45, 3883‐3915; (e) W. Liu, S. K.
Samanta, B. D. Smith, L. Isaacs, Chem Soc Rev 2017, 46, 2391‐
2403; (f) S. Peng, Q. He, G. I. Vargas‐Zúñiga, L. Qin, I. Hwang, S.
K. Kim, N. J. Heo, C. H. Lee, R. Dutta, J. L. Sessler, Chem Soc Rev
2020, 49, 865‐907.
[2] (a) C. J. Pedersen, Science 1988, 241, 536‐540; (b) Y. Han, Z.
Meng, Y. X. Ma, C. F. Chen, Acc Chem Res 2014, 47, 2026‐2040.
[3] (a) J.‐M. Lehn, Angew Chem. Int. Ed. Engl. 1988, 27, 89‐112; (b)
R. Ostaszewski, J. Jurczak, Tetrahedron 1997, 53, 7967‐7974; (c)
M. Ikeda, A. K. Sah, M. Iwase, R. Murashige, I. J. Ishi, M.
Hasegawa, C. Kachi‐Terajima, K.‐M. Park, S. Kuwahara, Y.
Habata, Dalton Trans 2017, 46, 3800‐3804; (d) Q. Wang, M.
Cheng, S. Xiong, X. Y. Hu, J. Jiang, L. Wang, Y. Pan, Chem
Commun 2015, 51, 2667‐2670.
[4] D. J. Cram, Angew Chem. Int. Ed. Engl. 1988, 27, 1009‐1020.
[5] (a) B. Scheiper, F. Glorius, A. Leitner, and A. Fürstner, PNAS,
2004, 101, 11960–11965; (b) M. M. Becker, B. J. Ravoo, Chem
Commun 2010, 46, 4369‐4371; (c) R. Iacovino, J. V. Caso, C. D.
Donato, G. Malgieri, M. Palmieri, L. Russo, C. Isernia, Curr Org
Chem.2017, 21, 162‐176.
[6] (a) J. Harrowfield, Chem Commun 2013, 49, 1578‐1580; (b) A.
Gorbunov, N. Sokolova, E. Kudryashova, V. Nenajdenko, V.
Kovalev, I. Vatsouro, Chem. Eur.J. 2016, 22, 12415‐12423.
[7] M. X. Wang, H. B. Yang, J Am Chem Soc 2004, 126, 15412‐
15422
Synthesis of Fe2.
By using the same procedure described for the synthesis of Fe1, Fe2
was obtained as a brown powder (0.12 g, 81%). FT‐IR (KBr, cm‐1):
3407 (m, vOH), 1609 (m, vNH), 1500 (m), 1452 (s, vCH2),1028 (s, Fe‐N),
754 (s); Anal. Calcd for Fe2 [C28N4H28Fe3Cl7(OH)2H2O]: N,6.30, C,
37.85, H, 3.63, Found: N, 6.25, C, 38.28, H, 3.58.
Synthesis of Fe3
By using the same procedure as that described for the synthesis of
Fe1, Fe3 was obtained as a brown powder (0.15 g, 84 %). FT‐IR (KBr,
cm‐1): 3423 (m,vOH), 1600 (m, vNH), 1494 (m), 1456 (s, vCH2), 1034 (s,
Fe‐N), 755 (m); Anal. Calcd for Fe3 [C35N5H35Fe3Cl8(OH)(H2O)2]: N,
6.80, C, 40.8, H, 3.91; Found: N, 6.57, C, 39.92, H, 4.10.
General procedure for the transfer hydrogenation of ketones
under nitrogen
Under a nitrogen atmosphere, the selected ketonic substrate (5.0
mmol) was dissolved in dry and degassed 2‐propanol (3 mL) under a
nitrogen atmosphere and the solution stirred and heated to 82 °C.
On reaching this temperature, a solution of base (5mmol) in 2‐
propanol (4 mL) was introduced followed by a solution of catalyst
(1‐10 μmol) in 2‐propanol (3 mL), taking the total volume of solvent
to 10 mL. At the specified reaction time (3 – 48 h), 0.1 mL of the
reaction mixture was sampled and immediately diluted with 0.5 mL
[8] (a) T. Hishiya, H. Asanuma, M. Komiyama, J Am Chem Soc 2002,
124, 570‐575; b) K. Jie, Y. Zhou, Y. Yao, F. Huang, Chem. Soc.
6 | J. Name., 2012, 00, 1‐3
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Please do not adjust margins
Journal Name
ARTICLE
Rev., 2015, 44, 3568‐3587.
[9] (a) Y. Li, S. Yu, X. Wu, J. Xiao, W. Shen, Z. Dong, J. Gao, J Am
Chem Soc 2014, 136, 4031‐4039; (b) A. Prevedello, I. Bazzan, N.
[15] A. M. Costero, M. L. Betancourt‐Mendiola, P. VGiewavAirñtiacl,e OLn.linEe.
Ochando, S. Gil, K. Chulvi, and E. Peña‐Cabrera, Eur. J. Org.
DOI: 10.1039/D0DT03257C
Chem. 2017, 6283–6290
Dalle Carbonare, A. Giuliani, S. Bhardwaj, C. Africh, C. Cepek, R. [16] B. Pan, B. Liu, E. Yue, Q. Liu, X. Yang, Z. Wang, W.-H. Sun,
Argazzi, M. Bonchio, S. Caramori, M. Robert, A. Sartorel, Chem.
Asian J. 2016, 11, 1281 – 1287; (c) N. Madhavan, T. Takatani, C. [17] A. Hoorfar, W. D. Ollis and J. F. Stoddart, J. Chem. Soc., Perkin
D. Sherrill, M. Weck, Chem. Eur. J. 2009, 15, 1186 – 1194; (d) C. Trans. 1, 1982, 1721‐1726.
D. Swor, D. R. Tyler, Coord. Chem. Rev. 2011, 255, 2860–2881; [18] For selected reviews, see (a) Q. Yang, Q. Wang, Z. Yu, Chem. Soc.
ACS Catal. 2016, 6, 1247-1253.
(e) S. U. Pandya, R. S. Dickins, D. Parker, Org. Biomol. Chem.,
2007, 5, 3842–3846;
[10] (a) D. Wei, C. Darcel, Chem Rev. 2019, 119, 2550‐2610; (b) Q.
Liang, D. Song, Chem Soc Rev 2020, 49, 1209‐1232.
[11] (a) S. Yu, W. Shen, Y. Li, Z. Dong, Y. Xu, Q. Li, J. Zhang, J. Gao, Adv.
Synth. Catal. 2012, 354, 818 – 822; (b) Y.‐Y. Li, S.‐L. Yu, W.‐
Y.Shen, J.‐X. Gao, Acc. Chem. Res. 2015, 48, 2587−2598.
[12] (a) R. Bigler, A. Mezzetti, Org Lett 2014, 16, 6460‐6463; (b) R.
Rev. 2015, 44, 2305 – 2329; (b) C. Gunanathan, D. Milstein,
Science 2013, 341, 249 – 260; (c) S. Michlik, R. Kempe, Nature
Chem. 2013, 5,140–144; (d) S. B. S. Imm, L. Neubert, M. Zhang,
H. Neumann, M. Beller, ChemCatChem 2011, 3, 1853 – 1864; (e)
A. J. A. Watson, J. M. J. Williams, Science 2010, 329, 635 – 636;
(f) G. Guillena, D. J. Ramýn, M. Yus, Chem. Rev. 2010, 110, 1611
– 1641; (g) G. E. Dobereiner, R. H. Crabtree, Chem. Rev. 2010,
110, 681 – 703.
Bigler, R. Huber, A. Mezzetti, Angew Chem Int Ed Engl 2015, 54, [19] Z. Wang, B. Pan, Q. Liu, E. Yue, G. A. Solan, Y. Ma, W.‐H. Sun,
5171‐5174; (c) A. Mezzetti, R. Bigler, R. Huber, Synlett 2016, 27, Catal. Sci. Technol., 2017, 7, 1654–1661.
831‐847; (d) A. Passera, A.Mezzetti, Angew. Chem. Int. Ed. 2020, [20] (a) J. S. Skuratowicz, I. L. Madden and D. H. Busch, Inorg. Chem.,
59, 187 –191.
2002, 16, 1721‐1725; (b) S. Schindler and D. J. Szalda, Inorg.
Chim. Acta, 1995, 228, 93‐101.
[13] For selected references, see: (a) P. O. Lagaditis, A. J. Lough, R. H.
Morris, J. Am. Chem. Soc. 2011, 133, 9662–9665; (b) A. A. [21] (a) A. Rajca, S. Rajca, S. R. Desai, J Am Chem Soc 1995, 117,
Mikhailine, M. I. Maishan, A. J. Lough, R. H. Morris, J. Am.
Chem. Soc. 2012, 134, 12266−12280; (c) R. H. Morris, Acc.
Chem. Res. 2015, 48, 1494−1502.
806‐816; (b) M. Yoshida, M. Goto, F. Nakanishi,
Organometallics 1999, 18, 1465‐1470.
[22] Z. C. Wu, Q. H. Guo, M. X. Wang, Angew Chem Int Ed Engl 2017,
56, 7151‐7155
[14] (a) R. M. Kohli, M. D. Burke, J. Tao, and C. T. Walsh, J Am Chem
Soc 2003, 125, 7160‐7161; (b) A. Grossmann, S. Bartlett, M. [23] (a) G. M. Sheldrick, Acta Cryst. 2015, A71, 3−8. (b) G. M.
Janecek, J. T. Hodgkinson, D. R. Spring, Angew. Chem. Int. Ed.
2014, 53, 13093 –13097.
Sheldrick, Acta Crystallogr., Sect. C: Struct. Chem. 2015, C71,
3−8.
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DOI: 10.1039/D0DT03257C
Graphical for Table of Contents
Aza‐crown Compounds by the Self‐condensation of 2‐Aminobenzyl alcohol over a
Pincer‐Ruthenium Catalyst and Applied in Transfer Hydrogenation of Ketones
Shanshan Zhang,a,# Zheng Wang,a,b,c,# Qianrong Cao,a,d,# Erlin Yue,b Qingbin Liu,a,*,Yanping Ma,b Tongling Liang,b and Wen‐Hua
Sunb,*
(#Shanshan Zhang, Zheng Wang, Qianrong Cao made an equal contribution in this work.)
aHebei Key Laboratory of Organic Functional Molecules, College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang
050024, China
bKey Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of
Sciences, Beijing 100190, China
c College of Science, Hebei Agricultural University, Baoding 071001, China
dHebei Research Institute of Microbiology, Baoding 071051, China
Three aza‐crown compounds are easily synthesized through the self‐condensation of 2‐aminobenzyl alcohol over a pincer‐ruthenium
catalyst, and applied in the efficient transfer hydrogenation of various ketones into secondary alcohols.
8 | J. Name., 2012, 00, 1‐3
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