Ru(II)-PBTNNXN complex bearing functional 2-(pyridin-2-yl)benzo[d]thiazole ligand catalyzed α-alkylation of nitriles with alcohols

Article abstract of DOI:10.1002/aoc.5451

Six tridentate NNN ligand precursors derived from 2-(pyridin-2-yl)benzo[d]thiazole(PBT) with different linkers, ^PBTNN^XN (X = NH, NMe, O, S) (1a–1f), have been successfully prepared. The electronic properties of ^PBTNN^XN ligands are well tunable by differing linkers between PBT skeleton and the pyridine ring, and/or by introducing electron-donating/withdrawing groups on the pyridine ring (R = OMe or F). The ligand precursors and representative complexes Ru (^PBTNN^NHN)Cl₂(PPh₃) (2a), Ru (^PBTNN^NMeN)Cl₂(PPh₃) (2b), and Ru (^PBTNN^SN)Cl₂(PPh₃) (2f) have been characterized by NMR spectroscopy, high-resolution mass spectroscopy, and Fourier transform infrared (FT-IR). The molecular structures of 1f, 2a, and 2f have been determined by X-ray diffraction study. The results indicate that ^PBTNN^NHN ligand in the complex presented coplanar with two five-membered chelating rings. It should be noted that 2a featuring a NH group exhibits superior performance compared to those with other linkers (such as NMe, O, or S). A variety of heterocyclic and aromatic nitriles with aromatic and aliphatic alcohols have been explored in α-alkylation for good to excellent yields. Based on kinetic experiments and mechanistic studies, a proposed mechanism was put forward. Ru-H species and benzaldehyde, which was oxidized from benzyl alcohol, were detected in the catalytic cycle.

Full text of DOI:10.1002/aoc.5451

Received: 21 September 2019
DOI: 10.1002/aoc.5451
Revised: 19 November 2019
Accepted: 26 November 2019
F U L L P A P E R
Ru(II)-PBTNNXN complex bearing functional 2-(pyridin-2-yl)
benzo[d]thiazole ligand catalyzed α-alkylation of nitriles
with alcohols
Shuang Huang1 | Xi Hong1 | Yong Sun2 | He-Zhen Cui1 | Quan Zhou1
Yue-Jian Lin1 | Xiu-Feng Hou1,2,3
|
1Department of Chemistry, Fudan
Six tridentate NNN ligand precursors derived from 2-(pyridin-2-yl)benzo[d]
thiazole(PBT) with different linkers, PBTNNXN (X = NH, NMe, O, S) (1a–1f),
have been successfully prepared. The electronic properties of PBTNNXN ligands
are well tunable by differing linkers between PBT skeleton and the pyridine
ring, and/or by introducing electron-donating/withdrawing groups on the pyri-
dine ring (R = OMe or F). The ligand precursors and representative complexes
Ru (PBTNNNHN)Cl2(PPh3) (2a), Ru (PBTNNNMeN)Cl2(PPh3) (2b), and Ru
University Jiangwan campus, 2005
Songhu Rd, Shanghai, 200438, China
2Key laboratory of toxicology, Ningde
Normal University, Ningde, 352000,
China
3Key Laboratory for Green Processing of
Chemical Engineering of Xinjiang
Bingtuan, Shihezi, 832003, China
(
PBTNNSN)Cl2(PPh3) (2f) have been characterized by NMR spectroscopy, high-
Correspondence
Xiu-Feng Hou, Department of Chemistry,
Fudan University Jiangwan campus, 2005
Songhu Rd. Shanghai 200438, China.
Email: xfhou@fudan.edu.cn
resolution mass spectroscopy, and Fourier transform infrared (FT-IR). The
molecular structures of 1f, 2a, and 2f have been determined by X-ray diffrac-
tion study. The results indicate that PBTNNNHN ligand in the complex pres-
ented coplanar with two five-membered chelating rings. It should be noted
that 2a featuring a NH group exhibits superior performance compared to those
with other linkers (such as NMe, O, or S). A variety of heterocyclic and
aromatic nitriles with aromatic and aliphatic alcohols have been explored in
α-alkylation for good to excellent yields. Based on kinetic experiments and
mechanistic studies, a proposed mechanism was put forward. Ru-H species
and benzaldehyde, which was oxidized from benzyl alcohol, were detected in
the catalytic cycle.
Funding information
Shanxi Science and Technology
Department, China; National Key R&D
Program of China, Grant/Award Number:
2018YFF0215400
K E Y W O R D S
2-(pyridin-2-yl)benzo[d]thiazole (PBT), α-alkylation, alcoholsnitrilesRu (II) complex
1 | INTRODUCTION
one of the most attractive and atom-economic transfor-
mation, with only water as a byproduct.[5,6]
α-Alkylated nitriles represent important structural scaf-
fold applied in versatile biomacromolecules, fine
chemicals, and carboxylic acid derivatives.[1–3] Conven-
tional synthesis of α-alkylated nitriles with hazardous
alkyl halides and strong bases often suffers from generat-
ing environmentally unfriendly byproducts.[4] Later,
alkylation of nitriles via borrowing hydrogen strategy
with alcohol as alkylation agent, has been developed as
Since 1981, when Grigg and co-workers first used
RuH2(PPh3)4 as a catalyst in the alkylation of nitriles
with alcohol,[7] a lot of effort has been devoted to explor-
ing various catalysts, including Ru,[8–15] Rh,[16,17] Ir,[18–22]
Pd,[23] Os,[24] Fe,[25] and Mn[26]. Of these, Ru complexes
are the most reported, for example Gunanathan's group
reported that Ru(PNP) (PNP
=
bis(2-(diph-
enylphosphino)-ethyl)amine) pincer complex showed
Appl Organometal Chem. 2020;e5451.
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© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5451

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HUANG ET AL.
good activity for α-alkylated reaction of arylmethyl
nitriles.[13] Kundu and co-workers demonstrated that Ru
complexes bearing N6,N60-dimethyl-2,2’-bipyridine-6,6’-
diamine ligand efficiently catalyzed α-alkylation of
arylacetonitriles with alcohols.[14] Recently, Ru catalyst
based on tridentate bipyridyl imidazoline catalyzed anal-
ogous reaction was reported by Song et al.[15]
2 | RESULTS AND DISCUSSION
2.1 | Synthesis of PBTNNXN (X = NH,
NMe, O, S) ligands
Our study started with the synthesis of ligands.
First,
6-(benzo[d]thiazol-2-yl)pyridin-2-amine
and
Metal–ligand cooperation (MLC)[27–32] plays an
important role in catalysis. It can dramatically promote
the catalytic activity applied in borrowing hydrogen catal-
ysis using ligands containing functional groups such as
NH[33–37] and OH[38–40]. Among them, NNN ligands[41–43]
bearing NH[44,45] coordinated with Ru metal could be
potential chelating ligands due to their synthetic accessi-
bility and excellent air- and moisture-stability compared
to phosphine ligands.
2-(6-fluoropyridin-2-yl)benzo[d]thiazole were prepared as
previously described[57] by the direct arylation of ben-
zothiazole with 2-amino-6-bromopyridine and 2-bromo-
6-fluoropyridine, respectively, as shown in Scheme 1.
Then the ligands 1a, 1c, and 1d were obtained by the
Buchwald method of Pd-catalyzed C-N bond formation.[58]
6-(Benzo[d]thiazol-2-yl)pyridin-2-amine
was
treated
with 2-bromopyridine, 2-bromo-6-methoxypyridine, and
2-bromo-6-fluoropyridine, respectively, in the presence
of Pd (II) and 1,3-bis (diphenylphosphino)propane
(DPPP) as catalyst to deliver the corresponding targeted
products 1a, 1c, and 1d in good yield.
Recently, our group explored the use of
benzothiazole/benzoxazole
derivatives.[46–49] Based on our research, we predicted that
2-(pyridin-2-yl)benzo[d]thiazole (PBT)-pyridine
PBTNNXN) ligands would be good candidates for the
and/or
benzimidazole
1
In the H NMR spectra, the protons of N-H linker of
(
ligands 1a, 1c, and 1d display signals at δ = 10.00, 7.40,
and 10.21 ppm, respectively (Supporting Information). It
is worth noting that the H signal observed from the NH
group in 1c with methoxy substituted on the pyridine
ring obviously occurred much further upfield, while the
proton signal observed in the fluorine-substituted ana-
logue of 1d was slightly downfield shifted from that of
1a. This illustrates that the electronic effect can be
adjusted by changing the electron-donating/withdrawing
groups on the pyridine ring of ligands. When the hydro-
gen atom on the NH moiety of 1a was replaced with
methyl by reacting with iodomethane (CH3I), 1b with
α-alkylation of nitriles with alcohols. They possess planar
geometry and an aromatic configuration with a large con-
jugated system. This has potential benefits for electronic
transfer, which is important for metal–ligand coopera-
tion.[27,28] The color-tuning of iridium complexes bearing
2-phenylbenzothiazole ligands has been achieved by
changing the chromophore and/or groups on the ben-
zothiazole moiety and/or phenyl ring, implying their prior
properties for easy structural modification and tuneable
electronic effect.[50–53] The catalytic activity for Suzuki
cross-coupling of Pd (SCN) pincer complexes supported by
thiophosphoryl-benzothiazole ligand is deeply influenced
by the attached substituent group, suggesting that they
could adjust catalytic reactivity.[54] Importantly, we have
developed cyclometalated ABON,P and ABON,C(carbene) che-
lated iridium-based complexes (ABO = 2-arylbenzo[d]
oxazole), which exhibit superior catalytic performance in
the α-alkylation of ketones, alcohols, and amines with pri-
mary alcohols[55] and the N-methylation of aromatic
amines with methanol,[56] respectively.
From this work, we became interested in developing
a new type of Ru catalyst based on 2-(pyridin-2-yl)
benzo[d]thiazole (PBT)-pyridine ligands (PBTNNXN). The
tuneable electronic properties of PBTNNXN ligands can be
achieved by the different linkers (such as NH, NMe, O,
and S) between the 2-(pyridin-2-yl)benzo[d]thiazole skel-
eton and the pyridine ring, and/or by introducing
electron-donating/withdrawing groups on pyridine ring
(R = OMe or F). This new kind of catalyst was applied in
the α-alkylation of nitriles and alcohols. It indicated that
the Ru (PBTNNNHN)Cl2(PPh3) complex featuring NH
linker exhibited excellent catalytic activity.
1
NMe linker was obtained. In the H NMR spectrum, 1b
shows one singlet for the methyl group at 3.74 ppm and
the resonance signal of NH group obviously disappears.
These results indicated the ligands 1a–1d were formed.
The ligands 1e and 1f, containing O and S linkers,
were synthesized by nucleophilic aromatic substitution
(SNAr) following our group's previous report.[47]
2-(6-Fluoropyridin-2-yl)benzo[d]thiazole reacted with
2-hydroxypyridine and 2-mercaptopyridine, respectively,
gave 1e and 1f in ca. 75 and 86% yield. The ligands were
characterized by 1H and 13C NMR spectra and high-
resolution mass spectrometry (HRMS). Fortunately, sin-
gle crystals of 1f for X-ray diffraction analysis were
obtained in n-hexane/dichloromethane. The molecular
structure is shown in Figure 1 and selected bond lengths
and angles are listed in Table 1. The benzothiazole and
pyridine ring of PBT are almost coplanar with a small
dihedral angle of 5.34ꢀ. Although the torsion angle of the
two pyridine rings is 75.88ꢀ, the PBTNNSN ligand is non-
coplanar, which benefits for the chelating coordination of
the ligand precursor with the metal centre.

HUANG ET AL.
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SCHEME 1 Synthesis of
PBTNNXN (X = NH, NMe, O, S)
ligands. [Pd] = Pd (OAc)2,
[Cu] = Cu (OAc)2ꢁH2O,
DPPP = 1,3-bis
(diphenylphosphino)propane
SCHEME 2 Synthesis of Ru (PBTNNXN)Cl2(PPh3) (X = NH,
NMe, S) complexes
1b and 1f with RuCl2(PPh3)3 in refluxing toluene for
0.5 hr yielded the corresponding complexes
Ru(PBTNNNHN)Cl2(PPh3) (2a), Ru(PBTNNNMeN)Cl2(PPh3)
(2b), and Ru(PBTNNSN)Cl2(PPh3) (2f). All these com-
plexes are stable.
The 31P NMR signals of 2a in dimethyl sulfoxide
(DMSO)-d6, and 2b and 2f in CDCl3 appear at 31.40,
46.03, and 42.18 ppm, respectively, which is similar to
the spectroscopic features of the Ru(II)-NNXN complexes
reported previously.[15,59] The 1H NMR chemical shifts of
2a reveal a multiplet peak at 9.73 ppm for the NH moiety,
which slightly shifts upfield 0.27 ppm from the ligand 1a
(δNH 10.00 ppm). The CH3 resonance of the NMe linker
in 2b appears at 5.30 ppm, a downfield shift of 1.56 ppm
in comparison to 1b. Complex 2a was further identified
by X-ray crystallography. It was grown from DMSO lay-
ered with anhydrous ether. As can be seen from Figure 2
and Table 2, 2a is converted to cation 2aꢁDMSO with a
Cl− as anion, which was coordinated with the Ru metal
center through sulfur atom of DMSO, which occurs easily
according to previous literature.[60] Cl− was lost from the
ruthenium atom. It formed a more stable cationic com-
pound 2aꢁDMSO with a weak coordinating anion Cl−. It
also adopts distorted-octahedral geometry surrounded by
FIGURE 1 Molecular structure of 1f. Thermal ellipsoids
shown at the 50% probability level. Hydrogen atoms and solvent
molecules are omitted for clarity
TABLE 1 Selected bond lengths and angles for ligand 1f
Bond length
(Å)
Bond angle
(ꢀ)
Bond
Bond
N(1)-C(7)
S(1)-C(7)
C(7)-C(8)
S(2)-C(12)
1.294(2)
C(13)-S(2)-C(12) 102.77(7)
1.7426(15)
1.471(2)
C(12)-N(2)-C(8)
C(8)-C(7)-S(1)
N(2)-C(8)-C(7)
N(3)-C(13)-S(2)
116.84(14)
119.09(11)
115.57(14)
121.84(12)
1.7877(17)
N(3)-C(13) 1.365(2)
a
PBTNNNHN ligand, triphenyl phosphine (PPh3), a Cl
2.2 | Synthesis of Ru(PBTNNXN)Cl2(PPh3)
(X = NH, NMe, S) complexes
atom, and a DMSO molecule. PBTNNNHN ligand coordi-
nates with the Ru atom via benzothiazolyl and bipyridyl
N atoms. The angles of N-Ru-P are close to right angles,
showing that PPh3 is situated trans to DMSO. The Ru-N
bond length is in the range of 2.04–2.13 Å. The
PBTNNNHN ligand in the 2aꢁDMSO is essentially coplanar
To further explore the properties of Ru complexes, three
representative compounds, 2a, 2b, and 2f, were synthe-
sized as shown in Scheme 2. Equivalent reaction of 1a,

4 of 13
HUANG ET AL.
FIGURE 3 Molecular structure of 2f. Thermal ellipsoids
shown at the 50% probability level. Hydrogen atoms and solvent
molecules are omitted for clarity
FIGURE 2 Molecular structure of 2aꢁDMSO. Thermal
ellipsoids shown at the 50% probability level. Hydrogen atoms, Cl-
counterion ion and solvent molecules are omitted for clarity
TABLE 3 Selected bond lengths and angles for complex 2f
Bond length
(Å)
Bond angle
(ꢀ)
TABLE 2 Selected bond lengths and angles for complex
2aꢁDMSO
Bond
Bond
N(1)-C(7)
S(1)-C(7)
S(2)-C(12)
1.323(2)
N(2)-Ru(1)-N(1)
N(2)-Ru(1)-N(3)
79.44(6)
92.58(6)
Bond length
(Å)
Bond angle
(ꢀ)
1.7243(18)
1.7692(19)
Bond
Bond
N(2)-Ru(1)-Cl(2) 85.89(4)
Ru(1)-N(2)
Ru(1)-N(4)
Ru(1)-N(1)
Ru(1)-S(2)
Ru(1)-P(1)
2.041(3)
2.109(3)
2.127(3)
2.3255(9)
2.3887(9)
N(2)-Ru(1)-N(4)
N(2)-Ru(1)-N(1)
91.77(11)
79.12(12)
Ru(1)-N(1) 2.0880(15)
Ru(1)-N(2) 2.0175(15)
Ru(1)-N(3) 2.1033(15)
N(2)-Ru(1)-P(1)
P(1)-Ru(1)-Cl(1)
95.10(4)
88.242(16)
N(4)-Ru(1)-N(1) 169.75(11)
N(2)-Ru(1)-S(2)
N(2)-Ru(1)-P(1)
N(4)-Ru(1)-P(1)
87.47(8)
90.48(8)
92.99(8)
2.3 | Catalytic activity for α-alkylation of
Ru(1)-Cl(1) 2.4339(9)
nitriles
with the two adjacent five-membered Ru-N-C-C-N che-
late rings.[61] This coplanar structure could be essential
for efficient π conjugation between a lone pair of the NH
linker and the PBT backbone. The resulting conjugated
system could confer fast electronic transfer, which helps
the reaction rate.[62]
Good-quality single crystals of 2f were recrystallized
from n-hexane/dichloromethane and characterized by
X-ray crystallography (Figure 3 and Table 3). The com-
plex shows typical distorted-octahedral geometry with
the ruthenium center coordinated by PBTNNSN and PPh3
as well as two chloride ligands. There is little change of
N-C, S-C bonds lengths in the benzothiazole and pyridine
rings compared to 1f. Due to coordination with the Ru
metal center, the dihedral angle of the two pyridine rings
decreases to 51.86ꢀ compared to 1f.
Next we investigated the catalytic activity of the Ru com-
plexes for α-alkylation of nitriles with alcohols. First, the
reaction of benzyl cyanide with benzyl alcohol was taken
as a benchmark reaction in the presence of KOtBu in tol-
uene at 135 ꢀC under nitrogen atmosphere (N2) for 0.5 hr
(Table 4).
Initially, 1 mol% of RuCl2(PPh3)3 with PBTNNXN
(X = NH, NMe, O, S) ligands 1a–1f as precatalyst in the
presence of 10 mol% KOtBu as base was used, providing
the desired product 2,3-diphenylpropanenitrile (A)
together with 2,3- diphenylacrylonitrile (B) as byproduct.
The result shows that using RuCl2(PPh3)3 with 1a
(X = NH) as catalyst affords A in 80% yield and B in 15%
yield (Table 4, entry 1). The catalytic activity of 1b
(X = NMe) was much lower than that of 1a, which clearly
emphasizes the performance of the acidic NH moiety in

HUANG ET AL.
5 of 13
TABLE 4 Optimization of Ru-catalyzed α-alkylation of nitrilea
Entry
1
Cat.
Base
Yield of A (%)b
Yield of B (%)b
1a + RuCl2(PPh3)3
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
NaOtBu
Cs2CO3
NaHCO3
KOH
80
82
49
51
65
59
43
45
35
14
37
26
54
0
17
16
33
34
21
24
29
33
32
77
53
69
36
0
2
2a
3
1b + RuCl2(PPh3)3
4
2b
5
1c + RuCl2(PPh3)3
6
1d + RuCl2(PPh3)3
7
1e + RuCl2(PPh3)3
8
1f + RuCl2(PPh3)3
9
2f
10
11
12
13
14
15c
16d
17e
18f
2a
2a
2a
2a
2a
2a
2a
2a
2a
K3PO3
KOtBu
KOtBu
KOtBu
KOtBu
10
5
78
82
22
0
53
>99
aReaction conditions: benzyl cyanide (1 mmol), benzyl alcohol (2 mmol), cat. (1 mol%), base (10 mol%), toluene (1 ml), N2, 135 ꢀC, 0.5 hr.
bWith 1,3,5 trimethoxybenzene as the internal standard.
cKOtBu (5 mol%).
dKOtBu (1.0 equiv).
dHeated at 125 ꢀC.
e1 hr.
catalytic activity enhancement[63] (Table 4, entry 3). It
should be noted that the activity of PBTNNNHN ligand
with electron-donating methoxy on the pyridine ring was
better than that of the electron-withdrawing fluoro sub-
stituent (Table 4, entries 5 and 6). When the reactions
with 1e (X = O) and 1f (X = S) were performed, 1e was
formed selectively in 34% yield (Table 4, entry 7) and 1f
produced a mixture of A and B in 45% and 33% yields,
respectively (Table 4, entry 8). The result further proves
the better reactivity of 1a containing NH linker than O or
S linkers. Similar product distribution could be achieved
under the catalysis of complexes 2a, 2b, and 2f to that of
the reactions catalyzed by RuCl2(PPh3)3 with 1a, 1b, and
1f as precatalyst (Table 4, entries 2, 4, and 9), indicating
that Ru(PBTNNXN) Cl2(PPh3) complex generated in situ
could be applied in the reaction of α-alkylation of nitrile
with alcohol. Other different bases, such as NaOtBu,
Cs2CO3, NaHCO3, KOH, and K3PO3, were then examined
(Table 4, entries 10–14). They rendered the reaction less
active than with KOtBu. Decreasing or increasing the
amount of KOtBu lowered the yields of desired product to
10% and 5%, respectively (Table 4, entries 15 and 16).
ꢀ
When the temperature was reduced 125 C, products of
A and B were obtained in 53% and 22% yields, respec-
tively (Table 4, entry 17). Finally, when the reaction time
with 2a was lengthened to 1 h, nearly quantitative yield
(99%) was obtained (Table 4, entry 18).
With the optimal reaction conditions known, we
explored the scope of substrates using 1 mol% of 2a as
catalyst and 10 mol% of KOtBu in toluene (1 ml) at
135 ꢀC under N2 atmosphere for 1 hr (Table 5).
In general, methyl (-Me) and methoxy (-OMe)
substituted nitriles reacted well with benzyl alcohol and
provided the corresponding alkylated products a1–a3 in

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HUANG ET AL.
excellent yields. Almost no effect on the reactivity was
observed by introducing an electron-withdrawing group
such as fluorine, chlorine, bromine, or iodine in the para-
or ortho- position of aromatic acetonitriles, and excellent
yields were obtained (a4–a8). Of these, interestingly,
2-fluorophenylacetonitrile was also well tolerated in 85%
yield by extending the reaction time (a5). A range of aro-
matic alcohols was further investigated. Moderate to high
yields for the reaction with benzyl cyanide were also
obtained for the 4-Me, 2-Me, 3,4-dimethyl, 4-OMe, and
3-Cl substituted alcohols derivatives (b1–b5). Gratify-
ingly, 2-naphthalenemethanol with benzyl cyanide and
1-naphthylacetonitrile with benzyl alcohol reacted
smoothly and the corresponding products c and d were
isolated in 73% and 87% yields, respectively. Heterocyclic
alcohols such as furfuryl alcohol and 2-(hydroxymethyl)
thiophene were efficiently transformed into desired prod-
ucts e1 and e2. Surprisingly, the highly challenging
nonactivated aliphatic alcohols were subjected to cataly-
sis. A variety of linear and nonlinear alcohols such as
ethyl alcohol, n-butanol, i-butanol, 1-pentanol, and
prolonged reaction time, providing moderate to high
yields (f1–f5). When 1,5-pentanediol smoothly reacted
with benzyl alcohol, the mono-substituted product g was
generated in moderate yield (52%) under optimal condi-
tions, while the dialkylated product 2,8-diphenylnonane-
dinitrile (h) was isolated in 41% yield. The raw materials
were almost completely converted. However, attempts to
react acetonitrile and n-butyronitrile with benzyl alcohol
were unsuccessful. Overall, Ru(PBTNNNHN)Cl2(PPh3)
showed excellent catalytic performance in catalysis of
α-alkylation of nitriles with alcohols.
2.4 | Kinetic experiments
To understand the reaction mechanism for α-alkylation
of nitriles catalyzed by 2a, kinetic profiles were recorded
1
under the optimal reaction conditions by H NMR. As
shown in Figure 4, both A and B were formed at the
beginning of the reaction in 10 min. A exhibited a signifi-
cantly increased initial reaction rate (initial turnover
frequency (TOF) = 222 hr−1) compared to B (initial
1-hexanol were also successfully converted in
a
TABLE 5 Scope of α-alkylation of nitriles with alcohols catalyzed by 2aa,b
aReaction conditions: nitriles (1 mmol), alcohols (2 mmol), 2a (1 mol%), KOtBu (10 mol%), toluene (1 ml), 135 ꢀC, N2, 1 hr.
bIsolated yield.
c2 hr.

HUANG ET AL.
7 of 13
TOF = 69 hr−1) in 20 min. A continued gradually produc-
ing and B began to decline after 1 hr. This result indicates
that generation of A and reduction of B occur simulta-
neously. Desired product A for nearly 99% yield were
almost completely formed within 1 hr, while B completely
disappeared in solution. We speculate that the superior
performance of 2a can be attributed to the coplanar
PBTNNNHN ligand with a large conjugated system in com-
parison with other reported Ru complexes.[13–15]
reaction. To further explore the reaction mechanism,
controlled experiments were carried out with 2a.
When the reaction occurred under an oxygen (O2)
atmosphere, no targeted product
A was detected
(Scheme 3a). The olefin product B was obtained in 99%
yield, indicating that the presence of O2 inhibits the for-
mation of alkylated product. On replacing benzyl alcohol
with benzaldehyde, benzyl cyanide reacted with benzal-
dehyde under optimal conditions to form B (97%),
whereas less than 3% yield of
A was detected
(Scheme 3b). When B and benzyl alcohol were reacted,
95% yield of A was generated (Scheme 3c), illustrating
that B is reduced to A when using benzyl alcohol as the
hydrogen source. These results suggest that the olefin
product B is the unsaturated intermediate for the
α-alkylated product A under N2.
2.5 | Mechanistic investigation
These results show that precursors containing the NH
moiety have much better catalytic activity than NMe, O
or S linkers (Table 4, entry 1–8) for the α-alkylation
FIGURE 4 Kinetic profiles
SCHEME 3 Mechanistic experiments

8 of 13
HUANG ET AL.
2.6 | Proposed mechanism
triplet was observed at δ −10.05 ppm, indicating the for-
mation of an Ru-H species.[64–66] Unfortunately, we failed
to isolate the Ru-H species from the system. A signal for
benzaldehyde was detected at δ 10.03 ppm. When 2a was
reacted with benzyl cyanide under the same conditions
as above, the Ru-H signal was not observed. This shows
that 2a reacts with the benzyl alcohol rather than benzyl
cyanide in the mixture. The benzaldehyde released and
Ru-H active species were formed. Vinyl nitrile intermedi-
ate was formed from benzaldehyde and benzyl cyanide,
which can undergo insertion into Ru-H on reaction with
Ru dihydride intermediate III to generate the intermedi-
ate IV. Further elimination of Ru-alkyl ligand and a
ligand backbone N-H proton can provide the α-alkylated
nitrile product and regenerate the intermediate I. Further
research into this mechanism is under way in our
laboratory.
On the basis of the above experimental results and previ-
ous reports,[13,15,26] a possible mechanism has been pro-
posed, as shown in Scheme 4. Through metal–ligand
cooperation,[27–32] the dearomatization/rearomatization
process can be achieved via deprotonation/reprotonation
of the NH linker. Since 2a containing the NH linker is
acidic, deprotonation occurs in the presence of base,
which leads to dearomatization of the pyridine ring. We
therefore speculated that the catalytic cycle is initiated by
the formation of intermediate I, from dechlorination and
deprotonation on reaction with KOtBu. This may explain
why 2a bearing an NH moiety dramatically improves the
catalytic performance compared to NMe, O or S linkers.
Regrettably, although we tried to obtain the intermediate
I, we failed. An active Ru-methoxy complex II was gener-
ated in the presence of benzyl alcohol. Complex II on
β-hydride abstraction generates the Ru-H species III,
releasing the transient benzaldehyde intermediate. To
detect the formation of any Ru-H species, the reaction of
2a with benzyl alcohol in the presence of KOtBu was car-
ried out under optimal reaction conditions. After remov-
ing solvent, the mixture was characterized by 1H NMR. A
3 | CONCLUSIONS
In summary, we have developed six PBTNNXN ligands,
including four kinds of linkers (X = NH, NCH3, O, S),
and have introduced electron-donating/withdrawing
groups on the pyridine ring (R = OMe or F) to adjust
electronic effect. Three Ru(PBTNNXN)Cl2(PPh3) com-
plexes,
Ru(PBTNNNHN)Cl2(PPh3),
Ru(PBTNNNMeN)
Cl2(PPh3), and Ru(PBTNNSN)Cl2(PPh3), bearing PBT -
pyridine ligands, were successfully prepared. The ben-
zothiazole and adjacent pyridine ring of PBT in the
ligand were determined to be coplanar by X-ray crystal-
lography. Importantly, the PBTNNNHN ligand in the com-
plex also presented as coplanar with two five-membered
chelate rings. In the α-alkylation of nitrile with alcohol,
Ru(PBTNNXN)Cl2(PPh3) complexes could be generated in
situ by the PBTNNXN ligands and RuCl2(PPh3)3. It was
found that Ru(PBTNNNHN)Cl2(PPh3) containing NH func-
tionality exhibited excellent catalytic activity in the α-
alkylation of nitriles and alcohols with yields of up to
98%. A large variety of nitriles with aromatic and ali-
phatic alcohols were converted into α- alkylated products
with high efficiency. Kinetic experiments and mechanis-
tic studies suggested the presence of O2 would inhibit the
formation of alkylated product A. Olefin byproduct B as
an unsaturated intermediate is reduced by benzyl alco-
hol. And benzyl alcohol is as hydrogen source. The mech-
anism of Ru(PBTNNNHN)Cl2(PPh3)-catalyzed α-alkylation
of nitriles with alcohols has been proposed. Benzyl alco-
hol is oxidized to benzaldehyde. The Ru-H species
formed in the catalytic cycle was confirmed by NMR.
Further mechanistic research and applications of this
newly developed type of Ru catalyst are ongoing in our
laboratory.
SCHEME 4 Proposed mechanism

HUANG ET AL.
9 of 13
4 | EXPERIMENTAL SECTION
4.1 | General procedures
4.2 | Synthesis of 1a–1f
The preparation of PBTNNXN (X = NH, NMe, O, S)
ligands 1a–1f started with synthesis of 6-(benzo[d]
thiazol-2-yl)pyridin-2-amine and 2-(6-fluoropyridin-2-yl)
benzo[d]thiazole, according to the reference.[57] The
reaction mixture of benzothiazole (2.0 mmol,
270.38 mg), 6-bromopyridin-2-amine or 2-bromo-
6-fluoropyridine (2.2 mmol), Pd (OAc)2 (1.0 mol%,
13.47 mg), Cu (OAc)2ꢁH2O (20 mol%, 79.84 mg), PPh3
(0.5 equiv, 262.2 mg), and K2CO3 (2.0 equiv, 552.8 mg)
in toluene (5 ml) was refluxed for 10 hr in air. The mix-
ture was filtered and the filtrate was evaporated under
reduced pressure. The residue was purified by silica gel
column chromatography to obtain the corresponding
product.
All commercially available compounds (Acros, Aldrich,
Fluka, Merck, etc.) (from China or other countries) were
used without purification. Dry solvents (such as dic-
hloromethane) were collected from the solvent dispenser
system. All reaction vials were purchased from Beijing
Synthware Glass (Changping district, Beijing, China).
Analytical thin layer chromatography was performed on
GF 254 plates. Flash chromatography was performed on
silica gel (200–300 mesh) by standard technical eluting
with solvents as indicated. Reaction temperatures are
reported as the temperature of the bath surrounding the
vessel unless otherwise stated. All starting materials for
substrates synthesis were purchased from Energy Chemi-
cal, Macklin, Aladdin (Shanghai city, China) and used as
1
received unless otherwise stated. H and 13C NMR spec-
4.2.1 | 6-(benzo[d]thiazol-2-yl)pyridin-
tra were recorded on a Bruker Avance III 400 MHz NMR
spectrometer (Germany) at 295 K in CDCl3 or DMSO-d6.
HRMS (electron spray ionization ESI) analyses were per-
formed at the EPSRC UK National Mass Spectrometry
Facility, Swansea, UK. GC-MS analysis was conducted on
an HP 5973 GCD system using a HP5MS column
(30 m × 0.25 mm). Compounds described in the literature
2-amine
79% isolated yield (white solid): 1H NMR (400 MHz,
DMSO): δ 8.12 (d, J = 7.9 Hz, 1H), 8.04 (d, J = 8.1 Hz,
1H), 7.55 (dt, J = 19.2, 7.6 Hz, 2H), 7.46 (dd, J = 13.9,
7.2 Hz, 2H), 6.62 (d, J = 8.2 Hz, 1H), 6.34 (s, 2H) ppm;
13C NMR (101 MHz, DMSO): δ 170.53 (s), 160.07 (s),
154.21 (s), 148.80 (s), 138.54 (s), 135.73 (s), 126.77 (s),
125.85 (s), 123.39 (s), 122.79 (s), 111.36 (s), 108.91
(s) ppm. HRMS (ESI) calcd for C12H9N3S [M + H+]
228.0595, found 228.0573.
1
were characterized by comparison of their H and/or 13C
NMR spectra to the previously reported data. Fourier
transform infrared (FT-IR) spectra were performed on a
Nicolet AVATAR-360 IR using KBr discs in the range of
4000–400 cm−1
.
Single crystal X-ray diffraction data for compounds
1f, 2aꢁDMSO, and 2f were collected on a Bruker D8
VENTURE-MetalJet diffractometer equipped with a
PHOTON II area detector and HELIOS multilayer
4.2.2 | 2-(6-fluoropyridin-2-yl)benzo[d]
thiazole
optics
monochromated
Ga-K
alpha
radiation
81% isolated yield (light yellow solid): 1H NMR
(400 MHz, CDCl3): δ 8.27 (d, J = 7.4 Hz, 1H), 8.10
(d, J = 8.2 Hz, 1H), 7.95 (dd, J = 14.5, 7.6 Hz, 2H), 7.53 (t,
J = 7.7 Hz, 1H), 7.44 (t, J = 7.6 Hz, 1H), 7.04 (d,
J = 8.1 Hz, 1H) ppm; 13C NMR (101 MHz, CDCl3) δ
164.18 (s), 154.12 (s), 142.02 (s), 136.22 (s), 126.46 (s),
125.92 (s), 123.70 (s), 122.05 (s), 117.97 (d, J = 3.9 Hz),
111.45 (s), 111.08 (s) ppm; 19F NMR (376 MHz, CDCl3): δ
−66.55 (s) ppm. HRMS (ESI) calcd for C12H7FN2S
[M + H+] 231.0392, found 231.0387.
Preparation of 1a, 1c, and 1d was according to a
previous report.[58] A 25-ml Schlenk flask was charged
with 6-(benzo[d]thiazol-2-yl)pyridin-2-amine, and the
corresponding 2-bromopyridine derivatives (1.2 equiv),
Pd2(dba)3 (2 mol%), DPPP (4 mol%), sodium tert-butoxide
(1.4 equiv), and dry toluene (5 ml). Undꢀer nitrogen atmo-
sphere, the mixture was stirred at 110 C for 12 hr. The
mixture was cooled to room temperature then
(lambda
=
1.34138 Å). The data reduction was
performed using APEX III software. Structures were
solved by direct methods and refined by full-matrix least-
squares methods based on F2 using SHELXL-2014 soft-
ware. If not noted otherwise hydrogen atoms were posi-
tioned geometrically in idealized positions and refined
with isotropic displacement parameters as riding atoms.
If not noted otherwise all non-hydrogen atoms were
refined anisotropically. Geometrical calculations were
performed using SHELXL-2014 programs.[67] A summary
of the crystal data and parameters of 1f, 2aꢁDMSO, and
2f is given in Table 6.
CCDC 1934841 (1f), 1934842 (2aꢁDMSO), and
1934843 (2f) contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.

10 of 13
HUANG ET AL.
TABLE 6 X-ray crystallographic data for 1f, 2aꢁDMSO, and 2f
1f
2aꢁDMSO
C37H33Cl2N4OPRuS2
816.73
2f
Formula
Formula weight
Crystal system
Space group
a (Å)
C17H11N3S2
321.41
C37H30Cl6N3PRuS2
925.50
Triclinic
Orthorhombic
P212121
Monoclinic
P21/c
P-1
8.9410(3)
9.8758(5)
11.9590(6)
14.9888(8)
22.0606(11)
90
b (Å)
9.0739(4)
15.6264(9)
22.6357(13)
90
c (Å)
α (o)
β (o)
γ (o)
10.5558(4)
86.9670(18)
75.7466(19)
62.5396(19)
734.68(5)
90
101.6710(10)
90
90
V (Å3)
3493.2(3)
3872.6(3)
Z
2
4
4
ρ calcd (mgꢁmm−3
)
734.68(5)
1.553
1.587
μ (mm−1
)
2.149
0.805
5.851
F (000)
332
1664
1864
θ range (o)
4.790 to 59.375
−11 ≤h ≤10,
−11 ≤k ≤11,
−13 ≤l ≤13
9308
1.799 to 26.999
−10 ≤h ≤12,
−19≤k ≤19,
−28≤l ≤28
24807
4.168 to 57.999
−15≤h ≤15,
−18 ≤k ≤18,
−27≤l ≤27
57907
Index ranges
Reflections collected
Independent reflections
3230 (R [int] = 0.0279)
99.1%
7610 (R [int] = 0.0388)
99.5%
8183 (R [int] = 0.0342)
99.9%
Completeness to theta = 53.594ꢀ
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
0.752 and 0.647
3230/0/199
1.028
0.802 and 0.758
7610/0/439
1.020
0.805 and 0.627
8183/27/470
1.057
Final R indices (I > 2sigma(I))
R1 = 0.0376,
wR2 = 0.1145
R1 = 0.0410,
wR2 = 0.1192
0.406 and −0.322 e.Å−3
R1 = 0.0275,
wR2 = 0.0529
R1 = 0.0345,
wR2 = 0.0551
0.455 and −0.349 e.Å-3
R1 = 0.0252,
wR2 = 0.0620
R1 = 0.0262, wR2 = 0.0625
R indices (all data)
Largest diff. Peak and hole
0.792 and −0.819 e.Å−3
concentrated in vacuo and purified by flash column chro-
matography with petroleum ether/ethyl acetate to afford
the corresponding ligands.
7.01–6.93 (m, 1H) ppm; 13C NMR (101 MHz, DMSO): δ
169.80 (s), 154.70 (s), 154.26 (s), 148.33 (s), 148.11 (s),
139.24 (s), 138.23 (s), 135.70 (s), 127.00 (s), 126.20 (s),
123.61 (s), 122.95 (s), 119.11 (s), 117.09 (s), 114.83 (s),
112.56 (s), 112.24 (s) ppm. HRMS (ESI) calcd for
C17H12N4S [M + H+] 305.0861, found 305.0855.
4.2.3 | 1a: 6-(benzo[d]thiazol-2-yl)-N-
(pyridin-2-yl)pyridin-2-amine
83% isolated yield (white solid): 1H NMR (400 MHz,
DMSO): δ 10.00 (s, 1H), 8.29 (dd, J = 4.9, 1.1 Hz, 1H),
8.19 (d, J = 7.4 Hz, 1H), 8.14 (d, J = 8.4 Hz, 1H), 8.09 (d,
J = 7.8 Hz, 1H), 7.91–7.76 (m, 3H), 7.67 (dd, J = 8.0,
0.8 Hz, 1H), 7.61–7.53 (m, 1H), 7.53–7.44 (m, 1H),
4.2.4 | 1c:6-(benzo[d]thiazol-2-yl)-N-
(6-methoxypyridin-2-yl)pyridin-2-amine
80% isolated yield (white solid): 1H NMR (400 MHz,
CDCl3): δ 8.11 (d, J = 8.1 Hz, 1H), 7.98 (d, J = 7.9 Hz,

HUANG ET AL.
11 of 13
1H), 7.93 (d, J = 7.4 Hz, 1H), 7.74 (t, J = 7.8 Hz, 1H),
7.68–7.56 (m, 2H), 7.52 (t, J = 7.7 Hz, 1H), 7.42
(dd, J = 14.5, 6.6 Hz, 2H), 7.35–7.25 (m, 1H), 6.40
(d, J = 7.9 Hz, 1H), 3.96 (s, 3H) ppm; 13C NMR
(101 MHz, CDCl3): δ 169.70 (s), 163.14 (s), 154.38 (s),
153.55 (s), 151.62 (s), 149.23 (s), 140.50 (s), 138.50 (s),
136.05 (s), 126.22 (s), 125.49 (s), 123.56 (s), 121.91 (s),
113.35 (s), 113.14 (s), 103.16 (s), 102.40 (s), 53.51 (s) ppm.
HRMS (ESI) calcd for C18H14N4OS [M + H+] 335.0967,
found 335.0963.
2-(6-fluoropyridin-2-yl)benzo[d]thiazole
(1
mmol),
Cs2CO3 (652 mg, 2 mmol, 2.0 equiv), 2-hydroxypyridine
or pyridine-2-thiol (2 mmol), and dimethyl formamide
(DMF) (2 ml), and the tube was sealed with a glass stop-
ꢀ
per. The mixture was warmed over a 120 C oil bath for
12 hr. When completed, the reaction solution was diluted
with NH4Cl solution (20 ml) and extracted with ethyl
acetate (3 × 10 ml). The organic layer was separated,
dried with anhydrous sodium sulfate, filtered, concen-
trated, and purified by flash chromatography with petro-
leum ether/ethyl acetate to afford the product.
4.2.5 | 1d: 6-(benzo[d]thiazol-2-yl)-N-
(6-fluoropyridin-2-yl)pyridin-2-amine
4.2.7 | 1e: 2-(6-(pyridin-2-yloxy)pyridin-
2-yl)benzo[d]thiazole
85% isolated yield (white solid): 1H NMR (400 MHz,
DMSO) δ 10.25 (s, 1H), 8.18 (d, J = 7.8 Hz, 1H), 8.11
(dd, J = 10.9, 5.0 Hz, 2H), 7.98 (dd, J = 16.6, 8.2 Hz, 1H),
7.94–7.84 (m, 2H), 7.53 (dq, J = 15.9, 7.5 Hz, 3H), 6.67
(dd, J = 7.8, 2.2 Hz, 1H) ppm; 13C NMR (101 MHz,
DMSO) δ 169.60 (s), 163.17 (s), 160.83 (s), 154.24
(d, J = 11.8 Hz), 152.86 (d, J = 15.8 Hz), 148.43 (s), 143.70
(d, J = 7.8 Hz), 139.54 (s), 135.73 (s), 127.09 (s), 126.32
(s), 123.71 (s), 122.99 (s), 115.06 (s), 113.29 (s), 108.85 (s),
100.36 (s) ppm; 19F NMR (376 MHz, DMSO): δ −69.51
(s) ppm. HRMS (ESI) calcd for C17H11FN4S [M + H+]
323.0767, found 323.0789.
75% isolated yield (white solid): 1H NMR (400 MHz,
DMSO): δ 8.39 (d, J = 7.7 Hz, 1H), 8.27–8.10 (m, 3H),
8.07–7.95 (m, 2H), 7.60 (t, J = 7.7 Hz, 2H), 7.53
(t, J = 7.5 Hz, 1H), 6.59 (d, J = 9.2 Hz, 1H), 6.48
(t, J = 6.7 Hz, 1H) ppm; 13C NMR (101 MHz, DMSO) δ
168.08 (s), 161.61 (s), 154.17 (s), 152.18 (s), 150.432 (s),
141.79 (s), 140.39 (s), 137.27 (s), 135.89 (s), 127.01 (s),
126.70 (s), 124.14 (s), 123.94 (s), 123.13 (s), 121.49 (s),
120.39 (s), 106.71 (s) ppm. HRMS (ESI) calcd for
C17H11N3OS [M + H+] 306.0701, found 306.0796.
Preparation of 1b was as follows. To a 25-ml Schlenk
flask was added 1a (1 mmol), excess iodomethane
(CH3I), and acetonitrile (2 ml). The mixture was stirred
under 80 ꢀC over an oil bath for 8 h. The reaction
solution was then concentrated under vacuum and puri-
fied by flash column chromatography to afford the
product.
4.2.8 | 1f: 2-(6-(pyridin-2-ylthio)pyridin-
2-yl)benzo[d]thiazole
86% isolated yield (white solid): 1H NMR (400 MHz,
CDCl3): δ 8.63 (d, J = 4.5 Hz, 1H), 8.16 (d, J = 7.7 Hz,
1H), 8.07 (d, J = 8.1 Hz, 1H), 7.90 (d, J = 7.9 Hz, 1H),
7.72 (d, J = 4.0 Hz, 3H), 7.44 (ddd, J = 23.4, 15.2,
7.5 Hz, 3H), 7.27 (d, J = 4.1 Hz, 1H) ppm; 13C NMR
(101 MHz, CDCl3) δ 168.80 (s), 157.63 (s), 155.26 (s),
154.17 (s), 151.42 (s), 150.25 (s), 137.62 (s), 137.06 (s),
136.22 (s), 127.66 (s), 126.21 (s), 125.63 (s), 123.56 (s),
122.39 (s), 121.90 (s), 117.95 (s) ppm. HRMS (ESI)
calcd for C17H11N3S2 [M + H+] 322.0473, found
322.0467.
4.2.6 | 1b:6-(benzo[d]thiazol-2-yl)-N-
methyl-N-(pyridin-2-yl)pyridin-2-amine
75% isolated yield (light yellow solid): 1H NMR
(400 MHz, CDCl3): δ 8.42 (d, J = 3.7 Hz, 1H), 8.09
(d, J = 8.1 Hz, 1H), 7.90 (dd, J = 12.7, 7.7 Hz, 2H), 7.63
(dd, J = 13.6, 6.9 Hz, 2H), 7.49 (t, J = 7.6 Hz, 1H), 7.37
(dd, J = 18.5, 8.1 Hz, 2H), 7.25 (d, J = 8.3 Hz, 1H),
7.01–6.91 (m, 1H), 3.74 (s, 3H) ppm; 13C NMR (101 MHz,
CDCl3): δ 170.34 (s), 157.34 (s), 156.82 (s), 154.38 (s),
149.12 (s), 148.18 (s), 137.90 (s), 137.29 (s), 136.17 (s),
126.06 (s), 125.32 (s), 123.41 (s), 121.83 (s), 117.93 (s),
115.79 (s), 114.41 (s), 112.72 (s), 35.92 (s) ppm. HRMS
(ESI) calcd for C18H14N4S [M + H+] 319.1017, found
319.1012.
4.3 | Synthesis of 2a, 2b, and 2f
The general procedure for 2a, 2b, and 2f was as follows.
To a 25-mL Schlenk flask was added RuCl2(PPh3)3
(0.194 g, 0.2 mmol) and 1a (1b or 1 f) (0.2 mmol) in 5 ml
toluene and the mixture was refluxed for 0.5 hr. The mix-
ture was cooled to room temperature and filtered. The
precipitate was washed with Et2O (3 × 10 ml) then dried
in vacuo to afford the corresponding solid.
Preparation of 1e and 1 f was according to our
published procedure.[47] To a 25-mL tube were added

12 of 13
HUANG ET AL.
4.3.1 | 2a 71% isolated yield (red-purple
solid): FT-IR (KBr):1637.47 (m), 1485.85 (s),
1460.21 (w), 1437.29 (w), 1172.57 (w), 1091.22
(w), 770.43 (w), 697.76 (w)
125.11 (s), 124.71 (s), 123.02 (s), 122.82 (s), 121.29
(s) ppm; 31P NMR (162 MHz, CDCl3): δ 42.18 (s) ppm.
HRMS (ESI) calcd for C35H26Cl2N3PRuS2 [M-Cl−]
720.0038 (100%), 722.0049 (59%), found 720.0012 (100%),
722.0010 (76%).
1H NMR (400 MHz, DMSO): δ 9.73 (d, J = 8.4 Hz, 1H),
9.42 (d, J = 6.0 Hz, 1H), 8.26 (d, J = 8.0 Hz, 1H), 7.86
(t, J = 7.5 Hz, 2H), 7.71 (ddd, J = 17.6, 15.6, 7.5 Hz, 3H),
7.51 (s, 1H), 7.37 (d, J = 8.2 Hz, 1H), 7.22 (dd, J = 8.1,
4.1 Hz, 3H), 7.08–6.96 (m, 13H), 6.81 (t, J = 6.5 Hz, 1H)
ppm; 13C NMR (101 MHz, DMSO): δ 167.66 (s), 153.47
(s), 152.53 (s), 151.56 (d, J = 17.2 Hz), 150.30 (s), 138.10
(s), 136.79 (s), 133.33 (s), 132.91 (d, J = 9.7 Hz), 131.13
(s), 130.75 (s), 130.09 (s), 128.43 (d, J = 9.0 Hz), 127.91
(s), 125.44 (s), 124.12 (s), 120.19 (s), 117.80 (s), 117.03 (s),
115.24 (s) ppm; 31P NMR (162 MHz, DMSO): δ 31.40
(s) ppm. HRMS (ESI) calcd for C35H27Cl2N4PRuS
[M-Cl−] 703.0426 (100%), 705.0437 (59%), found 703.0428
(100%), 705.0435 (83%).
4.4 | General procedure for α-alkylation
of nitriles with alcohols
Under nitrogen atmosphere,
a mixture of nitriles
(1 mmol), alcohols (2 mmol), 2a (1 mol%), KOtBu
(10 mol%), and dry toluene (1 ml) in a 15-ml Schlenk
ꢀ
tube was stirred at 135 C for the certain time. After the
reaction was complete, the solvents were removed under
vacuum and the residue was purified by silica gel column
chromatography (petroleum ether
/
ethyl acetate
(PE/EtOAc) 50:1–10:1) to afford the corresponding
product.
ACKNOWLEDGMENTS
4.3.2 | 2b 69% isolated yield (red-brown
solid): FT-IR (KBr):1635.42 (s), 1473.65 (m),
1432.12 (s), 1359.79 (m), 1091.48 (w), 750.99
(w), 698.12 (w), 528.19 (w)
We are grateful for financial support from the National
Key R&D Program of China (no. 2018YFF0215400) and
the Shanxi Science and Technology Department, China
(project no. MH2014-07).
1H NMR (400 MHz, CDCl3): δ 10.34 (d, J = 5.0 Hz, 1H),
9.50 (d, J = 9.0 Hz, 1H), 7.78–7.71 (m, 1H), 7.65
(d, J = 7.5 Hz, 1H), 7.56 (t, J = 7.8 Hz, 2H), 7.43–7.31
(m, 2H), 7.09 (t, J = 6.6 Hz, 3H), 7.03 (t, J = 6.5 Hz, 1H),
6.99–6.85 (m, 12H), 6.71 (d, J = 8.2 Hz, 1H), 6.67
(d, J = 8.1 Hz, 1H), 5.30 (s, 3H) ppm; 13C NMR
(101 MHz, CDCl3): δ 157.36 (s), 136.44 (s), 133.04 (s),
128.61 (s), 127.91 (s), 127.34 (s), 126.78 (s), 121.25 (s),
118.74 (s), 113.71 (s), 41.34 (s) ppm; 31P NMR (162 MHz,
CDCl3): δ 46.03 (s) ppm. HRMS (ESI) calcd for
C36H29Cl2N4PRuS [M-Cl−] 717.0583 (100%), 719.0593
(59%), found 717.0588(100%), 719.0574 (77%).
ORCID
Xiu-Feng Hou https://orcid.org/0000-0001-7513-4650
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solid): FT-IR (KBr): 1651.88 (m), 1456.27
(m), 1431.98 (s), 1390.37 (w), 1090.05 (w),
768.23 (w), 694.00 (w), 527.97 (w)
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8.85 (d, J = 8.5 Hz, 1H), 7.99–7.92 (m, 1H), 7.81
(d, J = 7.9 Hz, 1H), 7.61–7.48 (m, 2H), 7.37 (d, J = 7.2 Hz,
1H), 7.30 (s, 2H), 7.27–7.19 (m, 2H), 7.11 (dd, J = 14.3,
7.0 Hz, 9H), 7.02–6.85 (m, 6H) ppm; 13C NMR (101 MHz,
CDCl3): δ 160.70 (s), 159.74 (s), 155.50 (s), 153.21 (s),
135.37 (s), 134.80 (s), 134.38 (s), 133.66 (d, J = 9.0 Hz),
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
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How to cite this article: Huang S, Hong X,
Sun Y, et al. Ru(II)-PBTNNXN complex bearing
functional 2-(pyridin-2-yl)benzo[d]thiazole ligand
catalyzed α-alkylation of nitriles with alcohols.
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