Activation of nitriles by silver(I) N-heterocyclic carbenes: An efficient on-water synthesis of primary amides

Article abstract of DOI:10.1016/j.tet.2019.03.017

A first example of silver(I) N-heterocyclic carbene (Ag(I)-NHC) catalyzed on-water synthesis of primary amides by hydration of nitriles under mild reaction conditions is described. This organometallic catalytic system has excellent tolerance for various homo-aromatic, hetero-aromatic and aliphatic nitriles to afford primary amides in good yields in neat water.

Full text of DOI:10.1016/j.tet.2019.03.017

Accepted Manuscript
Activation of nitriles by silver(I) N-heterocyclic carbenes: An efficient on-water
synthesis of primary amides
Narasimha Swamy Thirukovela, Ramesh Balaboina, Shravankumar Kankala,
Ravindhar Vadde, Chandra Sekhar Vasam
PII:
S0040-4020(19)30292-3
https://doi.org/10.1016/j.tet.2019.03.017
TET 30203
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 19 December 2018
Revised Date: 17 February 2019
Accepted Date: 10 March 2019
Please cite this article as: Thirukovela NS, Balaboina R, Kankala S, Vadde R, Vasam CS, Activation
of nitriles by silver(I) N-heterocyclic carbenes: An efficient on-water synthesis of primary amides,
Tetrahedron (2019), doi: https://doi.org/10.1016/j.tet.2019.03.017.
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Activation of nitriles by silver(I) N-heterocyclic
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a
a
a,*
Narasimha Swamy Thirukovela , Ramesh Balaboina , Shravankumar Kankala , Ravindhar Vadde and
b,*
Chandra Sekhar Vasam
a
Department of Chemistry, Kakatiya University, Warangal, Telangana State-506009, India. E-mail:
ravichemkuc@gmail.com
b
Department of Pharmaceutical Chemistry, Telangana University, Nizamabad, Telangana State-503322, India.
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Activation of nitriles by silver(I) N-heterocyclic
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a
a
a
a,*
Narasimha Swamy Thirukovela , Ramesh Balaboina , Shravankumar Kankala , Ravindhar Vadde and
b,*
Chandra Sekhar Vasam
a
Department of Chemistry, Kakatiya University, Warangal, Telangana State-506009, India. E-mail:
ravichemkuc@gmail.com
b
Department of Pharmaceutical Chemistry, Telangana University, Nizamabad, Telangana State-503322, India.
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1
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Tetrahedron
journal homepage: www.elsevier.com
Activation of nitriles by silver(I) N-heterocyclic carbenes: An efficient on-water
synthesis of primary amides
a
a
a
a,
Narasimha SwamyThirukovela , Ramesh Balaboina , Shravankumar Kankala , Ravinder Vadde * and
b,*
Chandra Sekhar Vasam
a
Department of Chemistry, Kakatiya University, Warangal, Telangana State-506009, India. E-mail: ravichemkuc@gmail.com
Department of Pharmaceutical Chemistry, Telangana University, Nizamabad, Telangana State-503322, India.
b
E-mail: csvasam@telanganauniversity.ac.in
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A first example of silver(I) N-heterocyclic carbene (Ag(I)-NHC) catalyzed on-water synthesis of
primary amides by hydration of nitriles under mild reaction conditions is described. This
organometallic catalytic system has excellent tolerance for various homo-aromatic, hetero-
aromatic and aliphatic nitriles to afford primary amides in good yields in neat water.
Available online
2009 Elsevier Ltd. All rights reserved.
Keywords:
Silver(I) N-heterocyclic carbenes
nitrile hydration
on-water synthesis
primary amides
bi-phasic catalysis
1
. Introduction
Herein we present the results of on-water synthesis of
primary amides by water-insoluble Ag(I) N-heterocyclic carbene
The hydration of nitriles is one of the classic reactions in organic
synthesis to produce primary amides, which are ubiquitous
structural units in bio-molecules, drugs, plastics and fertilizers.
(Ag(I)-NHC) catalyzed nitrile hydration conducted in neat water.
Substrate scope has also been established using various aromatic,
aliphatic and hetero-aromatic nitriles to access the desired
primary amides selectively. It is noticeable that previously nitrile
hydration to primary amide synthesis was investigated in
homogeneous aqueous media using relatively expensive
1
Initially, this reaction was established by employing strong
Bronsted acids and bases as catalysts under elevated temperature
2
and pressure conditions. However, this classic approach was not
found to be a selective one and has some disadvantages such as
generation of reaction waste including carboxylic acids.
Therefore, the use of a variety of homogeneous/heterogeneous
4a-d
4a
4e
4f-g
transition metal complex catalysts of Ru,
Os, Pd and Rh
designed with a variety of N- and P-donor ligands. Besides,
nitrile hydration was also investigated in heterogeneous aqueous
3
4
catalysts in aqueous-organic or aqueous media is suggested for
the simultaneous activation of both nitrile group and water
nucleophile through coordination and thereby to achieve primary
amide selectivity exclusively.
4h-k
media using some supported transition metal catalysts
4l-o
including some silver catalysts. However, to our knowledge
there was no report available about the implementation of on-
water protocol using an organometallic catalyst in the synthesis
of primary amides. Generally speaking, it is well accepted that a
metal complex catalyst provides relatively better information
about reaction mechanism for an organic reaction than the
heterogeneous catalyst since the ligand can stabilize and fine tune
the activity of metal centre during catalytic cycle.
Though water is the reaction media for many living
5
biochemical process, the idea of organic synthesis in neat water
is not generally practiced. The considerable opinion/facts are (i)
water limits the use of acids and bases and (ii) most organic
compounds and catalysts don't dissolve completely in water.
6a
6b-k
However, according to Sharpless and other pioneers
the
Concerning the outstanding progress of Ag(I)-NHCs in
applicable Organometallic Chemistry, they have been primarily
emerged as carbene transfer agents to synthesize many important
unique physical and chemical properties of water viz., large
temperature window and hydrogen bonding capacity to stabilize
reaction intermediates allows the reactants and catalysts to
interact either in dissolved (homogeneous state i.e. in-water) or
in suspended (heterogeneous bi-phase state i.e. on-water) state to
provide the desired products selectively. In certain instances, the
on-water synthesis in heterogeneous aqueous media provided
better results than the same reaction conducted in homogeneous
aqueous media.
7,8
9
transition metal-NHC catalysts as highlighted by us and others.
However, recently the catalytic ability of Ag(I)-NHCs has been
realized in various C-C and C-heteroatom bond forming
homogeneous catalytic reactions, which was also highlighted by
8
10-16
us and others.
These catalytic transformations includes
8a
8b
cyclocondensation, Sonogashira coupling, multi-component
reactions,
8c&10
11
12
polymerization,
diboration,
direct-
e-mail: csvasam@telanganauniversity.ac.in

2
Tetrahedron
15
1
3
14
alkynylation,1 CO2 insertion,
alcohols oxidation
Ag(I)-NHC
and
Table 1. Catalyst screening
ACCEPTED MANUSCRIPT
6
cycloaddition.
Among
these
catalyzed
transformations, specifically the on-water concept was
13
implemented in direct alkynylation of isatins. In continuation of
our efforts to explore the aptness of Ag(I)-NHCs as catalysts in
wide variety of organic synthesis for the first time we disclose
the usefulness of water-insoluble Ag(I)-NHCs as catalysts for on-
water synthesis of primary amides via nitrile hydration conducted
in neat water.
o
b
Entry
1
Catalyst (mol%)
AgCl (10)
Time(h)
20
Temp( C)
Yield(%)
<5%
2
. Results and discussion
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
RT
2
3
4
5
6
7
8
9
AgOAc(10)
20
20
20
20
24
14
8
<10%
<5%
<5%
NR
<5%
41
At first, we have examined the hydration of benzonitrile
(
1a) as a model reaction in neat water in the presence of few
water-soluble Ag(I) salts and water-insoluble Ag(I)-NHCs
Figure 1) under aerobic conditions. In general, the metal-NHC
AgSbF (10)
6
AgPF (10)
6
(
organometallics having N-alkyl and N-aryl substituents on NHC
ring are water-insoluble. The nitrile hydration reaction conditions
and the results were summarized in Table 1. We have observed
that the hydration of 1a was sluggish or almost none in the
presence of 10 mol% simple water-soluble Ag(I)-salts even under
refluxing conditions and prolonged reaction times (Table 1,
entries1-6).
AgOTf (10)
AgBF (10)
4
3a (3)
3a (3)
3b (3)
3c (3)
3d (3)
3e (3)
3f (3)
3a (2)
50
91
8
50
79
1
1
1
1
1
0
1
2
3
4
8
50
84
8
50
59
9
50
57
9
50
41
8
50
81
a
Reaction was carried out with 1.0 mmol of benzonitrile (1a) in 1 mL water.
Isolated yields after column Chromatography.
b
Figure 1. Structures of Ag(I)-NHC catalysts
The effect of mixed aqueous solvent system on the
hydration of 1a was also investigated in the presence of same 3
mol% of catalyst 3a and the results are presented in Table 2. The
Next, we have investigated the catalytic efficacy of 3
mol% of water-insoluble Ag(I)-NHC catalyst (3a) in the
hydration of 1a at both room temperature (RT) and 50 °C in
neat water. When the reaction mixture was stirred at RT, it
was slow and produced 41% yield of desired benzamide (2a)
after 14 hrs (Table 1, entry 7). The low yield of 2a could be
due to the insoluble nature of catalyst 3a and benzonitrile (1a)
i.e. (0.005g/1 mL) in water at RT. Hence, the reaction mixture
was cloudy at RT during the reaction course. However, the
rate of hydration of 1a was improved dramatically at 50 °C
in the presence of same catalyst 3a and produced selectively
mixed EtOH-H O (4:1) solvent system has provided better yields
2
of benzamide (2a) (Table 2, entry 5) than the other mixed
organic-H O solvent systems (Table 2, entries 1-3 & 5). This
2
trend also indicates that as the reaction system become more
heterogeneous (Table 2, entries 6–8) i.e. with increasing in the
proportion of H O in EtOH-H O mixed system, the yield of
2
2
benzamide (2a) was gradually increased. Over all, it is confirmed
that the water as sole solvent in the hydration of 1a has provided
higher yields (up to 91%) of 2a (Table 2, entry 9). All these
observations suggested that the heterogeneous nature of reaction
system is more favourable factor to accelerate the hydration of
benzonitrile (1a) and support the usefulness of on-water concept.
the benzamide (2a) in 91% yield after 8 hrs (Table 1, entry 8)
.
It was noticed that the reactant and catalyst mixture was
appeared like a molten drop in water at 50 °C and cleared up at
the end of the reaction, which can be considered as on-water
6a
reaction system as suggested by Sharpless. Further, we have
also investigated the catalytic efficiency of few other water-
insoluble Ag(I)-NHCs designed with NHCs of varied N-
substituents (Figure 1). As shown in Table 1, the results indicate
that among the Ag(I)-NHC catalysts (3b-3f), those containing
sterically bulk N-substituents on NHC ligands have worked well
to produce higher yields of benzamide (2a) (Table 1, entries 9-
Table 2. Solvent screening
b
Entry
1
Solvent
DCM-H
Time
9
Yield(%)
c
2
O (4 : 1)
O (4 : 1)
DMSO-H O (4 : 1)
EtOH-H O (4 : 1)
MeOH-H O (4 : 1)
54
45
64
68
65
69
1
0). Catalyst loading tests with various concentrations of Ag(I)-
c
c
c
c
c
2
3
4
5
6
7
8
THF-H
2
10
8
NHC(a) confirmed that 3 mol % of catalyst 3a was the most
appropriate concentration for the hydration of benzonitrile (1a)
2
1
(
Table 1, entry 8). The formation of 2a was analyzed by H &
1
3
2
8
C NMR and mass spectral data, which is consistent with
4
the reported data.
2
8
EtOH-H
EtOH-H
2
2
O (1 : 1)
O (1 : 4)
8
d
8
84
91
d
H
2
O
8

3
a
10c, 11h, 17
Reaction was carried out with 1.0 mmol of benzonitrile (1a) and 3 mol % of
a plausible mechanism has been proposed to support
ACCEPTED MANUSCRIPT
a in 1 mL of solvent. Isolated yields after column chromatography.
d
b
c
3
the ‘on-water’ synthesis of amides. At first we would like to
describe the possible locality of the catalyzed reaction and then
Homogeneous Heterogeneous.
7, 8a, 18, 19
Having optimized reaction conditions in hand, we
how the structural features of labile Ag(I)-NHCs
i.e.
further extended the nitrile hydration protocol towards different
aromatic and aliphatic nitrile species to synthesize different other
primary amides and the results are presented in Table 3. We
would like to disclose that among the aromatic and aliphatic
nitriles used in the present work, only acetonitrile is completely
miscible with aqueous medium. The other organo nitrile reactants
used in this work are almost sparingly soluble according to the
data available in the literature and product catalog. Indeed it was
our intension to check the gradual transition to on-water reactions
with falling reactant water-solubility. The difference between
slightly soluble and very sparingly soluble is highly considerable
NHC-Ag(I)-Cl are useful in stabilizing the intermediates of
catalytic cycle and the reason for the restriction of hydrolysis at
amide stage.
When
water-immiscible
organic
substrates
(hydrophobic) are suspended in water, the mixtures can be
considered as bi-phasic (water + organic reactants and products).
However, now the issue is whether the catalytic cycle occurs in
the aqueous or the organic reactant phase/layer. If the reaction
occurs in water phase/layer, the hydrophobic reactant should
diffuse into the water phase. As a consequence, the rate of the
reaction would be limited by the low concentration of the
6
i
in attributing in-water to on-water reactions. When the reactants
are slightly soluble, it would be possible that both the on-water
and in-water reaction paths occurs together in nitrile hydration.
18
hydrophobic reactant in the aqueous phase. Besides, since the
Ag(I)-NHC catalyst used in the present work is also water-
insoluble, the chances are less to occur the nitrile hydration in
water phase. However, in our work the faster completion of
nitrile-hydration in pure water indicates the on-water reaction i.e.
accomplishment of catalytic nitrile hydration occurs in the
organic phase but not in aqueous phase. When the organic
reactant “solvent” is consumed, product plays role as “solvent”
and exhibits similar consequences (bi-phasic). The amide
products obtained in the present are almost water-insoluble or
sparingly soluble in water except 2u (Table 3). The established
structural features of labile Ag(I)-NHCs (i.e. NHC-Ag(I)-Cl)
Table 3. Substrate Scope
7, 8a, 17, 19
with a labile chloride
and its interactions with nitrile
functionality and H O via hydrogen bonding are practical in
2
proposing the valid reaction mechanism to form selectively the
amide as shown below (Scheme 1).
a
1
13
b
All the products were characterized by H and C NMR spectroscopy.
Isolated yields after column chromatography.
The substituted benzonitriles bearing electron-
withdrawing groups (Table 3, 2(h-o)) underwent nitrile hydration
efficiently and provided better yields of corresponding amides
than those benzonitriles bearing electron-donating groups (Table
Scheme 1. Proposed mechanism
3
, 2(b-g)). The reason could be the presence of the electron
withdrawing group on nitrile substance makes the nitrile carbon
more susceptible for the nucleophilic attack of water molecule.
Besides, the ortho-substituted benzonitriles (Table 3, 1d & 1j) are
relatively less reactive in nitrile hydration than meta (Table 3, 2c,
Since the bi-coordinate NHC-Ag(I)-Cl catalyst has a
labile chloride ligand and its ability to coordinate with the C≡N
bond, the catalyst certainly enters into the organic reactant
“
solvent” phase to process the catalytic cycle and participate in
2
i, 2l& 2o) and para-substituted benzonitriles (Table 3, 2b, 2(f-
the stabilization of catalytic intermediates. The involvement of
labile NHC-Ag(I)-Cl catalyst in multicomponent reaction was
h), 2k & 2(m-n)) due to steric hindrance. The nitrile hydration of
heterocyclic aromatic nitriles was also studied in our work (Table
10c
already reported. According to the scheme 1, firstly the NHC-
Ag-Cl initiates π-coordination with C≡N bond and then converts
to σ-coordination to form the activated intermediate A, in which
the chloride ligand was in hydrogen bonding with surface H of
3
, 2(p-s)). Finally, the optimized catalytic conditions described
here are also suited for the hydration of aliphatic nitriles (Table 3,
2u-x)) as well as biphenyl carbonitrile (Table 3, 2t) those have
(
wide synthetic scope. The characterization data of all the
products 2(a-x) is given in electronic supplementary information.
H O at the organic-water inter-phase. A previous report by Jung
2
6k
and Marcus provides theoretical study support for the rate
improvement of the on-water reaction. According to this study, in
bi-phasic reaction systems, the free and dangling OH groups of
water at the surface are available to extend into the organic phase
and ready to catalyse reactions. As a consequence, the
Mechanism
Based on the results of the present work and previously
4a, 6a, 6i, 6k,
reported experimental and theoretical study evidences,

4
Tetrahedron
(I) MANUSCRIPT
Endo, K.; Saito, S. Angew. Chem. Int. Ed. 2008, 47, 3607-3609;
j) Ramon, R. S.; Marion, N.; Nolan, S. P. Chem. Eur. J. 2009, 15,
electrophilicity of the C of σ-coordinated C≡
A
N
C
gr
C
ou
E
p
P
on
T
A
E
g
D
(
increases and the rate of nucleophilic attack of H O is further
2
‾
‾
8695-8697;
enhanced by the H-bonding of labile Cl ion with surface
hydrogens to form iminol intermediate B. In the next step, the
iminol species B is transformed into another intermediate C in
which both Cl and carbonyl oxygen were in H-bonding with
surface hydrogens of H O phase. Finally the intermediate C gives
rise to the formation of selective amide product. According to
scheme 1, over all the water phase plays important supporting
function in forming the amide bond, in stabilizing the Ag(I)-
amide coordination via hydrogen bonding followed by the de-
metalation of coordinated amide for next nitrile coordination and
4
.
(a) Gonzalez-Fernandez, R.; Crochet, P.; Cadierno, V.; Menendez,
M. I.; Lopez, R. Chem. Eur. J. 2017, 23, 15210-15221; (b) Tomas-
Mendivil, E.; Cadierno, V.; Menendez, M. I.; Lopez, R. Chem.
Eur. J. 2015, 21, 16874-16886; (c) Bolyog-Nagy, E.; Udvardy, A.;
Joo, F.; Katho, A.; Tetrahedron Lett. 2014, 55, 3615-3617; (d)
Wei Chih, L.; Sears, J. M.; Enow, R. A.; Eads, K.; Krogstad, D.
A.; Frost, B. J. Inorg. Chem. 2013, 52, 1737-1746; (e) Sharley, D.
D. S.; Williams, J. M. J. Tetrahedron Lett. 2017, 58, 4090-4093;
(f) Tomas-Mendivil, E.; Garcia-Alvarez, R.; Vidal, C.; Crochet,
P.; Cadierno. V. ACS Catal. 2014, 4, 1901-1910; (g) Charlotte,
M.; Djoman, K. B.; Naitajjou, A. Tetrahedron Lett. 2000, 41,
4845-4849; (h) Matsuoka, A.; Isogawa, T.; Morioka, Y.;
Knappett, B. R.; Wheatley, A. E. H.; Saito, S.; Naka, H. RSC Adv.
‾‾
2
4a
to stop the hydrolysis at amide stage.
. Conclusions
In conclusion, we have developed a robust method to
2
015, 5, 12152-12160; (i) Baig, R. B. N.; Nadagouda, M. N.;
3
Varma, R. S. Green Chem. 2014, 16, 2122-2127; (j) Kumar, S.;
Sharma, S.; Das, P.; Adv. Synth. Catal. 2016, 358, 2889-2894; (k)
Yong-Mei, L.; He, L.; Wang, M. M.; Cao, Y.; He, H. Y.; Kang-
Nian, F. ChemSusChem 2012, 5, 1392-1396; (l) Mitsudome, T.;
Mikami, Y.; Mori, H.; Arita, S.; Mizugaki, T.; Jitukawa, K.;
Kaneda, K. Chem. Commun. 2009, 3258-3260; (m) Sherbow, T.
J.; Downs, E. L.; Sayler, R. I.; Razink, J. J.; Juliette, J. J.; Tyler,
D. R. ACS Catal. 2014, 4, 3096-3105; (n) Ghosh, K.; AsifIqubal,
Md.; Molla, R. A.; Mishra, A.; Islam, K. Sk. Catal. Sci. Technol.
access variety of primary amides using organometallic Ag(I)-
NHC catalyzed nitrile hydration on water. This catalytic system
can efficiently mediates the hydration of wide range of nitriles,
including homo-aromatic, hetero-aromatic and aliphatic
examples with good yields under mild reaction conditions.
2
015, 5, 1606-1622; (o) Li, J.; Tang, G.; Wang, Y.; Wang, Y.; Li,
Acknowledgments
Z.; Li, H. New J. Chem.2016, 40, 358-364.
(a) Kitanosono, T.; Masuda, K.; Xu, P.; Kobayashi, S. Chem. Rev.
2
Rev. 2012, 41, 1415-1427; (c) Akiya, N.; Savage, P. E. Chem.
Rev. 2002, 102, 2725-2750.
(a) Narayan, S.; Muldoon, J.; Finn, M. G.; Fokin, V. V.; Kolb, H.
C.; Sharpless, K. B. Angew. Chem. Int. Ed. 2005, 21, 3157-3321;
(b) Kobayashi, S. Water in organic synthesis, Science of
synthesis, 1 ed. 2012, 44, 2474; (c) Surendra, K.; Krishnaveni, N.
S.; PavanKumar, V.; Sridhar, R.; Rama Rao, K. Tetrahedron Lett.
2
Tetrahedron 2005, 61, 6009-6014; (e) Wu, X.; Li, X.; King, F.;
Xiao, J. Angew. Chem. Int. Ed. 2005, 44, 3407-3411; (e) Zha, Z.;
Hui, A.; Zhou, Y.; Miao, Q.; Wang, Z.; Zhang, H. Org. Lett. 2005,
7, 1903-1905; (f) Dambacher, J.; Zhao, W.; Batta, A. E.; Anness,
R.; Jiang, C.; Bergdahl, M. Tetrahedron Lett. 2005, 46, 4473-
5
6
.
.
018, 118, 679-746; (b) Marc-Olivier, S.; Li, C. J. Chem. Soc.
The authors are thankful to the UGC-New Delhi (F.No: 17-
8
0/2009(SA-I) and DST-India (DST/INT/SA/P-15/2011 Indo-
South Africa project) for financial support.
Supporting Information Available
st
1
13
The characterization data and copies of H & C NMR spectra of
products 2(a-x) can be found, in the online version, at
http://dx.doi.org/
005, 46, 4581-4583; (d) Tong, K. H.; Wong, K. Y.; Chan, T. H.
References and notes
4
477; (g) Jun Li, C.; Chen, L. Chem. Soc. Rev. 2006, 35, 68; (h)
1
.
(a) Zabicky, J. The Chemistry of Amides, ed. Wiley-Interscience,
New York, 1970; (b) Greenberg, A.; Breneman, C. M.; Liebman,
J. F. The Amide Linkage: Structural Significance in Chemistry,
Biochemistry and Materials Science, ed. John Wiley & Sons, New
York, 2000; (c) Deopura, B. L.; Gupta, B.; Joshi, M.; Alagirusami,
R. Polyesters and Polyamides, ed. CRC Press, Boca Raton, 2008;
Chanda, A.; Fokin, V. V. Chem. Rev. 2009, 109, 725-748; (i)
Butler, R. N.; Coyne, A. G. Org. Biomol. Chem. 2016, 14, 9945-
9
(
5
960; (j) Hayashi, Y. Angew. Chem. Int. Ed. 2006, 45, 8103-8104;
k) Jung, Y.; Macus, R. A. J. Am. Chem. Soc. 2007, 129, 5492-
502.
(a) Lin, I. J. B.; Vasam, C. S. Coord. Chem. Rev. 2007, 251, 642-
7
.
(d) Carey, J. S.; Laffan, D.; Thomson, C.; Williams, M. T. Org.
6
2
8
2
70; (b) Lin, I. J. B.; Vasam, C. S. Comments Inorg. Chem. 2004,
5, 75-129; (c) Lin, I. J. B.; Vasam, C. S. Can. J. Chem. 2005, 83,
12-825; (d) Lin, I. J. B.; Vasam, C. S. J. Organomet. Chem.
005, 690, 3498-3512; (e) Wang, H. M. J.; Vasam, C. S.; Tsai, T.
Biomol. Chem. 2006, 4, 2337-2347; (e) Valeur, E.; Bradley, M.
Chem. Soc. Rev. 2009, 38, 606-631; (f) Constable, D. J. C.; Dunn,
P. J.; Hayler, J. D.; Humphrey, G. R.; Leazer, J. J. L.; Linderman,
R. J.; Lorenz, K.; Manley, J.; Pearlman, B. A.; Wells, A.; Zaks,
A.; Zhang, T. Y. Green Chem. 2007, 9, 411-420; (g) Allen, C. L.;
Williams, J. M. Chem. Soc. Rev. 2011, 40, 3405-3415; (h)
Mitsudome, T.; Mikami, Y.; Mori, H.; Arita, S.; Mizugaki, T.;
Jitsukawaa, K.; Kaneda, K. Chem. Commun. 2009, 3258-3260; (i)
Ghose, A. K.; Viswanadhan, V. N.; Wendoloski, J. J. J. Comb.
Chem. 1999, 1, 55-68.
Y. R.; Chen, S.-H.; Chang, A. H. H.; Lin, I. J. B. organometallics
005, 24, 486-493.
2
8
9
.
.
(a) Kankala, S.; Kankala, R.; Kommidi, D. R.; Mudithanapelli,
C.; Balaboina, R.; Vadde, R.; Jonnalagadda, S. B.; Vasam, C. S.;
RSC Adv. 2014, 4, 40305-40311; (b) Kankala, S.; Jonnalagadda, S.
B.; Vasam, C. S. RSC Adv. 2015, 5, 76582-76587; (c) Kankala, S.;
Pagadala, R.; Maddila, S.; Vasam, C. S.; Jonnalagadda, S. B.;
RSC Adv. 2015, 5, 105446-105452
(a) Garrison, J. C.; Youngs, W. J. Chem. Rev. 2005, 105, 3978-
4
4
Flores, J. C.; Jesus, E. Organometallics 2013, 32, 2814-2826; (d)
Lin, J. C. Y.; Huang, R. T. W.; Lee, C. S.; Bhattacharyya, A.;
Hwang, W. S.; Lin, I. J. B. Chem. Rev. 2009, 109, 3561-3598; (e)
Nomiya, K.; Morozumi, S.; Yanagawa, Y.; Hasegawa, M.;
Kurose, K.; Taguchi, K.; Sakamoto, R.; Mihara, K.; Kasuga, N. C.
Inorg. Chem. 2018, 57, 11322-11332.
2
3
.
.
(a) Dugger, R. W.; Ragan, J. A.; Ripin, D. H. B. Org. Process Res.
Dev. 2005, 9, 253-258; (b) Hirano, T.; Uehara, K.; Kamata, K.;
Mizuno, N. J. Am. Chem. Soc. 2012, 134, 6425-6433; (c)
Westfahl, J. C.; Gresham, T. L. J. Am. Chem. Soc. 1955, 77, 2910-
008; (b) Velazquez, H. D.; Verpoort, F. Chem. Soc. Rev. 2012,
1, 7032-7060; (c) Baquero, E. A.; Silbestri, G. F.; Sal, P. G.;
2
3
912; (d) Hall, J. H.; Gisler, M. J. Org. Chem. 1976, 41, 3769-
770; (e) Linke, S. Synthesis 1978, 4, 303-304.
(a) Singh, K.; Sarbajna, A.; Dutta, I.; Pandey, P.; Bera, J. K.
Chem. Eur. J. 2017, 23, 7761-7771; (b) Rong, M. K.; Duin, K.;
Dijk, T.; Pater, J. J. M.; Deelman, B. J.; Nieger, M.; Ehlers, A. W.;
Slootweg, J. C.; Lammertsma, K. Organometallics 2017, 36,
1
079-1090; (c) Jia, W. G.; Ling, S.; Fang, S. J.; Sheng, E. H.
1
1
0. (a) Cheng, C. H.; Chen, D. F.; Song, H. B.; Tang, L. F. J.
Organomet. Chem. 2013, 726, 1-8; (b) Chen, M. T.; Landers, B.;
Navarro, O. Org. Biomol. Chem. 2012, 10, 2206-2208; (c) Li, Y.;
Chen, X.; Song, Y.; Fang, L.; Zou, G. Dalton Trans. 2011, 40,
Polyhedron. 2017, 138, 1-6; (d) Nirmala, M.; Saranya, G.;
Viswanathamurthi. P.; Inorganica Chim. Acta. 2016, 442, 134-
1
44; (e) Gulyas, H.; Rivilla, I.; S. Curreli, Z. Freixa P. W. N. M.
Leeuwen, Catal. Sci. Technol. 2015, 5, 3822-3828; (f) Hirano, T.;
Uehara, K.; Kamata, K.; Mizuno, N. J. Am. Chem. Soc. 2012, 134,
2
046-2052.
1. (a) Talisman, I. J.; Kumar, V.; Razzaghy, J.; Malhotra, S. V.
Carbohydrate Res. 2011, 346, 883-890; (b) Li, P.; Wang, L.;
Zhang, Y.; Wang, M. Tetrahedron Lett. 2008, 49, 6650-6654; (c)
6
425-6433; (g) Muranaka, M.; Hyodo, I.; Okumura, W.; Oshiki,
T. Catal. Today. 2011, 164, 552-555; (h) Kim, E. S.; Kim, H. S.;
Kim, J. N. Tetrahedron Lett. 2009, 50, 2973-2975 (i) Goto, A.;

5
May, T. L.; Brown, M. K.; Hoveyda, A. H. Angew. Chem. Int. Ed.
ACCEPTED MANUSCRIPT
2
008, 47, 7358-7362; (d) Arnold, P. L. Heteroat. Chem. 2002, 13,
34-539; (e) Corberan, R.; Ramirez, J.; Poyatos, M.; Peris, E.;
5
Fernandez, E. Tetrahedron Asymm. 2006, 17, 1759-1762; (f)
Melaiye, A.; Sun, Z.; Hindi, K.; Milsted, A.; Ely, D.; Reneker, D.
H.; Tessier, C. A.; Youngs, W. J. J. Am. Chem. Soc. 2005, 127,
2
285-2291; (g) Requejo, M. M. D.; Pérez, P. J. J. Organomet.
Chem. 2005, 690, 5441-5450; (h) Sentman, A. C.; Csihony, S.;
Waymouth, R. M.; Hedrick, J. L. J. Org. Chem. 2005, 70, 2391-
2
393.
1
1
1
2. Ramirez, J.; Corberan, R.; Sanau, M.; Peris, E.; Fernandez, E.
Chem. Commun. 2005, 3056-3058;
3. Fu, X .P.; Liu, L.; Wang, D.; Chen, Y. J.; Li, C. J. Green Chem.
2
011, 13, 549-553.
4. (a) Yu, D.; Tan, M. X.; Zhang, Y. Adv. Synth. Catal. 2012, 354,
69-974; (b) Li, S.; Sun, J.; Zhang, Z.; Xie, R.; Fang, X.; Zhou,
9
M. Dalton Trans. 2016, 45, 10577-10584; (c) Yuan, Y.; Chen, C.;
Zeng, C.; Mousavi, B.; Chaemchuen, S.; Verpoort, F.
ChemCatChem. 2017, 9, 882-887.
1
1
5. Han, L.; Xing, P.; Jiang, B. Org. Lett. 2014, 16, 3428-3431.
6. Liu, Y. F.; Wang, Z.; Shi, J. W.; Chen, B. L.; Zhao, Z. G.; Chen,
Z. J. Org. Chem. 2015, 80, 12733-12739.
1
7. Rçhlich, C.; Wirth, A. S.; Kçhler, K. Chem. Eur. J. 2012, 18,
1
5485-15494.
1
1
8. Wang, H. M. J.; Lin, I. J. B. Organometallics 1998, 17, 972-975;
9. (a) Heath, R.; Muller-B. H.; Albrecht, M. Chem. Commun. 2015,
5
1, 8699-8701; (b) de Fremont, P.; Scott, N. M.; Stevens, E. D.;
Ramnial, T.; Lightbody, O. C.; Macdonald, C. L. B.; Clyburne, J.
A. C.; Abernethy, C. D.; Nolan, S. P. Organometallics 2005, 24,
6
301-6309; (c) Su, H. L.; Pérez, L. M.; Lee, S. J.; Reibenspies, J.
H.; Bazzi, H. S.; Bergbreiter, D. E. Organometallics 2012, 31,
063-4071; (d) Hintermair, U.; Englert, U.; Leitner, W.
Organometallics 2011, 30, 3726-3731.
4