Nanolayered cobalt-molybdenum sulphides (Co-Mo-S) catalyse borrowing hydrogen C-S bond formation reactions of thiols or H2S with alcohols

Article abstract of DOI:10.1039/c8sc05782f

Nanolayered cobalt-molybdenum sulphide (Co-Mo-S) materials have been established as excellent catalysts for C-S bond construction. These catalysts allow for the preparation of a broad range of thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds, nitriles, carboxylic esters and halogens has been demonstrated. It is also shown that the reaction takes place through a hydrogen-autotransfer (borrowing hydrogen) mechanism that involves Co-Mo-S-mediated dehydrogenation and hydrogenation reactions. A novel catalytic protocol based on the thioetherification of alcohols with hydrogen sulphide (H₂S) to furnish symmetrical thioethers has also been developed using these earth-abundant metal-based sulphide catalysts.

Full text of DOI:10.1039/c8sc05782f

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Nanolayered cobalt–molybdenum sulphides (Co–
Mo–S) catalyse borrowing hydrogen C–S bond
formation reactions of thiols or H2S with alcohols†
Cite this: DOI: 10.1039/c8sc05782f
All publication charges for this article
have been paid for by the Royal Society
of Chemistry
*
Ivan Sorribes ‡ and Avelino Corma
´
Nanolayered cobalt–molybdenum sulphide (Co–Mo–S) materials have been established as excellent
catalysts for C–S bond construction. These catalysts allow for the preparation of a broad range of
thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well
as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds,
nitriles, carboxylic esters and halogens has been demonstrated. It is also shown that the reaction takes
place through a hydrogen-autotransfer (borrowing hydrogen) mechanism that involves Co–Mo–S-
mediated dehydrogenation and hydrogenation reactions. A novel catalytic protocol based on the
thioetherification of alcohols with hydrogen sulphide (H2S) to furnish symmetrical thioethers has also
been developed using these earth-abundant metal-based sulphide catalysts.
Received 27th December 2018
Accepted 20th January 2019
DOI: 10.1039/c8sc05782f
rsc.li/chemical-science
therefore salts or acids (neutralized with the use of a base) are
still produced as by-products.
Introduction
An alternative methodology consists in the use of readily
available alcohols as electrophiles where water is formed as the
only stoichiometric residue. However, (primary and secondary)
alcohols are usually unreactive because the hydroxyl group
displays poor leaving character, their reactivity being slightly
increased in the presence of Brønsted or Lewis acid catalysts.7
In this context, the so-called borrowing hydrogen method-
ology, also known as the transition-metal-catalysed hydrogen
autotransfer process, offers compelling benets.8 In this reac-
tion sequence, alcohol is dehydrogenated to a more reactive
aldehyde or ketone intermediate, which is more prone to react
with a nucleophile present in the same reaction medium.
Subsequent hydrogenation of the resulting unsaturated inter-
mediate with the initially generated hydrogen (or metal
hydrides) yields the desired product in a one-pot domino
sequence.
The borrowing hydrogen methodology has been widely
applied for efficient C–N9 and C–C10 bond formation from
alcohols and using amines (including ammonia) or C-
nucleophiles as reagents. In contrast, the use of thiols or
hydrogen sulphide to accomplish the construction of C–S bonds
by means of this catalytic protocol remains largely unexplored.
To date, the only example has been reported by our group using
a bifunctional solid catalyst based on palladium nanoparticles
supported on high-surface area magnesium oxide (MgO). It
allows the synthesis of thioethers along with the formation of
disuldes.11 The reaction was specically applied for benzylic
alcohols that were dehydrogenated to benzaldehydes and in situ
reacted with thiols involving, most probably, the formation of
a hemithioacetal (in equilibrium with a hypothetical thionium
Reactions involving carbon–sulphur bond formation are of
great interest in organic synthesis and in materials science as
well as in the pharmaceutical industry.1 For instance, thioethers
exist in natural products and drugs, and they act as key building
blocks for the synthesis of various heteroatomic functional
groups, such as sulfoxides or sulfones, contained in many bio-
logically and pharmacologically active molecules.2
Traditional synthesis of thioethers involves the condensa-
tion of a metal alkyl or aryl thiolate with an alkyl halide under
strong basic conditions, resulting in the formation of large
amounts of salt and metal waste.1d,3 Consequently, many
catalytic methodologies aimed at the preparation of these
compounds through more sustainable chemical trans-
formations have been reported to date.1e,f,4 Currently, the most
popular routes for their synthesis rely on metal-mediated cross-
coupling reactions of organic halides with thiols,5 and on
metal-catalysed hydrothiolation of unsaturated carbon–carbon
bonds.5h,6 The latter reaction displays high atom efficiency;
however, it suffers from low availability of the starting alkenes
or alkynes, and presents regioselectivity limitations. The cross-
coupling transformations involve substitution reactions, and
´
´
`
Instituto de Tecnologıa Quımica, Universitat Politecnica de Valencia-Consejo Superior
´
de Investigaciones Cientıcas, Avenida Los Naranjos s/n, 46022 Valencia, Spain.
E-mail: acorma@itq.upv.es
† Electronic supplementary information (ESI) available: General information,
additional tables, schemes, gures, characterization data and NMR spectra of
isolated products. See DOI: 10.1039/c8sc05782f
´
´
´
‡ Present address: Departament de Quımica Fısica i Analıtica, Universitat Jaume I,
´
Av. Sos Baynat s/n, 12071 Castello, Spain.
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ion) and its reduction by the previously generated palladium groups. In addition, we have also extended this methodology to
hydride species (Scheme 1). It should be noted that the direct the use of H2S establishing a novel catalytic protocol for the
reductive suldation of carbonyl compounds with mercaptans preparation of symmetrical thioethers by thioetherication of
in the presence of a reducing agent, such as lithium aluminum the corresponding alcohols (Scheme 1) for the rst time.
hydride/aluminum chloride, triethylsilane, or pyridine-borane
in triuoroacetic acid, has also been described.12 However, the
use of more stable and readily available alcohols instead of
sensitive carbonyl compounds, and the absence of any addi-
tional reducing agent make the borrowing hydrogen method-
Results and discussion
Preparation and catalytic activity of nanolayered cobalt–
molybdenum sulphide catalysts
ology a more benign and practical strategy for the synthesis of Cobalt–molybdenum sulphide based materials are the most
thioethers.
commonly used catalysts for the hydrodesulfurization (HDS) of
Nowadays, the replacement of precious metals with earth- crude feedstocks in petroleum reneries, a process that involves
abundant metal-based catalysts is an exciting goal in catal- the C–S bond excision of sulphur-containing molecules.21
ysis,13 and this substitution would still provide greater benets Consequently, enormous efforts have been made worldwide to
to this methodology in terms of sustainability. In general, the improve the catalytic activity of these hydroprocessing catalysts. In
activation of alcohols in homogeneous catalysis by the this respect, the most signicant breakthrough lay in the devel-
borrowing hydrogen strategy to form C–C and C–N bonds has opment of the so-called Nebula catalyst, an unsupported material
been commonly performed with Ru or Ir complexes;14 however, with a large population of active sites per unit volume that is
recent efforts have led to the design of novel catalysts based on currently in use in several industrial units.22 Since its discovery,
Fe,15 Co,16 Cu,17 Mn18 or Re.19 Although these transformations unsupported materials have emerged as a convenient alternative
have been comparatively less investigated in heterogeneous to the use of conventional supported ones,23 and therefore several
catalysis, they have been accomplished with the use of precious methodologies have been reported for their preparation.24
metal-based catalysts to a higher extent,8f while only a handful
Very recently, we described the hydrothermal synthesis of
of Ni- or Cu-based heterogeneous catalysts have been applied.20 a series of nanolayered cobalt–molybdenum sulphide materials
Hence, the development of new strategies that make use of non- (Co–Mo–S–X; X ¼ Co/(Mo + Co) mole ratio) and disclosed their
noble metal-based heterogeneous catalysts for the borrowing useful applications as catalysts for chemo- and regioselective
hydrogen C–X (X ¼ C, N, S) bond construction from alcohols is hydrogenation of nitroarenes and N-heteroarenes.25 More
an active eld of research.
specically, we reacted an aqueous solution containing
In this context, we herein describe for the rst time, ammonium molybdate, sulphur and different amounts of
borrowing hydrogen synthesis of thioethers catalysed by a non- cobalt(II) acetate in an autoclave at 180 ꢀC in the presence of
noble metal-based catalytic system. We show that the use of hydrazine as a reductant. Depending on the amount of cobalt(II)
nanolayered cobalt–molybdenum-suldes as catalysts allows acetate used in their preparation, it was possible to synthesize
for efficient C–S bond formation by the reaction of primary as nanolayered materials with different chemical phase composi-
well as secondary alcohols with thiols displaying excellent tions, as they are predominantly constituted by MoS2 (along
chemoselectivity even in the presence of sensitive functional with the presence of Co–Mo–S-like structures) and cobalt
sulphides with diverse stoichiometries, such as CoS2, Co3S4
and/or Co9S8 (Table S1 in the ESI†). The catalytic activity of
these cobalt–molybdenum sulphide materials was ascribed to
the presence of transient Co–Mo–S-like structures,26 as well as to
the nature of the mixed phase of cobalt sulphides, with superior
activity when the latter is mainly composed of Co3S4 and lower
activity when increasing the relative content of Co9S8, while
CoS2 resulted in an inactive phase.25
Based on this background and with the aim to extend the
toolbox of useful synthetic transformations promoted by these
nanolayered cobalt–molybdenum sulphide materials, we
decided to investigate their application in hydrogen auto-
transfer processes. For that, the alkylation of benzenethiol (1a)
with benzyl alcohol (2a) to afford benzyl phenyl sulphide (3aa)
was selected as a benchmark reaction. Initial catalytic experi-
ments were performed under a nitrogen atmosphere (3.5 bar) at
180 ꢀC and using toluene as a solvent. Reaction proles,
depicted in Fig. 1, reveal diphenyl disulphide (4a) as the primary
product, and its relative amount increased parallel to benze-
nethiol (1a) conversion. Aer reaching a maximum, the
concentration of 4a starts to decrease or is maintained almost
constant, likely depending on the efficiency of the catalyst to
Scheme 1 Catalytic borrowing hydrogen (BH) synthesis of thioethers
from alcohols.
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Fig. 1 Yield–time diagram of benzyl phenyl sulphide (3aa) and diphenyl disulphide (4a) produced during alkylation of benzenethiol (1a) with
benzyl alcohol (2a) in the presence of the catalysts (a) Co–Mo–S-0.39, (b) Co–Mo–S-0.58, (c) Co–Mo–S-0.83 and (d) Co–Mo–S-0.91. Reaction
conditions: 1a (0.25 mmol), 2a (0.5 mmol), catalyst (13.1 mg), toluene (1.6 mL), 3.5 bar N2, 180 ꢀC.
hydrogenate the disulphide bond. The formation of this but with more separated and agglomerated non-active CoS2,25b
product is not surprising since its metal-catalysed formation displays considerably lower activity. As revealed in its reaction
usually involves lower activation energy than the formation of prole, besides a modest yield of 3aa, once diphenyl disulphide
thioethers.11
(4a) is formed it remains almost unreactive (Fig. 1b).
In the presence of the catalyst Co–Mo–S-0.83 the starting
thiol 1a is fully converted affording almost a quantitative yield
of the desired product 3aa with traces of the disulphide
compound 4a (2% yield) in 8 h, the latter being totally
consumed aer two additional hours (Fig. 1c and Table 1,
entries 1 and 2). This catalyst, which is constituted by a mixture
of MoS2, transient Co–Mo–S-like structures (determined
through an electrochemical study applying the voltammetry of
immobilized particles (VIMP) methodology),27 CoS2 and Co3S4
phases, also proved to be the most active catalytic system in
previously reported hydrogenation reactions.25b The use of the
catalyst Co–Mo–S-0.91, mainly formed by Co9S8 and MoS2, leads
to lower conversion of 1a affording the thioether product 3aa in
70% yield, which co-exists with the non-fully converted disul-
phide 4a (Fig. 1d). Similar reactivity is achieved in the presence
of the catalyst Co–Mo–S-0.39, a cobalt-promoted MoS2-based
material with cobalt species homogeneously distributed on
MoS2 and containing some separated CoS2 (Fig. 1a).25a It should
be noted that the high dispersion of cobalt species on MoS2
benets the adsorption of cobalt atoms at the edges of the
layered structure of MoS2, thus leading to the formation of Co–
Mo–S-like active structures to a larger extent.26 In fact, the
catalyst Co–Mo–S-0.58, being constituted by the same phases
Table 1 Alkylation of benzenethiol (1a) with benzyl alcohol (2a)a
Yieldb [%]
Conversionb
[%]
Entry
Catalyst
Solvent
3aa
4a
1
Co–Mo–S-0.83
Co–Mo–S-0.83
MoS2
Mo-free CoxSy
Co–Mo–S-0.83
Co–Mo–S-0.83
Co–Mo–S-0.83
Co–Mo–S-0.83
Co–Mo–S-0.83
Co–Mo–S-0.83
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
1,4-Dioxane
CH3CN
THF
>99
>99
76
45
94
80
98
82
64
96
98
53
15
89
50
84
48
1
2
—
18
25
8
10
5
15
—
—
2c
3
4
5d,e
6e,f
7e
8e
9e
10e
Ph-CF3
>99
94
a
Reaction conditions: 1a (0.25 mmol), 2a (0.5 mmol), catalyst (13.1 mg),
b
solvent (1.6 mL), 3.5 bar N2, 180 ꢀC, 8 h. Determined by GC with
c
d
respect to 1a using n-hexadecane as the internal standard. 10 h. 2a
(1.5 equiv.). e 18 h. f 150 ꢀC.
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In addition, we have also tested MoS2 and a molybdenum-
Interestingly, when the alkylation of benzenethiol (1a) with
free CoxSy catalyst based on a mixture of CoS2, Co3S4 and benzyl alcohol (2a) was carried out in the presence of the most
Co9S8 (see the ESI† for details of their preparation). MoS2 active catalyst Co–Mo–S-0.83 with an extra supply of hydrogen
displays moderate catalytic activity affording 3aa in 53% yield. gas pressure (2 bar N2 and 1.5 bar H2), higher reaction rate for
In contrast, in the presence of the molybdenum-free material as the formation of 3aa was achieved (Fig. S2†), thus suggesting
the catalyst, 3aa is achieved in only 15% yield while benzyl that the rate-controlling step of this reaction sequence is not the
alcohol remains largely unreactive (Table 1, entries 3 and 4; see dehydrogenation of the alcohol but the direct reductive thio-
also Fig. S1 in the ESI†).
lation. This result is in line with our previous nding that
It is worth noting that all synthesized Co–Mo–S materials are correlates the higher efficiency for the synthesis of 3aa with the
active in the borrowing hydrogen synthesis of benzyl phenyl increase of the hydrogenation activity of the catalysts when they
sulphide (3aa), which means that these catalysts are able to display similar dehydrogenation activity.
dehydrogenate benzyl alcohol (2a) to benzaldehyde (2a0) as well
Next, we explored the recycling of the catalyst Co–Mo–S-0.83
as hydrogenate the intermediate product formed by the reaction in the investigated model reaction for the formation of the
of 2a0 with the initial thiol 1a (see Scheme 2). Typically, in thioether 3aa. As shown in Fig. 2a, a decrease in the yield of 3aa
a borrowing hydrogen sequence the hydrogenation stage is is observed in the second run, while it remains almost constant
thermodynamically favoured, thus driving forward the initial in the third one. This catalytic behaviour suggests that different
dehydrogenation step. This is in agreement with the catalytic active species are responsible for the catalytic activity and that
activity tendency followed by these Co–Mo–S catalysts for the the fresh catalyst contains highly active but poorly stable cata-
synthesis of 3aa, being higher with the increase of their hydro- lytic species, which vanish during the rst catalytic run. As we
genation activity (Table S1†). However, the higher efficiency previously reported,25b these active structures correspond to Co–
shown by MoS2 in comparison with the molybdenum-free CoxSy Mo–S-like structures, which is well-established to consist of
catalyst is in contrast since, as previously reported,25b the hydro- MoS2 decorated at the edges with cobalt atoms.26 Due to their
genation activity of the latter is higher than that of MoS2. These metastable character, they vanish by the desorption of cobalt
results clearly show that in the borrowing hydrogen strategy, atoms from the MoS2 backbone during the rst catalytic run as
apart from the hydrogenation activity of the catalyst, its dehy- revealed ICP-MS analysis of the ltrate (Table S2 in the ESI;† see
drogenation ability is also important. In this sense, the presence also Fig. S3† for hot ltration experiments). Nevertheless,
of MoS2 in the investigated Co–Mo–S catalysts seems to be crucial excellent conversions of 1a towards the formation of the desired
to efficiently accomplish the dehydrogenation of the alcohol,28 product 3aa were obtained even aer the sixth run by increasing
since it remains largely unreactive when the molybdenum-free the reaction time, thus suggesting that in addition to the Co–
CoxSy material is used as the catalyst.
Mo–S like structures other active species are also responsible for
the catalytic activity of the catalyst Co–Mo–S-0.83. It is notice-
able that no more leaching occurred to the reaction medium in
the next runs. X-ray diffraction (XRD) characterization (Fig. 2b;
see also Fig. S4–S6† for high-resolution transmission electron
microscopy (HRTEM) studies) of the fresh and recycled catalysts
shows that they are slowly desulfurized during the reaction
cycles producing a subtle change in the composition of the
mixed phase of cobalt sulphides. More specically, CoS2 is
continuously transformed to the active phase of Co3S4, and
Scheme 2 Reaction steps for the catalytic borrowing hydrogen (BH)
synthesis of benzyl phenyl sulphide (3aa).
Fig. 2 (a) Catalyst recycling for the alkylation of benzenethiol (1a) with benzyl alcohol (2a). Reaction conditions: 1a (0.25 mmol), 2a (0.5 mmol),
Co–Mo–S-0.83 (13.1 mg), toluene (1.6 mL), 3.5 bar N2, 180 ꢀC, 10 h (runs 1–3) or 18 h (runs 4–6). (b) XRD patterns of the recycled catalyst.
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therefore aer losing the Co–Mo–S-like active structures in the
rst run, the catalytic activity is maintained or even slightly
increases along the reaction cycles.
All these results suggest that different active species are
responsible of the catalytic activity of the catalyst Co–Mo–S-0.83.
More specically, it depends on the composition of the mixed
phase of cobalt sulphides, with superior activity when the latter
is mainly composed by Co3S4, and it is also associated with the
presence of transient Co–Mo–S-like structures,26 which vanish
aer the rst catalytic run. In addition, MoS2 plays a key role not
only in the hydrogenation step, but also in the dehydrogenation
of the alcohol.28
Next, the borrowing hydrogen synthesis of 3aa was investi-
gated in more detail. Although benzaldehyde (2a0) appears to be
a detectable reaction intermediate when 2a is used as an alky-
lating reagent, a control experiment was run to rule out
a possible mechanism through a direct nucleophilic substitu-
tion of alcohols with the formation of carbocation intermedi-
ates.7 Under the previously used conditions, benzenethiol (1a)
was reacted with 2-phenyl-2-propanol (2b), a tertiary benzylic
alcohol that easily generates the stabilized carbocation.
Together with the formation of the disulphide product 4a (70%
yield), the corresponding thioether was obtained in negligible
yield (8%) aer 18 h, thus ruling out the direct nucleophilic
substitution mechanism (Scheme S1 and eqn (S1)†).
Other evidence that conrms the occurrence of the alcohol
dehydrogenation step of the borrowing hydrogen sequence
relies on the detection of molecular H2 in the gas-phase of the
reaction between 1a and 2a. Moreover, to get more clues on the
complete autotransfer mechanism, an additional two step-
control experiment was carried out by rst reacting the cata-
lyst Co–Mo–S-0.83 with benzyl alcohol (2a) under neat condi-
tions, and then using this pre-treated catalyst in the reaction of
1a with benzaldehyde (2a0) in toluene at 180 ꢀC (for more details
see Scheme S1 and eqn (S2a) and (S2b)†). Interestingly, the
desired thioether 3aa was obtained in 17% yield, which reveals
the presence of hydrogen-derived species on the pre-treated
catalyst generated by benzyl alcohol dehydrogenation and
their proper transfer to the hemithioacetal intermediate. All of
the above results conrm that the alkylation of thiols with
alcohols in the presence of the Co–Mo–S-0.83 catalyst is actually
taking place through a borrowing hydrogen sequence.
Since diphenyl disulphide (4a) was detected as a transient
product during the course of the reaction, we attempted to use it
as a reactant in the synthesis of benzyl phenyl sulphide (3aa) by
reaction with benzyl alcohol (2a) (Scheme S1 and eqn (S3)†).
Interestingly, 4a was almost fully converted (89%) aer 18 h at
180 ꢀC affording the thioether 3aa and the thiol 1a in 83 and 4%
yields, respectively, which shows the feasibility of synthesizing
thioethers from dithiols and alcohols in the presence of the
catalyst Co–Mo–S-0.83. In this reaction sequence, longer reac-
tion times are required because the dithiol compound needs to
be reduced to the corresponding thiol rst.
Scheme 3 Proposed reaction pathway for the Co–Mo–S-catalysed
alkylation of benzenethiol (1a) with benzyl alcohol (2a).
processes,21 an alternative reaction pathway through desulfur-
ization of this by-product to form the thioether 3aa should not
be ruled out. Indeed, the reaction of 5a with benzyl alcohol (2a)
afforded 3aa and 4a in 74 and 8% yields, respectively, aer 10 h
under the same reaction conditions used for the previous
catalytic reactions (Scheme S1 and eqn (S4)†).
Based on all the above results a mechanism for the synthesis
of the thioether 3aa by alkylation of 1a with the alcohol 2a in the
presence of the catalyst Co–Mo–S-0.83 is proposed in Scheme 3.
Benzyl alcohol (2a) is initially dehydrogenated to benzaldehyde
(2a0) generating molecular hydrogen and activated hydrogen
species on the Co–Mo–S catalyst. Then, the nucleophile ben-
zenethiol (1a) attacks the carbonyl carbon of 2a0 to give the
hemithioacetal intermediate I,11,12c which is Co–Mo–S-mediated
reduced to afford the thioether product 3aa. An alternative
pathway involving the formation and subsequent catalytic
hydrogenolysis of a,a-bis(phenylthio)toluene (5a) can also take
place. It should be mentioned that the formation of 5a through
a direct dehydration of the hemithioacetal intermediate (I) with
benzenethiol is unlikely as revealed by our unsuccessful
experiment with a more reactive tertiary alcohol (Scheme S2 and
eqn (S1)†). This suggests that the thioacetal 5a is most probably
formed through an additional borrowing hydrogen sequence
following analogous steps to those previously described.
In addition, according to the reaction proles depicted in
Fig. 1, the synthesis of 3aa under the present protocol also
involves the reversible formation of diphenyl disulphide (4a),
which is catalytically reduced to form the starting thiol 1a again.
That means reducing species should be formed in more than
stoichiometric amounts to get a quantitative yield of 3aa,
therefore giving a reasonable explanation for the need of using
an excess of the alcohol (2 equiv.) with respect to 1a (Table 1,
entry 5). Temperature is also a critical parameter since only 50%
yield of the thioether 3aa is obtained when the reaction is
ꢀ
conducted at a lower temperature (150 C) even aer a longer
reaction time (Table 1, entry 6). The use of other solvents, with
the exception of benzotriuoride, also led to detrimental results
(Table 1, entries 7–10).
Reaction scope of the borrowing hydrogen S-alkylation of
thiols with alcohols in the presence of nanolayered Co–Mo–S
catalysts
Another detected by-product, although at the trace level, was
the thioacetal a,a-bis(phenylthio)toluene (5a), presumably To investigate the scope of this catalytic protocol for the general
formed by the over-thiolation of benzyl alcohol. Taking into preparation of thioethers, we rst tested the alkylation of
account the extended used of MoS2-based catalysts in HDS structurally diverse thiols (1b–1t) with benzyl alcohol (2a) under
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ꢀ
a nitrogen atmosphere (3.5 bar) at 180 C using toluene as the thioacetate (3pa) in moderate yields along with the formation of
solvent. As shown in Table 2, aryl thiols functionalized with the corresponding ethers (Table 2, entries 15 and 16). 2-Phe-
alkyl or methoxy groups as well as naphthalene derivatives were nylethanethiol (1q) and cyclic, linear and even ester function-
converted into the desired thioethers 3ba–3ga in good to alized aliphatic thiols (1r–1t) also displayed good reactivity
excellent yields (Table 2, entries 1–7). Halogen-substituted toward the formation of the desired thioethers 3ra–3ta (Table 2,
benzenethiols 1h–1j also reacted efficiently and no dehaloge- entries 17–20).
nation products were detected (Table 2, entries 8–10). Interest-
Aer having demonstrated the excellent activity of the cata-
ingly, other reducible functionalities such as ketones, nitriles lyst Co–Mo–S-0.83 in the reaction of different thiols with benzyl
and carboxylic ester groups remained untouched with the cor- alcohol (2a), we proposed to extend this methodology to other
responding thioethers 3ka–3ma isolated in nearly 90% yield alcohols (Table 3). Under the same previously used conditions,
(Table 2, entries 11–13). The heterocyclic thiol 1n containing the reaction of benzenethiol (1a) with 2-naphthalenemethanol (2c)
benzothiazole moiety was transformed to the target product and 4-biphenylmethanol (2d) afforded the thioethers 3ac and
3na, which could be isolated in 82% yield (Table 2, entry 14).
3ad in 88 and 89% yields, respectively (Table 3, entries 1 and 2).
The alkylation reaction could also be carried out with thio- Different alkyl-substituted benzyl alcohols (2e–2g) and even the
benzoic and thioacetic acid (1o and 1p, respectively) as starting sterically hindered trimethyl-substituted 2h also displayed high
reactants affording benzyl benzothioate (3oa) and benzyl
Table 2 Co–Mo–S-catalysed alkylation of thiols with benzyl alcohol (2a)a
Yield [%]
Yield [%]
Entry
1d
Product
Conv.b [%]
>99
3c
4b
—
—
Entry
11
Product
Conv.b [%]
>99
3c
4b
—
—
91
85
92
90
2
>99
12
>99
3
4
>99
>99
90
78
4
6
13
>99
>99
89
82
—
—
14e
5
6
>99
>99
73
93
6
15f
16g
>99
>99
65
45
—
—
—
7
8
9
95
>99
>99
76
96
93
—
—
—
17
18
19
>99
97
89
78
70
2
—
10
95
10
>99
94
—
20h
>99
83
—
a
Reaction by-products:conditions: thiol 1a–1t (0.25 mmol), 2a (0.5 mmol), Co–Mo–S-0.83 (13.1 mg), toluene (1.6 mL), 3.5 bar N2, 180 ꢀC, 18 h.
Determined by GC with respect to the thiol using n-hexadecane as an internal standard. Yield of isolated products. Yield of the isolated
b
c
d
product starting from 10 mmol of thiol 1a. GC-yield of the by-products: e Benzo[d]thiazole (5%). f Benzyl benzoate (27%). g Benzyl acetate (47%).
h
Benzyl 3-(benzylthio)propanoate (10%).
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Table 3 Co–Mo–S-catalysed alkylation of benzenethiol (1a) with alcoholsa
Yield [%]
Yield [%]
Entry
1
Product
Conv.b [%]
>99
3c
4ab
Entry
11
Product
Conv.b [%]
>99
3c
4ab
88
3
93
2
2
3
>99
>99
89
96
—
—
12
93
76
73
7
9
13d
>99
4
5
>99
>99
95
91
—
—
14
15
>99
97
79
86
13
6
6
7
8
9
>99
>99
>99
82
82
84
81
51
11
—
—
15
16
17
18
19
>99
94
86
81
87
81
3
3
>99
92
9
—
10
95
80
8
20
>99
82
13
a
Reaction conditions: 1a (0.25 mmol), alcohol 2c–2v (0.5 mmol), Co–Mo–S-0.83 (13.1 mg), toluene (1.6 mL), 3.5 bar N2, 180 ꢀC, 18 h. b Determined
by GC with respect to 1a using n-hexadecane as an internal standard. c Yield of isolated products. GC-yield of by-products: d 3aa (4%).
reactivity towards the formation of the desired products 3ae– benzyl alcohols 2p and 2q remain untouched in the nal thio-
3ah (Table 3, entries 3–6).
ethers 3ap and 3aq, which were isolated in 79 and 86% yields,
In the presence of other electron-rich groups, such as respectively (Table 3, entries 14 and 15). Furthermore, hetero-
methoxy and thiomethyl, the alkylation reaction of benzene- aromatic alcohols also underwent the alkylation reaction of 1a
thiol (1a) proceeds in a similar manner (Table 3, entries 7 and in high yields (Table 3, entries 16 and 17). Interestingly, this
8), whereas in general the introduction of electron-withdrawing catalytic methodology could also be extended to the allylic
substituents leads to a slight decrease in the efficiency (Table 3, alcohol 2t affording 3at in 87% isolated yield (Table 3, entry 18).
entries 9 and 13). A drastic decline was observed with benzyl However, the use of aliphatic alcohols failed with this catalytic
alcohol functionalized with two uorine groups at the ortho system (Scheme S3 in the ESI†).
position, likely associated with electronic more than steric
Next, we were interested in the use of more challenging
effects (Scheme S2 in the ESI†). From the viewpoint of selec- secondary alcohols (Table 3, entries 19 and 20). Gratifyingly, the
tivity, the sensitive unsaturated double bond and ester group of alkylation of 1a with alcohols 2u and 2v proceeded efficiently,
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allowing the preparation of thioethers 3au and 3av in high of new methodologies to transform H2S into valuable and more
yields. It is worth noting that the formation of the dehydro- in-demand products is highly desirable.30
genated ketones was detected during the reaction and, in
In this regard, aer the general development of the alkyl-
accordance with our previous unsuccessful experiment with the ation of structurally diverse thiols with a wide range of alcohols,
tertiary alcohol 2b (see Scheme S1, eqn. (S1)†), this suggests that we proposed to extend this methodology to the reaction of
a borrowing hydrogen mechanism instead of a direct nucleo- alcohols with H2S. We therefore reacted benzyl alcohol (2a) at
philic substitution of the alcohol functionality takes place.7
180 ꢀC in the presence of the catalyst Co–Mo–S-0.83 under a N2/
H2S (10% v/v in H2S) atmosphere (4 bar) using toluene as the
solvent. Initially, as shown in Fig. 3, benzyl mercaptan (6a) and
dibenzyl sulphide (7a) are formed as reaction products, but the
concentration of 6a reaches a maximum and then starts to
decrease concomitant with the progressive formation of 7a,
which is afforded in 70% yield within 10 h. Benzaldehyde (2a0)
and dibenzyl disulphide (8a) are also formed during the reac-
tion. These results suggest that the formation of the symmet-
rical thioether 7a in this thioetherication reaction takes place
through two consecutive borrowing hydrogen sequences with
6a as the reaction intermediate (see Scheme 1; R3 ¼ H).
Thioetherication of alcohols with H2S
Hydrogen sulphide (H2S) is a major by-product produced in
petroleum reneries during hydrotreating processes carried out
for upgrading heavy crude feed-stocks. Due to its toxicity, the
release of H2S to the atmosphere is environmentally restricted.
Nowadays, the emission of the H2S produced in most of the
reneries is commonly mitigated through the conventional
Claus process, which converts this harmful gas into elemental
sulphur.29 However, the consumption of sulphur relative to its
current production is too high, and therefore the development
Notably, as shown in Fig. 4a the catalyst was conveniently
recycled affording the symmetrical thioether 7a in moderate
yields even aer the sixth run. As in the prior use of benzene-
thiol (vide supra), a signicant decrease of the catalytic activity is
achieved in the second run likely as result of the consumption
of the Co–Mo–S-like active structures. In contrast, in the present
case the catalyst continues to be slightly deactivated with
subsequent reaction cycles affording 7a in similar to lower
yields even aer longer reaction times. As revealed by the XRD
patterns of the recycled catalyst aer different catalytic runs
(Fig. 4b; see also Fig. S4, S7 and S8† for HRTEM characteriza-
tion), the catalyst is progressively sulfurized with H2S trans-
forming the active phase Co3S4 to CoS2, thus resulting in the
progressive decrease of the catalytic activity.
We next explored the synthesis of other symmetrical thio-
ethers from the corresponding functionalized alcohols
(Table 4). In addition to 2-naphthalenemethanol (2c) other
benzyl alcohols substituted with electron-donating groups, like
alkyl, methoxy and thiomethyl moieties, reacted efficiently
Fig. 3 Yield–time diagram for the thioetherification of benzyl alcohol
(2a) with H2S. Reaction conditions: 2a (0.25 mmol), Co–Mo–S-0.83
(13.1 mg), toluene (1.6 mL), 4 bar N2/H2S (10% v/v in H2S), 180 ꢀC.
Traces of dibenzyl ether (<5%) were also detected.
Fig. 4 (a) Catalyst recycling for the thioetherification of benzyl alcohol (2a) with H2S. Reaction conditions: 2a (0.25 mmol), Co–Mo–S-0.83 (13.1
mg), toluene (1.6 mL), 4 bar N2/H2S (10% v/v in H2S), 180 ꢀC, 10 h (runs 1–3) or 18 h (runs 4–6). (b) XRD patterns of the recycled catalyst.
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Table 4 Co–Mo–S-catalysed thioetherification of alcohols with H2Sa
Yield [%]
Yield [%]
Entry
1d,e
Substrate
Conv.b [%]
>99
6b
7c
8b
2
Entry
6b,j
Substrate
Conv.b [%]
6b
—
9
7c
8b
3
2
66
72
97
95
67
63
2b,f
>99
—
6
7b,k
5
3g
4h
>99
98
3
3
75
70
1
8l
99
93
—
—
54
56
—
—
9m
5
5i
>99
—
64
4
10n
>99
—
70
4
a
Reaction conditions: alcohol 2 (0.25 mmol), Co–Mo–S-0.83 (13.1 mg), toluene (1.6 mL), 4 bar N2/H2S (10% v/v in H2S), 180 ꢀC, 18 h. b Determined
c
d
by GC with respect to the alcohol using n-hexadecane as an internal standard. Yield of isolated products. Yield of the isolated product on
e
f
g
h
a 10 mmol scale. GC-yield of by-products: 2a0 (3%). 2c0 (3%) and 2-methylnaphthalene (11%). 2e0 (4%). 2i0 (3%) and 4-methylanisole (5%).
i
j
k
l
m
4-(Methylthio)toluene (5%). 4-Chlorotoluene (4%). 3-Bromotoluene (10%). 2o0 (1%) and 2-iodotoluene (9%).
2q0 (6%) and methyl p-
n
toluate (15%). 3,4-(Methylenedioxy)toluene (3%). Variable amounts (3–5%) of the corresponding symmetrical ethers were also detected in all
tested reactions.
producing the desired derivatives in good yields (Table 4, structures and with the composition of the mixed phase of
entries 2–5). A slight decrease in efficiency is observed in the cobalt sulphides, the activity being increased in the presence of
presence of electron-withdrawing substituents, such as halogen Co3S4 to a higher extent. In addition, the presence of MoS2 in
groups, which were well-retained in the nal symmetrical thi- the investigated Co–Mo–S catalysts seems to be crucial to effi-
oethers (Table 4, entries 6–8). Gratifyingly, the carboxylic ester ciently accomplish the dehydrogenation step of this borrowing
functionality of alcohol 2q remained untouched and the hydrogen sequence.
product 7q could be isolated in 56% yield (Table 4, entry 9). In
Application of the catalyst Co–Mo–S-0.83 allowed us the
addition, the heterocyclic alcohol 2r also successfully accom- preparation of a broad range of thioethers in good to excellent
plished this thioetherication reaction affording the corre- yields from structurally diverse thiols and primary as well as
sponding symmetrical product 7r in 70% isolated yield (Table 4, secondary alcohols. In general, this catalyst displays excellent
entry 10).
chemoselectivity towards carbon–sulfur bond formation even in
the presence of sensitive functionalities, such as halogens,
double bonds, ketones, nitriles and carboxylic esters, which
were well-retained in the nal thioethers. Furthermore, we have
also developed a novel methodology for the synthesis of
symmetrical thioethers by reaction of alcohols with H2S in the
presence of the catalyst Co–Mo–S-0.83.
Conclusions
In summary, we have disclosed for the rst time that, apart from
its well established use as hydrotreating catalysts, cobalt–
molybdenum sulphide (Co–Mo–S) unsupported materials are
also excellent catalysts for the inverse reaction, that is, carbon–
sulfur bond formation. Indeed, different Co–Mo–S catalysts
have been shown to be active in the reaction of benzenethiol
(1a) with benzyl alcohol (2a) to form benzyl phenyl sulphide
Experimental details
General procedure for the alkylation of thiols with alcohols
(3a). The reaction proceeds through a borrowing hydrogen Reactions were performed in a 7 mL reinforced glass reactor
sequence involving Co–Mo–S-mediated dehydrogenation and equipped with a pressure controller. The glass pressure tube
hydrogenation reactions. The catalytic activity of the most active containing a stirring bar was sequentially charged with Co–Mo–
catalyst (Co–Mo–S-0.83) for the aforementioned reaction is in S catalyst (13.1 mg), thiol (0.25 mmol), alcohol (0.5 mmol), n-
line with its previously reported hydrogenation activity, which hexadecane (30 mL) and toluene (1.6 mL). The pressure tube was
was associated with highly active but unstable Co–Mo–S-like then closed and the reactor was repeatedly purged with 5 bar of
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N2, pressurized to 3.5 bar and stirred and heated at 180 ꢀC in an
aluminium block previously preheated to this temperature.
Aer the desired reaction time, the reactor was cooled down to
room temperature and carefully depressurized. The reaction
mixture was diluted with ethyl acetate and an aliquot was taken
to be analysed by gas chromatography. To determine the iso-
lated yields, the diluted reaction mixture was ltered over Celite
to separate off the catalyst, and then puried by silica gel
chromatography affording the corresponding thioethers in the
reported yields.
Bioorg. Med. Chem. Lett., 2001, 11, 891–894; (d)
ˆ
A.-M. Faucher, P. W. White, C. Brochu, C. Grand-Maıtre,
J. Rancourt and G. Fazal, J. Med. Chem., 2004, 47, 18–21; (e)
J. W. Clader, W. Billard, H. Binch, L.-Y. Chen, G. Crosby,
R. A. Duffy, J. Ford, J. A. Kozlowski, J. E. Lachowicz, S. Li,
C. Liu, S. W. McCombie, S. Vice, G. Zhou and
W. J. Greenlee, Biorg. Med. Chem., 2004, 12, 319–326; (f)
S. Sciabola, E. Carosati, M. Baroni and R. Mannhold, J.
Med. Chem., 2005, 48, 3756–3767; (g) A. Gangjee, Y. Zeng,
T. Talreja, J. J. McGuire, R. L. Kisliuk and S. F. Queener, J.
Med. Chem., 2007, 50, 3046–3053; (h) F. Minghao,
T. Bingqing and H. L. a. X. J. Steven, Curr. Top. Med.
Chem., 2016, 16, 1200–1216.
General procedure for the synthesis of symmetrical thioethers
from H2S and alcohols
3 (a) H. B. Glass and E. E. Reid, J. Am. Chem. Soc., 1929, 51,
3428–3430; (b) G. Dougherty and P. D. Hammond, J. Am.
Chem. Soc., 1935, 57, 117–118; (c) N. Kharasch,
S. J. Potempa and H. L. Wehrmeister, Chem. Rev., 1946, 39,
269–332; (d) W. E. Parham and H. Wynberg, Org. Synth.,
1955, 35, 51; (e) S. Patai, The Chemistry of the Functional
Groups – The Chemistry of the Thiol Group, Wiley, London,
1974; (f) A. W. Herriott and D. Picker, J. Am. Chem. Soc.,
1975, 97, 2345–2349; (g) D. Landini and F. Rolla, Org.
Synth., 1978, 58, 143; (h) J. F. Boscato, J. M. Catala,
E. Franta and J. Brossas, Tetrahedron Lett., 1980, 21, 1519–
1520; (i) M. Kosugi, T. Ogata, M. Terada, H. Sano and
T. Migita, Bull. Chem. Soc. Jpn., 1985, 58, 3657–3658; (j)
F. J. A. Hundscheid, V. K. Tandon, P. H. F. M. Rouwette
and A. M. van Leusen, Tetrahedron, 1987, 43, 5073–5088;
(k) D. N. Harpp and M. Gingras, J. Am. Chem. Soc., 1988,
110, 7737–7745; (l) M. Gingras, T. H. Chan and
D. N. Harpp, J. Org. Chem., 1990, 55, 2078–2090; (m) C. J. Li
and D. N. Harpp, Tetrahedron Lett., 1992, 33, 7293–7294;
(n) J. Yin and C. Pidgeon, Tetrahedron Lett., 1997, 38, 5953–
The general procedure described above for the alkylation of
thiols with alcohols was applied with minor modications. The
glass pressure tube containing a stirring bar was sequentially
charged with Co–Mo–S catalyst (13.1 mg), alcohol (0.25 mmol),
n-hexadecane (30 mL) and toluene (1.6 mL). Aer the reactor was
sealed and purged with N2, it was pressurized to 4 bar with N2/
H2S (10% v/v in H2S).
Conflicts of interest
There are no conicts to declare.
Acknowledgements
Financial support by the Spanish Government-MINECO
through the program ‘‘Severo Ochoa” (SEV-2016-0683) is grate-
fully acknowledged. I. S. also acknowledges the Vice-Rectorate
for Research, Innovation and Transfer of the Universitat
`
`
Politecnica de Valencia (UPV) for a postdoctoral fellowship and
the Spanish Government-MINECO for a “Juan de la Cierva-
¨
5954; (o) J. Malmstrom, V. Gupta and L. Engman, J. Org.
´
Incorporacion” fellowship. The authors also acknowledge the
Chem., 1998, 63, 3318–3323; (p) P. Blanchard, B. Jousselme,
´
´
Microscopy Service of the UPV and Dr Jose Marıa Moreno for
`
P. Frere and J. Roncali, J. Org. Chem., 2002, 67, 3961–3964;
kind help with TEM and STEM measurements.
´
(q) N. Ichiishi, C. A. Malapit, Ł. Wozniak and
M. S. Sanford, Org. Lett., 2018, 20, 44–47.
4 (a) C. Shen, P. Zhang, Q. Sun, S. Bai, T. S. A. Hor and X. Liu,
Chem. Soc. Rev., 2015, 44, 291–314; (b) Z. Qiao and X. Jiang,
Org. Biomol. Chem., 2017, 15, 1942–1946.
5 (a) P. C. B. Page, S. S. Klair, M. P. Brown, M. M. Harding,
C. S. Smith, S. J. Maginn and S. Mulley, Tetrahedron Lett.,
1988, 29, 4477–4480; (b) I. P. Beletskaya and
A. V. Cheprakov, Coord. Chem. Rev., 2004, 248, 2337–2364;
References
1 (a) E. Block, Reactions of Organosulfur Compounds, Academic
Press, New York, 1978; (b) M. E. Peach, in The Chemistry of the
Thiol Group, ed. S. Patai, John Wiley & Sons, London, 1979,
pp. 721–723; (c) F. Bernardi, I. G. Csizmadia and
A. Mangini, Organic Sulfur Chemistry. Theoretical and
Experimental Advances, Elsevier, Amsterdam, 1985; (d)
R. J. Cremlyn, An Introduction to Organosulfur Chemistry,
John Wiley & Sons, New York, 1996; (e) T. Kondo and
T.-a. Mitsudo, Chem. Rev., 2000, 100, 3205–3220; (f) H. Liu
and X. Jiang, Chem.–Asian J., 2013, 8, 2546–2563.
2 (a) M. Artico, R. Silvestri, E. Pagnozzi, B. Bruno, E. Novellino,
G. Greco, S. Massa, A. Ettorre, A. G. Loi, F. Scintu and P. La
Colla, J. Med. Chem., 2000, 43, 1886–1891; (b) Z.-Y. Sun,
E. Botros, A.-D. Su, Y. Kim, E. Wang, N. Z. Baturay and
C.-H. Kwon, J. Med. Chem., 2000, 43, 4160–4168; (c)
Y. Wang, S. Chackalamannil, W. Chang, W. Greenlee,
V. Ruperto, R. A. Duffy, R. McQuade and J. E. Lachowicz,
´
´
(c) M. A. Fernandez-Rodrıguez, Q. Shen and J. F. Hartwig, J.
Am. Chem. Soc., 2006, 128, 2180–2181; (d) M. Arisawa,
T. Suzuki, T. Ishikawa and M. Yamaguchi, J. Am. Chem.
Soc., 2008, 130, 12214–12215; (e) A. Correa, M. Carril and
C. Bolm, Angew. Chem., Int. Ed., 2008, 47, 2880–2883; (f)
J.-R. Wu, C.-H. Lin and C.-F. Lee, Chem. Commun., 2009,
´
´
4450–4452; (g) M. A. Fernandez-Rodrıguez and
J. F. Hartwig, Chem.–Eur. J., 2010, 16, 2355–2359; (h)
I. P. Beletskaya and V. P. Ananikov, Chem. Rev., 2011, 111,
1596–1636; (i) M. Sayah and M. G. Organ, Chem.–Eur. J.,
2011, 17, 11719–11722; (j) M.-T. Lan, W.-Y. Wu,
S.-H. Huang, K.-L. Luo and F.-Y. Tsai, RSC Adv., 2011, 1,
Chem. Sci.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Edge Article
1751–1755; (k) J. R. Cabrero-Antonino, T. Garcıa, P. Rubio-
Chemical Science
´
7 (a) M. T. Martin, A. M. Thomas and D. G. York, Tetrahedron
Lett., 2002, 43, 2145–2147; (b) A. Saxena, A. Kumar and
S. Mozumdar, J. Mol. Catal. A: Chem., 2007, 269, 35–40; (c)
B. P. Bandgar, S. S. Gawande and D. B. Muley, Green Chem.
Lett. Rev., 2010, 3, 49–54; (d) K. Bahrami, M. M. Khodaei
and N. Khodadoustan, Synlett, 2011, 2206–2210; (e)
B. Basu, S. Kundu and D. Sengupta, RSC Adv., 2013, 3,
22130–22134; (f) H. Hikawa, M. Toyomoto, S. Kikkawa and
I. Azumaya, Org. Biomol. Chem., 2015, 13, 11459–11465; (g)
H. Hikawa, Y. Machino, M. Toyomoto, S. Kikkawa and
I. Azumaya, Org. Biomol. Chem., 2016, 14, 7038–7045; (h)
F. Santoro, M. Mariani, F. Zaccheria, R. Psaro and
N. Ravasio, Beilstein J. Org. Chem., 2016, 12, 2627–2635; (i)
K. Kucinski and G. Hreczycho, Eur. J. Org. Chem., 2017,
5572–5581.
8 (a) M. H. S. A. Hamid, P. A. Slatford and J. M. J. Williams, Adv.
Synth. Catal., 2007, 349, 1555–1575; (b) T. D. Nixon,
M. K. Whittlesey and J. M. J. Williams, Dalton Trans., 2009,
753–762; (c) D. Hollmann, ChemSusChem, 2014, 7, 2411–
2413; (d) J. Muzart, Eur. J. Org. Chem., 2015, 5693–5707; (e)
K.-i. Shimizu, Catal. Sci. Technol., 2015, 5, 1412–1427; (f)
A. Corma, J. Navas and M. J. Sabater, Chem. Rev., 2018,
118, 1410–1459.
´
´
Marques, J. A. Vidal-Moya, A. Leyva-Perez, S. S. Al-Deyab,
´
S. I. Al-Resayes, U. Dıaz and A. Corma, ACS Catal., 2011, 1,
147–158; (l) R. B. N. Baig and R. S. Varma, Chem. Commun.,
2012, 48, 2582–2584; (m) Y. Liao, P. Jiang, S. Chen, H. Qi
and G.-J. Deng, Green Chem., 2013, 15, 3302–3306; (n)
T.-J. Liu, C.-L. Yi, C.-C. Chan and C.-F. Lee, Chem.–Asian J.,
2013, 8, 1029–1034; (o) A. Kamal, V. Srinivasulu,
J. N. S. R. C. Murty, N. Shankaraiah, N. Nagesh,
T. Srinivasa Reddy and A. V. Subba Rao, Adv. Synth. Catal.,
2013, 355, 2297–2307; (p) S. D. Timpa, C. J. Pell and
O. V. Ozerov, J. Am. Chem. Soc., 2014, 136, 14772–14779; (q)
C.-F. Lee, Y.-C. Liu and S. S. Badsara, Chem.–Asian J., 2014,
9, 706–722; (r) A. M. Thomas, S. Asha, K. S. Sindhu and
G. Anilkumar, Tetrahedron Lett., 2015, 56, 6560–6564; (s)
M. S. Oderinde, M. Frenette, D. W. Robbins, B. Aquila and
J. W. Johannes, J. Am. Chem. Soc., 2016, 138, 1760–1763; (t)
K. Kanemoto, Y. Sugimura, S. Shimizu, S. Yoshida and
T. Hosoya, Chem. Commun., 2017, 53, 10640–10643; (u)
C.-W. Chen, Y.-L. Chen, D. M. Reddy, K. Du, C.-E. Li,
B.-H. Shih, Y.-J. Xue and C.-F. Lee, Chem.–Eur. J., 2017, 23,
10087–10091; (v) Z. Lian, B. N. Bhawal, P. Yu and
B. Morandi, Science, 2017, 356, 1059–1063; (w) Y. Fang,
T. Rogge, L. Ackermann, S.-Y. Wang and S.-J. Ji, Nat.
Commun., 2018, 9, 2240; (x) K. D. Jones, D. J. Power,
D. Bierer, K. M. Gericke and S. G. Stewart, Org. Lett., 2018,
20, 208–211.
9 (a) G. Guillena, D. J. Ramon and M. Yus, Chem. Rev., 2010,
110, 1611–1641; (b) S. Baehn, S. Imm, L. Neubert,
M. Zhang, H. Neumann and M. Beller, ChemCatChem,
2011, 3, 1853–1864; (c) Q. Yang, Q. Wang and Z. Yu, Chem.
Soc. Rev., 2015, 44, 2305–2329; (d) X. Ma, C. Su and Q. Xu,
Top. Curr. Chem., 2016, 374, 27.
6 (a) P. Kumar, R. K. Pandey and V. R. Hegde, Synlett, 1999,
1921–1922; (b) S. Kanagasabapathy, A. Sudalai and
B. C. Benicewicz, Tetrahedron Lett., 2001, 42, 3791–3794; (c) 10 (a) G. Guillena, D. J. Ramon and M. Yus, Angew. Chem., Int.
N. Morita and N. Krause, Angew. Chem., Int. Ed., 2006, 45,
1897–1899; (d) M. Kawatsura, Y. Komatsu, M. Yamamoto,
S. Hayase and T. Itoh, Tetrahedron Lett., 2007, 48, 6480–
Ed., 2007, 46, 2358–2364; (b) F. Huang, Z. Liu and Z. Yu,
Angew. Chem., Int. Ed., 2016, 55, 862–875; (c) Y. Obora, Top.
Curr. Chem., 2016, 374, 11.
´
6482; (e) S. Banerjee, J. Das, R. P. Alvarez and S. Santra, 11 A. Corma, J. Navas, T. Rodenas and M. J. Sabater, Chem.–Eur.
New J. Chem., 2010, 34, 302–306; (f) J. R. Cabrero-Antonino, J., 2013, 19, 17464–17471.
A. Leyva-Perez and A. Corma, Adv. Synth. Catal., 2012, 354, 12 (a) R. S. Glass, Synth. Commun., 1976, 6, 47–51; (b)
´
´
678–687; (g) J. R. Cabrero-Antonino, A. Leyva-Perez and
Y. Kikugawa, Chem. Lett., 1981, 1157–1158; (c) G. A. Olah,
Q. Wang, N. J. Trivedi and G. K. Surya Prakash, Synthesis,
1992, 465–466; (d) G. A. Olah, Q. Wang, X.-y. Li and
G. K. Surya Prakash, Synlett, 1993, 32–34.
A. Corma, Chem.–Eur. J., 2013, 19, 8627–8633; (h)
R. Castarlenas, A. Di Giuseppe, J. J. Perez-Torrente and
L. A. Oro, Angew. Chem., Int. Ed., 2013, 52, 211–222; (i)
´
´
´
X. Zeng, Chem. Rev., 2013, 113, 6864–6900; (j) K. Kucinski, 13 (a) L. Liu, P. Concepcion and A. Corma, J. Catal., 2016, 340,
´
´
P. Pawluc and G. Hreczycho, Adv. Synth. Catal., 2015, 357,
1–9; (b) L. Liu, F. Gao, P. Concepcion and A. Corma, J. Catal.,
3936–3942; (k) R. Kumar, Saima, A. Shard, N. H. Andhare,
Richa and A. K. Sinha, Angew. Chem., Int. Ed., 2015, 54,
2017, 350, 218–225; (c) R. Milian, L. Liu, M. Boronat and
A. Corma, J. Catal., 2018, 364, 19–30; (d) G. A. Filonenko,
R. van Putten, E. J. M. Hensen and E. A. Pidko, Chem. Soc.
Rev., 2018, 47, 1459–1483.
´
828–832; (l) M. Perez, T. Mahdi, L. J. Hounjet and
D. W. Stephan, Chem. Commun., 2015, 51, 11301–11304;
(m) L. Palacios, A. Di Giuseppe, M. J. Artigas, V. Polo, 14 (a) K. Taguchi, H. Nakagawa, T. Hirabayashi, S. Sakaguchi and
´
F. J. Lahoz, R. Castarlenas, J. J. Perez-Torrente and
Y. Ishii, J. Am. Chem. Soc., 2004, 126, 72–73; (b) S. Burling,
B. M. Paine, D. Nama, V. S. Brown, M. F. Mahon, T. J. Prior,
P. S. Pregosin, M. K. Whittlesey and J. M. J. Williams, J. Am.
Chem. Soc., 2007, 129, 1987–1995; (c) Y. Iuchi, Y. Obora and
Y. Ishii, J. Am. Chem. Soc., 2010, 132, 2536–2537; (d)
B. Blank and R. Kempe, J. Am. Chem. Soc., 2010, 132, 924–
925; (e) Y. Obora, Y. Anno, R. Okamoto, T. Matsu-ura and
Y. Ishii, Angew. Chem., Int. Ed., 2011, 50, 8618–8622; (f)
L. A. Oro, Catal. Sci. Technol., 2016, 6, 8548–8561; (n)
J. L. Kennemur, G. D. Kortman and K. L. Hull, J. Am. Chem.
Soc., 2016, 138, 11914–11919; (o) L. Palacios, Y. Meheut,
M. Galiana-Cameo, M. J. Artigas, A. Di Giuseppe,
´
F. J. Lahoz, V. Polo, R. Castarlenas, J. J. Perez-Torrente and
L. A. Oro, Organometallics, 2017, 36, 2198–2207; (p)
J. R. Cabrero-Antonino, M. Tejeda-Serrano, M. Quesada,
´
˜
J. A. Vidal-Moya, A. Leyva-Perez and A. Corma, Chem. Sci.,
M. Pena-Lopez, H. Neumann and M. Beller, Chem.
2017, 8, 689–696.
Commun., 2015, 51, 13082–13085; (g) L. Guo, X. Ma,
This journal is © The Royal Society of Chemistry 2019
Chem. Sci.

View Article Online
Chemical Science
Edge Article
H. Fang, X. Jia and Z. Huang, Angew. Chem., Int. Ed., 2015, 54,
4023–4027; (h) D. Shen, D. L. Poole, C. C. Shotton,
U. K. Das, Y. Ben-David, Y. Diskin-Posner and D. Milstein,
Angew. Chem., Int. Ed., 2018, 57, 2179–2182.
˜
A. F. Kornahrens, M. P. Healy and T. J. Donohoe, Angew. 19 P. Piehl, M. Pena-Lopez, A. Frey, H. Neumann and M. Beller,
Chem., Int. Ed., 2015, 54, 1642–1645; (i) Q. Zou, C. Wang, Chem. Commun., 2017, 53, 3265–3268.
J. Smith, D. Xue and J. Xiao, Chem.–Eur. J., 2015, 21, 9656– 20 (a) C. Carlini, A. Macinai, M. Marchionna, M. Noviello,
9661; (j) R. Ramachandran, G. Prakash, S. Selvamurugan,
P. Viswanathamurthi, J. G. Malecki, W. Linert and A. Gusev,
A. M. R. Galletti and G. Sbrana, J. Mol. Catal. A: Chem.,
2003, 206, 409–418; (b) F. Alonso, P. Riente and M. Yus,
Eur. J. Org. Chem., 2008, 4908–4914; (c) K.-i. Shimizu,
S. Kanno, K. Kon, S. M. A. Hakim Siddiki, H. Tanaka and
Y. Sakata, Catal. Today, 2014, 232, 134–138; (d)
˜
RSC Adv., 2015, 5, 11405–11422; (k) M. Pena-Lopez,
H. Neumann and M. Beller, Angew. Chem., Int. Ed., 2016, 55,
7826–7830; (l) Q. Wang, K. Wu and Z. Yu, Organometallics,
2016, 35, 1251–1256; (m) K. O. Marichev and J. M. Takacs,
´
´
´
G. Onyestyak, G. Novodarszki, R. Barthos, S. Klebert,
´
˚
´
ACS Catal., 2016, 6, 2205–2210; (n) A. Said Stalsmeden,
A. F. Wellisch and A. Pilbath, RSC Adv., 2015, 5, 99502–
99509; (e) J. Xu, H. Yue, S. Liu, H. Wang, Y. Du, C. Xu,
W. Dong and C. Liu, RSC Adv., 2016, 6, 24164–24174.
´
J. L. Belmonte Vazquez, K. van Weerdenburg, R. Rae,
P.-O. Norrby and N. Kann, ACS Sustainable Chem. Eng.,
2016, 4, 5730–5736.
21 (a) H. Topsøe, B. S. Clausen and F. E. Massoth, Hydrotreating
Catalysis, Science and Technology, Springer-Verlag,
Heidelberg, 1996; (b) K. Toshiaki, I. Atsushi and
Q. Weihua, Hydrodesulfurization and Hydrodenitrogenation:
Chemistry and Engineering, Wiley-VCH, Tokyo, 1999; (c)
15 (a) J. Yang, X. Liu, D.-L. Meng, H.-Y. Chen, Z.-H. Zong,
T.-T. Feng and K. Sun, Adv. Synth. Catal., 2012, 354, 328–
334; (b) M. Bala, P. K. Verma, U. Sharma, N. Kumar and
B. Singh, Green Chem., 2013, 15, 1687–1693; (c) T. Yan,
B. L. Feringa and K. Barta, Nat. Commun., 2014, 5, 5602; (d)
S. Elangovan, J.-B. Sortais, M. Beller and C. Darcel, Angew.
Chem., Int. Ed., 2015, 54, 14483–14486; (e) H.-J. Pan,
´
R. A. Sanchez-Delgado, Organometallic Modeling of the
Hydrodesulfurization and Hydrodenitrogenation Reactions,
Springer Netherlands, Kluwer, Dordrecht, 2002.
T. W. Ng and Y. Zhao, Chem. Commun., 2015, 51, 11907– 22 (a) Exxonmobil Pat., US Pat. 6,299,760, 2001; (b)
11910; (f) B. Emayavaramban, M. Roy and B. Sundararaju,
Chem.–Eur. J., 2016, 22, 3952–3955; (g) M. Mastalir,
F. L. Plantenga, R. Cerfontain, S. Eijsbouts, F. van Houtert,
G. H. Anderson, S. Miseo, S. Soled, K. Riley, K. Fujita and
Y. Inoue, Stud. Surf. Sci. Catal., 2003, 145, 407–410.
¨
B. Stoger, E. Pittenauer, M. Puchberger, G. Allmaier and
K. Kirchner, Adv. Synth. Catal., 2016, 358, 3824–3831; (h) 23 S. Eijsbouts, S. W. Mayo and K. Fujita, Appl. Catal., A, 2007,
˜
M. Pena-Lopez, H. Neumann and M. Beller, ChemSusChem,
322, 58–66.
2016, 9, 2233–2238; (i) T. Yan, B. L. Feringa and K. Barta, 24 (a) B. Yoosuk, C. Song, J. H. Kim, C. Ngamcharussrivichai
ACS Catal., 2016, 6, 381–388; (j) K. Polidano,
B. D. W. Allen, J. M. J. Williams and L. C. Morrill, ACS
Catal., 2018, 8, 6440–6445.
and P. Prasassarakich, Catal. Today, 2010, 149, 52–61; (b)
B. Yoosuk, D. Tumnantong and P. Prasassarakich, Fuel,
2012, 91, 246–252; (c) N. Liu, X. Wang, W. Xu, D. Guo,
J. Tang and B. Zhang, Prog. Chem., 2013, 25, 726–734; (d)
W. Wang, K. Zhang, L. Li, K. Wu, P. Liu and Y. Yang, Ind.
¨
16 (a) S. Rosler, M. Ertl, T. Irrgang and R. Kempe, Angew. Chem.,
Int. Ed., 2015, 54, 15046–15050; (b) N. Deibl and R. Kempe, J.
Am. Chem. Soc., 2016, 138, 10786–10789; (c) Z. Yin, H. Zeng,
J. Wu, S. Zheng and G. Zhang, ACS Catal., 2016, 6, 6546–
6550; (d) F. Freitag, T. Irrgang and R. Kempe, Chem.–Eur.
J., 2017, 23, 12110–12113; (e) G. Zhang, J. Wu, H. Zeng,
S. Zhang, Z. Yin and S. Zheng, Org. Lett., 2017, 19, 1080–1083.
17 S. Liao, K. Yu, Q. Li, H. Tian, Z. Zhang, X. Yu and Q. Xu, Org.
Biomol. Chem., 2012, 10, 2973–2978.
18 (a) S. Elangovan, J. Neumann, J.-B. Sortais, K. Junge,
C. Darcel and M. Beller, Nat. Commun., 2016, 7, 12641; (b)
A. Mukherjee, A. Nerush, G. Leitus, L. J. W. Shimon,
Y. Ben David, N. A. Espinosa Jalapa and D. Milstein, J. Am.
Eng.
Chem.
Res.,
2014,
53,
19001–19009;
(e)
V. Itthibenchapong, C. Ratanatawanate, M. Oura and
K. Faungnawakij, Catal. Commun., 2015, 68, 31–35; (f)
W. Wang, L. Li, K. Wu, G. Zhu, S. Tan, W. Li and Y. Yang,
RSC Adv., 2015, 5, 61799–61807; (g) W. Wang, L. Li, K. Wu,
K. Zhang, J. Jie and Y. Yang, Appl. Catal., A, 2015, 495, 8–
16; (h) W. Wang, L. Li, K. Wu, G. Zhu, S. Tan, Y. Liua and
Y. Yang, RSC Adv., 2016, 6, 31265–31271; (i) W. Wang,
L. Li, S. Tan, K. Wu, G. Zhu, Y. Liu, Y. Xu and Y. Yang,
Fuel, 2016, 179, 1–9; (j) W. Wang, K. Wu, L. Li, S. Tan,
G. Zhu, W. Li, Z. He and Y. Yang, Catal. Commun., 2016,
74, 60–64; (k) W. Wang, G. Zhu, L. Li, S. Tan, K. Wu,
X. Zhang and Y. Yang, Fuel, 2016, 174, 1–8.
˜
Chem. Soc., 2016, 138, 4298–4301; (c) M. Pena-Lopez,
P. Piehl, S. Elangovan, H. Neumann and M. Beller, Angew.
Chem., Int. Ed., 2016, 55, 14967–14971; (d) A. Bruneau- 25 (a) I. Sorribes, L. Liu and A. Corma, ACS Catal., 2017, 7,
´
´
Voisine, D. Wang, V. Dorcet, T. Roisnel, C. Darcel and
2698–2708; (b) I. Sorribes, L. Liu, A. Domenech-Carbo and
J.-B. Sortais, J. Catal., 2017, 347, 57–62; (e) N. Deibl and
A. Corma, ACS Catal., 2018, 8, 4545–4557.
R. Kempe, Angew. Chem., Int. Ed., 2017, 56, 1663–1666; (f) 26 (a) H. Topsøe, B. S. Clausen, R. Candia, C. Wivel and
S. Fu, Z. Shao, Y. Wang and Q. Liu, J. Am. Chem. Soc., 2017,
139, 11941–11948; (g) J. Neumann, S. Elangovan,
A. Spannenberg, K. Junge and M. Beller, Chem.–Eur. J.,
2017, 23, 5410–5413; (h) M. K. Barman, S. Waiba and
B. Maji, Angew. Chem., Int. Ed., 2018, 57, 9126–9130; (i)
S. Morup, J. Catal., 1981, 68, 433–452; (b) C. Wivel,
R. Candia, B. S. Clausen, S. Morup and H. Topsøe, J.
Catal., 1981, 68, 453–463; (c) B. S. Clausen, H. Topsøe,
R. Candia, J. Villadsen, B. Lengeler, J. Alsnielsen and
F. Christensen, J. Phys. Chem., 1981, 85, 3868–3872; (d)
M. Breysse, B. A. Bennett, D. Chadwick and M. Vrinat, Bull.
Chem. Sci.
This journal is © The Royal Society of Chemistry 2019

View Article Online
Edge Article
Soc. Chim. Belg., 1981, 90, 1271–1277; (e) N. Y. Topsøe and
Chemical Science
H. Topsøe, E. Lægsgaard, J. V. Lauritsen and
F. Besenbacher, J. Catal., 2010, 272, 195–203; (r) Y. Zhu,
Q. M. Ramasse, M. Brorson, P. G. Moses, L. P. Hansen,
C. F. Kisielowski and S. Helveg, Angew. Chem., Int. Ed.,
2014, 53, 10723–10727.
H. Topsøe, J. Catal., 1983, 84, 386–401; (f) S. Kasztelan,
H. Toulhoat, J. Grimblot and J. P. Bonnelle, Appl. Catal.,
1984, 13, 127–159; (g) H. Topsøe and B. S. Clausen, Appl.
Catal., 1986, 25, 273–293; (h) L. S. Byskov, J. K. Nørskov,
¨
´
B. S. Clausen and H. Topsøe, J. Catal., 1999, 187, 109–122; 27 (a) F. Scholz, U. Schroder, R. Gulaboski and A. Domenech-
´
(i) H. Schweiger, P. Raybaud and H. Toulhoat, J. Catal.,
2002, 212, 33–38; (j) J. V. Lauritsen, M. V. Bollinger,
E. Lægsgaard, K. W. Jacobsen, J. K. Nørskov, B. S. Clausen,
H. Topsøe and F. Besenbacher, J. Catal., 2004, 221, 510–
Carbo, Electrochemistry of Immobilized Particles and
Droplets, Springer, Berlin-Heidelberg, 2nd edn, 2014; (b)
A. Domenech-Carbo, J. Labuda and F. Scholz, Pure Appl.
Chem., 2012, 85, 609–631.
522; (k) H. Topsøe, Appl. Catal., A, 2007, 322, 3–8; (l) 28 (a) L. R. McCullough, D. J. Childers, R. A. Watson, B. A. Kilos,
J. V. Lauritsen, J. Kibsgaard, G. H. Olesen, P. G. Moses,
B. Hinnemann, S. Helveg, J. K. Nørskov, B. S. Clausen,
H. Topsøe, E. Lægsgaard and F. Besenbacher, J. Catal.,
2007, 249, 220–233; (m) G. Berhault, M. Perez De la Rosa,
D. G. Barton, E. Weitz, H. H. Kung and J. M. Notestein, ACS
Sustainable Chem. Eng., 2017, 5, 4890–4896; (b)
L. R. McCullough, E. S. Cheng, A. A. Gosavi, B. A. Kilos,
D. G. Barton, E. Weitz, H. H. Kung and J. M. Notestein, J.
Catal., 2018, 366, 159–166.
´
A. Mehta, M. J. Yacaman and R. R. Chianelli, Appl. Catal.,
´
A, 2008, 345, 80–88; (n) F. Besenbacher, M. Brorson, 29 (a) A. Pieplu, O. Saur, J.-C. Lavalley, O. Legendre and
´
B. S. Clausen, S. Helveg, B. Hinnemann, J. Kibsgaard,
J. V. Lauritsen, P. G. Moses, J. K. Nørskov and H. Topsøe,
C. Nedez, Catal. Rev.: Sci. Eng., 1998, 40, 409–450; (b)
J. S. Eow, Environ. Prog., 2002, 21, 143–162.
Catal. Today, 2008, 130, 86–96; (o) A. D. Gandubert, 30 (a) H. Huang, Y. Yu and K. H. Chung, Energy Fuels, 2009, 23,
E. Krebs, C. Legens, D. Costa, D. Guillaume and
P. Raybaud, Catal. Today, 2008, 130, 149–159; (p) E. Krebs,
B. Silvi and P. Raybaud, Catal. Today, 2008, 130, 160–169;
(q) J. Kibsgaard, A. Tuxen, K. G. Knudsen, M. Brorson,
4420–4425; (b) G. Singh, P. G. Nakade, D. Chetia, P. Jha,
U. Mondal, S. Kumari and S. Sen, Ind. Eng. Chem., 2016,
37, 190–197.
This journal is © The Royal Society of Chemistry 2019
Chem. Sci.