Synthesis of unsymmetrical benzilsviapalladium-catalysed a-arylation-oxidation of 2-hydroxyacetophenones with aryl bromides

Article abstract of DOI:10.1039/d0ob00575d

A diverse set of unsymmetrically substituted benzils were facilely synthesised by a cross-coupling reaction between 2-hydroxyacetophenones and aryl bromides in the presence of a palladium catalyst. Experimental studies suggested a reaction mechanism involving a one-pot tandem palladium-catalysed a-arylation and oxidation, where aryl bromides play a dual role as mild oxidants as well as arylating agents.

Full text of DOI:10.1039/d0ob00575d

View Article Online
View Journal
Organic &
Biomolecular
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: T. Matsuda and S.
Oyama, Org. Biomol. Chem., 2020, DOI: 10.1039/D0OB00575D.
Volume 15
Number 47
21 December 2017
Pages 9945-10124
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Organic &
Biomolecular
Chemistry
Accepted Manuscripts are published online shortly after acceptance,
rsc.li/obc
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
ISSN 1477-0520
PAPER
I . J. Dmochowski et al.
Oligonucleotide modifi cations enhance probe stability for
shall the Royal Society of Chemistry be held responsible for any errors
single cell transcriptome in vivo analysis (TIVA)
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
rsc.li/obc

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 1 of 4
View Article Online
DOI: 10.1039/D0OB00575D
ARTICLE
Synthesis of unsymmetrical benzils via palladium-catalysed α-
arylation–oxidation of 2-hydroxyacetophenones with aryl
bromides
Received 00th January 20xx,
Accepted 00th January 20xx
Takanori Matsuda* and Souta Oyama
DOI: 10.1039/x0xx00000x
A diverse set of unsymmetrically substituted benzils were facilely synthesised by a cross-coupling reaction between 2-
hydroxyacetophenones and aryl bromides in the presence of a palladium catalyst. Experimental studies suggested a reaction
mechanism involving a one-pot tandem palladium-catalysed α-arylation and oxidation, where aryl bromides play a dual role
as mild oxidants as well as arylating agents.
of aryl bromides as mild oxidants, under catalytic conditions. In
reactions of α-hydroxy ketones with two nucleophilic sites, C-
arylation is particularly favoured over O-arylation.10 Moreover,
a control experiment revealed that 2-hydroxyacetophenones
are more prone to α-arylation than acetophenone.
Introduction
1,2-Diketones are members of an important class of molecules
with diverse application potential in various fields. They are
useful building blocks for the synthesis of a range of carbo- and
heterocyclic
compounds,1
and
1,2-diketone-derived
compounds have been utilised as ligands for transition metals.2
Among these 1,2-diketones, benzils (diphenylethanediones) are
recognised as privileged scaffolds that have distinct properties,
and they can be converted into compounds with vicinal
diphenyl groups. Benzils are generally synthesised via oxidation
of the corresponding benzoins,3 diarylacetylenes,4 or other 1,2-
diphenyl derivatives.5 Thus, the traditional synthesis of
unsymmetrical benzils necessitates the preparation of
unsymmetrical starting materials, which can complicate the
process considerably. In this context, significant advances have
recently been made, whereby coupling strategies offer a viable
and effective procedure for the synthesis of unsymmetrical
benzils.6,7 In particular, a reaction employing an aryl halide as
the aryl source would be advantageous, as a large number of
aryl halides are currently commercially available and relatively
inexpensive.
Palladium-catalysed α-arylation of ketones with aryl halides,
enabling cross-coupling between an electrophilic aryl group and
a nucleophilic ketone enolate, represents a versatile and robust
method for the synthesis of α-aryl ketones.8 Although the α-
arylation of other carbonyl compounds, such as esters and
aldehydes, as well as nitriles, and nitroalkanes has been well
established,9 to date, there have been no reports on a reaction
utilizing α-hydroxy ketones as nucleophiles. In this paper, we
report that palladium(0)-catalysed α-arylation of 2-
hydroxyacetophenones with aryl bromides produces benzoins,
which are subsequently oxidised to benzils through the action
Results and discussion
2-Hydroxyacetophenone (1a) and 4-bromotoluene (2a, 2 equiv)
were heated in toluene at 100 °C in the presence of 10 mol%
Pd(PPh3)4 as the catalyst and NaOt-Bu as a base for 24 h (Table
1, entry 1). The reaction primarily resulted in a reductive
homocoupling to afford a biaryl, and no cross-coupling was
observed. In contrast, when [PdCl(allyl)]2 was employed as the
catalyst, cross-coupling between 1a and 2a occurred, but the
benzil product 3aa was isolated in only 9% yield (entry 2). The
anticipated α-arylation product, benzoin, was not detected in
the reaction mixture, indicating that oxidation had occurred
concomitantly during the reaction. To increase the product
yield, we examined various phosphine ligands and found that
XPhos11 was the most effective (36% yield) among those
examined (entries 3–8). As for the palladium complexes,
[PdCl(allyl)]2 was found to be the complex of choice for this
reaction (entries 8–11).
Table 1. Screening of palladium complexes and phosphine ligands for the palladium-
catalysed coupling of 2-hydroxyacetophenone (1a) with 4-bromotoluene (2a)a
Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka,
Shinjuku-ku, Tokyo 162-8601, Japan. E-mail: mtd@rs.tus.ac.jp
† Electronic Supplementary Information (ESI) available: Experimental procedures
and characterisation data for new compounds. See DOI: 10.1039/x0xx00000x
Please do not adjust margins

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 2 of 4
ARTICLE
Journal Name
Entry
1
Pd catalyst (mol%)
Pd(PPh3)4 (10)
[PdCl(allyl)]2 (5)
Yieldb (%)
<5
9
Entry
1
2
3
4
5
6
7
8
Base
Solvent
toluene
toluene
toluene
toluene
toluene
toluene
toluene
1,4-dioxane
THF
ClCH2CH2Cl
DMF
EtOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
Time (h) VieYwieAlrdtibcl(e%O)nline
DOI: 10.1039/D0OB00575D
NaOt-Bu
KOt-Bu
NaN(SiMe3)2
Cs2CO3
K2CO3
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
6
6
6
6
6
6
18
18
18
18
18
18
18
18
18
18
18
56
22
32
33
35
62
80
72
70
33
25
33
80
90
83
25
91
2
3
4
5
6
7
8
9
[PdCl(allyl)]2/PPh3 (5/20)
[PdCl(allyl)]2/DPPE (5/10)
[PdCl(allyl)]2/XANTPHOS (5/10)
[PdCl(allyl)]2/DavePhos (5/20)
[PdCl(allyl)]2/JohnPhos (5/10)
[PdCl(allyl)]2/XPhos (5/20)
Pd(OAc)2/XPhos (10/20)
Pd(OCOCF3)2/XPhos (10/20)
Pd2(dba)3/XPhos (5/20)
<5
14
5
20
35
36
21
31
33
9
10
11
10
11
12
13
14c
15c,d
16c,e
17c,f
a
Reaction conditions: 1a (0.100 mmol), 2a (0.200 mmol), Pd complex (10
mol%), phosphine ligand (20/10 mol% for monodentate/bidentate), NaOt-
Bu (0.200 mmol), and toluene (0.5 mL) at 100 °C for 24 h. b Isolated yield.
As the decomposition of benzil 3aa was observed with
longer reaction times under the conditions employing NaOt-Bu,
further optimisation was performed (Table 2). An extensive a Reaction conditions: 1a (0.100 mmol), 2a (0.200 mmol), [PdCl(allyl)]2 (0.005
investigation into the choice of base (entries 1–6) indicated that
the use of K3PO4 resulted in a cleaner reaction, furnishing 3aa in
62% yield within 6 h;12 the yield was further improved to 80%
when the reaction time was 18 h (entry 7). Notably, the reaction
proceeded smoothly without the need for stronger bases, such
as alkoxides. Solvent screening confirmed that t-BuOH was the
mmol, 10 mol% Pd), XPhos (0.020 mmol, 20 mol%), base (0.200 mmol) and
solvent (0.5 mL) at 100 °C for the indicated time unless otherwise noted.
b
c
d
Isolated yield. 2.5 Equiv (0.250 mmol) each of 2a and K3PO4 were used.
2.5 mol% [PdCl(allyl)]2 (5.0 mol% Pd) was used. e 1.0 mol% [PdCl(allyl)]2 (2.0
mol% Pd) was used. f 1a (6.00 mmol) was reacted under reflux.
The reaction proved efficient using an aryl triflate, providing
optimal solvent, giving superior results in terms of the 3aa in 98% yield (Scheme 1). A slight decrease in yield was
prevention of decomposition of α-hydroxy ketone 1a (entries 7– observed for aryl chlorides. In the case of an aryl iodide,
13). Finally, the use of 2.5 equiv of both the aryl bromide 2a and however, the yield was reduced to 52% due to the competing
the base afforded 3aa in 90% yield (entry 14). The reaction with biaryl homocoupling.
5 mol% catalyst loading provided a comparable yield, while the
yield deteriorated with further catalyst loading reduction to 2
mol% (entries 15 and 16). The coupling was successfully
performed on a gram scale to furnish 1.2 g of 3aa in 91% yield
(entry 17).
Table 2. Screening of bases and solventsa
Scheme 1. Comparison of the reactivity of aryl halides and triflate
With the optimised conditions in hand, we investigated the
scope of the coupling reaction and found that a diverse array of
unsymmetrical benzils, as well as the parent benzil could be
effectively synthesised (Table 3). Coupling of 1a with
bromobenzenes 2c–g bearing electron-donating and electron-
withdrawing substituents at the meta- or para-positions
afforded the corresponding benzils 3ac–ag in 61–98% yields
(entries 2–6). Moreover, it was established that the reaction
was effective in the presence of heteroatom substituents
(entries 7–10). The reaction using 2- and 1-naphthyl bromides
2l and 2m delivered 1,2-diketones 3al and 3am in 79% and 58%
yields, respectively, (entries 11 and 12). However, the yields of
3
declined
considerably
when
ortho-substituted
bromobenzenes 2n and 2o were used (entries 13 and 14). The
attempted reaction with 4-bromophenol afforded only a trace
amount of the desired product, and the formation of complex
product mixtures was observed with 1-bromo-3-nitrobenzene
and 3′-bromoacetophenone.13 Furthermore, a variety of α-
hydroxy ketones 1b–k, including naphthyl and heteroaryl
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
Organic & Biomolecular Chemistry
Please do not adjust margins
Journal Name
ARTICLE
ketones, also underwent the coupling reaction with 2a to Palladium-catalysed oxidation of alcohols using aVryielwhAartilcidleeOsnlianes
deliver 3ba–ka (entries 15–24).14 Finally, it was demonstrated oxidants has been reported.15 Indeed,DoOxI:id10a.t1i0o3n9/Do0fObBe00n5z7o5iDn
that additional unsymmetrical benzils, including highly (4ab) with 2a in the presence of the Pd–XPhos catalyst and
electronically biased 3ee, could be obtained by the coupling K3PO4 in t-BuOH furnished benzil (3ab) in a high yield, whereas
protocol (entries 25–31).
the oxidation of 4ab failed to occur in the absence of 2a
(Scheme 2C). In the case of the reaction with 1-bromo-4-(tert-
butyl)benzene (2c), the formation of tert-butylbenzene (42%)
was detected by GC along with the quantitative formation of
benzil 3ac (Scheme 2D). Another possible scenario involving an
initial oxidation of an α-hydroxy ketone to a glyoxal, which is
subsequently arylated, was excluded, and no arylation of
phenylglyoxal (6) was observed under our conditions (Scheme
2E).16
Table 3. Scope of palladium-catalysed α-arylation–oxidation of 1 with 2a
Entry
1
1 (Ar1)
1a (Ph)
2 (Ar2)
2b (Ph)
3
Yieldb [%]
88
86
98
78
70
61
89
98
76
49
79
58
45
44
92
95
78
64
79
71
74
72
55
76
71
59
65
70
62
61
82
3ab
3ac
3ad
3ae
3af
3ag
3ah
3ai
2
1a (Ph)
2c (4-t-BuC6H4)
2d (3-MeC6H4)
2e (4-MeOC6H4)
2f (4-F3CC6H4)
2g (3-MeO2CC6H4)
2h (4-FC6H4)
3
1a (Ph)
4
1a (Ph)
5
1a (Ph)
6
1a (Ph)
7
1a (Ph)
8
1a (Ph)
2i (4-Me3SiC6H4)
2j (3-MeSC6H4)
2k (3-(dan)BC6H4)c
2l (2-naphthyl)
2m (1-naphthyl)
2n (2-MeC6H4)
2o (2-MeOC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2a (4-MeC6H4)
2e (4-MeOC6H4)
2e (4-MeOC6H4)
2f (4-F3CC6H4)
2l (2-naphthyl)
2f (4-F3CC6H4)
2f (4-F3CC6H4)
2l (2-naphthyl)
9
1a (Ph)
3aj
3ak
3al
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
1a (Ph)
1a (Ph)
1a (Ph)
1a (Ph)
3am
3an
3ao
3ba
3ca
3da
3ea
3fa
3ga
3ha
3ia
1a (Ph)
1b (4-MeC6H4)
1c (3-MeC6H4)
1d (3-MeOC6H4)
1e (4-F3CC6H4)
1f (4-FC6H4)
1g (2-MeC6H4)
1h (2-naphthyl)
1i (1-naphthyl)
1j (2-furyl)
1k (2-thienyl)
1d (3-MeOC6H4)
1e (4-F3CC6H4)
1g (2-MeC6H4)
1g (2-MeC6H4)
1h (2-naphthyl)
1i (1-naphthyl)
1k (2-thienyl)
3ja
3ka
3de
3ee
3gf
3gl
3hf
3if
3kl
Scheme 2. Control experiments (conditions: 5 mol% [PdCl(allyl)]2, 20 mol% XPhos,
2.5 equiv K3PO4, t-BuOH, 100 °C)
Based on these experimental observations, we conclude
that the present reaction involves an initial α-arylation of 2-
hydroxyacetophenone (1a) followed by oxidation of the
resulting benzoin 4 to benzil 3, both of which are catalysed by a
palladium complex equipped with XPhos; two equivalents of
aryl bromide are consumed during the process (Scheme 3).17
a Reaction conditions: 1 (0.200 mmol), 2 (0.500 mmol), [PdCl(allyl)]2 (0.010 mmol,
10 mol% Pd), XPhos (0.040 mmol, 20 mol%), K3PO4 (0.500 mmol) and t-BuOH (0.5
mL) at 100 °C for 18 h.
b
c
Isolated yield.
B(dan) = naphtho[1,8-
de][1,3,2]diazaborinin-2-yl.
Several control experiments were conducted to elucidate
the mechanistic aspects of the coupling reaction (Scheme 2).
When the reaction was terminated after 1 h, benzoin 4aa was
isolated in 49% yield in addition to benzil 3aa (37%), suggesting
that 4aa is the initial product, and that 3aa is subsequently
formed by the oxidation of 4aa (Scheme 2A). The preference of
α-arylation of α-hydroxy ketone 1a over acetophenone (5) was
confirmed by a competition experiment with equimolar
amounts of 1a and 5 under the standard conditions. After 1 h,
3aa and 4aa were isolated in 85% combined yield while 5,
lacking the hydroxyl group, remained intact (Scheme 2B).
Scheme 3. Mechanism for α-arylation–oxidation
Conclusions
In summary, we have developed a novel synthetic method for
accessing unsymmetrical benzils starting from 2-
hydroxyacetophenones, achieved by a tandem α-arylation–
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Organic & Biomolecular Chemistry
Page 4 of 4
ARTICLE
Journal Name
5235–5242; (g) P. Hirapara, D. Riemer, N. Hazra,ViJe.wGAartijceleraO,nMline.
Finger and S. Das, Green Chem., 2017, 19, 5356–5360; (h) Y.
Kumar, Y. Jaiswal and A. Kumar, Eur. J.DOOrgI:.1C0.h1e03m9./,D200O1B80,0459754D–
505.
For one-pot syntheses via Sonogashira/Heck coupling–
oxidation, see: (a) H. Min, T. Palani, K. Park, J. Hwang and S.
Lee, J. Org. Chem., 2014, 79, 6279–6285; (b) D. Saberi, H.
Hashemi and K. Niknam, Asian J. Org. Chem., 2017, 6, 169–
173; (c) V. G. Jadhav, S. A. Sarode and J. M. Nagarkar,
Tetrahedron Lett., 2017, 58, 1834–1838; (d) P. Niesobski, I. S.
Martínez, S. Kustosz and T. J. J. Müller, Eur. J. Org. Chem.,
2019, 5214–5218.
oxidation sequence, both of which are catalysed by a
palladium–XPhos system. Readily available aryl bromides
initially function as arylating agents to form C–C bonds, and
then subsequently oxidise the resulting benzoins to benzils,
with concomitant hydrodebromination. The widely applicable
transformation can be conducted under mild and virtually
redox-neutral conditions.18
7
Conflicts of interest
There are no conflicts to declare.
8
9
(a) M. Palucki and S. L. Buchwald, J. Am. Chem. Soc., 1997,
119, 11108–11109; (b) B. C. Hamann and J. F. Hartwig, J. Am.
Chem. Soc., 1997, 119, 12382–12383.
(a) W. A. Moradi and S. L. Buchwald, J. Am. Chem. Soc., 2001,
123, 7996–8002; (b) S. Lee, N. A. Beare and J. F. Hartwig, J.
Am. Chem. Soc., 2001, 123, 8410-8411; (c) E. M. Vogl and S. L.
Buchwald, J. Org. Chem., 2002, 67, 106–111; (d) D. A. Culkin
and J. F. Hartwig, J. Am. Chem. Soc., 2002, 124, 9330–9331; (e)
R. Martín and S. L. Buchwald, Angew. Chem., Int. Ed., 2007,
46, 7236–7239; (f) G. D. Vo and J. F. Hartwig, Angew. Chem.,
Int. Ed., 2008, 47, 2127–2130. For a review on α-arylation, see:
(g) C. C. C. Johansson and T. J. Colacot, Angew. Chem., Int. Ed.
2010, 49, 676–707.
Notes and references
1
(a) C. Rogers, W. S. Perkins, G. Veber, T. E. Williams, R. R. Cloke
and F. R. Fischer, J. Am. Chem. Soc., 2017, 139, 4052–4061;
(b) S. Sundar and R. Rengan, Org. Biomol. Chem., 2019, 17,
1402–1409; (c) A. Y. Dubovtsev, D. V. Dar'in, M. Krasavin and
V. Y. Kukushkin, Eur. J. Org. Chem., 2019, 1856–1864; (d) Y.
Nakagawa, R. Sekiguchi, J. Kawakami and S. Ito, Org. Biomol.
Chem., 2019, 17, 6843–6853; (e) A. Rashidizadeh, H. Ghafuri,
H. R. E. Zand and N. Goodarzi, ACS Omega, 2019, 4, 12544–
12554; (f) G. Li, Y. Han, Y. Zou, J. J. C. Lee, Y. Ni and J. Wu,
Angew. Chem., Int. Ed., 2019, 58, 14319–14326; (g) T. T.
Nguyen, N.-P. T. Le, T. T. Nguyen and P. H. Tran, RSC Adv.,
2019, 9, 38148–38153.
10 (a) M. Palucki, J. P. Wolfe and S. L. Buchwald, J. Am. Chem.
Soc., 1997, 119, 3395–3396; (b) K. E. Torraca, X. Huang, C. A.
Parrish and S. L. Buchwald, J. Am. Chem. Soc., 2001, 123,
10770–10771; (c) H. Zhang, P. Ruiz-Castillo and S. L. Buchwald,
Org. Lett., 2018, 20, 1580–1583.
11 2-Dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl
12 The use of organic bases, such as Et3N and DBU resulted in
virtually no reaction.
2
3
(a) K. Ohta, Y. Inagaki-Oka, H. Hasebe and I. Yamamoto,
Polyhedron 2000, 19, 267–274; (b) J. L. Dempsey, B. S.
Brunschwig, J. R. Winkler and H. B. Gray, Acc. Chem. Res. 2009,
42, 1995–2004; (c) F. Wang and C. Chen, Polym. Chem. 2019,
10, 2354–2369.
For recent examples, see: (a) P. Muthupandi and G. Sekar,
Tetrahedron Lett., 2011, 52, 692–695; (b) Y. Yu, C. Lin, B. Li, P.
Zhao and S. Zhang, Green Chem., 2016, 18, 3647–3655; (c) A.
Saha, S. Payra and S. Banerjee, New J. Chem., 2017, 41,
13377–13381; (d) A. R. Patel, G. Patel and S. Banerjee, ACS
Omega, 2019, 4, 22445–22455.
For recent examples, see: (a) J.-W. Xue, M. Zeng, X. Hou, Z.
Chen and G. Yin, Asian J. Org. Chem. 2018, 7, 212–219; (b) S.
W. Kim, T.-W. Um and S. Shin, J. Org. Chem., 2018, 83, 4703–
4711; (c) J. Zhou, X.-Z. Tao, J.-J. Dai, C.-G. Li, J. Xu, H.-M. Xu
and H.-J. Xu, Chem. Commun. 2019, 55, 9208–9211; (d) W.
Yang, Y. Chen, Y. Yao, X. Yang, Q. Lin and D. Yang, J. Org.
Chem., 2019, 84, 11080–11090; (e) A. Y. Dubovtsev, N. V.
Shcherbakov, D. V. Dar'in and V. Y. Kukushkin, J. Org. Chem.,
2020, 85, 745–757.
13 The reaction of 1a with 2-bromopyridine led to
decomposition of the starting materials.
14 The attempted coupling of ethyl hydroxyacetate with 2a
failed, producing
a
complex mixture of products.
Hydroxyacetone was not suitable for the reaction.
15 (a) A. S. Guram, X. Bei and H. W. Turner, Org. Lett., 2003, 5,
2485–2487. (b) C. Berini, D. F. Brayton, C. Mocka and O.
Navarro, Org. Lett., 2009, 11, 4244–4247. (c) Q. Gao and S. Xu.
Org. Biomol. Chem., 2018, 16, 208–212. (d) M. Kuriyama, S.
Nakashima, T. Miyagi, K. Sato, K. Yamamoto and O. Onomura,
Org. Chem. Front., 2018, 5, 2364–2369.
4
16 Syntheses of benzophenones by the palladium-catalysed
coupling of benzaldehydes with aryl halides have been
reported. (a) B. Suchand and G. Satyanarayana, J. Org. Chem.,
2016, 81, 6409–6423; (b) T. Wakai, T. Togo, D. Yoshidome, Y.
Kuninobu and M. Kanai, ACS Catal., 2018, 8, 3123–3128.
17 The reaction with 1.2 equiv 2a under air afforded 3a in 45%
yield, indicating that aerobic oxidation was impractical under
our conditions. See ref. 6a.
5
6
For recent examples, see: (a) X. Liu and W. Chen,
Organometallics, 2012, 31, 6614–6622; (b) X. Zeng, C. Miao,
S. Wang, C. Xia and W. Sun, RSC Adv., 2013, 3, 9666–9669; (c)
J.-W. Yu, S. Mao and Y.-Q. Wang, Tetrahedron Lett., 2015, 56,
1575–1580.; (d) R. Chebolu, A. Bahuguna, R. Sharma, V. K.
Mishra and P. C. Ravikumar, Chem. Commun., 2015, 51,
15438–15441; (e) J. M. Khurana, A. Lumb and A. Chaudhary,
Monatsh. Chem., 2017, 148, 381–386.
For oxidative coupling reactions, see: (a) Q. Zhang, C.-M. Xu,
J.-X. Chen, X.-L. Xu, J.-C. Ding and H.-Y. Wu, Appl. Organomet.
Chem., 2009, 23, 524–526; (b) X. Guo, W. Li and Z. Li, Eur. J.
Org. Chem., 2010, 5787–5790; (c) M. R. Rohman, I.
Kharkongor, M. Rajbangshi, H. Mecadon, B. M. Laloo, P. R.
Sahu, I. Kharbangar and B. Myrboh, Eur. J. Org. Chem., 2012,
320–328; (d) Y. Su, X. Sun, G. Wu and N. Jiao, Angew. Chem.,
Int. Ed., 2013, 52, 9808–9812; (e) W.-X. Lv, Y.-F. Zeng, S.-S.
Zhang, Q. Li and H. Wang, Org. Lett., 2015, 17, 2972–2975; (f)
J. B. Bharate, S. Abbat, R. Sharma, P. V. Bharatam, R. A.
Vishwakarma and S. B. Bharate, Org. Biomol. Chem., 2015, 13,
18 For an account on the synthesis 1,2-diketones from α-hydroxy
ketones, see: H. Liang, H. Liu and X. Jiang, Synlett, 2016, 27,
2774–2782.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins