ARTICLE
Werner transition-metal complex (WTMC)-mediated mild and
efficient chemo-selective acylation of phenols and anilines under
solvent-free condition
Abdulla Sarief
1
| SK Manirul Haque
1
| Syed Mudabbir Feroze
2
| Mohammed Arifuddin
2
1
Department of Chemical and Process Engineering
Technology, Jubail Industrial College, Jubail,
Saudi Arabia
2
Department of Medicinal Chemistry, National
Institute of Pharmaceutical Education and
Research (NIPER), Hyderabad, India
Correspondence
SK Manirul Haque, Department of Chemical and
Process Engineering Technology, Jubail Industrial
College, P.O. Box No-10099, Jubail 31961, Saudi
Arabia.
Email: haque_m@jic.edu.sa
Werner-type transition-metal complexes (WTMC) such as [Co(NH
3
)
5
Cl]Cl
2
, Cu
[(NH
3
)
4
]SO
4
, Mn(acac)
3
, Ni[(NH
3
)
6
]Cl
2
, Ni[(en)
3
]S
2
O
3
, and Hg[Co(SCN)
4
] effi-
ciently promote the chemoselective acetylation of phenols and anilines under
solvent-free condition. The results of this study clearly shows that the optimal con-
dition for the acetylation of anilines/phenols (1 mmol) (2a–r) with acetic anhydride
(1.2 mmol) in the presence of WTMC (1 mmol) and two drops of H
3
PO
4
on heat-
ing for 10 min under solvent-free condition gives the corresponding acetanilides/
phenyl acetate (3a–r) in good to excellent yield. Furthermore, the method is sim-
ple, efficient, chemoselective, and eco-friendly under solvent-free condition for the
acetylation of anilines and phenols promoted by WTMC by using acetic anhydrate
as the acetylating agent. The simple preparation of the catalyst, easy procedure of
the acetylation reaction, and simple work-up indicate the importance of WTMC for
such reactions.
KEYWORDS
acetylation, anilines, phenols, solvent-free condition, Werner-type
transition-metal complexes (WTMC)
1 | INTRODUCTION
Complex organic molecules are formed through synthesis and
depend on the functional groups of each compound.
[1]
The
most common multistep organic transformation reaction is
acylation. The acetyl group is frequently used as the protecting
group because it can be easily deprotected and is stable in
acidic media.
[2]
Hydroxyl and amine groups are also used as
the protecting groups. The acetyl group is more popular
because of its simple structure and easy protection by hydroly-
sis in the presence of a base.
[3]
Generally, acetic anhydride or
acetyl chloride, with triethyl amine and pyridine acting as cata-
lyst, is utilized for the acylation reaction.
[4–6]
It was found that
the presence of 4-(dimethylamino) pyridine (DMAP) will sub-
stantially increase the rate of the reaction.
[7]
The acylation of
alcohols, phenols, and amines is catalyzed with a variety of
catalysts such as cobalt chloride (CoCl
2
),
[8]
Sc(OTf )
3,
[9]
TaCl
5,
[10]
montmorillonite K10,
[11]
HY zeolite,
[12]
In(OTf )
3,
[13]
Cu(OTf )
2,
[14]
silica gel-supported sulfuric
acid,
[15,16]
yittria/zirconia-based Lewis acid,
[17]
InCl
3
/Mont. K
10,
[18]
sodium dodecyl sulfate (SDS),
[19]
ammonium acetate in
acetic acid,
[20]
manganese (III) bis(2-hydroxyanil)acetylaceto-
nato complex,
[21]
silica sulfate,
[22]
p-MeC
6
H
4
SO
2
NBr
2,
[23]
DBDMH or TCCA,
[24]
ZnCl
2,
[25]
H
6
P
2
W
18
O
62
24H
2
O,
[26]
vanadyl sulfate,
[27]
La(NO
3
)
3
6H
2
O,
[28]
2,4,6-triacyloxy-
l,3,5-triazine (TAT),
[29]
zinc dust,
[30]
ionic liquid based on
morpholin,
[31]
borated zirconia,
[32]
DMAP-saccharin,
[33]
copper-catalyzed azidation reaction of anilines(primary
amine),
[34]
acylation of phenol and salicylic acid in the pres-
ence of zirconium phosphate (ZP) nanoparticles,
[35]
oxidative
acylation of phenols with N-heteroarylmethanes under transi-
tion metals,
[36]
N-alkylation of amines with alcohols in
Received: 10 January 2018 Revised: 11 March 2018 Accepted: 27 March 2018
DOI: 10.1002/jccs.201800013
© 2018 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2018;1–6. http://www.jccs.wiley-vch.de 1