Communication
doi.org/10.1002/chem.202101827
Chemistry—A European Journal
Pd-Catalysed Decarbonylation Free Approach to
Carbonylative Esterification of 5-HMF to Its Aryl Esters
Synthesis Using Aryl Halides and Oxalic Acid as C1 Source
Arvind Singh Chauhan,[a, b] Ajay Kumar,[a, b] Ajay Kumar Sharma,[a, b] and Pralay Das*[a, b]
ylation of 5-HMF also noticed under microwave assisted flow
Abstract: A decarbonylation free, polystyrene-supported,
Pd (Pd@PS)-catalysed carbonylative esterification of the
conditions using Pd-Hydrotalcite as catalyst.[16] In literature,
maximum reports have been published on the decarbonylation
hydroxy group of 5-hydroxymethyl furfural (5-HMF) to its
of 5-HMF and furfural, derived by heterogeneous Pd catalysts.
corresponding aryl esters has been developed. The use of
More recently, Wu et al. reported the decarbonylation of
Pd@PS, oxalic acid as CO source, and aryl halides was first
aldehyde group from 5-HMF and its in situ participation in
explored for the aryl ester of 5-HMF synthesis. Here, we
carbonylative esterification with aryl iodide, Rh(cod)BF4 as
investigated the vital role of a polystyrene support to avoid
the commonly known decarbonylation of 5-HMF. The
reaction exhibits vast substrate scope with comparably
good yield and catalyst recyclability.
catalyst and DPPP as ligand for furfuryl esters synthesis. In this
report, they have also noticed the labile behaviour of À CHO
group under milder conditions and used 5-HMF as an in situ CO
precursor for esterification reaction.[17] Therefore, the synthesis
of aryl esters of 5-HMF keeping the labile À CHO functional
group intact following a highly selective manner approaches
under heterogeneous Pd-catalysed conditions using oxalic acid
In this context, 5-HMF is an important furan-based platform
intermediate obtained by acidic dehydration of carbohydrates
for the production of various valuable chemicals.[1] Among
them, aryl esters of 5-HMF are the important class of molecules
having several applications such as fungicides, additives and
surfactants.[2] Moreover, the 5-HMF aryl esters are also consid-
ered as a potential candidate against sickle cell anaemia. The
esters of 5-HMF exhibited threefold of anti-sickling potency
than normal 5-HMF (Aes-103).[3,4] However, the synthetic
procedures for the selective esterification of 5-HMF is still
unexplored and less-developed due to highly labile À CHO
functional group. In most of the reported protocols, 5-HMF has
been majorly highlighted for the decarbonylation of À CHO
functional group under the influence of various metals such as
Pd, Rh, Ru and Ir-catalysed conditions.[5-13] In 2015, Rauchfuss
and co-workers reported the Pd/C-catalysed decarbonylation of
as CO source could be a challenging task in recent era of
methodology development. Last one decade, we are dedicat-
edly involved for polystyrene supported transition metal nano-
particles (NPs) as heterogeneous catalyst development, their
characterizations (XPS, XRD, SEM, TEM, HR-TEM, EDS, SAED, etc.)
and applications in different challenging area of organic
synthesis.[18] Further, we have also explored oxalic acid as a
bench-stable, easy-to-handle C1 surrogate by additive free
thermal decomposition and its applications for different carbon-
ylation reactions.[19] Under this study, first time we have applied
Pd@PS catalyst and oxalic acid as CO source for aryl esters of 5-
HMF synthesis. In this approach, crucial roles of polystyrene
surface (PS) in combination with Pd catalyst and oxalic acid
have been investigated to achieve aryl esters of 5-HMF avoiding
the decarbonylation of labile À CHO functional group in
considerably good yield.
5-HMF to corresponding furfuryl alcohol synthesis in good yield
The Pd@PS catalyst was prepared following our earlier
reported reduction deposition approach and well characterized
by X-ray diffraction (XRD), scanning electron microscopy (SEM),
transmission electron microscopy (TEM), high resolution trans-
mission electron microscopy (HR-TEM), energy dispersive spec-
troscopy (EDS) and selected area electron diffraction studies
(SAED).[18a,19] In addition to this, the use of oxalic acid as CO
source also made the established protocol eco-friendly and
operationally simple without the need of any high-pressure
sophisticated equipment.
In order to develop an efficient and facile approach for aryl
esters of 5-HMF synthesis, we started our optimisation studies
choosing 5-HMF and 4-iodoanisole as standard reactants.
Further, various reaction parameters such as base, solvent, CO
surrogate, catalyst and their equivalency as well as effect of
temperature and time were scrutinized carefully to access the
anticipated product with maximum yield. The initial screening
[14]
°
at 120 C in 1,4-dioxane solvent conditions (Scheme 1a).
Furthermore, Kawanami et al. also observed the labile nature of
the aldehyde (À CHO) group of 5-HMF under Pd/Al2O3 catalyst
conditions under compressed CO2 and got furfuryl alcohol as
[15]
°
major product at 145 C (Scheme 1b).
Similarly, decarbon-
[a] A. Singh Chauhan, A. Kumar, A. Kumar Sharma, Dr. P. Das
Chemical Technology Division
CSIR-Institute of Himalayan Bioresource Technology
Palampur 176061, H.P. (India)
E-mail: pdas@ihbt.res.in
[b] A. Singh Chauhan, A. Kumar, A. Kumar Sharma, Dr. P. Das
Academy of Scientific & Innovative Research (AcSIR)
Ghaziabad 201002 (India)
E-mail: pralaydas1976@gmail.com
Supporting information for this article is available on the WWW under
Chem. Eur. J. 2021, 27, 1–6
1
© 2021 Wiley-VCH GmbH
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