Highly regioselective O-allylation of phenol derivatives using MMZCu(I)Y catalyst

Article abstract of DOI:10.1080/00397911.2019.1695838

A clean and effective method has been developed for the regioselective of O-allylation of phenol derivatives using a recyclable Cu(I)-exchanged multi-size porous material. Ease of preparation of catalyst through simple solid-state exchange and its compatibility in producing excellent amount of O-allylated products and a plausible mechanistic pathway for the regioselectivity are highlighted. This reported procedure is not requiring any external stabilizing ligand for Cu(I) species and further purification of products.

Full text of DOI:10.1080/00397911.2019.1695838

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Highly regioselective O-allylation of phenol
derivatives using MMZCu(I)Y catalyst
Cheirmakani Thangapriya, Simsonrubarathinam Ilaamirthamani &
Mayilvasagam Kumarraja
To cite this article: Cheirmakani Thangapriya, Simsonrubarathinam Ilaamirthamani &
Mayilvasagam Kumarraja (2019): Highly regioselective O-allylation of phenol derivatives using
MMZCu(I)Y catalyst, Synthetic Communications, DOI: 10.1080/00397911.2019.1695838
To link to this article: https://doi.org/10.1080/00397911.2019.1695838
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https://doi.org/10.1080/00397911.2019.1695838
Highly regioselective O-allylation of phenol derivatives
using MMZCu(I)Y catalyst
Cheirmakani Thangapriyaa, Simsonrubarathinam Ilaamirthamanib, and
Mayilvasagam Kumarrajab
b
aDepartment of Chemistry, Sri Kaliswari College (Autonomous), Sivakasi, India; Centre for Research and
Post-Graduate Studies in Chemistry, Ayya Nadar Janaki Ammal College (Autonomous), Sivakasi, India
ABSTRACT
ARTICLE HISTORY
Received 29 July 2019
A clean and effective method has been developed for the regioselec-
tive of O-allylation of phenol derivatives using a recyclable Cu(I)-
exchanged multi-size porous material. Ease of preparation of catalyst
through simple solid-state exchange and its compatibility in produc-
ing excellent amount of O-allylated products and a plausible mech-
anistic pathway for the regioselectivity are highlighted. This reported
procedure is not requiring any external stabilizing ligand for Cu(I)
species and further purification of products.
KEYWORDS
MMZCu(I)Y; O-allylation;
regioselectivity
GRAPHICAL ABSTRACT
Where X ¼ H, p–Br, p–COCH3, O–CHO, O–COCH3, O–Cl, p–Cl, Ph, Py,
heterobicyclic (3 examples).
Introduction
Allylation of functional moieties always receives much attention in synthetic organic
chemistry since the external double bond finds scope for further derivatization like ring
closer leads to the formation of heterobicyclic system such as chromones and coumar-
ones[1], hydrogenation, radical substitution reaction, click reaction[2], epoxidation,
Claisen Rearrangement[3], 1,3-hydrogen shift, [3,3]-sigma tropic rearrangement[4] and
polymerization reactions[5], as an educt for Suzuki–Miyaura coupling reaction, protect-
ing groups for alcohols[6] and also as the accelerators for rubber vulcanization, explo-
sives, lubricant oils, gasoline anti-corrosive additives[7], etc. These allylic ethers also find
many pharmaceutical applications which involve as a protected intermediate in the
CONTACT Mayilvasagam Kumarraja
dr.kumarraja@gmail.com
Centre for Research and Post-Graduate Studies in
Chemistry, Ayya Nadar Janaki Ammal College (Autonomous), Sivakasi, Tamil Nadu 626 124, India.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article is available online at https://doi.org/10.1080/00397911.2019.1695838
ß 2019 Taylor & Francis Group, LLC

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T. CHEIRMAKANI
synthesis of diclofenac, a non-steroidal anti-inflammatory, dicycloxygenase inhibitor,
and as precursors for the benzo-fused coumarins having anti-tumor activity[8].
However, the synthesis of allyl phenyl ethers is always a very challenging task because
of achieving regioselectivity. The traditional methods for the synthesis of allyl ethers
normally require strongly basic metal alkoxide anion, highly active alkyl species, and a
stoichiometric amount of coupling agents such as DEAD and triphenylphosphine[9]. In
addition, to activate the allyl alcohol, either the use of ligands, supporting agent, addi-
tives, or elevated temperatures are also necessary due to its less reactivity. There are
other few reports also available which includes metal complexes like Ru[10], Pd[11]
,
Ir[12], Mo(II)[13], In[14], Au[15], Rh[16] for the allylation of phenolic compounds.
Recently, nanoferrites[17], lead composite[18], PTC[19], cyclodextrins[20] are also reported.
However, most of the reported procedures involve both C- and O-allylation by the use
of expensive ligands for the complex formation, toxic solvents, limited substrate scope,
strong base, harsh reaction conditions, non-recyclable catalyst, and poor selectivity.
Our recent report on allylation of dicarbonyl compounds[21] using hierarchically
architectured MMZCu(I)Y prompted us to extend the study of the allylation of functional
moieties like OH groups as the reported catalytic system can influence the outcome of
product selectivity. Moreover, the catalyst reserves its own advantages like functional
tolerance, tunable acidity, basicity and pore sizes, recycling nature with same impact on
product distribution, easy separation, etc.
Consequently, this challenging task on achieving a selective allylation by the use of
simple and affordable method led us to explore this study by the use of a MMZCu(I)Y
catalyst and interesting results are discussed here.
Results and discussion
The optimization study of screening of catalysts and solvents is performed in which
phenol and allylbromide are used as model substrates and results are summarized in
Tables 1 and 2.
Either the presence of catalyst or base alone has not produced any significant result.
Similarly, there is no reaction with Na-exchanged zeolite (entry 1). However, KY has
produced considerable amount of allylated product but with no selectivity (entry 2).
Both O- and C-allylation occurred in other cases also like with LiY and CsY (entries 4
and 5). To check the influence of Bronsted acidity, we employed HY zeolite (entry 3),
but the yield is poor when compared with other cations. It is due to the acidic sites pre-
sent in HY prevents the formation of phenolate ion to attack by the allylating agent.
However, transition metals enhance the product yield with good selectivity towards
O-allylation by the expense of C-allylated product. Our recent research on the explor-
ation of multi-size porous material MMZ with various cations for fine selectivity
prompted us to employ them in the present study also. MMZNiY and MMZCu(II)Y have
produced 91% and 80% of allylation (entries 6 and 7), however, with considerable
amount of C-allylation also. Surprisingly, the Cu(I)Y zeolite has produced an excellent
amount of O-allylation selectively with a trace amount of C-allylation (entry 8). In fact,
this interesting result further incited us to employ MMZCu(I)Y and which produced only
O-allylation (entry 9) with almost same amount of yield. We have also examined the

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3
Table 1. Screening of catalysts for the regioselective O-allylation.a
Yieldb (%)
Entry
Catalyst
Time
(3)
(4)
1.
2.
3.
4.
5.
6.
7.
8.
9.
NaY
KY
HY
LiY
CsY
MMZNiY
MMZCu(II)Y
Cu(I)Y
24
24
10
24
24
10
10
10
10
–
–
48
20
40
45
67
72
91
89
27
c
–
21
26
24
8
2
–
MMZCu(I)Y
aReaction conditions: Stirred the mixture of Phenol (1 mmol), allyl bromide (1 mmol), catalyst (100 mg), ethanol (3 mL),
K2CO3 (1 mmol) at 70 ꢀC for the reaction time as specified in the table.
bIsolated yields.
cTrace amount of C-allylated product also noted (confirmed by GC-MS).
Table 2. Optimization of the solvent.a
Yieldb (%)
Entry
Solvent
Polarity[26]
(3)
(4)
1.
2.
3.
4.
5.
6.
CHCl3
DMF
DMSO
ACN
CH3CH2OH
CH3OH
0.259
0.386
0.444
0.46
0.654
0.762
25
11
45
21
89
67
7
–
28
3
–
9
aReaction conditions: stirred the slurry containing Phenol (1 mmol), allyl bromide (1 mmol), MMZCu(I)Y (100 mg), solvent
(3 mL), K2CO3 (1 mmol) at 70 ꢀC for 10 hr.
bIsolated yields.
recycling of MMZCu(I)Y to see its efficiency which afforded the same yield even after
two time usage.
Solvents having high polarity influence the reaction to good extend as evident from
its scaling range if above 0.5, particularly methanol and ethanol are found to be more
suitable for the present study. Comparing methanol, ethanol produces a very clean reac-
tion without any by products at 70 ꢀC. To check the functional tolerance of MMZCu(I)Y
catalyst, various substituted phenolic compounds are also employed and the results are
presented in Table 3. The reaction finds faster with all substituents as evident from the

4
T. CHEIRMAKANI
a
Table 3. O-Allylation of different phenolic compounds using MMZCu(I)Y
.
(3 A)
(3 B)
(3 C)
89%
(3 D)
94%
(3 E)
92%
(3 F)
87%
(3 G)
89%
(3 H)
93%
(3 I)
92%
(3 J)
76%
84%
(3 K)
97%
80 %
aReaction conditions: stirred the slurry containing Phenolic compounds (1 mmol), allyl bromide (1 mmol), MMZCu(I)Y
(100 mg), solvent (3 mL), K2CO3 (1 mmol) at 70 ꢀC for 10 hr.
observed yields 76–97%. In most of the cases, the reaction is not required any further
purification technique since it piped out exclusively O-allylated products.
Generally, para substituents are giving better yields than ortho substituents under the
present experimental conditions. There is no difficulty at all to allylate even for bulkier
phenolic compounds like p-substituted thiazole phenolic compounds and 7-hydroxycou-
marin (entries 10 and 11). In such cases, we believe that the mesopores present in
MMZCu(I)Y allows to mobilize the bulkier molecules easily to reach the active sites pre-
sent in catalyst and pipes out the O-allylated products.

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5
Scheme 1. Proposed mechanism for the regioselective O-allylation catalyzed by MMZCu(I)Y
.
The mechanistic pathway passes through the oxidative addition of allyl bromide to
Cu(I) sites [A] in MMZ occurs in a c-selective manner following SN20 mechanism
with anti-stereochemistry, giving p-allyl complex [B] by expelling the leaving group
bromide. Meanwhile, the simpler base K2CO3 yields phenolate ion which undergoes a
nucleophilic attack at the metal center followed by reductive elimination gives selectively
O-allylated product in excellent yields.
Conclusions
In summary, we have developed a simple procedure for a clean regioselective O-
allylation of phenol derivatives by a one pot strategy promoted by an inexpensive,
reusable, nontoxic, and environmentally benign catalytic system of MMZCu(I)Y material.
The other advantages of this procedure are no need of external stabilizing ligand for
CuI metal ion, use of a simple base, shorter reaction time and excellent regioselectivity
with higher yield.
Experimental section
Synthesis and characterization of hierarchical nanoporous material (MMZCu(I)Y
)
MMZY zeolite was synthesized from the commercially available NH4-Y zeolite according
to the procedure Ryoo et al. reported[22]. A mixture of CuCl (500 mg) and MMZY (1 g)
was grounded well by pestle and mortar; it was heated in flowing nitrogen atmospþhere
at a heating rate of 10 ꢀC/min. The ion-exchange of Cu(I) in solid CuCl with H in
MMZY zeolite occurred at over 300 ꢀC and the maximum ion-exchange rate was
reached at 340 ꢀC with the consequent release of HCl gas[23]. The rate of ion-exchange
was determined using H/D titration method[24]. After the preparation was over, the
MMZCu(I)Y was kept under vacuum. The as-prepared catalyst was characterized using
SEM, TEM, EDAX, and powder XRD analysis[25]
.

6
T. CHEIRMAKANI
General procedure for the selective synthesis of O-allyl phenolic derivatives (3a–i)
using MMZCu(I)Y
100 mg of MMZCu(I)Y was taken in a reaction tube containing ethanol (3 mL) as a solv-
ent and K2CO3 (1 mmol) as base. A mixture of equimolar (1 mmol) phenol (1a) and
allylbromide (2a) was added simultaneously to the reaction tube. The reaction mixture
was allowed to stir for 10 hr at 70 ꢀC, and the proceedings of the reaction were con-
stantly monitored by TLC. After 10 hr, products were extracted from MMZCu(I)Y using
excess amount of solvent. The organic layer was separated, dried, and concentrated in
vacuo and the residue was subjected to column chromatography over silica gel [60–120
1
mesh, petether:ethylacetate, (8:2)]. The isolated products were characterized by H and
13C-NMR spectra on Bruker Instrument (300 MHz and 75 MHz, respectively) in CDCl3.
GC-MS spectrum recorded in Agilent GC 7820 A and MS 5977E Model using DB-5
Column and the new products also by HR-MS spectrums.
1
Full experimental details, H and 13C-NMR spectra of all new compounds can be
found via the “Supplementary Content” section of this article’s webpage.
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