Pd/C catalyzed phenoxycarbonylation using: N -formylsaccharin as a CO surrogate in propylene carbonate, a sustainable solvent

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Pd/C Catalyzed Phenoxycarbonylation Using N-Formylsaccharin as

a CO Surrogate in Propylene Carbonate as a Sustainable Solvent

Received 00th January 20xx,

Accepted 00th January 20xx

Prashant Gautam, Prasad Kathe and Bhalchandra M. Bhanage*

This work reports the first Pd/C catalyzed phenoxycarbonylation of aryl iodides using N-formylsaccharin as a CO surrogate.

Advantageously, the reaction could be carried out in propylene carbonate as an environmentally benign and sustainable

polar aprotic solvent under CO surrogacy. Using N-formylsaccharin as a CO surrogate, allows the cheaper and readily

available phenols as the coupling partner. A range of phenyl esters could be synthesized under mild, co-catalyst free,

ligand free and additive free conditions, including multi-substituted novel phenyl esters. The Pd/C catalyst could be

recycled up to four times with only a slight loss in activity. The reaction could be scaled up to gram scale synthesis.

DOI: 10.1039/x0xx00000x

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stoichiometric or excess amount of reagents, reactive

substrates and harsh conditions, thus leading to generation of

large amounts of waste and poor atom economy.

Introduction

The synthesis of aromatic estersis an important reaction

which forms part of the bulk and fine chemical industry.

Aromatic esters constitute some of the most important

structural motifs encountered in agrochemicals, fungicides and

pharmaceutical drugs(Figure 1). They are also vital building

blocks in multi-step organic synthesis.¹

In the 1970’s, Heck pioneered the use of palladium

catalysed carbonylative cross-coupling reaction as a powerful

tool for the synthesis of carboxylic acid and its derivatives.³

The protocol involves the conversion of an aryl/vinyl halide in

the presence of carbon monoxide as a C-1 building block and a

suitable O,N-nucleophile to afford carboxylic acid derivatives

with high atom economy.Although Heck carbonylation has

found diverse applications for the synthesis of a plethora of

molecules, the use of gaseous CO limits the application of

carbonylation at the industrial scale and in academic

laboratories. This is attributed to the fact that CO is an

odourless, colourless and inflammable gas whose inhalation

even in ppm amount can be lethal. The need to transport and

store gaseous CO in cylinders, along with specialized high

pressure reactors required for handling CO and carrying out

carbonylation reactions pose safety risks andfurther impede its

use. These limitations can be addressed by using CO

surrogates wherein carbonylation can be carried out without

using gaseous CO. The chemistry of CO surrogates has gained

impetus over the last decade as several surrogate molecules

and improvised methodologies have been investigated for

carrying out carbonylation reactions.⁴

Figure 1. Representative examples of pharmaceutically important phenyl esters.

Conventionally, esters are synthesized by reacting

a

carboxylic acid with an alcohol/phenol in the presence of a

strong mineral acid (sulfuric acid, hydrogen chloride, p-

toluenesulfonic acid and chlorosulfuric acid) or lewis acid.

Other processes include alkylation of carboxylate salts of alkali

metal, alkaline-earth metal, copper and silver, acylation of

alcohols with acid chlorides, acid anhydrides and ketenes,

alcoholysis of nitriles and acylation of olefins with carboxylic

acids.²However, most of these protocols suffer from use of

Different CO surrogates, catalytic systems and reaction

methodologies have been applied for the synthesis of aromatic

esters. Skrydstrup and co-workers reported the use of 9-

methyl-fluorene-9-carbonyl chloride (COgen) as a CO surrogate

for the synthesis of tertiary esters⁵and activated esters⁶from

aryl bromides through the two-chamber system. Oxalyl

chloride⁷and very recently glyoxalic acid⁸were also usedas

surrogate molecules for ex-situ CO generation through the

^a.Department of Chemistry, Institute of Chemical Technology, N.P. Marg, Matunga-

400019, Mumbai, India. E-mail: bm.bhanage@ictmumbai.edu.in;

bm.bhanage@gmail.com

†Electronic Supplementary Information (ESI) available: [Characterization data,

copies of ¹H NMR, ¹³C NMR, ¹⁹F NMR and SC-XRD data of 5ad]. See

DOI: 10.1039/x0xx00000x

two-chamber

system.

Molybdenum

hexacarbonyl,⁹

paraformaldehyde,¹⁰formic acid¹¹and aryl formates¹²have

been used for the synthesis of aromatic esters from aryl

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iodides, bromides and even chlorides¹³through in situ CO while using phenyl formate as a CO surrogate, the product

generation. (phenyl ester) ends up with the pre-installed phenoxy (OPh)

N-formylsaccharin, developed as a formylating agent,¹⁴was group present in the formate. This limits the synthesis of

applied for the first time as a CO surrogate for the reductive diverse phenyl esters and makes the process commercially not

carbonylation of aryl halides by Manabe and co-workers.¹⁵viable as the more expensive formate esters are used as the

Later, the same group reported the fluorocarbonylation of aryl coupling partners as compared to the economical and readily

halides, thus leading to the synthesis of carboxylic acid available phenols.N-formylsaccharin after decarbonylation

derivatives in a two-step, one-pot fashion.¹⁶Fleischer and co- results in the formation of saccharin. Since saccharin has

workers reported the synthesis of aliphatic esters by the comparatively lesser nucleophilicity (pK_a= 1.6) as compared to

alkoxycarbonylation of alkenes using N-formylsaccharin.¹⁷

phenol (pK_a= 6-10), we envisaged that the use of N-

Although, the synthesis of aromatic esters with aliphatic formylsaccharin as a CO surrogate would allow the application

alkoxy (OR) group is well documented using different CO of phenols as coupling partners in phenoxycarbonylation

surrogates, the synthesis of aromatic phenyl esters has largely reactions (Scheme 1).

been carried out using phenyl formate (HCOOPh). However,

Scheme 1. Comparison of the decarbonylation of phenyl formate and N-formylsaccharin.

Traditionally, phenoxycarbonylation reactions using CO

surrogates have been carried out under homogeneous

catalytic protocols. Although, advantageously, the cheaper

aryl bromides have been used as coupling partners, most of

the reaction methodologies suffer from high catalyst

loading, use of phosphine ligands, stoichiometric amount of

additives.Further, reactions using N-formylsaccharin have

their synthesis from renewable feedstocks. This thus makes

them eco-friendly and further increases their potential as

benign solvents in organic synthesis. The GlaxoSmithKline

O

been

carried

out

in

polar

aprotic

N,N-

(1)

(2)

dimethylformamide^15,16(N,N-DMF) and dichloromethane.¹⁷

Although, N-formylsaccharin is known to readily undergo

decarbonylation in the aforementioned solvents, amide and

chlorinated solvents are considered unsustainable and

hazardous. Moreover, in contemporary chemistry, the

impact and consequence of reaction solvents on human

health and environment needs to be carefully considered.

Under REACH¹⁸(Registration, Evaluation, Authorisation and

Restriction of CHemicals), a regulation which addresses the

production and use of chemical substances, along with their

potential impact on human health and environment, the

usage of solvents will be subjected to scrutiny and/or

restricted in the near future. We thus endeavoured to

identify an alternate sustainable polar aprotic solvent.

Figure 2.Structures of (1) ethylene carbonate and (2) propylene carbonate.

(GSK) solvent selection guide rates ethylene and propylene

carbonate (Figure 2)good to excellent, thus showing no

points of concern across all criteria.²¹Furthermore, as

compared to N,N-DMF, ethylene and propylene carbonate

have higher boiling points (low vapour pressure), thus

resulting in lower atmospheric emissions and making them

safer to store and handle. Since cyclic carbonates are

comprised of only carbon, hydrogen and oxygen, they do

not produce oxides of nitrogen and sulfur on combustion or

incineration. Ethylene carbonate being a solid at room

temperature is disadvantageous to use. However,

propylene carbonate being a liquid, is a benign and

sustainable alternative to N,N-DMF and dichloromethane.

Despite these advantages, organic carbonates have only

been seldom used in carbonylation reactions.²²

Organic carbonates, especially cyclic carbonates, have

gained prominence as environmentally friendly solvents in

synthetic chemistry.¹⁹They are biodegradable, non-toxic,

odourless, possess low vapour pressure and synthesized at

the industrial scale at very low costs.²⁰Moreover, greener

and sustainable methodologies have been established for

Homogeneous catalytic protocols suffer from catalyst

product separation and the inability to recycle the catalyst.

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Palladium on activated charcoal (Pd/C) is a commercially

available and inexpensive heterogeneous catalyst which

addresses the problems associated with homogeneous

catalysis. Further, Pd/C is seldom explored as a catalyst in

CO surrogate chemistry.²³Considering our continued

interest in Pd/C catalyzed carbonylation reactions,²⁴we

herein report the first Pd/C catalysed phenoxycarbonylation

of aryl iodides using N-formylsaccharin as a CO surrogate in

propylene carbonate as an environmentally benign and

sustainable solvent (Scheme 2).

Scheme 2. Comparison of previous reaction protocols with the current protocol.

Results and Discussion

We carried out the reaction optimization by monitoring the

of phenyl benzoate 5a(Table 1).Initially we carried out the

reaction using Pd(OAc)₂and PdCl₂as homogenous

palladium precursors

carbonylative

cross-coupling

reaction

between

iodobenzene3a and phenol4athus leading to the synthesis

Table 1. Optimization of reaction parameters.^a

Entry

^bPd

Ligand

(mol%)

Base

CO source

concentration

(mmol)

Solvent

Time

(h)

Temperature

(°C)

Conversion^c

(%)

Selectivity^c

(%)

source

(mol%)

Effect of palladium source

1

2

3

4

Pd(OAc)₂

(3 mol%)

PdCl₂

‒

Na₂CO₃

N-formylsaccharin

0.50

N,N-DMF

24

100

95

71

32

45

100

95

(3 mol%)

Pd/C

100

(3 mol%)

Pd/C

(5 mol%)

Effect of base

Pd/C

(5 mol%)

5

PPh₃

Na₂CO₃

N-formylsaccharin

0.50

N,N-DMF

24

100

90

100

(10 mol%)

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6

Pd/C

PPh₃

(10 mol%)

PPh₃

Et₃N

K₂CO₃

N-formylsaccharin

0.50

N,N-DMF

24

100

16

70

59

21

79

(5 mol%)

Pd/C

7

8

9

100

(5 mol%)

Pd/C

(10 mol%)

PPh₃

K₃PO₄

(5 mol%)

Pd/C

(10 mol%)

PPh₃

TMEDA^d

(5 mol%)

(10 mol%)

Effect of time

10

11

12

Pd/C

PPh₃

(10 mol%)

PPh₃

Na₂CO₃

N-formylsaccharin

0.50

N,N-DMF

12

18

24

100

66

87

90

100

(5 mol%)

Pd/C

(5 mol%)

Pd/C

(10 mol%)

PPh₃

(5 mol%)

(10 mol%)

Effect of temperature

13

14

15

Pd/C

(5 mol%)

Pd/C

PPh₃

(10 mol%)

PPh₃

Na₂CO₃

N-formylsaccharin

0.50

N,N-DMF

18

60

80

56

85

87

100

(5 mol%)

Pd/C

(10 mol%)

PPh₃

100

(5 mol%)

(10 mol%)

Effect of ligand loading

16

Pd/C

(5 mol%)

Pd/C

PPh₃

(10 mol%)

PPh₃

Na₂CO₃

N-formylsaccharin

0.50

N,N-DMF

18

80

85

84

100

17

(5 mol%)

Effect of solvent

18

19

20

21

22

Pd/C

(5 mol%)

Pd/C

PPh₃

(10 mol%)

PPh₃

Na₂CO₃

N-formylsaccharin

0.50

Toluene

18

80

06

10

90

76

67

100

1,4-

(5 mol%)

Pd/C

(10 mol%)

PPh₃

dioxane

Propylene

carbonate

Propylene

carbonate

Ethylene

carbonate

(5 mol%)

Pd/C

(10 mol%)

‒

(5 mol%)

Pd/C

‒

(5 mol%)

Effect of CO source

23

24^e

25

Pd/C

(5 mol%)

Pd/C

‒

Na₂CO₃

Gaseous CO

Phenyl formate

Formalin

1 bar

0.50

Propylene

carbonate

Propylene

carbonate

Propylene

carbonate

Propylene

carbonate

18

80

99

79

02

‒

100

‒

(5 mol%)

Pd/C

(5 mol%)

Pd/C

26

Paraformaldehyde

‒

(5 mol%)

Effect of N-formylsaccharin concentration

27

28

29

30

Pd/C

(5 mol%)

Pd/C

‒

Na₂CO₃

N-formylsaccharin

0.25

0.30

0.50

0.60

Propylene

carbonate

Propylene

carbonate

Propylene

carbonate

Propylene

carbonate

18

80

30

45

76

78

100

(5 mol%)

Pd/C

(5 mol%)

Pd/C

(5 mol%)

a

Reactions conditions: 3 (0.25 mmol), 4 (0.25 mmol), base (0.5 mmol), solvent (2 mL).^b10% Pd/C.^cConversion and selectivity were based on iodobenzene and

determined by GC-MS. ^dTMEDA = N,N,N′,N′-Tetramethylethylenediamine. ^ePhenol was not added.

in N,N-DMF and the reaction proceeded with 95% and 71%

palladium precursor with heterogeneous 10% Pd/C (3

conversion respectively. Subsequently, we replaced the

mol%) and observed a 32% conversion with a complete

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selectivity towards 5a. Increasing the amount of catalyst to

5 mol% lead to a marginal increase in conversion from 32%

to 45% (Table 1, entries 1-4).

compared to propylene carbonate (Table 1 entries 20-22).

Moreover, being a solid, ethylene carbonate is difficult to

handle. Hence propylene carbonate was chosen as the

solvent of choice.

In order to increase the conversion of 3a towards 5a

,

we studied the effect of base and ligand. Addition of 10

mol% of PPh₃increases the conversion to 90% when

Na₂CO₃is used as the base. However, changing the base to

Et₃N brings down the conversion drastically to 16% with a

decrease in selectivity as well. Other inorganic (K₂CO₃and

K₃PO₄) and organic bases (TMEDA) gave inferior conversion

and selectivity as compared to Na₂CO₃(Table 1, entries

5‒9). Next, we studied the effect of time and temperature

on the conversion. Decreasing the reaction time to 12 h

brings down the conversion to 66%, but when the reaction

is carried out for 18 h, 87% conversion was observed at 100

°C. The conversion falls to 56% when the reaction

temperature is brought down to 60 °C. However, at 80 °C,

when the reaction is carried out for 18 h, 85% conversion

was observed (Table 1, entries 10-15). Decreasing the PPh₃

loading from 10 mol% to 5 mol% gave an almost similar

conversion (Table 1 entries 16 and 17). The solvent study

revealed that the reaction does not proceed in non-polar

solvents (Table 1, entries 18 and 19). We were delighted to

observe that the reaction proceeded under ligand-free

Subsequently, we studied the effect of different sources

of CO, including gaseous CO. While using gaseous CO (1

bar). It gives 99% conversion and 100% selectivity towards

5a. When phenyl formate was applied as a CO source, a

comparable conversion to N-formylsaccharin with complete

selectivity towards 5a was obtained. However, the reaction

did not proceed in the presence of formalin and

paraformaldehyde as sources of CO (Table 1, entries 23-26).

Since N-formylsaccharin would allow the use of phenols as

coupling partner, it was chosen as the surrogate of choice.

We also studied the effect of concentration of N-

formylsaccharin on the conversion and selectivity. Using

0.25 mmol and 0.30 mmol of N-formylsaccharin brings

down the conversion to 30% and 45% respectively (Table 1,

entries 27 and 28). However, increasing the concentration

to 0.60 mmol does not have any profound effect on the

conversion (Table 1, entry 30). Hence, 0.50 mmol of N-

formylsaccharin was chosen as the optimised concentration

(Table 1, entry 29).Having established the optimised

conditions, we focussed our attention on the scope of

different phenyl esters that could be synthesized under the

developed protocol (Table 2).

conditions in propylene carbonate to give

a 76%

conversion. Ethylene carbonate gave a lower conversion as

Table 2. Scope of the Pd/C catalyzed phenoxycarbonylation using N-formylsaccharin.^a

1.^c

2.^c

3.^c

4.^b

5.^b

6.^b

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7.^b

8.^b

9.^b

10.^b

11.^c

12.^b

13.^b

14.^b

15.^b

16.^b

19.^b

22.^b

17.^b

20.^b

23.^b

18.^b

21.^b

24.^b

25.^b

26.^b

27.^b

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28.^b

29.^b

30.^b

31.^b

32.^b

^aReaction conditions: 3(0.25 mmol, 4(0.25 mmol), Na₂CO₃(0.5 mmol), N-formylsaccharin (0.5 mmol), propylene carbonate (2 mL), 10% Pd/C (5 mol%) at 80 °C for 18 h.

^bIsolated yield. ^cGC-MS yield.

Electron-donating substituents, ortho-methyl and para-

methoxy, present on the aryl iodide could be coupled with

phenol to give the phenyl esters 5b and 5c in 57% and 71%

yields respectively (Table 2, entries 1 and 2). Electron-

withdrawing substituents, para-cyano, meta-fluoro, meta-

and para-nitro on the aryl iodidewere also smoothly

to afford the halo substituted esters, 5ac, 5ad and 5ae, in

61% to 67% yields (Table 2, entries 28-30). Phenyl ester 5ad

was isolated as a crystalline solid and the structure was

elucidated by single crystal X-ray crystallography (Figure

3).1-chloro-2-iodobenzene and 1-iodo-2-nitrobenzene

could be carbonylatively coupled with 5-bromo-2,3-

difluorophenol to afford the ester, 5af, bearing chloro,

bromo and fluoro substituents and ester 5ag in 58% and

49% yields respectively (Table 2, entries 31 and 32).

Notably, multi-substituted esters, 5af and 5ag may

represent potential building blocks in organic synthesis.

coupled to yield the phenyl esters5d, 5e, 5g and 5h in 46%,

70%, 64% and 55% yields respectively (Table 2, entries 3, 4,

6 and 7). Phenyl 1-naphthoate (5f) could be synthesized in

65% yield from phenol and 1-iodonaphthalene (Table 2,

entry 5). 3-nitrophenol, guaiacol (2-methoxyphenol) and

para-cresol were transformed into the phenyl esters 5i, 5j,

5k and 5l in 67%, 75%, 83% and 62% yields respectively

(Table 2, entries 8-11). Biphenyl esters 5m and 5n were

synthesized in 85% and 90% yields respectively by

carbonylatively

coupling

2-phenylphenol

and

4-

phenylphenol with iodobenzene (Table 2, entries 12 and

13).3,4-Dimethoxyphenyl esters, 5o (66%) and 5p (50%),

could be synthesized from 3,4-dimethoxyphenol, and ester

5q(52%), containing a 3,4-methylenedioxy unit could be

synthesized from sesamol (Table 2, entries 14-16). Para-

bromophenyl esters, 5r and 5s, and 6-bromonaphthyl

Figure 3. ORTEP diagram of phenyl ester 5ad.

The phenoxycarbonylation of 4-bromoanisole and 4-

chloroanisole under the optimized reaction conditions did

not yield the corresponding phenyl esters. The aryl halides

failed to undergo any conversion and were recovered as

such.

esters, 5t, 5u and 5v, could be synthesized in yields ranging

from 51% to 81% (Table 2, entries 17-21).

Organo-fluorine compounds form a vital backbone of

pharmaceutically active drug molecules and are considered

very important in medicinal chemistry.²⁵2,4-Difluorophenyl

Next, we focussed our attention on the recyclability of

Pd/C under CO surrogacy. Given the high cost of palladium

and catalyst-product separation problems associated with

homogenous catalytic protocols, recycling palladium will

bring down the overall cost of the process, thus making the

protocol economically viable and sustainable. The reaction

between iodobenzene (3a) and phenol (4a) leading to the

synthesis of phenyl benzoate (5a) was chosen as the model

reaction for checking the recyclability. After the fresh run,

the reaction mixture was centrifuged at 10,000 rpm for 15

min and Pd/C was separated from the reaction mixture,

washed with ethyl acetate to remove traces of the product

and dried at 100°C overnight. The dried Pd/C was applied

esters, 5w, 5x and 5y were synthesized by carbonylatively

coupling 2,4-difluorophenol with the corresponding aryl

iodide in 79% to 85% yields respectively (Table 2, entries

22-24). The trifluoro phenyl ester, 2,4-difluorophenyl-3-

fluorobenzoate, 5z, was synthesized by carbonylatively

coupling 2,4-difluorophenol and 1-fluoro-3-iodobenzene in

89% yield (Table 2, entry 25). Phenyl esters, 5aa and 5ab

,

containing the trifluoromethyl substituent were

synthesized in 83% and 90% yields respectively (Table 2,

entries 26 and 27). The phenol bearing fluoro and bromo

substituents,

5-bromo-2,3-difluorophenol,

was

carbonylatively coupled with the corresponding aryl iodides

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for the next run after charging with substrates, N-

formylsaccharin and propylene carbonate. Notably, Pd/C

could be recycled up to four times with only a marginal

decrease in conversion (Figure 4).

F

Figure 4. Recyclability study of Pd/C catalyzed phenoxycarbonylation using N-

formylsaccharin.

Scheme 4.Proposed mechanism for the Pd/C catalyzed phenoxycarbonylation

using N-formylsaccharin as the CO surrogate.

The ICP-AES analysis of the reaction mixture separated

from the catalyst by centrifugation after the fourth recycle

showed that the palladium content was less than 0.1 ppm,

thus indicating negligible palladium leaching.

Conclusions

In conclusion, we have established the first Pd/C

catalyzed phenoxycarbonylation of aryl iodides using N-

formylsaccharin as a CO surrogate in propylene carbonate

as an environmentally benign and sustainable polar aprotic

solvent. The methodology does not require the need for

gaseous CO and a high pressure reactor. The protocol uses

A scale up experiment (gram scale) was carried out to

study the present protocol. Delightfully, the reaction

between iodobenzene (3a) and phenol (4a) could be carried

out at gram scale resulting in the synthesis of phenyl

benzoate (5a) in 71% yield (Scheme 3).

Pd/C as

a

commercially

available,

recyclable,

heterogeneous catalyst. Advantageously, the protocol is a

one-step process and is co-catalyst free, ligand free and

additive free. A range of phenyl esters could be synthesized

under mild conditions, including novel multi-substituted

ester molecules. The Pd/C catalyst could be recycled up to

four times under CO surrogacy and the process could be

scaled up to gram scale synthesis. The use of Pd/C in

combination with propylene carbonate, thus represents a

green and sustainable methodology for the synthesis of

phenyl esters.

Scheme 3. Gram scale Pd/C catalyzed phenoxycarbonylation using N-

formylsaccharin.

Experimental Section

The mechanism for the Pd/C catalyzed carbonylative

General

synthesis of phenyl esters using N-formylsaccharin as the

CO surrogate is shown in Scheme 4. The aryl iodide (3a

undergoes oxidative addition to the Pd(0) centre resulting

in the aryl palladium species N-formylsaccharin

)

All chemicals and solvents were purchased from different

commercial sources and were used as received without

further purification. The progress of the reaction was

monitored by GC-MS and thin layer chromatography using

Merck silica gel 60 F254 plates. The products were

visualized with a 254 nm UV lamp. The GC-MS-QP 2010

instrument (Rtx-17, 30 m × 25 mm ID, film thickness (d_f) =

0.25 µm) (column flow 2 mL min⁻¹, 100 °C to 240 °C at 10 °C

min⁻¹rise) was used for the mass analysis of the products.

Products were purified by column chromatography on 100–

200 mesh silica gel. The ¹H and ¹⁹F NMR spectra were

recorded on 500 MHz spectrometers in CDCl₃using

tetramethylsilane (TMS) as an internal standard. The ¹³C

NMR spectra were recorded on 125 MHz spectrometers in

CDCl₃. Chemical shifts were reported in parts per million (δ)

relative to tetramethylsilane as an internal standard and

A

.

undergoes decarbonylation in the presence of Na₂CO₃and

the CO released coordinates to the aryl palladium species

to give

B. Subsequent CO insertion gives C which reacts

with phenol (4a) to afford the phenyl ester product (5a).

Simultaneous reductive elimination regenerates Pd(0) for

the next catalytic cycle.

8 | J. Name., 2012, 00, 1-3

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J(coupling constant) values were reported in hertz. The

splitting patterns of protons are described as s (singlet), d

(doublet), dd (doublet of doublets), t (triplet) and m

(multiplet). High resolution mass analysis was performed on

quadrupole-time of flight Bruker MicroTOF-Q II mass

spectrometer equipped with an ESI and APCI source. Single

crystal X-ray diffraction was done on a Bruker D8 VENTURE

diffractometer equipped with CMOS Photon 100 detector

and Mo-Kα (λ = 0.71073 Å) radiation was used.

carbonate. The product yields were calculated by subjecting

the reaction mixture at each cycle to GC-MS analysis.

Acknowledgements

P.G. is thankful to the Council of Scientific and Industrial

Research (CSIR), New Delhi, Government of India, for

providing a Senior Research Fellowship (SRF). The authors

thank Shashikant Gatkal from the Central Instrumentation

Facility (CIF), Savitribai Phule Pune University (SPPU) for

carrying out High-Resolution Mass Spectrometry (HR-MS)

analysis. The authors also thank Lalit Mohan Jha and

Anusha Upadhyay from the Central Instrumentation Facility

(CIF), Indian Institute of Science Education and Research

(IISER)-Bhopal for carrying out Single Crystal X-ray

diffraction and Debamitra Chakravarty from the Central

Instrumentation Facility (CIF), Savitribai Phule Pune

University (SPPU) for solving the structure.

Typical procedure for Pd/C catalyzed phenoxycarbonylation of

aryl iodide using N-formylsaccharin as a CO surrogate

To a 15 mL pressure tube, aryl iodide (0.25 mmol), phenol

(0.25 mmol), Na₂CO₃(0.5 mmol), N-formylsaccharin (0.5

mmol), 10% Pd/C (5 mol%, 13 mg) were added.

Subsequently, 2 mL of propylene carbonate was added to

the reaction mixture. The reaction mixture was stirred at 80

°C for 18 h. After completion of the reaction, the reaction

mixture was centrifuged for 15 mins at 10,000 rpm. Pd/C

was separated from the reaction mixture and washed with

2 mL ethyl acetate to remove traces of the product.The

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Graphical Abstract

Recyclable and commercially available Pd/C catalyzes the phenoxycarbonylation reaction using

N-formylsaccharin as a CO surrogate in propylene carbonate as an environmentally benign and

sustainable polar aprotic solvent under co-catalyst free, ligand free and additive free conditions.

Article Doi

Pd/C catalyzed phenoxycarbonylation using: N -formylsaccharin as a CO surrogate in propylene carbonate, a sustainable solvent

DOI: 10.1039/c6gc03027k

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Full text of DOI:10.1039/c6gc03027k

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