Rhodium/Phosphine catalysed selective hydroformylation of biorenewable olefins

Article abstract of DOI:10.1002/aoc.4478

This work reports rhodium catalyzed selective hydroformylation of natural olefins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl based Buchwald phosphine ligands (S-Phos (L₁), t-Bu XPhos (L₂), Ru-Phos (L₃), Johnphos (L₄) and DavePhos (L₅). Ru-Phos (L₃) ligand exhibited high impact on the hydroformylation of eugenol providing high selectivity (90%) of linear aldehyde as major product. In addition, internal natural olefins like anethole and prenol provided moderate to high selectivity (65% and 85% respectively) of branched aldehydes as a major products. The various reaction parameters such as influence of ligands, P/Rh ratio, syngas pressure, temperature, time and solvents have been studied. A high activity and selectivity gained on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl and isopropoxy groups present in L₃ phosphine ligand. Moreover, this catalytic system was smoothly converting natural olefins into corresponding linear and branched aldehydes with higher selectivity under the mild reaction conditions.

Full text of DOI:10.1002/aoc.4478

Received: 5 April 2018
DOI: 10.1002/aoc.4478
Revised: 26 April 2018
Accepted: 26 May 2018
F U L L P A P E R
Rhodium/Phosphine catalysed selective hydroformylation
of biorenewable olefins
Samadhan A. Jagtap | Bhalchandra M. Bhanage
Department of Chemistry, Institute of
This work reports rhodium catalyzed selective hydroformylation of natural ole-
fins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl
based Buchwald phosphine ligands (S‐Phos (L1), t‐Bu XPhos (L2), Ru‐Phos
(L3), Johnphos (L4) and DavePhos (L5). Ru‐Phos (L3) ligand exhibited high
impact on the hydroformylation of eugenol providing high selectivity (90%)
of linear aldehyde as major product. In addition, internal natural olefins like
anethole and prenol provided moderate to high selectivity (65% and 85%
respectively) of branched aldehydes as a major products. The various reaction
parameters such as influence of ligands, P/Rh ratio, syngas pressure, tempera-
ture, time and solvents have been studied. A high activity and selectivity gained
on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl
and isopropoxy groups present in L3 phosphine ligand. Moreover, this catalytic
system was smoothly converting natural olefins into corresponding linear and
branched aldehydes with higher selectivity under the mild reaction conditions.
Chemical Technology, N. Parekh Marg,
Matunga, Mumbai 400 019, Maharashtra,
India
Correspondence
Bhalchandra M. Bhanage, Department of
Chemistry, Institute of Chemical
Technology, N. Parekh Marg, Matunga,
Mumbai 400 019, Maharashtra, India.
Email: bm.bhanage@ictmumbai.edu.in;
bm.bhanage@gmail.com
KEYWORDS
biorenwable olefins, homogeneous catalysis, hydroformylation, phosphines, rhodium
1 | INTRODUCTION
processes employed rhodium catalysts modified with
monophosphine or diphosphine ligands speak to the
Hydroformylation of olefins represents one of the most
significant and largest homogeneous catalytic industrial
process for the production of oxochemicals produced
10–12 million tonnes every year.[1–3] Since it was
invented by Otto Roelen in 1938, this transformation
has been widely explored and has made great progress
in recent decades.[4,5] It is also called as oxo process for
the conversion of olefins into aldehydes, alcohols, carbox-
ylic acid and derivatives in presence of transition metal
catalyst under syngas (CO/H2) pressure.[6–8] It is atom
economical process, however it has challenges in control-
ling the selectivity of products, isomerisation and hydro-
genation.[9,10] Although the conversion of terminal
olefins proceeded well, the hydroformylation of internal
olefins is difficult to provide aldehydes with high regiose-
lectivity.[11,12] Most of the industrial hydroformylation
issue of regioselectivity and stereoselectivity.[13]
The phosphine or phosphite ligands were played an
important role in improving the regio‐selectivity to the lin-
ear or branched aldehydes.[14–16] Our group has
investigated the synthesis and application of simple and
efficient biphosphinite ligand in regioselective hydro-
formylation of vinyl esters and various olefins.[17,18] Biaryl
phosphine ligands were first illustrated by Buchwald in
1998 for their use in palladium‐catalyzed cross coupling
reactions to the C‐N and C‐C bonds synthesis.[19–21] We
have successfully applied a variety of efficient and
privileged biphenyl Buchwald ligands for Rh‐catalyzed
regio‐selective semihydrogenation of alkynes to respec-
tive E and Z alkenes with high selectivity.[22] Based on
our ongoing research interest in this field, we made
efforts to improve the selectivity and activity for the
Appl Organometal Chem. 2018;e4478.
wileyonlinelibrary.com/journal/aoc
© 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4478

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JAGTAP AND BHANAGE
hydroformylation of natural alkenes into respective lin-
ear and branched aldehydes with excellent selectivity in
presence of Buchwald phosphine ligands (Figure 1).
Rhodium catalyzed hydroformylation of simple and
functionalized olefins has been well explored in the
literature for the fine chemical synthesis.[23,24]
Hydroformylation of biomass derived olefins has great
importance in fragrance and flavour industries.[25]
Biorenewable olefins such as eugenol, prenol, anethole
and estragole represents a class of natural products which
as significant potential for industrial manufacturing of
perfumes, fragrances, flavors, food and pharmaceuti-
cals.[26–31] Natural olefins are readily available from
nature and it is greener alternative supply of
biorenewable raw material in flavor and fragrance indus-
tries.[32,33] Naturally occurring olefins like eugenol,
anethole and estragole are bio‐renewable sources derived
from (biomass) cloves, basil and sweet basil, respec-
tively.[34] Prenol and isoprenol are natural olefins
obtained from citrus fruits, cranberry, bilberry, currants,
grapes, raspberry, blackberry, tomato, hop oil, coffee,
cloudberry and passion fruit.[35]
however, it reports lower selectivity for alehyde prod-
ucts.[38] Silva et al. disclosed hydroformylation of various
allylbenzenes and propenylbenzenes with high chemose-
lectivity using Rh/phosphine as a catalyst which has
similarity in the substracts like eugenol.[39] Several
homogenous catalytic procedure were developed for the
selective hydroformylation of eugenol.[40–43] Tan and co‐
workers developed the construction of β‐hydroxy‐acid
and aldehyde products via regioselective hydroformy-
lation of allylic alcohols.[44] Furthermore, selective
hydroformylation of terminal and internal olefins into
linear aldehydes using tetraphosphorus ligands was also
reported.[45] There is a need to develop an efficient and
selective protocol for the hydrformylation of these natural
olefins. To the best of our knowledge, Buchwald phos-
phine ligands is not reported yet for the important class
of hydroformylation of eugenol.
Herein, we report regioselective hydroformylation of
natural alkenes like eugenol, anethole, estragole, prenol
and isprenol etc. catalyzed by rhodium catalyst in
presence of Buchwald posphine ligands (Scheme 1). The
main objective of this work is the screening and evalua-
tion of biphenyl based Buchwald phosphine ligands such
as (S‐Phos (L1), t‐Bu XPhos (L2), Ru‐Phos (L3), Johnphos
(L4) and DavePhos (L5). Out of these phosphine ligands,
Ru‐Phos ligand was found to be the active ligand for the
Even though the hydroformylation of the natural ole-
fins, such as eugenol, prenol, anethole, estragole etc. has
been quite extensively investigated.[36,37] Siegel et al.
accounted the Rh‐catalyzed hydroformylation of eugenol,
FIGURE 1 Biphenyl based Buchwald
Phosphine ligands used for the
regioselective hydrofor‐mylation of
natural olefins
SCHEME 1 Selective hydroformylation of eugenol using Rh/Phosphine as a simple and an efficient catalyst[a][a] Reaction Conditions:
Eugenol (1 mmol), Rhacac (CO)2 (0.0015 mmol), Ligand (0.0045 mmol), CO/H2 (30 bar), Toluene (10 ml), 80 °C, 10 h.[b] Determined by
GC and GC–MS.

JAGTAP AND BHANAGE
3 of 9
selectively providing the linear aldehydes as major prod-
uct. The higher selectivity towards the linear aldehydes
was observed as major product, it was found may be
due to the bulky groups present in Ru‐phos ligand. More-
over, the natural olefins were easily converted to respec-
tive linear and branched aldehydes as major product
under mild conditions.
eugenol (1a) to the production of corresponding linear
aldehyde i.e. 4‐(3‐hydroxy‐4‐methoxyphenyl) butanal
(1d) was selected as a model reaction. In situ generated
Rh (I)/phosphine as catalytic system was used for this
reaction. The electronic and steric effects of the phos-
phine ligand structure on the reactivity and selectivity
of the reaction was studied using a set of eight
monophosphine ligands.
2 | EXPERIMENTAL
3.2 | Steric and electronic influence of
ligands on rhodium catalyzed
hydroformylation of eugenol
2.1 | Materials and Methods
The chemicals and solvents were procured from Sigma
Aldrich, Alfa Aesar, Spectrochem Pvt. Ltd., India and
utilized as received without additional purification.
Buchwald phosphine ligands were purchased from Sigma
Aldrich, India. Syngas containing mixture of carbon mon-
oxide and hydrogen gas with equal concentration were
procured from Rakhangi Gas Service, Mumbai. The reac-
tion progress was monitored by gas chromatography on
Perkin Elmer Clarus 400 GC equipped with flame ioniza-
tion detector with a capillary column (Elite‐1, 30 m x
0.32 mm x 0.25 μm) using external standard method.
GC–MS‐QP 2010 instrument (Rtx‐17, 30 m × 25 mm ID,
film thickness 0.25 μm df) (column flow 2 10 mlmin‐1,
80 °C to 240 °C at 10°/min rise).
As the ligands play significant role in activity and
selectivity, the choice of an proper ligand is one of the
critical issues in the transition metal catalyzed
hydroformylation reactions.
Primarily, we studied a set of Buchwald phosphine
ligands on the hydroformylation of eugenol (1a) as shown
in Table 1. Eight different ligands, as shown in Figure 1,
were explored in the rhodium catalyzed hydrofor-
mylation of eugenol at 30 bar syngas pressure and at
80 °C. As shown in Table 1, the ligands like PPh3 and
PCy3 showed good activity, but the moderate selectivity
was observed in terms of linear aldehydes (Table 1, entries
1 and 2). The BINAP ligand showed the better perfor-
mance for the activity, but moderate selectivity was found
in terms of linear aldehydes 1d (Table 1, entry 3). The
ligands L1, L3 and L5 with the same bulky tricyclohexyl
backbone exhibited rather different performances refer-
ring to regioselectivity and activity. The ligand L1 showed
the high conversion as well as better selectivity of aldehyde
with moderate selectivity of linar aldehyde (1d) (Table 1,
2.2 | Typical experimental procedure for
selective hydroformylation of Eugenol
All the experiments were carried out in stainless steel
high pressure reactor of 100 ml capacity equipped with
a magnetic stirrer. Eugenol (1 mmol), [Rh (acac)(CO)2]
(0.0015 mmol), Ru‐Phos ligand (0.0045 mmol) were
added in 10 ml of toluene as solvent. The autoclave was
closed, flushed three times with nitrogen and pressurized
with 30 bar of syngas pressure. Then reactor was heated
at 80 °C with a 700 rpm stirring speed for 10 h. After
the completion of the reaction, the reactor was cooled to
room temperature. The remaining syngas gas was vented
out carefully. Then organic mixture was passed through
filter paper with dry sodium sulphate to eliminate traces
of moisture if present. Afterwads, the obtained reaction
mixture was subjected to further GC and GC–MS
analysis.
TABLE 1 Rhodium catalyzed hydroformylation of eugenol
using various biphenyl phosphine ligandsa
Yield of
total
Ald. (%)b
Selectivity
(%)b
1b:1c:1d
L/Rh
ratio
Conv.
(%)b
Entry
Ligand
1
2
3
4
5
6
7
8
9
PPh3
PCy3
BINAP
L1
3
3
3
3
3
3
6
3
3
89
82
76
74
85
89
78
92
90
78
82
10:12:78
12:15:73
15:16:69
12:12:76
16:19:65
03:07:90
05:10:85
10:14:76
06:10:84
90
94
L2
85
L3
98
3 | RESULTS AND DISCUSSION
L3
100
90
L4
3.1 | General hydroformylation reaction
of eugenol
L5
92
aReaction Conditions: Eugenol (1 mmol), [Rhacac (CO)2] (0.0015 mmol),
The conversion of biomass derived olefins into value
added chemicals via selective hydroformylation of
Syngas (30 bar), Toluene (10 ml), Temp. (80 °C), Time (10 h).
bConfirmed by GC and GC–MS analysis.

4 of 9
JAGTAP AND BHANAGE
entry 4). The ligand L2 was marginally less active than the
ligand L1 in terms of substrate conversion and selectivity
of 1d (Table 1, entry 5). Then L3 ligand showed the
remarkable effect with increase in the activity as well as
selectivity of linear aldehydes (Table 1, entry 6). A high
activity and selectivity obtained linear aldehydes as major
product could be cause of the steric crowding bulky groups
such as isopropyl and cyclohexyl present in RuPhos (L3)
ligand. We increase the concentration of ligand L3 to
rhodium from 3 to 6, then both the conversionof 1a and
selectivity of 1d not affected as much (Table 1, entry 7).
Then ligand L4 showed the better activity with moderate
selectivity of linear aldehyde (Table 1, entry 8). Finally,
the ligand L5 also provided the high activity and good
selectivity of 1d (Table 1, entry 9).
From the above description, it was conclude that the
electronic as well as steric bulky group and concentration
of phosphine ligand was found to be key limit to
supervise the catalytic activity and selectivity. Because,
the phosphine ligands has electron donating property
and it has a long history as a soft. Ru‐Phos ligand acts
as powerful ligand for the hydroformylation of eugenol
and prenol because it has bidentate (‐O, and –P donor)
ligand containing di‐isopropoxy bulky groups may
enhance selectivity towards the linear aldehydes for
terminal natural olefins.
3.3 | Optimization of reaction parameters
for the selective hydroformylation eugenol
Initially, a set of experiments were carried out to optimize
the various reaction conditions such as effect of syngas
(CO/H2) pressure, time, temperature and solvent on
model reaction. The results achieved are shown in
Table 2. In the optimization study, primarilly we investi-
gated the effect of syngas pressure in the range of 20–
40 bar using toluene as a solvent at 80 °C for 10 h. The
40 bar of syngas pressure, 99% conversion and 85% selec-
tivity of the product (1d) achieved (Table 2, entry 1). The
optimum pressure for this reaction was 30 bar, furnished
98% conversion of 1a and 90% selectivity of 1d (Table 2,
entry 2). We reduced the pressure up to 20 bar, then con-
version was reduced to 87% and selectivity of 1d
decreased up to 82% (Table 2, entry 3). Its happened
due to lowering of syngas pressure increase in isomeriza-
tion of alkene reduces the selectivity of product 1d.[45]
Next we studied the effect of time in the range of 4 h to
12 h to achieve the high activity and selectivity for the
hydroformylation of eugenol. If we increased the reaction
time from 4 h to 8 h, both the conversion increased from
72% to 94% and selectivity of 1d was also increased from
74% to 86% respectively (Table 2, entries 4–6). The opti-
mum reaction time was 10 h, as the best results are
a
TABLE 2 Optimization of the reaction conditions for the hydroformylation of eugenol with ligand L3
Selectivity (%)b
(1b:1c:1d)
Entry
Pressure in bar (CO/H2)
Time (h)
Temp. (°C)
Solvent
Conv. (%)b
Effect of pressure
1
40
30
20
10
10
10
80
80
80
Toluene
Toluene
Toluene
99
98
87
05:10:85
03:07:90
08:10:82
2
3
Effect of time
4
30
30
30
30
4
6
80
80
80
80
Toluene
Toluene
Toluene
Toluene
72
85
10:16:74
08:12:80
05:09:86
06:10:84
5
6
8
94
7
12
100
Effect of temperature
8
30
30
30
30
10
10
10
10
40
60
Toluene
Toluene
Toluene
Toluene
58
78
06:10:84
05:08:87
06:12:82
10:15:75
9
10
100
120
99
11
100
Effect of solvents
12
13
30
30
10
10
80
80
THF
92
86
10:08:82
15:09:76
1,4 Dioxane
aReaction Conditions: Eugenol (1 mmol), Rhacac (CO)2 (0.0015 mmol), L3 (0.0045 mmol), Solvent (10 ml), 700 rpm.
bConfirmed by GC and GC–MS analysis.

JAGTAP AND BHANAGE
5 of 9
obtained by providing 98% conversion and 90% selectivity
of 1d (Table 2, entry 2). If we increased the reaction time
up to 12 h, then the conversion increases from 94% to
100%, and selectivity of 1d slightly reduced to 84%
(Table 2, entry 7). It may occurs due to increase in time
increases the percentage of isomerisation and hydrogena-
tion (Table 2, entry 7).
Furthermore, we studied the effect of temperature in
the range of 40 °C to 120 °C to determine the optimum
temperature better activity and selectivity performance.
At low temperature of 40 °C, 58% conversion and 84%
selectivity was observed (Table 2, entry 8). As we raise
the reaction temperature up to 60 °C, the conversion
increased to 78% and the selectivity of 1d also increases
to 87% (Table 2, entry 9). At high temperature of
100 °C, 99% conversion observed with marginal decrease
in selectivity up to 82% (Table 2, entry 10). Finally, at
higher temperatures of 120 °C, the conversion doesn't
have any effect but the selectivity of 1d decreases
(Table 2, entry 11). The reaction temperature of 80 °C
was observed as optimum temperature for the model
reaction, afforded 98% conversion of 1a and 90% selectiv-
ity of 1d (Table 2, entry 2). As we increase the tempera-
ture the conversion increases but the selectivity initially
increases and then gradually decreases at higher temper-
ature. Because at higher temperature olefins get easily
isomerized and hydrogenated Afterwards, we screened
various solvents like THF, Toluene and Dioxane to attain
high activity and selectivity (Table 2, entries 2, 12 and 13).
Among them non polar toluene as favourable solvent for
this reaction.
3.4 | Influence of various metallic
precursor on selective hydroformylation of
eugenol
In the absence of the metal precursor, reaction was not
proceed assuring that the catalyst is responsible for the
reaction (Table 3, entry 1). We studied the various
metallic precursors of ruthenium, rhodium and cobalt
metals for the hydroformylation of eugenol in the pres-
ence of Ruphos (L3) ligand in toluene as solvent.
Among them rhodium metal precursors was found to
be more active for the hydroformylation of 1a. The
ruthenium metal precursors like Ru3CO12 and RuCl3
provided the average activity and selectivity of 1d
(Table 3, entries 2 and 3). Then we screened various
rhodium precursors such as RhCl3; [Rh (acac)(CO)2];
[Rh (COD)Cl]2; Rh (COD)2[BF4]; [Rh2 (OAc)4] affording
good to excellent conversion and also furnished good to
excellent selectivity towards 1d (Table 3, entries 4–9).
From these rhodium precursors, Rh (acac)(CO)2 precur-
sor was active for hydroformylation of 1a, it afforded
98% conversion of 1a and 90% selectivity of 1d
(Table 3, entry 6). We have also employed the cobalt
precursors such as Co2 (CO)8 and CoCl2.6H2O, these
precursors are less active than rhodium for
hydroformylation of 1a. It provides average conversion
and selectivity even at harsh reactions, such as high
pressure (50 bar) and high temperature (100 °C) for
12 h (Table 3, entries 10 and 11).
TABLE 3 Effect of metallic precursors on selective
hydroformylation of eugenol (1a) in presence of ligand L3
a
Yield of Selectivity
Metallic
Entry precursors
Conc.
Conv. total Ald.
(%)b
1b:1c:1d
(mmol) (%)b (%)b
1
‐
Ru3 (CO)12
RuCl3
‐
‐
‐
‐
2
0.015
0.050
0.020
68
59
68
94
98
90
85
89
65
60
48
56
63
86
92
84
81
84
58
54
12:23:65
10:22:68
16:20:64
08:10:82
03:07:90
10:14:76
14:20:66
10:18:72
16:22:62
16:26:58
3
4
RhCl3
5
Rh (acac)(CO)2 0.001
Rh (acac)(CO)2 0.0015
[Rh (COD)Cl]2 0.0020
Rh (COD)2BF4 0.0020
6
7
8
9
Rh2 (OAc)4
Co2 (CO)8
0.0020
0.020
0.055
10c
11c
CoCl2.6H2O
aReaction Conditions: Eugenol (1 mmol), L3/Metal ratio (3), CO/H2
(30 bar), Toluene (10 ml), 700 rpm, 80 °C, 10 hr.
bConfirmed by GC and GC–MS analysis.
c50 bar, 100 °C, 12 hr.
SCHEME 2 Selective hydroformylation of prenol using Rh/Phosphine as a simple and an efficient catalyst[a][a] Reaction Conditions:
Prenol (4 mmol), Rhacac (CO)2 (0.002 mmol), L3 (0.006 mmol), CO/H2 (35 bar), Toluene (10 ml), 80 °C, 12 h.[b] Determined by GC and
GC–MS.

6 of 9
JAGTAP AND BHANAGE
conversion and selectivity of product 2b (Scheme 2). Ini-
tially, we used the ligands such as PPh3, PCy3 and BINAP
with L/Rh ratio 3, it was provide the good activity and
yield of total aldehydes with better selectivity of 2b
(Table 4, entries 1–3). Then we examined effect of L1
and L2 ligand, good activity was noted but the moderate
selectivity towards the 2b was observed (Table 4, entries
4 and 5). Remarkable effect of ligand L3 was found on
hydroformylation of 2a providing high conversion (95%)
as well as selectivity (84%) of 2b (Table 4, entry 6). If we
increase the concentration of L3, then conversion was
almost same but slightly decrease in selectivity of 2b
(Table 4, entry 7). It was observed that the L4 and L5
ligands also shows high activity, but slightly lesser selec-
tivity of 2b (Table 4, entries 8 and 9). Hence we used
ligand L3 for further optimization study.
3.5 | Steric and electronic influenece of
ligands on rhodium catalyzed
hydroformylation of prenol
Furthermore, we studied the hydroformylation of natural
aliphatic internal alkene as prenol (2a) to get excellent
TABLE 4 Rhodium catalyzed hydroformylation of prenol
with various biphenyl phosphine ligandsa
Yield of
total
Ald. (%)b
Selectivity
(%)b
2b:2c:2d
L/Rh
ratio
Conv.
(%)b
Entry
Ligand
1
2
3
4
5
6
7
8
9
PPh3
PCy3
BINAP
L1
3
3
3
3
3
3
5
3
3
82
85
86
90
80
95
98
86
92
67
76
79
80
75
86
85
74
80
75:05:20
78:04:18
80:05:15
72:08:20
76:04:20
84:06:10
82:08:10
78:05:17
80:04:16
3.6 | Optimization study for the
hydroformylation of prenol
L2
L3
We studied the influence of different reaction parame-
ters such as influence of syngas pressure, time, temper-
ature and solvent using Rh/L3 as catalyst shown in
Table 5. We studied the reaction at 45, 35 and 25 bar
of syngas, among them 35 bar syngas pressure was the
optimum to getting high activity and selectivity of 2b
(Table 5, entries 1–3). We observed the high conversion
L3
L4
L5
aReaction Conditions: Prenol (4 mmol), Rhacac (CO)2 (0.002 mmol),
Syngas (30 bar), Toluene (10 ml), Temp. (80 °C), Time (10 h).
bConfirmed by GC and GC–MS analysis.
a
TABLE 5 Optimization of the reaction conditions for the selective hydroformylation of prenol with ligand L3
Pressure
in bar CO/H2)
Selectivity (%)b
(2b:2c:2d)
Entry
Time (h)
Temp. (°C)
Solvent
Conv. (%)b
Effect of pressure
1
45
35
25
10
10
10
80
80
80
Toluene
Toluene
Toluene
100
95
67:10:23
78:06:16
70:10:20
2
3
90
Effect of time
4
35
35
35
35
4
6
80
80
80
80
Toluene
Toluene
Toluene
Toluene
65
82
92
99
70:10:20
75:05:20
72:10:18
85:05:10
5
6
8
7
12
Effect of temperature
8
35
35
35
12
12
12
40
60
Toluene
Toluene
Toluene
78
80
70:10:20
74:08:18
82:06:12
9
10
100
100
Effect of Solvent
11
12
35
35
12
12
80
80
THF
89
85
75:10:15
78:08:16
Dioxane
aReaction Conditions: Prenol (4 mmol), Rhacac (CO)2 (0.002 mmol), L3 (0.006 mmol), Solvent (10 ml), 700 rpm.
bConfirmed by GC and GC–MS analysis.

JAGTAP AND BHANAGE
7 of 9
TABLE 6 Substrate study of selective hydroformylation of
natural olefinsa
(95%) and selectivity (78%) at 35 bar of syngas (Table 5,
entry 2). Then we studied the reaction time from 4 h to
12 h using toluene as solvent 80 °C reaction tempera-
ture (Table 5, entries 4–7). As we increase the reaction
time then also the conversion, yield of total aldehydes
and selectivity of 2b increases. At 12 h of optimum reac-
tion time, high conversion (99%) and selectivity (85%) of
2b was observed (Table 5, entry 7).
Selectivity
Yield of
total
Ald. (%)b
(%)b
1b‐9b:1c‐
9c:1d‐9d
Conv.
(%)b
Entry
1
Substrates
98
92
03:07:90
Consequently, we studied the temperature in range of
40–120 °C for 12 h at 35 bar syngas pressure under
toluene as solvent (Table 5, entries 8–10). Temperature
80 °C was found to be optimum temperature, furnished
99% conversion and 85% selectivity towards 2b (Table 5,
entry 7). At the end of the optimization study of
hydroformylation of prenol, we screened the solvent
Toluene, THF and dioxane to furnishing high activity
and selectivity (Table 5, entries 7, 11 and 12). Tolune sol-
vent provides best conversion and high selectivity towards
2b as major product (Table 5, entry 7). Therefore the stan-
dard optimized reaction conditions used for hydroformy-
lation of prenol are: Rhacac (CO)2 (0.002 mmol), L3
(0.006 mmol), CO/H2 (35 bar), Temp. (80 °C), Time
(12 h), 700 rpm. (rpm = revolutions per minute).
2c
3
99
99
96
86
92
87
85:05:10
03:10:87
25:65:10
4d
5
6
98
92
89
89
13:12:75
10:12:78
7
8
9
96
96
89
88
82
78
14:14:72
10:10:80
12:18:70
3.7 | Hydroformylation of various natural
olefins like eugenol and prenol
Optimized standard reaction conditions were used fur-
ther to study the substrate applicability of current proto-
col. Typically, internal alkenes afforded selectively
branched aldehydes as major products while terminal
alkenes provided selectively linear aldehydes as a major
products. The substrates of allyl benzenes containing
aReaction Conditions: Olefin (1 mmol), Rhacac (CO)2 (0.0015 mmol), L3
(0.0045 mmol), CO/H2 (30 bar), Toluene (10 ml), 80 °C, 10 h.
bConfirmed by GC and GC–MS analysis.
cPrenol (4 mmol), Rhacac (CO)2 (0.002 mmol), L3 (0.006 mmol), 80 °C, 12 h,
35 bar.
d90 °C, 16 h, 40 bar.
FIGURE 2 Plausible reaction
mechanism for the regioselective
hydroformylation of eugenol using Rh/
Phosphine as efficient catalytic system[a]
aReaction Conditions: Eugenol
(1 mmol), [Rhacac (CO)2] (0.0015 mmol),
L3 (0.0045 mmol), Syngas (30 bar),
Toluene (10 ml), 80 °C, 10 h.

8 of 9
JAGTAP AND BHANAGE
electron‐rich groups (−Me, –OMe, –OH) and electron
deficient group (CF3) were easily transformed into the
expected aldehydes as major products. Eugenol (1a) used
for model reaction afforded high 98% conversion and 92%
yield of aldehydes with high selectivity (90%) of linear
aldehyde (1d) (Table 6, entry 1). In addition, we also stud-
ied the aliphatic internal natural alkene prenol (2a)
which was smoothly converted into branched aldehyde
2b with 85% selectivity (Table 6, entry 2). Afterwards,
aliphatic terminal alkene isoprenol (3a) provided the
99% conversion and 92% yield of aldehydes with 87%
selectivity towards linear aldehyde (3d) (Table 6, entry
3). The hydroformylation of anethole as internal alkene
furnished 96% conversion, 87% yield of aldehydes with
65% selectivity towards branched aldehyde 4c (Table 6,
entry 4). Moreover, we have also studied the derivatives
of allyl benzene containing electron rich groups (–Me,
–OMe, –OH) and electron deficient group (–CF3) which
were easily converted into linear aldehydes with good to
high selectivity (Table 6, entries 5–9).
Johnphos (L4) and DavePhos (L5) have been successfully
employed for the selective hydroformylation of natural
olefins. From all of these phosphine ligands, Ru‐Phos
(L3) provided the preeminent conversion and high selec-
tivity to the linear aldehydes. Ru‐Phos ligand acts as
bidentate (‐O, and –P donor) ligand containing di‐
isopropoxy bulky groups may enhance selectivity towards
the linear aldehydes for terminal natural olefins. In addi-
tion, the branched aldehydes was found to be major prod-
uct in case of internal alkenes like prenol and anethole,
though it was difficult to do the hydroformylation of inter-
nal olefins.[12] Natural olefins with electron deficient and
rich groups were easily converted to respective linear and
branched aldehydes as major products. This protocol
provides straightforward access towards the synthesis of
linear and branched aldehydes which are broadly used as
raw materials in the cosmetics, pharmaceutical, fragrances
and agrochemicals industry.
ACKNOWLEDGEMENT
Here, we propose a plausible mechanistic pathway as
shown in Figure 2 on the basis of experimental results
and previous literature [1(a), 4(a), 5(a)]. Initially, olefin
co‐ordinates with the complex [HRh (CO)L2] to the
formation of complex (A). Then two isomers of alkyl rho-
dium complexes formed namely linear (A1) and branched
(A2). Accordingly, migratory insertion of carbon monox-
ide to the complex A1 and A2 further provides two iso-
mers linear acylrhodium complex B1 and branched
acylrhodium complex B2. Furthermore, the oxidative
addition of hydrogen molecule to complex B1 and leads
to the formation of complex C1. Finally, expected linear
aldehyde (1d) obtained by reductive elimination of com-
plex C1 with formation of active catalytic species [HRh
(CO)L2] and completion of the catalytic cycle. In the
same way, it was happened in case of complex B2 to the
formation of complex C2 fallowed by reductive elimina-
tion to get the branched aldehydes (2b and 2c) as major
product. In case of styrene, branched aldehyde was
formed as major product due to the formaytion of stable
benzylic rhodium species. In case of anethole (4a),
formed three isomers of aldehydes product 4b:4c:4d with
ratio 25:65:10, because it has three position to
isomerisation double bond.
The author S.A.J. is thankful to the Council of Scientific
and Industrial Research (CSIR) New Delhi, India for
providing a Senior Research Fellowship (SRF).
ORCID
Bhalchandra M. Bhanage
http://orcid.org/0000-0001-
9538-3339
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How to cite this article: Jagtap SA, Bhanage
BM. Rhodium/Phosphine catalysed selective
hydroformylation of biorenewable olefins. Appl
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