Hydroformylation and hydroalkylcarbonylation of 3,4-dihydro[2H]pyran catalysed by Co2(CO)8 under syngas conditions

Article abstract of DOI:10.1007/s11243-013-9750-4

In the cobalt-catalysed hydroformylation of 3,4-dihydro[2H]pyran, the influence of different reaction parameters such as time, pressure, triphenylphosphine addition, catalyst and substrate concentration has been investigated. 2-formyl-tetrahydropyran, tetrahydropyran and a hydroalkylcarbonylation product were the main reaction products. The selectivity towards 2-formyl-tetrahydropyran formation is favoured at constant catalyst and substrate concentration. The coordination of the pyran's oxygen to the cobalt atom seems to be an important intermediate for the formation of 2-formyl-tetrahydropyran. Different substrate or catalyst concentrations promote the formation of other reduced products. The addition of triphenylphosphine to the catalyst leads to a less active species, which decreases the yield and promotes the hydroalkylcarbonylation reaction.

Full text of DOI:10.1007/s11243-013-9750-4

Transition Met Chem
DOI 10.1007/s11243-013-9750-4
Hydroformylation and hydroalkylcarbonylation
of 3,4-dihydro[2H]pyran catalysed by Co (CO)
under syngas conditions
2
8
Jos e´ L. Arias
•
Pankaj Sharma
•
•
Armando Cabrera
•
•
Fernando Beristain
Cesar Arizmendi
Rafael Sampere
Received: 20 May 2013 / Accepted: 15 July 2013
Ó Springer Science+Business Media Dordrecht 2013
Abstract In the cobalt-catalysed hydroformylation of
,4-dihydro[2H]pyran, the influence of different reaction
intermediates for the synthesis of fine chemicals [5], nat-
ural products or pharmaceuticals [6]. In 1964, Falbe et al.
[7] reported Co (CO) -catalysed hydroformylation of di-
3
parameters such as time, pressure, triphenylphosphine
addition, catalyst and substrate concentration has been
investigated. 2-formyl-tetrahydropyran, tetrahydropyran
and a hydroalkylcarbonylation product were the main
reaction products. The selectivity towards 2-formyl-tetra-
hydropyran formation is favoured at constant catalyst and
substrate concentration. The coordination of the pyran’s
oxygen to the cobalt atom seems to be an important
intermediate for the formation of 2-formyl-tetrahydropy-
ran. Different substrate or catalyst concentrations promote
the formation of other reduced products. The addition of
triphenylphosphine to the catalyst leads to a less active
species, which decreases the yield and promotes the hy-
droalkylcarbonylation reaction.
2
8
hydropyran under very drastic conditions (300 atm CO/H2
1:1 at 190 °C) and obtained 2 hydroxymethyl-tetra-
hydropyran as a major reaction product along with small
quantities of its 3-isomer and tetrahydropyran. Similar
results were obtained by Polo and co-workers [8],
employing a dinuclear rhodium complex with phosphine,
but in this case, both 2- and 3-substituted aldehydes were
detected as main products in 2:1 yield. To the best of our
knowledge, after these two reports, no information has
appeared on the carbonylation of pyrans using either Rh or
Co as catalyst. In continuation of our interest in cobalt-
catalysed carbonylation reactions [9–11], here we report a
systematic study on the influence of different reaction
parameters, such as time, pressure, PPh addition, catalyst
3
and substrate concentration, on the homogeneous hydro-
formylation of 3,4-dihydro[2H]pyran, Scheme 1.
Introduction
Hydroformylation reactions have been regarded as one of
the most important catalytic processes, [1, 2] but only a few
reports on the hydroformylation of functionalised cyclic
and acyclic alkenes are known [3, 4]. These substrates
yield aldehydes that are of interest for the preparation of
Experimental
Tetrahydrofuran was dried and deoxygenated by distilla-
tion under argon from sodium benzophenone ketyl before
use. Co (CO) was purchased from Strem Chemical
2
8
Company, PPh3 from Aldrich, CO and H2 were from
Matheson and used without further purification.
J. L. Arias (&) ꢀ F. Beristain ꢀ R. Sampere ꢀ C. Arizmendi
Departamento de Qu ´ı mica, Facultad de Estudios Superiores
Cuautitl a´ n, Universidad Nacional Aut o´ noma de M e´ xico,
CP 54700 Cuautitl a´ n Izcalli, Estado de M e´ xico, M e´ xico
e-mail: jlartell@unam.mx
The high-pressure catalytic reactions were carried out in
a 80-ml Parr reactor. A typical experiment was performed
as follows: a solution of 3,4-dihydro[2H]pyran (1 ml,
-
1
1
0.1 mmol) and Co (CO) (0.034 g, 1.0 9 10 mmol) in
2 8
P. Sharma ꢀ A. Cabrera
THF (5 ml) was introduced by suction into an evacuated
high-pressure reactor described above. Before introducing
Instituto de Qu ´ı mica, Universidad Nacional Aut o´ noma de
M e´ xico, Ciudad Universitaria, Circuito Exterior, Coyoac a´ n,
CP 04510 M e´ xico, DF, M e´ xico
the mix CO/H at the desired pressure, the system was
2
123

Transition Met Chem
Scheme 1 Different reaction
products obtained in the
hydroformylation of 3,4-
dihydro[2H]pyran
O
CO H
2
H
+
+
H
Co (CO)
2
8
O
O
O
O
O
O
OH
+
O
O
O
O
O
purged 2 or 3 times with CO. Then, the reaction vessel was
closed, pressurised and heated with stirring at a tempera-
ture of 150 °C from 1 to 10 h. At the end of the time, the
reactor was cooled (final pressure was 650 psi) and the
gases were liberated. The solution was percolated through a
column packed with alumina and the resulting yellow
solution was analysed on a JEOL JMS-AX505HA GC–MS
instrument with a 25 m 9 0.25 mm glass column packed
with 5 % phenylsilicone and quantified by GC using hex-
ane as an internal standard in a Hewlett Packard 5890
analyser with a 30 m 9 0.53 mm glass column packed
Table 1 Effect of time: reaction conditions
%
1
compounds/time (h)
2
4
6
8
10
Tetrahydropyran
–
1
1
2
3
3
3
3
4
3
4
3
3
2
3
2
-formyl-tetrahydropyran
-formyl-tetrahydropyran
19 39 44 54 60 65
-hydroxymethyl-tetrahydropyran
-hydroxymethyl-tetrahydropyran
–
2
3
1
3
4
1
5
6
2
6
7
3
8
8
3
10
10
Hydroalkylcarbonylation
product
1
13
with methylsilicone. The H and C NMR spectra, of the
crude products in THF, were recorded on a JEOL 300 MHz
Ester
–
1
1
2
3
4
Total transformation
Total aldehyde
Total alcohol
25 51 63 77 89 99
20 41 47 57 63 68
spectrometer using (CH ) Si as internal reference in CDCl
3
3
4
as solvent at 25 °C. The IR spectra were obtained by using
a Nicolet FTIR Magna 750 spectrometer.
2
4
6
8
11 13
Aldehyde selectivity
80 80 75 74 71 69
2 8
Co (CO) 0.1 mmol; 3,4-dihydro-[2H]-pyran 10.1 mmol; THF 5 ml;
2
H /CO 1:1 P = 54.4 atm; temperature 150 °C
Results and discussion
These reactions were performed at relatively low pressures,
and 2- and 3-formyl-tetrahydropyrans, their corresponding
alcohols, tetrahydropyran and bis (2-tetrahydropyra-
nyl)methanol (the hydroalkylcarbonylation product hacp)
were obtained. 2-Tetrahydropyranyl tetrahydropyran-2-
carboxylate was also obtained in a very low yield. The
selectivity towards the formation of 2-aldehyde, tetrahy-
dropyran and hacp depends on the experimental conditions
7
0
50
(
Table 1).
3
1
0
0
Effect of time
In order to observe the effect of time on hydroformylation
reaction of dihydropyran, experiments were performed at
constant syngas pressure, substrate and catalyst concen-
tration at a temperature of 150 °C for 1–10 h. The results
are shown in Table 1 and Fig. 1, which indicate a pro-
portional increase in aldehyde, alcohol and hacp yields
with time, obtaining 68 % as maximum yield for the total
aldehyde with a selectivity of 21:1, (2- to 3-formyl-tetra-
hydropyran). This high selectivity may be due to the
1
2
4
6
8
10
Time (h)
Fig. 1 Aldehyde formation as a function of time (1–10 h). Co
0
2 8
(CO)
.1 mmol; 3,4-dihydro[2H]pyran 10.1 mmol; THF 5 ml; H /CO 1:1
2
pressure 54.4 atm; temperature 150 °C. Circle total aldehyde,
diamond total alcohol and star hacp
1
23

Transition Met Chem
Scheme 2 Coordination of the
pyran’s oxygen atom to the
cobalt atom
CO
Co
O
O
O
CO
CO
CO
CO
Co
H
CO
OC
Co
H
CO CO
CO
CO
O
CO
O
O
Co
CO
CO
Co
CO
CO
OC
0
coordination of pyran s oxygen atom to the cobalt atom
bringing the a-position closer to cobalt, (Scheme 2). Under
such conditions, tetrahydropyran, a reduction product, was
obtained in a very small amount, \4 %, and this yield is
based on the amount of 3,4-dihydro[2H]pyran introduced.
90
8
0
0
0
0
Effect of catalyst concentration
6
4
2
The effect of catalyst concentration was carried out in the
range 0.1–0.5 mmol. The results obtained are given in
Fig. 2, which shows that an initial increase in catalyst
concentration increases the aldehyde concentration up to
0
.2 mmol, after which further increment in the catalyst
concentration decreases the aldehyde formation. A similar
trend is observed with the alcohol, although it is less pro-
nounced. Moreover, the tetrahydropyran concentration
increases significantly and is proportional to the catalyst
addition. The formation of tetrahydropyran takes place via
an alkyl-metalated intermediate as reported earlier with
other non-functionalised alkenes, [12] Scheme 3. Under
such conditions, the hacp was not detected.
0.1
0.2
0.3
0.4
8
(CO) (mmol)
0.5
Concentration of Co
2
Fig. 2 Aldehyde and alkane formation as a function of Co
concentration (0.1–0.5 mmol). 3,4-dihydro[2H]pyran 10.1 mmol; THF
ml; H
2 8
(CO)
Effect of substrate concentration
5
2
/CO 1:1 pressure 54.4 atm; temperature 150 °C, time 10 h.
Figure 3 shows the influence of substrate concentration
studied in an interval of 10.1–30.3 mmol. A decrease in the
aldehyde formation with the increase in substrate concen-
tration was observed, and an increase in both tetrahydropyran
and hacp yields was also noted. Under these experimental
conditions, the decrease in aldehyde concentration cannot be
explained by its transformation to the corresponding alcohol,
as this compound was not detected in a significant amount.
On the other hand, the main reaction product was hacp,
though under hydroformylation conditions, the formation of
diorganyl ketones can be observed using relatively simple
olefins, which is in contrary to complex olefins [13, 14]. The
hacp was generated from the reductive elimination of the
Circle total aldehyde, diamond total alcohol and square tetrahydropyran
acyl-Co and alkyl-Co species formed due to the excess of the
substrate. Under the experimental conditions used in this
work, it was not possible to detect the carbonyl compound,
suggesting that the reduction step of hacp is too fast to isolate
the dipyranyl ketone. In these conditions, tetrahydropyran
was obtained in appreciable amounts.
Effect of total pressure
The effect of syngas pressure on the products formation
was studied in a range of 27.2–54.4 atm (400–800 psi), and
123

Transition Met Chem
Scheme 3 Formation of
H
tetrahydropyran and 2-formyl-
tetrahydropyran via a common
alkyl-cobalt intermediate
H
O
Co
CO
O
H
H2
OC
CO
HCo(CO)3
Co2(CO)8
CO
O
O
Co
CO
CO
CO
CO
O
Co CO
CO
H
O
OC
O
HCo(CO)3
7
0
0
70
6
60
4
2
0
0
4
2
0
0
%
27.2
34.0
40.8
47.6
54.4
10.1
15.15
20.2
25.25
30.3
Pressure (atm)
Concentration of sustrate (mmol)
Fig. 4 Aldehyde formation as a function of the pressure (27.2–
54.4 atm). Co (CO) 0.1 mmol; 3,4-dihydro[2H]pyran 10.1 mmol;
Fig. 3 Products formation as a function of substrate concentration
10.1–30.3 mmol). Co (CO) 0.1 mmol; THF 5 ml; H /CO 1:1
pressure 54.4 atm; temperature 150 °C; time 10 h. Circle total
aldehyde, square tetrahydropyran and star hacp
2
8
(
2
8
2
THF 5 ml; H /CO 1:1 pressure 54.4 atm; temperature 150 °C; time
2
10 h. Circle total aldehyde, diamond total alcohol and star hacp
7
5
0
0
these results are shown in the Fig. 4. It is observed that the
total transformation increases with the increasing pressure,
for instance from 26 % at 27.2 atm. to 99 % at 54.4 atm.
This suggests that catalytic species is more active at ele-
vated pressure, whereas lowering of syngas pressure
deactivates it.
3
1
0
0
Effect of PPh addition
3
The effect of PPh addition as a ligand with Co (CO) in a
3
2
8
Co/PPh ratio of 1:2 was studied and the results are shown
3
2
4
6
8
10 11
in the Fig 5. The graph suggests the participation of less
active catalytic species in the reaction when phosphine-
modified cobalt system is used rather than the unmodified
system. It was observed that the reaction proceeds slowly
and the aldehyde yield after 11 h is 54 %, which is less
Reaction time (h)
Fig. 5 AldehydeformationwiththeCo
of time (1–11 h). Co (CO) 0.1 mmol; PPh
2H]pyran 10.1 mmol; THF 5 ml; H /CO 1:1 pressure 54.4 atm; temper-
ature 150 °C. Circle total aldehyde, diamond total alcohol and star hacp
2 8
(CO) /PPh
3
systemasafunction
2
8
3
0.2 mmol; 3,4-dihydro
[
2
1
23

Transition Met Chem
Fig. 6 a IR spectra of
unmodified catalyst. b IR
spectra of modified catalyst
than the yield obtained using the unmodified system. Fur-
thermore, the alcohol yield decreases slightly with the
modified Co system, and the catalytic species HCo
Co (CO) solution, the bands observed at 2,045 and between
2 8
-1
1,894and1,885 cm disappearedandnewbandsappearedin
-1
the1,986and1,957 cm regions, indicatingthepresenceofa
disubstituted species [16] (Fig. 6).
(
CO) PPh seems to promote the reaction between mono-
3 3
nuclear species in order to increase the hacp yield.
IR results
Conclusion
The carbonyl vibration frequencies of modified and unmodi-
fied catalytic systems were also studied. In the unmodified
Cobalt-catalysed hydroformylation of 3,4-dihydro[2H]pyran
was investigated, and the selective formation of the aldehyde,
tetrahydropyran and the hacp as a function of the reaction
parameters was studied. The coordination of the pyran’s
oxygen to the cobalt seems to be an important intermediate to
the 2-formyl-tetrahydropyran formation. Surprisingly, the
generation of the hacp was favoured at high substrate
-1
Co (CO) , bands at 2,045, 2,070 and 2,022 cm
2
were
8
detected, which correspond to the terminal CO group, and a
-1
widebandlocalisedbetween1,894and1,885 cm indicating
the presence of HCo(CO) , similar results were observed
4
earlier also [15]. However, when PPh was added to the
3
123

Transition Met Chem
concentration, in spite of the fact that it contains a relatively
hindered structure. The active catalytic intermediates appear
to be efficient in order promote the hydroalkylcarbonylation
reaction. To the best of our knowledge, this is the first sys-
tematic study on the hydroformylation of pyran using
Co (CO) as catalytic system. It is to be mentioned that only a
3. Botteghi C, Gonzerla R, Lenarda M, Moretti G (1987) J Mol
Catal 40:129
4
. Lazzaroni R, Settambolo R, Uccello-Barretta G (1995) Organo-
metallics 14:4644
5. Burke SD, Cobb JE, Takeniche KJ (1990) J Org Chem 55:2138
6. Siegel H, Himmele W (1980) Angew Chem Int Ed Engl 19:178
7
8
. Falbe F, Korte F (1964) Chem Ber 47:1104
. Polo A, Claver C, Castill o´ n S, Ruiz A (1992) Organometallics
2
8
report using Rh has appeared in the early 80’s for the hydro-
formylation of the pyran ring.
1
1:3525
9. Arias JL, Cabrera A, Sharma P, Garc ´ı a JL, Velasco L, P e´ rez FJ,
Rosas N (1997) J Mol Catal (A) 118:167
Acknowledgments We are grateful to General Direction of Aca-
demics Affairs from National Autonomous University of M e´ xico City
for financial support for this research, project PAPIIT IN 215112.
10. Cabrera A, Sharma P, Le-Lagadec R, Arias JL, Ledezma R
(1999) Main Group Met Chem 95:103
11. Cabrera A, Sharma P, Arias JL, Velasco L, Perez-Flores J,
´
G o´ mez RM (2004) J Mol Catal 212:19
2. Damoense L, Datt M, Green M, Steekamp C (2004) Coord Chem
1
Rev 248:2393
3. Murata K, Matsuda A (1981) Bull Chem Soc Jpn 54:245
4. Murata K, Matsuda A (1981) Bull Chem Soc Jpn 54:2089
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