New polymeric sulfide-borane complexes: Convenient hydroborating and reducing reagents

Article abstract of DOI:10.1080/17415993.2011.590489

New polymeric borane adducts have been synthesized from polymeric sulfides, which are solids with a minimal odor. Adducts containing a high concentration of borane have significant stability and are soluble in tetrahydrofuran. They act as hydroborating and reducing reagents with behavior similar to that of borane-methyl sulfide, making them attractive borane sources.

Full text of DOI:10.1080/17415993.2011.590489

Journal of Sulfur Chemistry
Vol. 32, No. 4, August 2011, 287–295
New polymeric sulfide-borane complexes: convenient
hydroborating and reducing reagents
a
a
b
a†
Keith Smith *, Asim A. Balakit , Ramchand T. Pardasani and Gamal A. El-Hiti
a
b
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK; Department
of Chemistry, University of Rajasthan, Jaipur 302 055, India
(Received 11 April 2011; final version received 19 May 2011)
New polymeric borane adducts have been synthesized from polymeric sulfides, which are solids with a
minimal odor. Adducts containing a high concentration of borane have significant stability and are soluble
in tetrahydrofuran. They act as hydroborating and reducing reagents with behavior similar to that of
borane-methyl sulfide, making them attractive borane sources.
OH
OH
(
(
1) Borane adduct,THF
2) H2O2, NaOH
R
R
R
+
Major
Minor
O
OH
H
Borane adduct
THF
R1
R2
R1
R2
Keywords: polymeric sulfides; borane adducts; hydroboration; reduction; carbonyl compounds
1
.
Introduction
Borane complexes are highly versatile reagents with numerous applications in organic syntheses
and industrial processes (1–3). The most commonly used are borane-tetrahydrofuran (BH3 · THF)
(
4) and borane-dimethyl sulfide (BH3 · SMe2, BMS) (5). However, both these reagents possess
certain unfavorable characteristics (5). BH3 · THF is commercially available only as a dilute
solution, nominally 1.0 M in BH3, and it undergoes slow decomposition via cleavage of THF
at room temperature. BMS is free from these disadvantages, as it is a neat complex, 10.0 M
in BH3, can be used in a variety of solvents and is highly stable. However, BMS liberates a
stoichiometric amount of water-insoluble dimethyl sulfide, which has an obnoxious odor, high
volatility and flammability, thereby creating environmental and safety problems, particularly for
large scale use. This prompted Brown and co-workers (6) in 1992 to introduce 1,4-oxathiane
*
Corresponding author. Email: smithk13@cardiff.ac.uk
†
Present address: Chemistry Department, Faculty of Science, Tanta University, Tanta 31527, Egypt.
ISSN 1741-5993 print/ISSN 1741-6000 online
©
2011 Taylor & Francis
DOI: 10.1080/17415993.2011.590489
http://www.informaworld.com

2
88 K. Smith et al.
as a less volatile carrier for borane. Subsequently, Brown and co-workers (7, 8) demonstrated
the utility of a series of liquid organic sulfides as borane carriers, bis(hydroxymethyl)sulfide (9)
possessing the additional advantage of being water soluble, while 2-(perfluorooctyl)ethyl methyl
sulfide (10) is a recyclable borane carrier. A few solid borane complexes with bis-sulfides (2a)
have also been patented, and borane complexes with hindered tertiary amines such as N-ethyl-
N-iso-propylaniline (11) or 5-ethyl-2-methylpyridine (12) have been advocated. Clearly, there
is a strong desire for safe borane carriers that can be easily handled. However, to be attractive
as replacements for the commonly used complexes, alternative adducts must be fairly high in
borane content (to avoid having to transport large quantities), be stable enough for long-term
storage, have distinct advantages in terms of handling (e.g. avoiding obnoxious odors, avoiding
high flammability or allowing easy recovery of the carrier), be relatively inexpensive and match
BH3 · THF or BMS in terms of reactivity profile. To date, no other complex has fulfilled these
criteria sufficiently well to rival the common complexes.
Polymer-bound borane complexes offer the possibility of stable and easily handled materials
of low volatility, with minimal odor and with easily recoverable polymeric carriers. Indeed, a
number of polymer-bound complexes have been reported, including BH3 complexes of several
cross-linked polymeric sulfides (13), a cross-linked poly(4-vinylpyridine)-borane complex in
which the borane content was up to 7.8 mmol/g (14), and borane and haloborane complexes of
poly(propylene sulfide) grafted onto cross-liked polystyrene (15). Although all of these reagents
have been used for hydroboration of alkenes and/or reduction of aldehydes and ketones to produce
the corresponding alcohols, acid catalysis was required in the case of the poly(vinylpyridine)
complex (16). Thus, its reactivity profile is significantly different (and less useful) from that of
borane-THF or BMS, so it cannot be viewed as a potential replacement.A similar situation pertains
to polymer-supported ethylenediamine borane complexes prepared using a Merrifield resin or a
1
,6-hexanediol diacrylate-cross-linked polystyrene resin (17). These materials have been used
for reduction of aldehydes to the corresponding alcohols in high yields at room temperature, but
the concentration of borane in the complexes is already low and the use of a two molar excess of
the polymeric reagent was required (17). However, the polymer could be regenerated easily and
reused without loss in reactivity.
The borane content of the grafted poly(propylene sulfide) complex was also low (around
2
.44 mmol BH3/g) (15). A higher borane content (up to 7.05 mmol BH3/g of polymer) was
claimed for a homo poly(propylene sulfide) complex, but this material was prepared and used
only as a dilute solution in dichloromethane and it is not clear whether removal of the solvent
would have left a solid with such a high concentration of borane (15). There are no reports of these
complexes ever having been applied to synthesis, possibly because of the low borane content of
the solid borane-polymer complex and the inconvenience of transporting a dilute solution of the
homo poly(propylene sulfide)-borane complex.
Our long-standing interests in the use of solids in green methodologies (18) and in boron
chemistry (1, 19) led us to consider the possibility of other polymeric sulfides as suitable borane
carriers. In particular, we wished to develop complexes possessing high molarity in BH3, based
on solids that are easy to prepare, convenient to handle, have mild odor and low volatility and are
environmentally benign. We now report the results of our efforts to develop such reagents.
2
. Results and discussion
Polymeric sulfides 1–6 were synthesized based on literature procedures (for the synthesis of
polymeric materials, see (20)). Unlike poly(propylene sulfide), these contain unbranched alkylene
chains. The complexing ability of the polymers toward borane was investigated by bringing them

Journal of Sulfur Chemistry 289
into contact with BH3 · THF or diborane gas using four procedures: (i) reaction of neat solid
sulfide 1–6 with BH3 · THF, (ii) reaction of neat polymer with diborane gas, (iii) reaction of a
solution of the polymeric material with BH3 · THF and (iv) reaction of a solution of the polymeric
material with diborane gas. Interestingly, and uniquely, no uptake of borane to give complex 7
was observed for the sulfide 1 (n = 2) under any of the conditions tried. This was surprising in
view of the reported uptake of up to 7 mmol/g of borane by poly(propylene sulfide), which is
simply a methyl-substituted version of this polymer. The other linear polymeric sulfides (2–6)
all absorbed significant quantities of borane by all of the procedures, and, after considerable
experimentation, it was found that the passage of diborane gas, generated from BF3 · OEt2 and
sodium borohydride (21), into a solution of the polymeric sulfide (3 g) in dichloromethane (20 ml)
at room temperature was the most convenient method for producing the corresponding borane
adducts 8–12 (Scheme 1). In this procedure, the adducts were precipitated, but were not separated
by filtration or decantation. Instead, the solvent was removed by blowing nitrogen over the mixture
to leave the solid adducts. Table 1 gives their borane content and 11B NMR data. We also placed
a sample of adduct 8 under oil pump vacuum for 20 min, during which there was no loss of mass,
indicating that on a larger scale, the solvent could be removed under reduced pressure rather than
by blowing with nitrogen.
BH3
B2H6 gas
DCM, 2h
..
(
CH2)n
S
(CH2)n
S
x
x
Polymer
n
Borane adduct
1
2
3
4
5
6
2
3
4
5
6
8
7 (did not form)
8
9
10
11
12
Scheme 1. Synthesis of the polymeric sulfide-borane adducts 8–12.
The effect of other solvents in the preparative procedure was also tested. Adducts resulting
from reaction in chloroform or diglyme possessed a hydride content that was lower by about 10%
than for complexes formed in dichloromethane. Use of more dilute dichloromethane solutions
also resulted in lower hydride content of the precipitated complexes. The gas analyses of adducts
8
–12 indicated that around two-thirds of the total sulfur atoms had been coordinated with borane.
1
1
The B NMR spectra of all complexes showed a single resonance at δ −20.8 to −20.9 ppm,
consistent with the formation of adducts.
Table 1. Preparation of borane adducts 8–12 from the corresponding polymeric
sulfides 2–6 according to Scheme 1.a
Polymeric sulfide
Adductb
n
B/S ratioc
mmol BH3/g
2
3
4
5
6
8
9
10
11
12
3
4
5
6
8
0.68
0.65
0.65
0.67
0.68
8.17
6.69
5.85
5.36
4.44
a
Notes: All adducts were prepared by passing diborane gas into a suspension of the polymeric
sulfides (3 g) in dichloromethane (20 ml).
b
White powders at room temperature.
Ratio of BH3 molecules (estimated by measurement of hydrogen evolved on hydrolysis in
c
THF:glycerol:3 M HCl (1:1:1) to S atoms present (measured by microanalysis).

2
90 K. Smith et al.
The borane adducts 8–12 were white powders at room temperature and exhibited a very mild
‘
borane’ odor when transferred in air. They were soluble in THF, which is typically used for
hydroborationandreductionreactions.Theyappearedtobestableoverlongperiodsundernitrogen
there was no change in borane content after three weeks at room temperature under nitrogen and
(
the hydride content had reduced by only 30% even after five years in a simple septum-sealed
flask). They were fairly stable even in air, decomposing only slowly on standing in air at room
temperature. The stability of the complexes in air was readily ascertained by recording infrared
−
1
spectra at regular intervals (from 5 min to 24 h). Two distinct peaks at 2398 and 1095 cm , which
may be attributed to B-H and B-S stretching vibrations, respectively (22), appeared in the spectra
−
1
of freshly prepared pure samples of the complexes. No peak around 3200 cm corresponding to
boric acid was observed initially. After samples had stood for 4 h in air, the peaks at 2398 and
−
1
−
1
1
095 cm began to diminish noticeably and a strong peak around 3200 cm began to appear,
thereby indicating hydrolysis of the adduct. Only on prolonged standing did the solid begin to
darken. This significant stability in air enabled the solid borane adducts to be weighed on a simple
balance without protection from air. Their very mild odors were further indication that they did
not release borane readily, and thermogravimetric analysis of adduct 8 indicated that no loss of
◦
borane occurred until above 110 C. These features and their reasonable solubilities make the
adducts potentially attractive and easy-to-handle reagents.
To establish the synthetic applicability of the new borane complexes, hydroboration–oxidation
of alkenes was studied. Initially, hydroboration–oxidation of 1-octene (Scheme 2; R = n-C6H13)
in THF at room temperature was conducted with the borane adducts 8–12 for 4 h. In each case, a
high yield (by GC) of a mixture of 1- and 2-octanol was obtained, indicating that the reactivities
of the new borane adducts were comparable with those of BMS (4) and BH3 · THF (23). Thus,
hydroboration of other representative alkenes was conducted initially with 8 as the borane adduct
(
Scheme 2). Adduct 8 was chosen because its polymer’s repeating unit has the lowest relative
mass, so that its borane content is higher in terms of mass than the others. The results are recorded
in Table 2.
R
OH
R
B
H O
OH
8
2
2
R
R
B
R
R
+
+
R
NaOH
THF
R
Major
Minor
R
Major
Minor
Scheme 2. Hydroboration–oxidation of alkenes with the borane adduct 8.
Table 2. Hydroboration–oxidation of alkenes with the borane adduct 8 in THF according
to Scheme 2 at room temperature for 4 h.a
Alkene
Product
Yield (%)b
1
1
-Octene
-Hexene
1-Octanol
59
2
71
2
2
-Octanol
1-Hexanol
-Hexanol
2
Cyclopentene
Cyclohexene
Cyclopentanol
Cyclohexenol
80
86
a
◦
Notes: Alkene (9.0 mmol) was added to a solution of 8 (ca. 3.6 mmol BH3) in THF (14 ml) at 0–5 C and
◦
stirred for 4 h at room temperature. The mixture was oxidized at 0–5 C using NaOH (3.0 M, 3.0 ml) and
H2O2 (30%, 3.5 ml) followed by warming to room temperature for 1 h to ensure complete oxidation.
b
By GC analysis using hexadecane as internal standard.

Journal of Sulfur Chemistry 291
The procedure involved the addition of an alkene (9.0 mmol) to the solution of borane complex
◦
(
3.6 mmol of BH3) in THF at 0–5 C followed by stirring for 4 h at room temperature and then
oxidative work up with alkaline hydrogen peroxide. The alcohols produced were analyzed by
quantitative GC. The yields of alcohols obtained were in the range of 61–86%.
Several experiments were conducted in order to find conditions under which higher yields
of alcohols could be obtained. It was found that the use of a longer reaction time (16 h) gave
satisfactory results. Therefore, this procedure was applied to a range of alkenes. The results
obtained are recorded in Table 3.
Reactions conducted over this longer reaction period gave good yields (84–99%). The regios-
electivities of hydroboration of 1-hexene and styrene were similar to those reported for BMS
(
5) and BH3 · THF (24). Thus, the hydroboration of 1-hexene formed 1- and 2-hexanols in the
ratio of 84:4, while styrene gave 1- and 2-phenylethanols in the ratio 79:12. The hydroboration
of 1-methylcyclohexene produced trans-2-methylcyclohexanol in essentially quantitative yield.
The adduct 8 therefore functioned very similarly to BMS in hydroboration reactions, but with the
significant advantage that the reactions are odor-free and do not liberate dimethyl sulfide.
To establish further the synthetic potential of the new borane adduct 8, the reduction of repre-
sentative organic functional groups was studied (e.g. see Scheme 3 for the reduction of aldehydes
and ketones) and the results are recorded in Table 4.
The procedure adopted was to add a standard solution of the organic compound in THF to an
◦
appropriate quantity of complex in THF at 0 C and then reflux the mixture for 4 h. The excess
borane was then quenched with methanol and the product was analyzed by GC. Reduction of most
substrates was straightforward and gave high yields (85–100%) of the corresponding alcohols,
similar to BMS (24, 25). Although the reactions were carried out under standard conditions
of reflux for 4 h, such forcing conditions were often not necessary. However, the reduction of
benzamide was slow and a yield of only 66% of benzylamine was obtained even after a longer
reaction time (16 h).
The sulfide polymer could be recovered following either hydroboration or reduction reactions.
The polymeric material 2 was precipitated as a white solid by the addition of diethyl ether during
the work-up process and was removed by filtration. It was washed with a saturated solution of
sodium hydroxide to remove any boric acid, then washed thoroughly with water and left to dry in
a vacuum oven. The recovered polymer was reused again to prepare 8. The adduct obtained was
virtually identical to the initial one. It had the same borane content and showed the same behavior
when used as a hydroborating and reducing agent.
Table 3. Hydroboration–oxidation of alkenes with the borane adduct 8 in THF according
to Scheme 2 at room temperature for 16 h.a
Alkene
Product
Yield (%)b
1
-Octene
-Hexene
1-Octanol
-Octanol
1-Hexanol
-Hexanol
2-Phenylethanol
-Phenylethanol
trans-2-methylcyclohexanol
Cyclopentanol
Cyclohexenol
81
4
80
4
79
12
99
84
86
2
1
2
Styrene
1
1-Methylcyclohexene
Cyclopentene
Cyclohexene
a
Notes: Alkene (9.0 mmol) was added to a solution of 8 (ca. 3.6 mmol of borane) in THF (14 ml) at
◦
◦
◦
0
–5 C and stirred for 30 min at 0 C and 16 h at room temperature. The mixture was oxidized at 0–5 C
using NaOH (3.0 M, 3.0 ml) and H2O2 (30%, 3.5 ml) followed by warming to room temperature for 1 h
to ensure complete oxidation.
b
By GC analysis using hexadecane as internal standard.

2
92 K. Smith et al.
O
OH
H
8
R1
R2
THF
R1
R2
Scheme 3. Reduction of aldehydes and ketones with the borane adduct 8.
Table 4. Reduction of functional groups with 8 in THF under reflux for 4 h.a
Starting material
Benzaldehyde
8 (mol. eq.)
Product
Yield (%)b
0.4
0.4
1.2
1.2
0.8
0.8
0.7
1.9
0.4
Benzyl alcohol
2-Hexanol
1-Hexanol
Benzyl alcohol
Benzyl alcohol
Benzyl alcohol
Benzyl alcohol
Benzylamine
Cyclohexanol
100
94
92
90
99
97
88
2-Hexanone
Caproic acid
Benzoic acid
Methyl benzoate
Butyl benzoate
Phenyl benzoate
Benzamidec
d
51 (66)
Cyclohexene oxide
85
a
◦
Notes: Organic compound (5 mmol) was added to a solution of 8 in THF and the mixture was stirred at 0 C for 30 min
and then refluxed for 4 h. Methanol (3 ml) was added and the mixture was stirred for 15 min, then the product was
extracted into diethyl ether (20 ml).
b
By GC analysis using hexadecane as internal standard.
After reaction HCl (1.0 M, 3 ml) was added and the mixture was refluxed, cooled to 0 C, then diethyl ether (20 ml)
c
◦
and NaOH (pellets) were added to neutralize the solution followed by the separation of the organic layer.
d
The reaction time was 16 h.
Our attention was next turned to the use of borane adduct 11, to test whether it showed any
significant differences in activity compared with 8. Adduct 11 was tested in hydroboration of
representative alkenes and reduction of representative carbonyl compounds under conditions
similar to those used with adduct 8 (Schemes 2 and 3, respectively). The results obtained are
recorded in Tables 5 and 6, respectively.
The results recorded in Table 5 clearly indicated that adduct 11 can be used as a hydroborating
agent. The small variations in yields obtained compared with those obtained from similar reactions
involving the use of adduct 8 may be due to losses during work-up. However, the selectivities
observed were entirely comparable. For example, hydroboration of 1-octene produced a mixture
of 1- and 2-octanols in 77% and 4% yields, respectively, compared with 81% and 4%, respectively,
with adduct 8. With styrene, 1- and 2-phenylethanols were formed in the ratio of 84:13, similar
to the 79:12 ratio obtained with adduct 8.
Table 5.a Hydroboration–oxidation of alkenes with the borane adduct 11 in THF at room temperature
for 16 h.
Alkene
Product
Yield (%)b
1
-Octene
-Hexene
1-Octanol
-Octanol
1-Hexanol
-Hexanol
2-Phenylethanol
-Phenylethanol
77
4
73
5
84
13
83
88
2
1
2
Styrene
1
1-Methylcyclohexene
Trans-2-methylcyclohexanol
Cyclopentanol
Cyclopentene
a
◦
Notes: Alkene (9.0 mmol) was added to a solution of 11 (ca. 3.6 mmol BH3) in THF (15 ml) at 0–5 C and was stirred
◦
◦
for 30 min at 0 C and for 16 h at room temperature. The reaction mixture was oxidized at 0–5 C using NaOH (3.0 M,
3
.0 ml) and H2O2 (30%, 3.5 ml) followed by warming to room temperature for 1 h to ensure complete oxidation.
b
By GC analysis with hexadecane as an internal standard.

Journal of Sulfur Chemistry 293
Table 6. Reduction of some carbonyl compounds with borane adduct 11 in THF.a
Entry
Starting material
11 (mol. eq.)
Product
Yield (%)b
1
2
3
4
Benzaldehyde
2-Hexanone
Caproic acid
Ethyl benzoate
0.4
0.4
1.1
0.8
Benzyl alcohol
2-Hexanol
1-Hexanol
100
84
93
Benzyl alcohol
94
a
◦
Notes: Carbonyl compound (5.0 mmol) was added to a solution of 11 in THF and stirred at 0 C for 30 min
and refluxed for 4 h. Methanol (3 ml) was added and the mixture was stirred for 15 min then extracted
with diethyl ether (20 ml).
b
By GC analysis using hexadecane as internal standard.
Table 6 shows that adduct 11 can also be used as a reducing reagent for various carbonyl
compounds to produce the corresponding alcohols in high yields (84–100%). Again, the reactions
were carried out under standard conditions at reflux for 4 h, although not all examples needed
such forcing conditions.
3
. Conclusions
In conclusion, borane adducts derived from polymeric sulfides are solids of high hydride con-
tent that can be readily weighed in air. Their mild smell, good solubility in THF and reactivity
comparable to that of BMS, make them attractive borane sources. Consequently, complex 8, in
particular, is a highly promising, new hydroborating reagent, which might well be suitable for
large-scale industrial application.
4
4
.
Experimental section
.1. General
All reactions were performed under a nitrogen atmosphere. Glassware was oven-dried, assembled
hot and allowed to cool under a stream of nitrogen gas.All reagents were purchased from commer-
cial sources and used as received. THF was distilled from sodium benzophenone ketyl and other
solvents were purified by standard procedures (26). Infrared spectra were recorded on a Perkin
1
11
Elmer Spectrum One FT-IR spectrometer. H and B NMR spectra were recorded on a Bruker
1
11
AV400 spectrometer operating at 400 MHz for H or 128 MHz for B measurements. Chemical
shifts δ are reported in parts per million (ppm) relative to TMS and BF3 · Et2O, respectively. GC
analyses were carried out on a Shimadzu Gas Chromatograph fitted with a ZEBRON ZB-5 (5%
◦
phenyl polysiloxane) 30 m length column. The GC conditions used for analysis were: 40 C for
◦
◦
◦
1
min, ramped to 250 C at 20 C/min and held for 3 min. The injection temperature was 250 C
and the detection temperature was 250 C. Hexadecane was used as a GC standard. Microanalyses
were performed by Warwick analytical service at the University of Warwick.
◦
4
.2. Borane adducts: typical experimental procedure for preparation of borane adduct 8
Diborane gas generated by the reaction of sodium borohydride (5.67 g, 0.15 mol) in diglyme
(
50 ml) with BF3 · Et2O (24.5 ml, 0.20 mol) was passed slowly through a dichloromethane (25 ml)
solution of polymeric sulfide 2 (3.0 g) at room temperature over a period of 2 h. Excess diborane
was allowed to absorb in THF (15 ml) in a second bubbler. A white solid precipitated out in the

2
94 K. Smith et al.
flask containing the polymer when passage of the borane gas was nearing completion. The solvent
was removed from the mixture by blowing with nitrogen. The resulting borane-sulfide adduct 8
was analyzed for active hydride by a standard procedure (27) using THF:glycerol:3 M HCl (1:1:1)
as the hydrolyzing mixture. The ratio of BH3 units to S atoms in the polymer was ca. 0.68. δB
(
128 MHz, CDCl3; Me4Si) −20.9.
4
.3. Hydroboration–oxidation of alkenes: typical procedure for hydroboration of 1-hexene
with 8
Adduct 8 (0.44 g, 3.6 mmol BH3) was placed in an oven-dried 50 ml flask protected by a rubber
◦
septum. The flask was cooled to 0 C under a stream of nitrogen and freshly distilled THF (14 ml)
◦
was added. 1-Hexene (0.757 g, 9.0 mmol) was added and the mixture was stirred at 0 C for 30 min
and then at room temperature for 16 h. The reaction mixture was cooled to 0 C and NaOH (3.0 M,
◦
3.0 ml) was added, followed by slow addition of hydrogen peroxide (30%, 3.5 ml). The contents
were further stirred at room temperature for 1 h to ensure complete oxidation. Hexadecane (0.75 g)
was added followed by the addition of diethyl ether (10 ml) to precipitate the liberated polymeric
sulfide. GC of the organic layer showed that the combined yield of 1- and 2-hexanols was 84%
in ca. 80:4 ratio.
4
.4. Reduction of functional groups: typical procedure for reduction of benzaldehyde with 8
A 50 ml two-neck flask equipped with a reflux condenser and a magnetic bar was flushed with
◦
nitrogen and charged with 8 (0.24 g, 2.0 mmol BH3) and cooled to 0 C. THF (10 ml) was added
◦
and the resulting colorless solution was cooled to 0 C. Benzaldehyde (0.53 g; 5.0 mmol) was
then added dropwise. The reaction mixture was stirred at 0 C for 30 min and a further 4 h under
reflux conditions. The flask was then cooled to 0 C and methanol (3 ml) was added to quench any
◦
◦
excess borane. Subsequently, diethyl ether (10 ml) was added to precipitate the released polymeric
sulfide. GC analysis of the organic layer showed the formation of benzyl alcohol (100%). The
organic layer from the reaction was washed with brine (3 × 20 ml), and most of the solvent
was removed under vacuum. Hexane (10 ml) and ether (10 ml) were added to the residue, which
further precipitated the polymeric material. The polymer was filtered off and the filtrate was
dried (MgSO4). The solvent was removed under reduced pressure to give benzyl alcohol (0.45 g,
4
.17 mmol, 83%) as a colorless oil identical to an authentic sample.
Acknowledgements
We thank the Iraqi Government and Cardiff University for financial support.
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