Efficient and catalytic conversion of epoxides into 1,3-dioxolanes with LiBF4

Article abstract of DOI:10.1081/SCC-200057978

Lithium tetrafluoroborate catalysis the efficient conversion of epoxides with acetone to the corresponding 1,3-dioxolanes in excellent isolated yields. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200057978

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Efficient and Catalytic
Conversion of Epoxides into
1,3‐Dioxolanes with LiBF4
F. Kazemi a , A. R. Kiasat a & S. Ebrahimi a
a Chemistry Department, College of Science, Shahid
Chamran University, Ahvaz, Iran
Version of record first published: 17 Dec 2010.
To cite this article: F. Kazemi , A. R. Kiasat & S. Ebrahimi (2005): Efficient
and Catalytic Conversion of Epoxides into 1,3‐Dioxolanes with LiBF4 , Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 35:11, 1441-1445
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Synthetic Communicationsw, 35: 1441–1445, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200057978
Efficient and Catalytic Conversion of
Epoxides into 1,3-Dioxolanes with LiBF4
F. Kazemi, A. R. Kiasat, and S. Ebrahimi
Chemistry Department, College of Science, Shahid Chamran University,
Ahvaz, Iran
Abstract: Lithium tetrafluoroborate catalysis the efficient conversion of epoxides with
acetone to the corresponding 1,3-dioxolanes in excellent isolated yields.
Keywords: Cyclic acetals, dioxolanes, epoxides, lithium tetrafluoroborate
Cyclic acetals, in particular 1,3- dioxolane, are among the most important and
popular protective groups for carbonyl compounds and diols with special
interest in carbohydrates and steroid chemistry.[1–4] The formation of 1,3-
dioxolane starting from oxiranes and carbonyl compounds can occur in two
ways: (a) by hydrolysis of the oxirane to the appropriate diol, followed by
acetalization with subsequent elimination in the presence of carbonyl
compound, and (b) by direct condensation of the oxirane with the carbonyl
compound. In the latter reaction no water is formed, which makes direct con-
densation, in some cases, a more suitable method than other procedures
involving removal of water to shift the equilibrium.
The preparation of 1,3-dioxolanes from oxiranes and carbonyl compounds
using Lewis acids as catalysts has been known for a long time. In 1933, a report
by Boget and Roblin[5] outlined the application of SnCl4 as a Lewis acid catalyst
for this purpose and produced 1,3-dioxolanes in low to moderate yields. Since
that time sporadic reports of cyclic acetalization using oxiranes in the presence
Received in Poland December 10, 2004
Address correspondence to A. R. Kiasat, Chemistry Department, College of Science,
Shahid Chamran University, Ahvaz 6137-4-3169, Iran. Fax: þ986113337009; E-mail:
kazemi_f@cua.ac.ir, kiasat_a@cua.ac.ir
1441

1442
F. Kazemi, A. R. Kiasat, and S. Ebrahimi
of Lewis acids have appeared. Among these, anhydrous copper sulfate[5] has
been reported to produce the dioxolanes, but the yields in most cases are low
with relatively long reaction times. TiCl4 has been reported to convert the
only aryl substituted epoxides into their corresponding 1,3-dioxolanes in
[6]
moderate yield. BF3 Et2O has been successfully used for conversion of
.
different types of carbonyl compounds to their corresponding 1,3-dioxolanes
with only ethylene and propylene oxides. There was no reaction of epoxides
carrying electron-releasing groups. Some other Lewis acids have been
studied for this transformation, but most of them failed to give the desired
product.[7–11] Unfortunately, these methods involve some disadvantages.
Consequently, it seems that there is still a need for development of newer
methods that proceed under mild and economically appropriate conditions.
Recently, application of efficient catalysts such as RuCl3,[3] TiO(TFA)2,[12]
TiCl3(OTf),[12]and bismuth(III) salts[13] for this proposes was also reported.
In our development of new methods for functional group transform-
ations,[14] we are especially interested in exploring the potential use of
various types of catalyst. The successful applications of LiBF4 in organic
synthesis,[15–18] prompted us to explore the potential of this lithium salt as
.
alternative to BF3 Et2O and HBF4 for catalyzing direct conversion of
epoxides into the corresponding 1,3-dioxolanes.
The catalyst, LiBF4, can be easily prepared[19] from tetraflouroboric acid
.
and LiOH and in comparison with BF3 Et2O is solid and stable. We examined
the catalytic ability of LiBF4 for the reaction of epoxides with acetone under
reflux conditions. This catalyst acted very efficiently and it was observed that
0.2 molar equivalent of the catalyst is sufficient to convert epoxides to their
corresponding 1,3-dioxolanes in excellent yields within 15–120 min. It is
worth mentioning that lower quantities of LiBF4 (i.e., 0.1 molar equivalent)
also gave satisfactory results with a longer reaction time.
The promoting effect of LiBF4 was definitely confirmed by the reaction of
styrene oxide with acetone under similar conditions, without adding LiBF4,
GC and TLC analysis of the reaction mixture did not show formation of
any product after 12 h.
The procedure turned out to be general for range of structurally diverse
epoxides. Epoxides with both electron releasing and withdrawing groups

Conversion of Epoxides
1443
Table 1. Conversion of Epoxides to 1,3-Dioxolanesa in Refluxing Acetone in the
Presence of 0.2 Molar Equivalent of LiBF4
Substance
Product
Time (min)
120
Yield b (%)
90
15
25
30
96
94
93
15
15
20
95
95
90
aProducts were identified by comparison of their of physical and spectral data, IR,
and NMR spectra with known samples.
bIsolated yields.
were easily and efficiently protected and afforded the corresponding 1,3-
dioxolanes as the exclusive products in excellent yield (Table 1).
In conclusion this catalytic method can be applied to conversion of
different classes of epoxides carrying activated and deactivated groups into
their corresponding 1,3-dioxolanes. Excellent yields, short times, simple
workup, and mild reaction conditions make this method a useful addition to
the present methodologies.
EXPERIMENTAL
General
Required carbonyl compounds were purchased from Fluka and Merck.
Products were characterized by comparison of their physical data, IR, and

1444
F. Kazemi, A. R. Kiasat, and S. Ebrahimi
1H NMR spectra with known samples. The purity determination of the
products and reaction monitoring were accomplished by TLC on silica gel
polygram SILG/UV 254 plates.
General Procedure for Conversion of Epoxide to 1,3-Dioxolane
To a solution of epoxide (1 mmol) in dry acetone (5 mL), LiBF4 (0.2 mmol)
was added, and the reaction mixture was stirred under reflux conditions for
the appropriate time as listed in Table 1. The progress of the reaction was
monitored by TLC and GC. After the disappearance of the starting material,
the solvent was evaporated; NaOH 10% (15 mL) was added and extracted
with diethyl ether (3 ꢀ 15 mL). The organic layer was washed with water
and dried over anhydrous Na2SO4. Evaporation of the ethereal layer followed
by short column chromatography (petroleum ether) furnished the desired
1,3-dioxolane in 90–96% yields.
Compound 2a: nD20 ¼ 1.5271 (lit.[13] nD20 ¼ 1.5270); 1H-NMR (CDCl3), d:
7.26 (5H, s), 5.01 (1H, dd), 4.25 (1H, dd), 3.63 (1H, dd), 1.5 (3H, s), 1.43 (3H,
s); IR (neat): 3060, 2990, 2870, 1600, 1495, 1450, 1365, 1230, 1150, 1055,
945, 850, 755, 700 cm21
.
Compound 2b: nD15 ¼ 1.4361 (lit.[13] nD15 ¼ 1.4359); 1H-NMR (CDCl3), d:
4.32–3.14 (5H, m), 1.32 (3H, s), 1.2 (3H, s); IR (neat): 2960, 2900, 2860,
.
1450, 1375, 1250, 1165, 1080, 1025, 935, 870, 740 cm21
Compound 2c: nD20 ¼ 1.4321 (lit.[13] nD20 ¼ 1.4318); 1H-NMR (CDCl3), d:
5.95–4.77 (3H, m), 4.35–3.35 (7H, m), 1.33 (3H, s), 1.25 (3H, s); IR (neat):
.
3050, 3000, 2920, 2850, 1455, 1360, 1320, 1250, 1090, 920, 840, 755 cm21
Compound 2d: nD20 ¼ 1.4169 (lit.[13] nD20 ¼ 1.4170); 1H-NMR (CDCl3), d:
4.37–3.3 (6H, m), 1.37 (3H, s), 1.27 (3H, s), 1.2–1 (6H, d); IR (neat): 2970,
2930, 2870, 1460, 1380, 1365, 1260, 1125, 1070, 1030, 920, 850, 735 cm21
.
Compound 2e: mp 648C (lit.[13] mp 638C); H-NMR (CDCl3), d: 7.47–
6.72 (5H, m), 4.65–3.64 (5H, m), 1.42 (3H, s), 1.3 (3H, s); IR (KBr): 3070,
2990, 2920, 1600, 1585, 1490, 1445, 1344, 1240, 1210, 1170, 1035, 910,
1
810, 747 cm21
.
Compound 2f: nD20 ¼ 1.2497 (lit.[13] nD20 ¼ 1.2495); 1H-NMR (CDCl3), d:
4.2–3.3 (3H, m), 1.72–1.13 (16H, m), 0.95–0.7 (3H, t); IR (neat): 2970,
.
2915, 2860, 1460, 1375, 1250, 1160, 1050, 950, 850, 730 cm21
Compound 2g: nD20 ¼ 1.4469 (lit.[13] nD20 ¼ 1.4465); 1H-NMR (CDCl3), d:
4.34–4.05 (2H, m), 2.58–2.07 (4H, m), 1.35 (6H, s), 1.24–1 (4H, m); IR (neat):
.
2980, 2930, 2870, 1440, 1355, 1260, 1180, 1080, 960, 885, 835, 780 cm21
ACKNOWLEDGMENT
Authors acknowledge the partial support of this work by Shahid Chamran
Ahvaz University Research Council.

Conversion of Epoxides
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