Efficient, mild and highly regioselective cleavage of epoxides with elemental halogen catalyzed by 2-phenyl-2-(2-pyridyl)imidazolidine(PPI)

Article abstract of DOI:10.1055/s-1998-1958

The highly regioselective conversion of epoxides into corresponding vicinal halohydrins with elemental halogen are catalyzed by imidazolidine derivative. This method occurs under neutral and mild conditions with high yields in various aprotic solvents even when sensitive functional groups are present.

Full text of DOI:10.1055/s-1998-1958

December 1998
SYNLETT
1343
Efficient, Mild and Highly Regioselective Cleavage of Epoxides with Elemental Halogen
Catalyzed by 2-Phenyl-2-(2-pyridyl)imidazolidine(PPI)
Hashem Sharghi*, Hossein Naeimi
Department of Chemistry, College of Sciences, Shiraz University, Shiraz, 71454, Iran
Fax: +98(071)20027
Received 31 July 1998
Abstract: The highly regioselective conversion of epoxides into
corresponding vicinal halohydrins with elemental halogen are catalyzed
by imidazolidine derivative. This method occurs under neutral and mild
conditions with high yields in various aprotic solvents even when
sensitive functional groups are present.
Epoxides are versatile intermediates in organic synthesis and a large
variety of reagents are known for the ring opening of these
1,2
3
compounds. Among the numerous transformations already reported,
little attention was given to the opening of the epoxide ring to the
corresponding vicinal halohydrins. The reaction was typically
performed with hydrogen halides, but the harsh reaction conditions and
the low observed regioselectivity in the opening of asymmetrical
epoxides have prompted a search for more selective and milder
1
procedures. Recently, it has been found that epoxides can be converted
4
into halohydrins by means of elemental halogen, but this method has
some limitations such as low yield, long reaction times, low
regioselectivity and formation of acetonides as byproducts in addition to
the expected iodoadduct in acetone solution. Furthermore, iodination
does not occur in other aprotic solvents.
In conjunction with ongoing work in our laboratory on the synthesis and
formation of complex heterocyclic compounds containing donor
nitrogen atoms, with neutral molecules such as iodine and bromine, we
found out that the new compound 2-phenyl-2-(2-pyridyl)imidazolidine
(PPI) efficiently catalyzed the addition of elemental halogen to epoxides
under mild reaction conditions with high regioselectivity. In this study,
we wish to report the synthesis of PPI, and the results of the reactions of
some epoxides with elemental iodine and bromine in the presence of
catalytic amount of PPI (Scheme, Table 1).
catalyst was found to be 0.01 mole for 1 mole of epoxide and halogen.
As indicated in entries 9 and 10 in which only the trans isomer is
obtained, the reactions are completely anti-stereoselective. As for the
regioselectivity, attack of the nucleophile preferentially occurs at the
5,6
less substituted epoxide carbon.
A contra-Markovnikov type
regioselectivity is generally observed in these reactions. In many cases,
this type of regioselectivity appears to be the opposite of that observed
in ring opening of the same epoxides with hydrohalogenic acids, under
7
classic acidic conditions.
On the basis of our study on the complexation of PPI and other works
8-18
reported on the different ligands
with elemental halogen, it seems
-
that in these reactions trihalide ion, X , was formed and used as
3
nucleophile. The electronic absorption spectra of the related addition of
PPI to iodine has shown two strong absorption bands at 292 and 364 nm
and a strong band at 272 nm in addition of PPI to bromine, presumably
due to the complex formation of this ligand with I and Br . While none
2
2
of the initial reactants show any measurable absorption in these regions.
It should be noted that the bands of 292, 364 nm and 272 nm are
-
-
characteristic for the formation of I and Br ions, respectively, in the
3
3
process of complex formation of different electron-pair donor ligands
10-15
16-18
with iodine
and bromine.
In order to ascertain the effect of
nature of solvent, these reactions on the styrene oxide in various aprotic
solvents were carried out. The results are shown in Table 2. As found
out that, the above reactions appeared to be largely dependent on the
nature of solvent.
Scheme
In conclusion, this new method appears to be highly competitive with
the other methods reported in the literature. The reaction occurs in
neutral and mild conditions on the acid sensitive substrates and vicinal
halohydrins were obtained in high yields and regioselectivity. The
catalyst is easily recovered and can be reused several times.
As shown in Table 1, in each case, cleavage of the epoxide ring occurs
and, upon thiosulfate-workup, iodohydrin and bromohydrin are
obtained. The yields obtained with this new methodology are good to
excellent and the reaction times are very low. The optimum amount of

1344
LETTERS
SYNLETT
1
1-(p-chlorophenoxy)-3-bromo-2-propanol(2i): H NMR(CDCl , 250
3
MHz) δ 2.21 (s, 1H), 3.42 (d, 2H, J=5.0 Hz), 3.81 (q, 1H, J=2.0 Hz),
4.39 (d, 2H, J=7.0 Hz), 7.26 (d, 2H, J=7.5 Hz), 7.65 (d, 2H, J=5.1 Hz);
IR(neat) 649(m), 664(m), 695(m), 743(m), 768(w), 821(m), 938(m),
1005(s), 1132(s), 1245(m), 1282(m), 1318(w), 1449(m), 1492(s),
1581(m), 1596(m), 1615(m), 2858(m), 2928(s), 2956(m), 3406(br, s)
-1
cm .
1
1-(p-chlorophenoxy)-3-iodo-2-propanol (2b): H NMR(CDCl , 250
3
MHz)δ 2.25 (s, 1H), 3.38 (d, 2H, J=5.1 Hz), 3.86 (q, 1H, J=2.0 Hz), 4.41
(d, 2H, J=7.0 Hz), 7.22 (d, 2H, J=7.3 Hz), 7.61 (d, 2H, J=5.0 Hz);
IR(neat) 632(w), 648(w), 667(s), 694(m), 742(m), 818(s), 893(m),
936(m), 1004(s), 1088(m), 1167(s), 1239(s), 1282(s), 1374(w),
1456(m), 1488(s), 1580(m), 1593(m), 2869(m), 2925(s), 2952(m),
-1
3412(br, s) cm .(
General procedure for the synthesis of catalyst:
Acknowledgment: We gratefully acknowledge the support of this work
Ethylenediamine (0.240 gr, 4 mmol) was added to a solution of phenyl-
2-pyridyl ketone (0.733 gr, 4 mmol) in methanol. The reaction mixture
was refluxed with stirring for about 16 hours. Then, the solvent was
evaporated to give a solid product. The crude product was recrystallized
from dichloromethane.
by the Shiraz University Research Council.
References and Notes:
(1) Bonini, C.; Righi, G. Synthesis 1994, 225.
(2) Shimizu, M.; Yoshida, A.; Fujisawa, T. Synlett 1992, 204.
Iranpoor, N.; Mohammadpour Baltork, I. Synth. Commun. 1990,
20, 2789.
2-Phenyl-2-(2-pyridyl) imidazolidine (PPI): white solid; 95% yield;
m.p.= 84-86 C; IR(KBr): 610(m), 631(s), 663(s), 702(s), 748(s), 758(s),
o
(3) Smith, J.G. Synthesis 1984, 629.
852(br,s), 950(s), 965(s), 990(m), 1016(s), 1042(s), 1130(m), 1382(s),
1423(s), 1446(s), 1565(s), 1585(s), 2880(s), 2930(m), 2981(s), 3041(s),
(4) Konaklieva, M. I.; Dahi, M. L.; Turos, E. Tetrahedron Lett. 1992,
-1
1
3250(s), 3320(m) cm ; H NMR(CDCl , 250 MHz) δ 2.54 (b, 2H),
33, 7093.
3
3.01(dt, 4H, J =5.5 Hz, J =2.2 Hz), 7.25-7.72 (complex, 8H), 8.51
1
2
(5) Dela More, P.B.D.; Bolton, R. Electrophilic addition to
unsaturated system, Elsvier Scientific: Amsterdam, 1982.
13
(d,1H, J=4.5 Hz); C NMR(CDCl , 62.9 MHz) δ 45.86, 85.60, 96.09,
3
121.61, 123.34, 126.85, 127.76, 136.07, 146.26, 149.65, 163.74; MS: m/
(6) Chini, M.; Crotti, P.; Giovani, E.; Macchia, F.; Pineschi, M.
+
+
z= 227 (M +2, 0.7), 226 (M +1, 4.6), 197 (3.1), 196 (26.9), 195 (70.6),
168 (23.8), 167 (24.5), 148 (19.8), 147 (base peak), 118 (11.1), 91 (6.3),
Synlett 1992, 303.
(7) Chini, M.; Crotti, P.; Gardelli, C.; Macchia, F. Tetrahedron 1992,
78 (7.8), 77(8.2), 44 (44.1); UV(CH Cl ) : λ 254.5 nm (ε =27400).
2
2
max
48, 3805.
Anal. Calcd. For C
H N : C, 74.67; H, 6.68; N, 18.67; Found:
14 15 3
(8) Semnani,A.;Shamsipur, M. J. Chem. Soc. Dalton Trans. 1996,
C,74.69; H, 6.71; N,18.64.
General procedure for halogenative cleavage of epoxide:
Epoxide (1 mmol) in CH Cl (5 ml) was added to a stirred solution of
2215.
(9) Serguchev, Y. A.; Petrenko, T. I. Teor. Eksp. Khim. 1977,13, 705.
2
2
(10) Hopkins, H. P.; Jahagirdar, D.V.; Windler, F. J. Phys. Chem. 1978,
catalyst (0.01 mmol) in CH Cl (5 ml) at room temperature. Then a
2
2
82, 1254.
solution of elemental halogen (1 mmol) in CH Cl (5 ml) was added
2
2
dropwise (15 min) to the above mixture. The progress of reaction was
monitored by TLC and GLC. After complete disappearance of the
starting material, the reaction mixture was washed with 10% aqueous
(11) Nour, E. M.; Shahada, L. A. Spectrochim. Acta, part A 1988, 44,
1277.
(12) Nour, E. M. Spectrochim. Acta, part A 1991, 47, 473.
(13) Lang, R. P. J. Phys. Chem. 1974, 78, 1657.
Na S O (2 x 10ml) and water (2 x 10ml). The organic layer was dried
2
2 3
over MgSO and evaporated to give crude alcohol-catalyst. The crude
4
(14) Andrews, L. J.; Prochaska, E. S.; Loewenschuss, A. Inorg. Chem.
1980, 19, 463.
products were purified by crystallization in diethyl ether. After cooling,
the catalyst was filtered off and washed with cold ether. The solvent of
filtrate was evaporated and pure halohydrin was obtained. The
halohydrins were identified by comparison with authentic samples
(15) Mizuno, M.; Tanaka, J.; Harada, I. J. Phys. Chem. 1981, 85, 1789.
(16) Spivey, H.D.; Shedlovsky, T. J. Phys. Chem. 1967, 71, 2165.
(17) Shchori, E.; Grodzinski, J. J. J. Am. Chem. Soc. 1972, 94, 7957.
(18) Buckles, R. E.; Yuk, J. P. J. Am. Chem. Soc. 1953, 75, 7043.
19-24
prepared in accordance with literature procedures.
1
1-(p-tolyloxy)-3-bromo-2-propanol(2j): H NMR(CDCl , 250 MHz) δ
3
2.12 (s, 1H), 2.53(s, 3H), 3.16 (d, 2H, J=5.0 Hz), 3.47 (q, 1H, J=2.0 Hz),
4.11 (d, 2H, J=7.0 Hz), 6.93 (d, 2H, J=7.1 Hz), 7.19 (d, 2H, J=5.2 Hz);
IR(neat), 659(s), 819(m), 1016(s), 1075(w), 1123(s), 1242(s), 1285(m),
1381(w), 1458(m), 1512(s), 1585(m), 1613(m), 2875(m), 2927(s),
(19) Masuda, H.; Takase, K.; Nishio, M.; Hasegavw, A.;Nishiyama,
Y.;Ishii, Y. J. Org. Chem. 1994, 59, 5550.
(20) Iranpoor, N.; Kazemi, F.; Salehi, P. Synth. Commun. 1997, 27,
1247.
-1
2962(m), 3035(m), 3425(br, s) cm .
(21) Suh, Y.G.; Koo, B.A.; Ko, J.A.; Cho, Y.S. Chem. Lett. 1993, 1907.
(22) Bajwa, J. S.; Anderson, R.C.; Tetrahedron Lett. 1991, 32,3021.
1
1-(p-tolyloxy)-3-iodo-2-propanol(2c): H NMR(CDCl , 250 MHz)δ
3
2.15 (s, 1H), 2.49 (s, 3H), 3.02 (d, 2H, J=5.0 Hz), 3.46 (q, 1H, J=2.0
Hz), 4.16 (d, 2H, J=7.0 Hz), 6.95 (d, 2H, J=7.2 Hz), 7.23 (d, 2H, J=5.0
Hz); IR(neat) 665(s), 743(w), 814(m), 1015(s), 1072(w), 1123(s),
1240(s), 1286(m), 1378(w), 1462(m), 1512(s), 1586(m), 1611(m),
(23) Pfeiffer, P.; Bauer, K. Chem. Ber. 1947, 80, 7. Chem. Abstr., 1947,
41, 3098d.
(24) Naqvi, S.M.; Horwitz, J.P.; Filler, R. J. Am. Chem. Soc. 1957, 79,
-1
2875(m), 2928(s), 2962(m), 3038(m), 3422(br, s) cm .
6283.