J. S. Yadav, B. V. S. Reddy, M. S. Reddy, N. Niranjan, A. R. Prasad
-Chloro-2-(3,4-dichlorophenyl)-6-(3-phenoxyphenyl)tetrahydro-2H-
FULL PAPER
4
Conclusion
1
pyran (3b): Liquid (769 mg, 89% yield). H NMR (CDCl
1
4
3
): δ ϭ
.85 (dd, J ϭ 11.0, 12.6 Hz, 2 H), 2.40 (dd, J ϭ 4.5, 12.6 Hz, 2 H),
.20 (m, 1 H), 4.45 (dd, J ϭ 4.5, 11.0 Hz, 2 H), 6.85Ϫ7.05 (m, 7
The ionic liquid [bmim]Al Cl has been shown to be a
useful and novel reaction medium for Prins cyclizations, eli-
minating the need for the use of more volatile chlorinated
2
7
H), 7.20Ϫ7.40 (m, 5 H). EIMS: m/z ϭ 436 [Mϩ2], 434 [Mϩ], 399,
97, 364, 362, 287, 239, 237, 235, 197, 77. IR (KBr): ν˜ ϭ 3075,
3
Ϫ1
hydrocarbons such as chloroform or dichloromethane by 3050, 2960, 1510, 1455, 1280, 1150, 1025 cm . C H Cl O
2
3
19
3
2
playing a dual role both as solvent and as Lewis acid cata- (433.76): calcd. C 63.69, H 4.41, Cl, 24.52; found C 63.70, H 4.43,
lyst. The substrates show significant increases in reactivity, Cl, 24.56.
which reduces the reaction times and improves the yields
4
-Chloro-2,6-bis(4-methylphenyl)tetrahydro-2H-pyran (3c): Liquid
substantially. The experimental procedure is quite simple
and convenient, and the reaction conditions are amenable
to scale-up. This method provides easy access to the syn-
thesis of functionalized tetrahydropyrans with diverse
1
(
558 mg, 93% yield). H NMR (CDCl
3
): δ ϭ 1.90 (dd, J ϭ 11.0,
12.0 Hz, 2 H), 2.35 (s, 6 H), 2.35 (dd, J ϭ 4.0, 12.0 Hz, 2 H), 4.25
(
(
tt, J ϭ 2.5, 12.0 Hz, 1 H), 4.50 (dd, J ϭ 4.0, 11.0 Hz, 2 H), 7.17
d, J ϭ 7.8 Hz, 4 H), 7.25 (d, J ϭ 7.8 Hz, 4 H). EIMS: m/z ϭ 302
chemical structures. This method also showed the reaction [Mϩ2], 300 [Mϩ], 287, 285, 265, 250, 119, 92, 91, 77. IR (KBr):
rates increasing with corresponding increases in the molar ν˜ ϭ 3040, 2930, 1610, 1515, 1450, 1315, 1160, 1030, 950, 775, 715
Ϫ1
fraction of the AlCl in ionic liquid, affording high to quan- cm . C19H21ClO (300.82): calcd. C 75.86, H 7.04, Cl, 11.79; found
titative levels of conversion in short reaction times.
3
C 75.87, H 7.07, Cl, 11.81.
4
-Chloro-2-(4-methoxyphenyl)-6-phenyltetrahydro-2H-pyran (3d):
1
Liquid (531.4 mg, 88% yield). H NMR (CDCl
J ϭ 1.5, 11.0, 12.0 Hz, 2 H), 2.45 (m, 2 H), 3.80 (s, 3 H), 4.30 (m,
H), 4.50 (dt, J ϭ 4.0, 11.0 Hz, 2 H), 6.85 (d, J ϭ 8.0 Hz, 2 H),
3
): δ ϭ 1.92 (ddd,
Experimental Section
1
General Remarks: Ionic liquids were prepared as described pre-
7.20 (d, J ϭ 8.0 Hz, 2 H), 7.30 (m, 5 H). EIMS: m/z ϭ 304 [Mϩ2],
302 [Mϩ], 267, 197, 169, 167, 166, 105, 104, 77. IR (KBr): ν˜ ϭ
[
17]
viously.
3 g, 23.1 mmol for X (AlCl
.6 g, 42 mmol for X (AlCl ) ϭ 0.67, strongly acidic ionic liquid) was
added slowly over 30 min to 1-butyl-3-methylimidazolium chloride found C 71.42, H 6.35, Cl, 11.73.
21 mmol) in a glove box, to afford a clear liquid upon stirring.
Preparation of chloroaluminate() ionic liquids: AlCl
3
(
3
) ϭ 0.52, mildly acidic ionic liquid, or 3035, 3010, 2950, 1590, 1470, 1420, 1150, 1080, 1050, 830, 760, 695
Ϫ1
5
3
2
cm . C18H19ClO (302.79): calcd. C 71.40, H 6.32, Cl, 11.71;
(
4
-Chloro-2,6-bis(3-chlorophenyl)tetrahydro-2H-pyran (3e): Solid,
The round-bottomed flask was sealed with a septum and removed
from the glove box.
1
m.p. 132 °C, (646 mg, 95% yield). H NMR (CDCl
3
): δ ϭ
1.84Ϫ1.97 (m, 2 H), 2.43Ϫ2.49 (ddd, J ϭ 2.1, 4.2, 12.5 Hz, 2 H),
Melting points were recorded on Buchi R-535 apparatus and are
4.26Ϫ4.31 (m, 1 H), 4.53Ϫ4.57 (dd, J ϭ 4.0, 11.4 Hz, 2 H),
7.26Ϫ7.41 (m, 8 H). EIMS: m/z ϭ 344 [Mϩ2], 342 [Mϩ], 305, 201,
200, 165, 151, 138, 129, 103, 89, 77, 63. IR (KBr): ν˜ ϭ 3050Ϫ2850,
1635, 1590, 1560, 1450, 1410, 1360, 1330, 1180, 1100, 1040, 860,
uncorrected. IR spectra were recorded on a PerkinϪElmer FT-IR
1
2
40-c spectrophotometer with KBr optics. H NMR spectra were
recorded on a Gemini 200 spectrometer in CDCl
3
, with TMS as
Ϫ1
internal standard. Mass spectra were recorded on a Finnigan MAT
750, 660 cm . C H Cl O (341.66): calcd. C 59.76, H 4.42, Cl,
1
7
15
3
1020 mass spectrometer operating at 70 eV. CHN analyses were 31.13; found C 59.78, H 4.45, Cl, 31.15.
recorded on a Vario EL analyser.
4
-Chloro-2,6-dicyclohexyltetrahydro-2H-pyran (3f): Liquid (517 mg,
1
General Procedure: [bmim]Cl·xAlCl
3
(x ϭ 2.0 equiv., N ϭ 0.67)
91% yield). H NMR (CDCl ): δ ϭ 0.90Ϫ2.30 (m, 26 H), 2.9 (m,
3
ionic liquid (2 mL) was added to a mixture of homoallyl alcohol
2 mmol) and aldehyde (2 mmol), and the resulting mixture was
stirred for the specified time. After completion of the reaction (as
indicated by TLC), the reaction mass was quenched with icecold
water and extracted with diethyl ether (3 ϫ 10 mL). The combined
2 H), 3.9 (tt, 2 H, J ϭ 5.0, 12 Hz). EIMS: m/z ϭ 286 [Mϩ2], 284
(
[Mϩ], 248, 203, 201, 83, 28. IR (KBr): ν˜ ϭ 2820, 1150, 1080, 750
Ϫ1
cm . C H ClO (284.86): calcd. C 71.68, H 10.26, Cl 12.45;
1
7
29
found C 71.70, H 10.29, Cl 12.47.
organic layers were dried over anhydrous Na
vacuo and purified by column chromatography on silica gel
Merck, 100Ϫ200 mesh, ethyl acetate/hexane, 0.5Ϫ9.5) to afford
2
SO
4
, concentrated in
4-Chloro-2,6-bis(4-fluorophenyl)tetrahydro-2H-pyran (3g): Liquid
1
(550.8 mg, 90% yield). H NMR (CDCl
3
): δ ϭ 1.92 (dd, J ϭ 11.2,
(
12.5 Hz, 2 H), 2.48 (dd, J ϭ 4.5, 12.5 Hz, 2 H), 4.20 (m, 1 H), 4.45
(dd, J ϭ 4.5, 11.2 Hz, 2 H), 6.85Ϫ7.05 (m, 7 H), 7.20Ϫ7.40 (m, 5
H). EIMS: m/z ϭ 310 [Mϩ2], 308 [Mϩ], 273, 215, 213, 185, 96,
pure 4-chlorotetrahydropyran. The products were characterized by
IR and NMR spectroscopy and by their physical constants. The
characterization data were found to be consistent with authentic
95. IR (KBr): ν˜ ϭ 3050, 2920, 2850, 1610, 1515, 1450, 1410, 1350,
[
5Ϫ8,18]
Ϫ1
samples.
procedure.
All the products 3aϪm were prepared by the same
2
1170, 835, 760 cm . C17H15ClF O (308.75): calcd. C 66.13, H
4.90, Cl 11.48, F 12.31; found C 66.15, H 4.94, Cl 12.33, F 12.34.
4
-Chloro-2,6-diphenyltetrahydro-2H-pyran (3a): Liquid (516.8 mg,
4-Chloro-2-(3-nitrophenyl)-6-phenyltetrahydro-2H-pyran
(3h):
1
1
95% yield). H NMR (CDCl
3
): δ ϭ 1.90 (dd, J ϭ 11.0, 12.5 Hz, 2
Liquid (551.6 mg, 87% yield). H NMR (CDCl ): δ ϭ 1.95 (dd,
3
H), 2.45 (dd, J ϭ 4.5, 12.5 Hz, 2 H), 4.25 (tt, J ϭ 2.5, 12.5 Hz, 1 J ϭ 11.2, 12.4 Hz, 2 H), 2.45 (m, 2 H), 4.3 (m, 1 H), 4.60 (ddd,
1
3
H), 4.50 (dd, J ϭ 4.5, 11.0 Hz, 2 H), 7.2Ϫ7.4 (m, 10 H) ppm.
C
J ϭ 2.0, 6.0, 11.2 Hz, 2 H), 7.35 (m, 5 H), 7.55 (t, J ϭ 7.5 Hz, 1
H), 7.72 (d, J ϭ 7.5 Hz, 1 H), 8.15 (dd, J ϭ 7.5, 2.0 Hz, 1 H), 8.22
NMR (proton decoupled, CDCl ): δ ϭ 44.9, 56.3, 78.7, 126.2,
3
1
1
1
29.9, 128.7, 142.1. EIMS: m/z ϭ 274 [Mϩ2], 272 [Mϩ], 237, 197, (s, 2 H). EIMS: m/z ϭ 319 [[Mϩ2]], 317 [Mϩ], 282, 213, 211, 149,
95, 169, 167, 106, 105, 77. IR (KBr): ν˜ ϭ 3030, 2960, 2890, 1505, 77. IR (KBr): ν˜ ϭ 3070, 2930, 1630, 1540, 1125, 1055, 740, 695
Ϫ1
Ϫ1
460, 1290, 1150, 1030, 760, 690 cm . C17
H17ClO (272.77): calcd.
cm . C17
3
H16ClNO (317.77): calcd. C 64.26, H 5.07, Cl 11.16, N
C 74.86, H 6.28, Cl 13.0; found C 74.90, H 6.30, Cl 13.02.
4.41; found C 64.29, H 5.11, Cl 11.17, N 4.43.
1782
2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 1779Ϫ1783