M. R. Dintzner et al. / Tetrahedron Letters 45 (2004) 79–81
81
þ
products, bis- and tris-prenylated material (M ¼ 230
and 298, respectively), become trapped in the interstitial
layers of the clay and eventually render it inactive.
However, activity can be completely restored by wash-
ing the clay with methanol and pumping on it to remove
residual solvent.
5. Meragelman, K. M.;McKee, T. C.;Boyd, M. R. J. Nat.
Prod. 2001, 64, 546.
6
. Verotta, L.;Appendino, G.;Beelloro, E.;Bianchi, F.;
Sterner, O.;Lovati, M.;Bombardelli, E. J. Nat. Prod.
2
002, 65, 433.
7
8
. Hoarau, C.;Pettus, T. R. R. Synlett 2003, 1, 127–137.
. Dintzner, M. R.;McClelland, K. M.;Coligado, D.
Progress Toward the Synthesis of an Anti-inflammatory
Acetophenone Glucoside. Abstracts of Papers, 225th
National Meeting of the American Chemical Society,
New Orleans, LA, 2003;American Chemical Society:
Washington, DC;ORGN 429.
As Ôgreen chemistryÕ becomes more prevalent in organic
1
2–18
synthesis,
environmentally benign clays are becom-
ing attractive alternatives to more toxic Lewis acid cat-
19;20
alysts for an array of reactions,
and optimization of
9
. In this paper the [i; j] sigmatropic shift notation is used as
it was in DaubenÕs original work (see Ref. 10).
conditions for their use is necessary. We found that the
conversion of 1 to 2a is catalyzed more effectively by
Montmorillonite K10 than KSF clay, and proceeds
fastest in dichloromethane at room temperature, but
most selectively in carbon tetrachloride at room tem-
perature. At lower temperatures, the regio-selectivity
1
1
0. Dauben, W. G.;Cogen, J. M.;Behar, V.
Lett. 1990, 31, 3241.
1. (1): IR 3062, 3029, 2975, 2861, 1677, 1599, 1495, 1383,
ꢀ1
Tetrahedron
1
333, 1299, 1239, 1172, 1154, 1111, 1078, 1029, 1008 cm
;
1
3
H NMR (CDCl ) d 7.33–7.27 (m, 3H), 6.99–6.94 (m,
(
ratio of 2a:2b) in dichlormethane increases, but reaction
2
H), 5.53 (t, J ¼ 6:8 Hz, 1H), 4.51 (d, J ¼ 6:8 Hz, 2H),
1
3
rate drops off dramatically. In general, prolonged
exposure of 2a to Montmorillonite clay at ambient
temperature results in its cyclization to coumaran 2c.
The clay can be recycled as long as higher molecular
weight compounds are completely removed by washing
with methanol. The work reported here has proved
important in our ongoing efforts to demonstrate the
utility of Montmorillonite clays in organic synthesis,
and may prove useful for others as well. We are cur-
rently applying this methodology to the synthesis of a
variety of biologically active natural products.
1.83 (s, 3H), 1.77 (s, 3H); C NMR (CDCl ) d 159.24,
3
138.61, 129.83, 120.99, 120.11, 115.03, 65.02, 26.28, 18.61;
þ
GC–MS (70 eV), t
R
¼ 9:076 min, m=z 162, M (3%);94,
þ
þ
[
M)68] (100%);69, [M )93] (28%);( 2a): IR 3445, 3031,
2
1
969, 2917, 2857, 1591, 1493, 1453, 1377, 1341, 1218,
1
ꢀ1
171, 1092, 1042, 981, 920, 839, 752 cm
; H NMR
(
CDCl
3
) d 7.16–7.12 (m, 1H), 6.91–6.76 (m, 3H), 5.37–
5
.30 (m, 1H), 3.40 (d, J ¼ 7=2 Hz, 2H), 1.81 (s, 3H), 1.80
13
(
3
s, 3H); C NMR (CDCl ) d 154.71, 135.24, 130.38,
1
27.95, 121.16, 116.11, 38.03, 30.24, 26.22;GC–MS
þ
(
70 eV),
t
R
¼ 9:822 min, m=z 162,
M
(50%);147,
þ
þ
þ
[M)15] (39%);107, [M )55] (100%);91, [M )71]
þ
(
25%);77, [M )85] (22%);( 2b): IR (CHCl
3
) 3334, 2967,
916, 1597, 1512, 1473, 1447, 1375, 1232, 1101, 820, 753,
2
6
6
ꢀ
1
1
91 cm ; H NMR (CDCl
.78 (d, J ¼ 8:5 Hz, 2H), 5.32 (t, J ¼ 7:4 Hz, 1H), 3.29 (d,
3
) d 7.06 (d, J ¼ 8:5 Hz, 2H),
Acknowledgements
1
3
J ¼ 7:3 Hz, 2H), 1.76 (s, 3H), 1.73 (s, 3H); C NMR
We thank DePaul UniversityÕs College of Liberal Arts &
Science, the Claire Boothe Luce Foundation and the
Illinois Louis Stokes Alliance for Minority Participation
in Undergraduate Research for funding.
(CDCl ) d 153.91, 134.46, 132.68, 130.09, 129.78, 123.95,
3
115.56, 33.83, 26.19, 18.20;GC–MS (70 eV),
þ
þ
t
R
¼ 10:278 min, m=z 162, M (57%);147, [M )15]
þ
þ
(
100%);107, [M )55] (35%);91, [M )71] (19%);77,
þ
[
M)85] (16%).
2. Zhao, H.;Malhotra, S. V. Aldrichim. Acta 2002, 35, 75–
3.
3. Li, M.;Xu, Z.;Ma, C.;Zhang, W.
Daxue Xuebao 2002, 30, 500–504.
4. Tundo, P.;Perosa, A. Chem. Rec. 2002, 2, 13–23.
1
1
1
8
ZhejiangGon yg e
References and Notes
1
2
3
4
. Mori, K.;Waku, M.;Sakakibara, M. Tetrahedron 1985,
15. Onaka, M. Gendai Kagaku 2002, 371, 14–20.
16. Onaka, M. Petrotech 2001, 24, 837–841.
17. Cave, G. W. V.;Raston, C. L.;Scott, J. L.
Comnun. 2001, 21, 2159–2169.
18. Reed, S. M.;Hutchison, J. E. J. Chem. Educ. 2000, 77,
1627–1629.
19. Nagendrappa, G. Resonance 2002, 64.
20. Corey, E. J.;Wu, L. I. J. Am. Chem. Soc. 1993, 115, 9327–
9328.
41, 2825.
. W €a chter, G. A.;Hoffmann, J. J.;Furbacher, T.;Blake, M.
E.;Timmermann, B. N. Phytochemistry 1999, 52, 1469.
. Fukui, H.;Feroj Hassan, A. F. M.;Ueoka, T.;Kyo, M.
Phytochemistry 1998, 47, 1037.
Chem.
. Ghirtis, K.;Pouli, N.;Marakos, P.;Skaltsounis, A.-L.;
Heterocycles
Leonce, S.;Caignard, D. H.;Atassi, G.
000, 53, 93.
2