dimethyl effect,” observed for the dimethyl substituted substrates (8a) and (11a) may be explained in terms
1
2
of the “reactive rotamer effect” described by Jung.
TABLE III. Intramolecular Diels-Alder Reactions of 8b and 11b in o-DCB
Entry
Substrate Additive (mol %)
Temp., °C
Time, h
Product
Yield, %
1
2
3
4
5
6
8b
8b
—
180
180
180
150
180
180
24
8
9b
9b
6
15
24
19
42
28
Sc(OTf) (10)
3
8b
Cu(OTf) (10)
8
9b
2
11b
11b
11b
Cu(OTf) (10)
4
12b
12b
12b
2
Cu(OTf) (2)
2
2
Cu(OTf) (10)
1
2
REFERENCES AND NOTES
1
2
3
.
.
.
For reviews on the Diels-Alder reaction of oxazoles, see A. Hassner and B. Fischer, Heterocycles,
993, 35, 1441 and references cited therein.
(a) J. I. Levin and S. M. Weinreb, J. Am. Chem. Soc., 1983, 105, 1397; (b) Idem, J. Org. Chem.,
984, 49, 4325.
1
1
(a) S. Shimada and T. Tojo, Chem. Pharm. Bull., 1983, 31, 4247; (b) C. Subramanyam, M.
Noguchi, and S. M. Weinreb, J. Org. Chem., 1989, 54, 5580; (c) J. I. Levin, Tetrahedron Lett.,
1
989, 30, 2355; (d) M. E. Jung and S. M. K. Dansereau, Heterocycles, 1994, 39, 767; (e) A.
Padwa, M. A. Brodney, B. Liu, K. Satake, and T. Wu, J. Org. Chem., 1999, 64, 3595; (f) M. Ohba,
H. Kubo, T. Fujii, H. Ishibashi, M. V. Sargent, and D. Arbain, Tetrahedron Lett., 1997, 38, 6697;
(
g) M. Ohba, H. Kubo, and H. Ishibashi, Tetrahedron, 2000, 56, 7751.
4
5
.
.
M. Ohba, R. Izuta, and E. Shimizu, Tetrahedron Lett., 2000, 41, 10251.
(a) J. L. Herrmann and R. H. Schlessinger, J. Chem. Soc., Chem. Commun., 1973, 711; (b) B. E.
Hudson, Jr. and C. R. Hauser, J. Am. Chem. Soc., 1941, 63, 3156.
6
.
(a) U. Schöllkopf and R. Schröder, Angew. Chem., 1971, 83, 358; (b) R. Schröder, U. Schöllkopf,
E. Blume, and I. Hoppe, Liebigs Ann. Chem., 1975, 533; (c) M. Ohba, H. Kubo, S. Seto, T. Fujii,
and H. Ishibashi, Chem. Pharm. Bull., 1998, 46, 860.
7
8
.
.
A. J. Mancuso and D. Swern, Synthesis, 1981, 165.
(a) D. B. Dess and J. C. Martin, J. Org. Chem., 1983, 48, 4155; (b) Idem, J. Am. Chem. Soc.,
1991, 113, 7277; (c) R. E. Ireland and L. Liu, J. Org. Chem., 1993, 58, 2899.
9
.
H. Oda, T. Kobayashi, M. Kosugi, and T. Migita, Tetrahedron, 1995, 51, 695.
1
1
0. H. Jin, J. Uenishi, W. J. Christ, and Y. Kishi, J. Am. Chem. Soc., 1986, 108, 5644.
1. (a) K. Takai, K. Kimura, T. Kuroda, T. Hiyama, and H. Nozaki, Tetrahedron Lett., 1983, 24, 5281;
(
b) K. Takai, M. Tagashira, T. Kuroda, K. Oshima, K. Utimoto, and H. Nozaki, J. Am. Chem. Soc.,
986, 108, 6048.
2. M. E. Jung, Synlett, 1999, 843.
1
1