T. Bach, M. Bartels / Tetrahedron Letters 43 (2002) 9125–9127
9127
matenoids with a C3-substituent at position C-5. As an
example, we prepared the racemic trans-diol eupo-
matenoid-9 (1h) from intermediate 1d (Scheme 4). In
analogy to a known semi-synthetic procedure,3b the
alkene was converted into the monoacylated diol by
treatment with m-CPBA and concomitant ring opening
by m-chlorobenzoic acid (89%). Upon cleavage of the
m-chlorobenzoate with K2CO3 the silyl protective
group was simultaneously removed (86%) and the
desired product 1h was obtained.
3. (a) Bowden, B. F.; Ritchie, E.; Taylor, W. C. Austr. J.
Chem. 1972, 25, 2659–2669; (b) Picker, K.; Ritchie, E.;
Taylor, W. C. Austr. J. Chem. 1973, 26, 1111–1119; (c)
Read, R. W.; Taylor, W. C. Austr. J. Chem. 1979, 32,
2317–2321; (d) Carroll, A. R.; Taylor, W. C. Austr. J.
Chem. 1991, 44, 1615–1626; (e) Carroll, A. R.; Taylor, W.
C. Austr. J. Chem. 1991, 44, 1627–1633 and references
cited therein.
4. For alternative synthetic approaches, see: (a) Ahmed, R.;
Stevenson, R. Phytochemistry 1975, 14, 2710–2712; (b)
McKittrick, B. A.; Stevenson, R. J. Chem. Soc., Perkin
Trans. 1 1983, 475–482; (c) Engler, T. A.; Chai, W.;
LaTessa, K. O. J. Org. Chem. 1996, 61, 9297–9308; (d)
Engler, T. A.; Chai, W. Tetrahedron Lett. 1996, 37,
6969–6970.
5. For references on cross-coupling reactions of heterocy-
cles, see: (a) Li, J. J.; Gribble, G. W. Palladium in
Heterocyclic Chemistry; Pergamon Press: Oxford, 2000;
(b) Brandsma, L.; Vasilevsky, S. F.; Verkruijsse, H. D.
Application of Transition Metal Catalysts in Organic Syn-
thesis, Springer: Berlin, 1999; (c) Diederich, F.; Stang, P.
J. Metal-Catalyzed Cross-coupling Reactions; Wiley-
VCH: Weinheim, 1998.
In summary, we have established a short and efficient
synthesis of 2,3,5-trisubstituted benzofurans by three
consecutive cross-coupling reactions. The applicability
of the method was exemplified by the preparation of
various naturally occurring eupomatenoids but it is
expected to be also useful for the synthesis of other
benzofurans.
Acknowledgements
This research was supported by the Deutsche
Forschungsgemeinschaft (Ba 1372-5/2) and the Fonds
der Chemischen Industrie.
6. Cugnon de Sevricourt, M.; Robba, M. Bull. Soc. Chim.
Fr. 1977, 139–141.
7. (a) Karlsson, J. O.; Gronowitz, S.; Frejd, T. J. Org.
Chem. 1982, 47, 374–377; (b) Carpita, A.; Rossi, R.;
Veracini, C. A. Tetrahedron 1985, 41, 1919–1929; (c)
Carpita, A.; Rossi, R. Gazz. Chim. Ital. 1985, 115, 575–
583.
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