187. Asymmetric [4 + 3] Cycloadditions between Benzofuranyldiazoacetates and Dienes:  Formal Synthesis of (+)-Frondosin B

Authors: Jeremy P. Olson and Huw M. L. Davies

Org. Lett.,

2008, 10 (4), 573–576


The reaction of benzofuranyldiazoacetates with 1,3-dienes catalyzed by the dirhodium tetracarboxylate Rh2(R-DOSP)4, generates formal [4 + 3] cycloadducts with >94% de and 91−98% ee. The reaction proceeds by a tandem cyclopropanation/Cope rearrangement followed by a stereoselective tautomerization. This methodology was extended to a formal synthesis of (+)-frondosin B.

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