One-pot Diels–Alder cycloaddition/gold(I)-catalyzed 6-endo-dig cyclization for the synthesis of the complex bicyclo[3.3.1]alkenone framework

• Boubacar Sow,
• Gabriel Bellavance,
• Francis Barabé and
• Louis Barriault

Beilstein J. Org. Chem. 2011, 7, 1007–1013, doi:10.3762/bjoc.7.114

• [3.3.1]alkanones in yields ranging from 48–93%. Keywords: bicyclo[3.3.1]nonenone; carbocyclization; Diels–Alder; gold catalysis; one-pot process; Introduction Highly oxygenated and densely substituted carbon-bridged medium sized rings such as 1 are commonly found in nature as structural frameworks of

• , which upon exposure to the Au(I) complex 6 (2 mol %) provided the desired bicyclo[3.3.1]nonenone 11 in 88% yield. It is important to note that the Au(I)-catalyzed cyclization proceeds in high yields in a sterically congested environment. The synthesis of the core of papuaforin (11) was achieved in five

• steps from enone 8. However, one might recognize that the low chemical yields encountered in some steps undermine the efficacy of the Au(I)-catalyzed cyclization approach. In order to solve this issue, we assumed that bicyclo[3.3.1]nonenone scaffolds can be directly obtained through an intermolecular