Stereoselective total synthesis of (±)-3-oxosilphinene through intramolecular Diels–Alder reaction

Abstract

The angular tricyclopentanoid sesquiterpene (±)-3-oxosilphinene (1) was stereoselectively synthesized through intramolecular Diels–Alder reaction as the key step. On heating, the (E,E)-sulphenyltriene (16), derived from 3-bromo-2-methylcyclopent-2-enone (13), gave only one stereoisomer of the tricyclo[7.3.0.0^1,5]dodecene derivative (17) having all four contiguous asymmetric centres with the required stereochemistry. The cycloadduct (17) was converted into the racemate of the natural product (1)via ring contraction.