Sesquiterpenes. Part IV. Synthesis of some tricyclo[5,4,0,03,5]undecanones and related compounds

Abstract

The tricyclo[5,4,0,0^3,5]undec-8- and -9-enes (VI), (XII), and (XIII) have been prepared from the corresponding tricycloundecanones (IV), (X), and (III). Allylic oxidation of the olefin (VI) with sodium dichromate in acetic acid solution gave the αβ-unsaturated ketone (X). In the reduction of the αβ-unsaturated thioacetals (XI) and (XV) by lithium in liquid ammonia a partial isomerisation of the double bond was observed. Reduction of the unsaturated ketones (I), (II), and (X) with lithium in liquid ammonia afforded the saturated ketones (IV), (V), and (VII) in high yield.