Studies on Intramolecular Cyclisations. Synthesis of Ring Systems Related to Sesquiterpene Noids

Abstract

Intramolecular reactions of diazocarbonyl compounds have provided¹ synthetic routes to many novel ring systems. For synthetic entry into the basic carbon skeleta of several tricyclic sesquiterpenoids, we have studied acid-catalysed intramolecular cyclisations of a few diazo-ketones derived from suitably substituted indanones and tetralones. The tricyclic dienediones 1 ⁺, 2, 3 and 4 have been prepared in this way in 42%, 16%, 24% and 26% yields respectively from the acids 8, 13, 16, and 18. Although the yields are

not high, the method is convenient since the starting materials are readily accessible and the pure dienediones are easily isolated from the crud products through chromatography on silica gel.