Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

Zakir Hussain,Khurshid Ayub,Henning Hopf,S Holger Eichhorn

doi:10.3762/bjoc.8.77

Abstract

Synthesis of hydroazulene derivatives has been carried out through a ring-enlargement route by using carbene adduct intermediates. The protocol can be applied for the construction of functionalized hydroazulene skeletons as key components of many natural products as well as the core system of novel liquid-crystalline materials.

Highlights

Hydroazulene skeletons provide the basic ring systems of natural products, such as guaianolide sesquiterpenes [1,2] and the so-called furanether B series [3,4]
In 1951, the ring expansion of indanes was reported for the synthesis of such systems, but it delivered only very low yields [9]
We recently employed [10,11] the method reported by Keehn et al [12] using Birch reduced indanes for the synthesis of 2,6-disubstituted perhydroazulene systems as core elements of novel liquidcrystalline (LC) materials

Summary

Introduction

Hydroazulene skeletons provide the basic ring systems of natural products, such as guaianolide sesquiterpenes [1,2] and the so-called furanether B series [3,4]. The complete characterization of intermediates 2 and 3 and carbene adduct 4 was carried out by NMR and related analytical techniques, similar to previous reports [18], while the 3D structure of 4 was further established based on the X-ray data of its derivative 6 [20].

Results

Conclusion