Synthesis of indole-based propellane derivatives via Weiss–Cook condensation, Fischer indole cyclization, and ring-closing metathesis as key steps

Sambasivarao Kotha,Arti Tiwari,Ajay Kumar Chinnam

doi:10.3762/bjoc.9.307

Abstract

A variety of highly functionalized indole-based [n.3.3]propellane derivatives is described. The synthesis of the propellane derivatives involves a Weiss–Cook condensation, a Fischer indole cyclization, and a ring-closing metathesis as key steps.

Highlights

Propellanes are tricyclic systems conjoined with carbon–carbon single bonds (Figure 1) [1,2,3], and they are found to be highly congested
The synthesis of indole alkaloid derivatives containing a propellane ring system is a challenging task due to the presence of quaternary centers involved with these systems [35]
We report a new synthetic strategy to indole-based propellane derivatives and our approach has several points of diversification: (i) various aryl and heteroaryl fused indole derivatives can be assembled by choosing an appropriate hydrazine derivative, (ii) during the alkylation of diketone 2 [43] various unsaturated alkenyl fragments may be incorporated either in a symmetrical or in an unsymmetrical manner, (iii) various func

Summary

Introduction

Propellanes are tricyclic systems conjoined with carbon–carbon single bonds (Figure 1) [1,2,3], and they are found to be highly congested. The synthesis of indole alkaloid derivatives containing a propellane ring system is a challenging task due to the presence of quaternary centers involved with these systems [35]. We envisioned a new synthetic route to diindole based propellane derivatives involving the Weiss–Cook condensation [36], Fischer indole cyclization [37,38], and ring-closing metathesis as key steps [39,40,41,42] (Figure 3).

Results

Conclusion