Design and Synthesis of Cage Molecules as High Energy Density Materials for Aerospace Applications

Abstract

This account deals with our work on cage systems that was reported during the past two decades. Here, we summarized various new synthetic routes to diverse cage polycycles by employing Claisen rearrangement, Diels−Alder (DA) reaction, [2+2] photocycloaddition, Grignard addition, Fischer indolization, ring‐closing metathesis (RCM), Van Leusen oxazole synthesis, and rearrangement reaction as key steps. Several heterocyclic cage frameworks (oxacycles and oxazoles), polycyclic bisindoles, cage spirocycles, cage energetic systems, D3‐trishomocubanes, cage propellanes and unusual polycycles were designed starting with inexpensive and easily accessible starting materials. In some occasions, we also prepared biologically important triquinane frameworks starting with readily available cage diones via photo‐thermal olefin metathesis strategy under microwave irradiation conditions. This new protocol avoids specialized equipment such as flash vacuum pyrolysis. Additionally, we have also shown interesting rearrangements in cage frameworks to generate unusual new and cage systems with the aid of the Lewis acids such as BF3.OEt2. Moreover, these functionalized cage systems can be considered as a useful candidates in material science, medicinal chemistry, and also in drug in design.

Design and Synthesis of Highly Decorated Oxa‐Cage Systems via Olefin Metathesis

“…Polycyclic cage systems are categorized as carbocyclic and heterocyclic caged molecules [7c] . Selective, representative examples of cage compounds are shown in Figure 1 [8d] .…”

Editorial: The Catalysis of Ring Synthesis

“…A Review by Kotha and co‐authors summarizes new synthetic methods to diverse cage polycycles potentially useful for high energy density materials synthesis [1] . In the Review paper by Neto and Zeni the diverse variety of synthesis of pyrrole derivatives using the reaction of alkynes with nitrogen‐compounds under transition metal‐catalyzed and metal‐free conditions, is presented [2] .…”

“…This Special Collection "The Catalysis of Ring Synthesis" covers the most recent strategies of ring synthesis and presents the current advances in the field.A Review by Kotha and co-authors summarizes new synthetic methods to diverse cage polycycles potentially useful for high energy density materials synthesis. [1] In the Review paper by Neto and Zeni the diverse variety of synthesis of pyrrole derivatives using the reaction of alkynes with nitrogencompounds under transition metal-catalyzed and metal-free conditions, is presented. [2] A Minireview from the group of Das reflects the impressive state of the art in photoredox catalysis and the recent applications of photocatalysis to [2 + 2] and [4 + 2] cycloaddition reactions under the irradiation of visible light.…”

Design and Synthesis of Nitro Cage Heterocycles as Energetic Materials Derived from Pentacycloundecane (PCUD) Systems

“…Based on these aspects, a new strategic approach to the design of HEDMs [9] is conceived. Oxidizers, energetic fuels, and propellants have been discovered for importance in civil, industrial, defence and also usages in aerospace industry [2b] . Because of their importance in energy aspects, current studies have been focussed on the enhancement of efficient synthetic protocols towards nitrogen‐rich cage molecules [10]…”