Design and synthesis of C 3-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

An overview of the synthetic strategies of C3-symmetric polymeric materials containing benzene and triazine cores and their biomedical applications

C3-symmetric star-shaped materials are an emerging category of porous organic polymers with distinctive properties such as permanent porosity, good thermal and chemical stability, high surface area, and appropriate functionalization that promote outstanding potential in various applications. This review is mostly about constructing benzene or s-triazine rings as the center of C3-symmetric molecules and using side-arm reactions to add functions to these molecules. Over and above this, the performance of various polymerization processes has been additionally investigated in detail, including the trimerization of alkynes or aromatic nitriles, polycondensation of monomers with specific functional groups, and cross-coupling building blocks with benzene or triazine cores. Finally, the most recent progress in biomedical applications for C3-symmetric materials based on benzene or s-triazine have been summarized.

Application of Multi-component Reaction in the Synthesis of Heterocyclic [3.3.3] Propellane Derivatives

Abstract:

Propellanes and derivatives have attractive properties due to their unique structure. Therefore, [3.3.3] propellanes, containing tricyclic structures with one of the carbon-carbon bonds common in three rings, were used in natural products, pharmaceutical compounds, and heterocyclic compounds, which were biologically important. The various multi-component reactions were applied in the synthesis of propellanes, which were highlighted throughout this review

Modular Approaches to Cyclopentanoids and their Heteroanalogs

Cyclopentanoids and their derivatives are interesting targets in synthetic organic chemistry due to their extensive applications in various branches of chemical sciences like pharmaceuticals, natural and non-natural products. In view of these applications, several synthetic strategies have been developed in the past three to four decades. In this article, we describe our work towards the synthesis of cyclopentanoids and their heteroanalogs involving diverse synthetic strategies during the past two decades. Among these, photo-thermal olefin metathesis, ring-closing metathesis, ring-rearrangement metathesis, cyclopentane annulation, [2+2+2] cycloaddition and Diels–Alder reactions have been used to assemble cyclopentane rings of diverse architecture.

1 Introduction

2 Synthesis of Spiro[4.4]nonane (A1) Derivatives

3 Synthesis of Octahydropentalene (A2) Derivatives

4 Synthesis of Linear Triquinanes (A3)

5 Synthesis Spiro Triquinanes (A4)

6 Synthesis of Angular Triquinane (A5) Systems

7 Synthesis of Hexahydro-2′H-spiro[cyclopentane-1,1′-pentalene] (A6) Ring System

8 Synthesis of Dispiro[4.1.47.25]tridecane (A7) Ring System

9 Synthesis of Hexahydro-1H-3a,7a-propanoindene Ring System

10 Synthesis of Linear Tetraquinanes (A11 and A12)

11 Synthesis of Tetrahydro-1′H,3′H-dispiro[cyclopentane-1,2′-pentalene-5′,1′′-cyclopentane] (A13) Ring System

12 Synthesis of Decahydro-1H,8H-dicyclopenta[a,h]pentalene (A14) Ring System

13 Synthesis of Dodecahydro-1H-dicyclopenta[a,d]pentalene (A15) Ring System

14 Synthesis of Octahydro-1′H-spiro[cyclopentane-1,2′-cyclopenta[c]pentalene] (A16) Ring System

15 Synthesis of Decahydrospiro[cyclopentane-1,7′-cyclopenta-[a]pentalene] (A17) Ring System

16 Synthesis of Compact Tetraquinane (A18)

17 Synthesis of Higher Polyquinanes

18 Conclusions

19 Acronyms

Far Away from Flatland. Synthesis and Molecular Structure of Dihetera[3.3.n]propellanes and Trihetera[3.3.n]propellanes: Advanced Analogues of Morpholine/Piperazine

An approach to di- and trihetera[3.3.n]propellanes (n = 2-4 ), advanced morpholine and piperazine analogues, is developed. The key step of the reaction sequence included a [3 + 2] cycloaddition reaction of unsaturated vicinal dicarboxylic acid derivatives and in situ generated azomethine ylide resulting in the formation of the pyrrolidine ring. One more heteroaliphatic ring (i.e., pyrrolidine or tetrahydrofuran) was annelated by nucleophilic cyclization of the appropriate 1,4-dielectrophilic intermediates. There were 11 examples of the title products obtained in 3-5 steps on a multigram scale with 10-72% overall yields. Additionally, molecular structures of homologous dihetera[3.3.n]propellanes, analogues of morpholine, were obtained from X-ray diffraction studies and analyzed using exit vector plots (EVPs). It was shown that the scaffolds obtained are somewhat larger as compared to the parent morpholine and bicyclic 3-oxa-7-azabicyclo[3.3.0]octane. Moreover, despite very similar chemical structures, they provide a very distinct spatial position of heteroatoms, which is clearly seen from the conformation adopted by a formal eight-membered ring including both N and O atoms (i.e., crown, boat-chair, twist chair-chair, and boat-boat for the oxaza[3.3.2]-, -[3.3.3]-, -[4.3.3]propellanes, and 3-oxa-7-azabicyclo[3.3.0]octane, respectively).

Synthetic Approaches to Star-Shaped Molecules with 1,3,5-Trisubstituted Aromatic Cores

Herein, we summarize the synthetic approaches that have been developed for the synthesis of star-shaped molecules. Typically, to design such highly functionalized molecules, simple building blocks are first assembled through trimerization reactions, starting from commercially available starting materials. Then, these building blocks are synthetically manipulated to generate extended star-shaped molecules. We also discuss the syntheses of star-shaped molecules that contain 2,4,6-trisubstituted 1,3,5-triazine or 1,3,5-trisubstituted benzene rings as a central core and diverse substituted styrene, phenyl, and fluorene derivatives at their periphery, which endows these molecules with extended conjugation. A variety of metal-catalyzed reactions, such as Suzuki, Buchwald-Hartwig, Sonogashira, Heck, and Negishi cross-coupling reactions, as well as metathesis, have been employed to functionalize a range of star-shaped molecules. The methods described herein will be helpful for designing a wide range of intricate compounds that are highly valuable in the fields of supramolecular chemistry and materials science. Owing to space limitations, we will not cover all of the publications on this topic. Instead, we will focus on examples that were reported by our research group and other relevant recent literature. Apart from the trimerization sequence, this Minireview has been structured based on the key reactions that were used to prepare the star-shaped molecules and other higher analogues. Finally, some examples that do not fit into this classification are discussed.