The hetero-Friedel-Crafts-Bradsher Cyclizations with Formation of Ring Carbon-Heteroatom (P, S) Bonds, Leading to Organic Functional Materials.

Joanna Skalik,Piotr Bałczewski,Marek Koprowski,Ewa Różycka-Sokołowska

doi:10.3390/ma13214751

Abstract

The interest in functional materials possessing improved properties led to development of new methods of their synthesis, which allowed to obtain new molecular arrangements with carbon and heteroatom motifs. Two of the classical reactions of versatile use are the Friedel-Crafts and the Bradsher reactions, which in the new heteroatomic versions allow to replace ring carbon atoms by heteroatoms. In the present work, we review methods of synthesis of C–S and C–P bonds utilizing thia- and phospha-Friedel-Crafts-Bradsher cyclizations. Single examples of C–As and lack of C–Se bond formation, involving two of the closest neighbors of P and S in the periodic table, have also been noted. Applications of the obtained π-conjugated molecules, mainly as semiconducting materials, flame retardants, and resins hardeners, designed on the basis of five- and six-membered cyclic molecules containing ring phosphorus and sulfur atoms, are also included. This comprehensive review covers literature up to August 2020.

Highlights

During the last years, π-conjugated molecules containing various ring heteroatoms, such as boron, nitrogen, silicon, sulfur, oxygen, or phosphorus atoms incorporated into polycyclic ring systems gained an increasing importance due to their unique optical and electronic properties which made them useful functional materials, especially in the area of semiconducting materials [1]
Double of phospha-Friedel-Crafts-Bradsher with phosphorus trichloride, followed by sulfurization of the dichlorophosphine obtained with reaction of (181) in the presence of Lewis acid (AlCl3) in ortho-dichlorobenzene (ODCD)
Introduction of heteroatoms into cyclic, π-conjugated molecules usually delivers new materials with enhanced properties compared to carbon analogs. This was the case with five- and six-membered heteroacenes containing ring phosphorus and sulfur atoms

Summary

Introduction

Π-conjugated molecules containing various ring heteroatoms, such as boron, nitrogen, silicon, sulfur, oxygen, or phosphorus atoms incorporated into polycyclic ring systems gained an increasing importance due to their unique optical and electronic properties which made them useful functional materials, especially in the area of semiconducting materials [1]. Despite the close proximity in main groups and in the third row of the table, the properties of materials containing these two heteroatoms vary considerably due to differences in atomic radii, electronegativities, and a number of free electron pairs available They are incorporated in five- or six-membered ring systems, mainly thiophene and phosphole derivatives. It is known that heteroatom cations generated from p-block-elements including phosphorus and sulfur may interact with (hetero)arenes to form heteroarenium species and enable introduction of ring heteroatoms in place of carbon atoms This type of modification, which may be referred as a hetero-Friedel-Crafts-Bradsher reaction, is a useful tool for incorporation of heteroatoms into π-conjugated frameworks. The thia- and phospha-Friedel-Crafts-Bradsher reactions outlined in this review

Cyclisation of Sulfur Derivatives

Cyclization of Phosphorus Derivatives

Findings

Conclusions