Abstract
The aniline moiety is the key component in the formation of CN bonds, embedded in natural and synthetic products. Anilines have played a significant role in the growth of the chemical industry since their first usage in the synthesis of dyes and pigments. They are essential precursors in pharmaceuticals, polymers and agrochemicals, ultimately making their synthesis attractive. Preliminary studies have demonstrated efficient routes to accessing anilines; however, they require undesirable conditions that do not align with green chemistry principles.
Herein, we developed a protocol for the reduction of nitroarenes to anilines using a mild, air- and moisture-stable, cost-effective reducing agent, polymethylhydrosilane (PMHS). The protocol proposed a facile, benign way to synthesise an aniline derivative in 30 minutes, with a yield of 84%. The depth of the study is covered in chapter 2, where optimisation studies revealed that the combination of PMHS and a palladium catalyst produces palladium-encapsulated siloxane colloids, which are presumed to drive the reduction of nitroarenes to form anilines. Based on the preceding findings, the colloids were subjected to recyclability studies and a mercury test to investigate the true nature of the catalyst using the mercury poisoning test.
The substrate library of the protocol was investigated in Chapter 3, demonstrating the protocol's effectiveness with nitroarenes bearing electron-donating and electron-withdrawing substituents. The protocol favoured the electron-donating groups, substituents affording anilines in yields up to 97%. However, chlorinated substituents and cyano substituents were refluxed to form the desired product.
Notably, one of the functionalisations of anilines is their transformation to amides, which is the focus of Chapter 4. Palladium-catalysed aminocarbonylation of aryl halides with nitroarenes was explored in this section to synthesise amides, using molybdenum hexacarbonyl as both the reducing agent and the carbonyl source. This was achieved through reaction optimisation studies which investigated various bases, ...