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Microwave and conductive heating mediated H/D exchange reactions, the latter under continuous flow processing in the presence or absence heterogeneous or homogeneous catalysts have been studied in this thesis. The aim of this study was to validate an efficient way to introduce multiple deuterium atoms into compounds of interest. Such deuterated substrates could be useful for the investigation of pharmacological and metabolic properties. Aniline and aniline derivatives as well as a series of aminopyridine derivatives were used as substrates in this study, due to the importance of the corresponding labelled compounds as drug compounds or as precursors for the synthesis of clinical agents. Pd/C as a heterogeneous catalyst was employed under microwave–assisted and flow chemistry conditions and the %D incorporation and chemical yields were compared. The H/D exchange reaction using platinum as a homogeneous catalyst with aniline derivatives provided the means to incorporate deuterium efficiently at all aromatic positions. Furthermore, metal catalysis was able to facilitate exchange in alkyl side chains with high efficiency, provided that there was no quaternary centre in the alkyl group. The study also demonstrated that the H/D exchange of aniline derivatives in the absence of a metal catalyst proceeded as anticipated and was able, on deuterio-protio exchange under acidic conditions, to deliver meta-deuterated targets. The H/D exchange of aminopyridine derivatives using a platinum catalyst was also highly efficient, giving high deuterium incorporation in many cases. Mechanistic proposals have been put forwards for these processes. This research has provided a new method for the preparation of meta functionalized aniline- and highly functionalized pyridine-derivatives suitable for further elaboration. The Pt-catalyzed process has provided a means for deuteration at multiple aromatic positions in a single cycle, short reaction time and high efficiency.