A highly selective Ru(3)(CO)(12)-catalyzed deuteration method using t-BuOD as deuterium source is reported. Electron-rich and electron-poor N-heteroarenes such as indoles, azaindoles, deazapurines, benzimidazole, quinolines, isoquinolines, and pyridines were efficiently deuterated at specific positions with high selectivity; in most cases, deuterium incorporation was close to the theoretically possible values. To further increase deuteration degrees, several cycles of the reaction protocol can be carried out which gave superior deuteration degrees employing a much lower excess of deuterating agent compared to established protocols. It was proved that the same protocol can in principle be applied to tritiation reactions important for radioactive labeling of bioactive molecules.

Alkynylation reactions of N-protected tetrahydroisoquinolines have been performed using several different protocols of cross dehydrogenative coupling. Initially, a CuCl-catalyzed method was investigated, which worked well with three different N-protecting groups, namely phenyl, PMP, and benzyl and t-BuOOH as oxidant in acetonitrile as solvent. The peroxide could then be replaced by simple air and acetonitrile for water, leading to an overall very environmentally friendly protocol. Finally, a decarboxylative alkynylation protocol starting from alkynoic acids was also developed using again air as oxidant. This avoids the use of gaseous alkynes in the introduction of short-chained alkyne substituents.Graphical abstract

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