Bioorthogonal reactions have a central role in medicinal therapeutics and diagnostics. Extracellularly binding substances, like antibodies, are often used as targeting agents and are coupled with a bioorthogonal reaction agent. The most popular combination nowadays is the inverse electron demand Diels-Alder reaction between a trans-cyclooctene and a tetrazine. The aim of this thesis is to show that this kind of reaction is not only able to be used for in vitro reactions but as well for intracellular reactions. Therefore, an intracellular targeting agent, ibrutinib, was synthesized. It binds covalently to Bruton tyrosine kinase (BTK), which is expressed by chronic lymphocytic leukemia (CLL) and other leukemia diseases. Through the introduction of an amine-group, this targeting agent can be modified without preventing its ability to covalently bind to BTK. Besides this classic click reaction, bioorthogonal bond cleavage reactions have recently been discovered, e.g. click-to-release chemistry, which was used in combination with the ibrutinib model to develop a tool to study intracellular bioorthogonal elimination. To enable release upon tetrazine ligation, a leaving group was introduced at the allylic position of TCO. This reaction can be employed to achieve intracellular release of a variety of compounds (e.g. drugs), which is thus of increasing interest. As a proof-of-concept, within this thesis three different ibrutinib derivatives were prepared in multistep synthetic sequences and evaluated. We were able to show that bioorthogonally modified ibrutinib still specifically binds to BTK. Intracellular reactions were confirmed by cell uptake measurements using radiolabeled tetrazines. The click-to-release reaction was studied and confirmed in vitro applying a drug-TCO-dye conjugate. Consequently, the ibrutinib model was shown to be a valuable tool to study intracellular bioorthogonal reactions. This will not only enable the development of imaging techniques that can be used for diagnostics and to attain a better understanding of biosystems, but moreover allow us to investigate intracellular bioorthogonal elimination reactions towards theranostic applications.