Arenes and heteroarenes are very important structural building blocks and are ubiquitously seen in several life science products and agrochemicals. Since a larger pool of inert and planar aromatic compounds is accessible from the processing of coal and petroleum feedstocks, including bio-based resources, they can be readily modified and or functionalized using a variety of well-established synthetic techniques such as nitration, halogenation, cross-coupling, and many more, especially for preparing core drug analogs. In turn, straightforward access to privileged 3D chemical space using ubiquitous aromatic feedstocks is of prime importance, as their integration into the complex organic framework holds extensive value in drug development (Figure ) and finds application in a multitude of organic reactions. The dearomative selective reduction of (hetero)arenes and reductive deuteration, especially nitrogenous het-erocyclic compounds represent the shortest way to leverage the construction of saturated nitrogen-containing heterocycles (cyclic amines), which are advanced chemical building blocks enabling their exploration for targeted therapies. For instance, substituted 1,2,3,4-tetrahydroquinolines, piperidines, piperazines, indolines, pyrrolidines, and related ring systems are integral parts of 3D-pharmacophores, orally bioavailable drugs, as well as bio-active natural products (Figure ). However, generating saturated N-heterocyclic analogues can be a substantial synthetic burden and labor-intensive. Therefore, the expansion of robust methodologies is necessary not only to access nitrogen-based 3D-like sp -rich fragments for efficient clinical research but also to search for innovative pharmaceutical compounds with enhanced therapeutic efficiency. In addition, the latest accomplishments in the medicinal chemistry community invented "escaping from flatland" i.e., increasing saturation as a tool for improving clinical development success. In this sense, saturated heterocyclic rings allow improved F(sp 3 ) carbon fraction, increased substitution, and greater structural diversity, as well as enhanced aqueous solubility that may lead to higher bioavailability, which makes them appealing in the drug discovery setting (Figure ). In contrast, excessive flat sp -rich aromatic cores are associated with some parameters like low specificity (selectivity) and poor solubility in aqueous media. For this reason, saturated carbo-and/or heterocyclic ring motifs are present in a large number of top-selling pharmaceuticals and FDA-approved drugs, signifying that 82% of small-molecule therapeutics contain at least one N-heterocycle, with the piperidine, piperazine, and pyrrolidine analogs ring being the most prime ones. 6 In recent years, various research groups have achieved significant advances in the reduction of N-heteroarenes, namely, quinolines, pyridines, and related heterocycles. Despite remarkable progress, there is still a notable gap in the substrate scope. The substrate scope of quinoline derivatives is divided into two types (Figure ): 1) substituents present on the phenyl ring and 2) substituents present on the Nheteroarene ring. Although the first one is well-established, there are still drawbacks with some functional group compatibility. For example, during the ring saturation process, the persistence of the iodine (I) moiety situated on the benzene core of quinoline is subpar. Further, methods that tolerate sulfur groups are inadequate, and phosphorus, as well as silanes and many more are barely known. On the other hand, the second type, i.e., the tolerance of the substituents on the reducible nitrogen ring, remains conspicuously incipient. Additionally, the catalytic reduction of functionalized pyridines offers a gateway to piperidine analogs that are found in a vast array of FDA-approved drugs , which is due to the increased fraction of sp 3 carbon atoms (Fsp 3 ) that manifest improved drug-like properties. Alternatively, piperidines can be prepared by multiple synthetic techniques, such as cycloadditions, ring expansions, radical cyclizations, nucleophilic substitutions, etc. Among all of these, the reduction of pyridines is an ideal route to access diverse piperidines on a large scale owing to the availability of bulk pyridine derivatives and step-economy. One of the key problems in this chemistry is the binding of coordinating nitrogen atoms to the metal center or the presence of weak C-H bonds close to nitrogen atoms that assist unwanted side reactions. Due to this reason, the aromatic reduction of unprotected functionalized pyridines is less known. Thus, it is not able to expand the wider piperidine-based 3D chemical space in the small molecule drug discovery process.