## 1 Introduction  
Organic synthesis has tremendously advanced since the advent of transition metal catalysis. Over the years, not only a considerable synthetic efficiency was achieved but also concatenations of organometallic elementary steps were established that led to an unprecedented increase in structural complexity. By name, these processes are commonly referred to as metal catalyzed domino, tandem, or cascade reactions [1]. During the past two decades, in spite of their different literal meaning all these terms have been progressively used in this context as synonyms since by design they all fall into the realm of one-pot transformations, which have been recently reviewed [2; 3; 4]. A particular advantage of these concepts is the huge increase in structural complexity facilitated by the use of even the simplest starting materials. This is also one of the driving factors for constant research advancements in this field [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17]. In general, transition metal catalyzed cascade reactions can be categorized into two groups, either being domino reactions that constantly repeat the same elementary step [15; 16; 17], or they are constituted by reaction steps that consist of fundamentally different elementary transformations [18; 19; 20; 21; 22; 23; 24; 25]. As such, transition metal catalyzed domino reactions involve organometallic intermediates which are constantly regenerated and yield complex, often polycyclic, organic products after numerous insertion steps and after a concluding elimination. Mostly in palladium catalyzed processes, unimolecular reactions that proceed intramolecularly, for instance via cyclic carbopalladation [26; 27; 28], generate complex polycyclic structures beginning with linear polyunsaturated substrates. Moreover, metal catalyzed cascade reactions that proceed in a parallel or sequential manner [18; 22] offer even more versatility if the catalyst bears the capability of performing different catalytic processes, especially if the adjustment of the reaction conditions from step to step with additives can trigger different catalytic steps. Conceptually however, for obvious reasons, parallel catalysis is more difficult to develop than sequential catalysis. According to [PERSON]'s and [PERSON] terminology, sequential catalysis can be categorized as bi- or multicatalytic one-pot processes, assisted tandem catalysis or auto tandem catalysis, respectively [1]. Consequently, the most demanding part in the development of such processes is the identification of an apt precatalyst which has the potential to catalyze various reactions in a one-pot fashion, thereby rapidly enabling the access to complex molecular scaffolds in diversity oriented syntheses [29; 30; 31; 32; 33]. One of the two essential requirements to the catalytic system is the generation or retention of a functional group which is then appropriate for a subsequent reaction. Secondly, the catalyst or catalyst precursor has to be present in the reaction medium at the outset without any further addition of catalyst after the initial step. Additives to trigger the subsequent step might be added stepwise though. To date, sequentially transition metal catalyzed processes predominantly make use of palladium [34; 35], rhodium [36], and ruthenium [37] as metal sources. Recently, an overview focusing on cycling metal catalyzed processes in the sense of auto and assisted tandem catalysis according to [PERSON]'s and [PERSON] classification in mind [1], gave an insight into this concept [38]. Here, we specifically focus on syntheses of heterocycles employing sequentially palladium catalyzed processes that are one-pot reactions _in sensu stricto_. Special attention will be given to Pd-catalyzed alkynylation and insertion sequences, sequences based upon animations, processes that are intercepted by cyclocondensation events, and a few specific sequentially catalyzed processes.