## 4 Sequences Intercepted by Cyclizations  
Reactive members of the class of three-carbon building blocks are alkynones [110] and 1,3-diaryl propenones [111], so-called chalcones, which can be rapidly transformed into five-, six-, and even seven-membered heterocycles in a Michael-addition cyclocondensation sequence. A catalytic access to yonnes [79,112] and enones [113, 114, 115, 116] by Sonogashira-coupling therefore provides an entry to the preparation of a variety of heterocycles. Based on this motivation, the concept has been studied in great detail and elaborated into well-established protocols by the group of [PERSON] in the last decade. Since major advancements of this one-pot methodology have been already reviewed [117, 118, 119, 120] only recent conceptual achievements with respect to sequentially Pd-catalyzed processes [34] will be highlighted here. One of these achievements is a consecutive three-component synthesis of pyrazoles using (hetero)aroyl chlorides, terminal alkynes, and hydrazines to regioselectively access substituted heterocyclic structures [121,122]. As an example the combination with an electrophilic halogenation led to a one-pot four-component sequence of 4-halo pyrazoles **29** (Scheme 19) [123]. Further elaboration of the previously reported concept afforded the transformation of the in situ generated 4-halo pyrazole **29** in the presence of catalytic metal complexes in a Suzuki-coupling [123]. In the sense of an assisted tandem catalysis, the addition of catalytic amounts of triphenylphosphine to the reaction mixture for the retention of the correct oxidation state of the Pd source gave rise to the formation of 1,3,4,5-tetrasubstituted pyrazoles **30** in a four-step sequence comprising Sonogashira-coupling, addition-cyclocondensation, halogenation, and Suzuki-coupling in a one-pot fashion (Scheme 20, Table 10). All title compounds feature intense blue fluorescence and high quantum yields. The concatenation of Sonogashira and Suzuki coupling in a one-pot process, intercepted by cyclocondensation with hydrazines, was successfully applied to the efficient microwave-assisted consecutive four-component synthesis of 1-, 3-, and 5-biarylsubstituted pyrazoles **31**, **32**, and **33** (Scheme 21, Table 11) [124]. This robust protocol allows the introduction of bromo aryl substituents on all three substrates as points of diversification. In every case the one-pot sequence terminates with a Suzukiylation by adding (hetero)aryl boronates or boronic acids to the reaction mixture. This diversity-oriented approach enables tailoring, fine-tuning, and optimization of absorption and emission properties. By physical organic studies, including molecular modelling, high fluorescence quantum yields up to 97% (compound **33a**) were achieved. **Scheme 20. ** Sequentially Pd-Cu-catalyzed Sonogashira alkynylation-cyclocondensation-bromination-Suzuki aylation synthesis of 1,3,4,5-tetrasubstituted pyrazoles **30**. **Table 10.** Selected 1,3,4,5-tetrasubstituted pyrazoles **30** via sequentially Pd-Cu-catalyzed Sonogashira alkynylation-cyclocondensation-halogenation-Suzuki aylation synthesis. **Entry** **(Hetero)aroylchloride** **Alkyne** **Boronic Acid** **1,3,4,5-Tetrasubstituted Pyrazoles 30 (Yield)**