From Ketoesters, Diynes, and Arynes to Functionalized Pyranones, Naphthalenes, and Anthracenes

This study aimed to create new possibilities in the syntheses of aryl-arylethynyl-naphthalene and anthracene derivatives. Starting from simple structures, i.e., ß-ketoesters, 1,4-di(aryl, heteroaryl)buta-1,3-diynes, and arynes, via 5-aryl-4-(arylethynyl)pyran-2-ones, the target structures were successfully obtained by a simple procedure (in a one-pot or a two-step version). On the way to the final structures, an innovative and very effective synthetic method for obtaining aryl-arylethynyl-pyran-2-ones was developed. This unprecedented procedure turned out to be fully regioselective, namely only 5-aryl-4-(arylethynyl)-3,6-dimethylpyran-2-ones were obtained in the reaction involving ethyl 2-methyl-3-oxobutanoate and 1,4-diarylbuta-1,3-diyne mediated by a Re-catalyst. It seems that steric effects associated with the Re─C and C─C bond lengths play a decisive role with regard to the regioselectivity. Importantly, the aforementioned procedure is very simple, which makes it completely different from the only previously described procedure dedicated to structurally similar pyranones. Undoubtedly, such substituted 2-pyranones, naphthalenes, and anthracenes are practically unavailable via any other way, especially via such a simple and convenient synthetic route. All the newly obtained aryl-arylethynyl-pyran-2-ones and aryl-arylethynyl-arenes were fully characterized, including DFT calculations and thermal, optical, and electrochemical properties. The presence of a triple bond in the obtained compounds definitely changes their properties, especially in comparison to structures without a triple bond.