Four-Membered Ring Systems

Accessing the Rare Diazacyclobutene Motif

“…Efforts are underway currently to expand the substrate scope of this transformation by exploring new triazoline diones and electron-rich alkynes, to probe the mechanism of the transformation, and to explore the further synthetic manipulation and biological activity of this unique molecular scaffold. More broadly, this study contributes to the challenging research area devoted to the preparation of four-membered and other strained heterocycles. , …”

Intermolecular sp3-C–H Amination for the Synthesis of Saturated Azacycles

“…Cyclic amines also appear in designed molecules because of the unique and disparate physicochemical and topological properties of such heterocycles. , Accordingly, numerous methods, which rely on both conventional and modern C–N bond-forming tactics including C–H oxidation, enable access to pyrrolidine and piperidine derivatives. − We have been interested in developing a general protocol for assembling substituted azacycles of differing ring size, with a specific focus on azetidine structures. The value of such amines is considerable in synthesis, pharmacology, and medicine. − Herein, we present a method for the preparation of small ( n = 3–5) and medium ( n = 6–8) ring-sized azacycles that capitalizes on selective, intermolecular sp 3 -C–H amination of brominated hydrocarbon substrates (Scheme ). The efficient functionalization of substrates in which the desired site of C–H oxidation is proximal to an electron-withdrawing halogen group is unprecedented and underscores recent advances in Rh-catalyzed amination. − …”