Synthetic Approaches for the Construction of Five- and Six-Membered Silaazacycles

Abstract

Silaazacycles, containing both nitrogen and silicon atoms, are emerging as the appealing ring structures in the development of silicon-containing functional molecules. Development of general and efficient methods towards these motifs has therefore attracted considerable attentions of synthetic chemists. This short review intends to highlight the representative advances in the synthesis of five- and six-membered silaazacycles.

Yttrium‐Catalyzed Intermolecular Anti‐Markovnikov Hydroamination and Sequential Intermolecular Hydroamination/Endocyclization of Vinylsilanes

“…While hydroamination/cyclization of aminoalkenes usually results in exocyclic hydroamination products, [3a–d,4a,b] double hydroamination of divinyldimethylsilane with our catalyst prepared in benzene unexpectedly resulted in 6‐membered endo cyclization products, providing access to industrially relevant 1,4‐azasilinanes [25–27] . While the intermolecular anti‐Markovnikov hydroamination of vinylsilanes proceed with catalysts prepared in benzene and THF with similar activity, the endo cyclization does not proceed, even if only 2 equiv.…”

“…Hence, our method provides a simple catalytic alternative for traditional stochiometric procedures with primary amines. The resulting 1,4‐azasilinanes have recently attracted interest due to their potential applications, e. g. as insect repellants, [25] antibiotics, [26] among others [27] . Moreover, bioactive silicon compounds have demonstrated advantages, such as higher bioactivity, over their conventional carbon drug‐scaffolds, highlighting the importance for new synthetic methods [28]…”

Scalable Synthesis of Silacyclohexanones and Ready Access to Silicon Building Blocks

“…One of the contributing factors would be limited access to silicon-containing building blocks that could be further transformed to bioactive heterocycles. In this regard, there is a growing interest in developing efficient methods to access organosilane building blocks, especially silacycles . In line with our research group’s interest in the silicon switch approach, it was envisaged that a silicon-containing ketone would be useful for the synthesis of diverse silaheterocycles.…”

Controllable Si–C Bond Formation from Trihydrosilanes En Route to Synthesis of 1,4-Azasilinanes with Diverse Silyl Functionalities

“…1,4-Azasilinane, a heavier congener of piperidine, is a valuable silaazacycle widely used in silicon-containing drug discovery . Current methods to functionalize this molecule have focused on decorating the nitrogen, which ignores the potentially useful silyl functionality (Scheme a).…”