Murase Takashi, Suto Toru, Suzuki Honoka
Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata-shi, Yamagata, 990-8560, Japan.
Chem Asian J. 2017 Apr 4;12(7):726-729. doi: 10.1002/asia.201700096. Epub 2017 Mar 22.
Aromatic hydroxamic acids (Ar-CO-NOH-Ar') were used as bidentate chelating ligands to generate the corresponding boron hydroxamate complexes, which were subsequently transformed into nitrogen-containing helicenes (azahelicenes) using an oxidative photocyclization method that is frequently used for stilbene-type (Ar-CH=CH-Ar') precursors of carbohelicenes. The nitrogen atom of the hydroxamate linker was thus directly embedded into the helicene core without using nitrogen-containing aromatic rings in the stilbene-type precursors. In a batch photoreaction, aza[4]helicenes were readily and efficiently prepared, but aza[6]helicenes underwent severe decomposition upon irradiation. Alternatively, a continuous flow photoreactor was employed to furnish an amide-type aza[6]helicene.
芳香族异羟肟酸（Ar-CO-NOH-Ar'）被用作双齿螯合配体，以生成相应的异羟肟酸硼配合物，随后使用一种常用于碳螺旋烯的芪型（Ar-CH=CH-Ar'）前体的氧化光环化方法，将这些配合物转化为含氮螺旋烯（氮杂螺旋烯）。异羟肟酸连接基的氮原子因此直接嵌入到螺旋烯核心中，而无需在芪型前体中使用含氮芳香环。在间歇光反应中，可以轻松高效地制备氮杂[4]螺旋烯，但氮杂[6]螺旋烯在光照下会发生严重分解。另外，采用连续流光反应器来制备酰胺型氮杂[6]螺旋烯。
