Synthesis of spiropyridazine-benzosultams by the [4 + 2] annulation reaction of 3-substituted benzoisothiazole 1,1-dioxides with 1,2-diaza-1,3-dienes

• Wenqing Hao,
• Long Wang,
• Jinlei Zhang,
• Dawei Teng and
• Guorui Cao

Beilstein J. Org. Chem. 2024, 20, 280–286, doi:10.3762/bjoc.20.29

• developed by means of [4 + 2] annulation reaction of 3-substituted benzoisothiazole 1,1-dioxides with 1,2-diaza-1,3-dienes. This approach displays advantages such as mild reaction conditions, wide substrate range tolerance, simple operation, compatibility with gram-scale preparation. Keywords: [4 + 2

• ] annulation reaction; 1,2-diaza-1,3-dienes; spiro-benzosultams; 3-substituted benzoisothiazole 1,1-dioxides; Introduction Spirobenzosultams have various biological activities [1][2][3] such as antiviral, anticancer, antimicrobial, antimalarial, and antileukemia, and are widely used in the pharmaceutical

• detected and a similar result was observed as for the R3 group (Scheme 2, 3ah,ai vs 3aj,ak,al). To further expand the substrate scope, we next tested other 3-substituted benzoisothiazole 1,1-dioxides 1a–c. As seen from Scheme 2, dienophiles with a bulky and branched isopropyl group (1b) could also be