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

• ketimine and its subsequent [4 + 2] annulation reaction with 1,2-diaza-1,3-diene in the presence of Et3N (2.0 equiv) in diethyl ether at room temperature (Table 1, entry 1). However, no product was detected under these conditions. We then replaced diethyl ether with toluene, which resulted in the desired

• spiropyridazine-benzosultam 3aa with 10% yield and high diastereoselectivity (Table 1, entry 2). Encouraged by this result, we tested several solvents to determine their effect on the [4 + 2] annulation reaction. Acetonitrile showed the best result, providing the highest yield (Table 1, entries 3–7). We also

Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides

• Shuai Qiu,
• Choon-Hong Tan and
• Zhiyong Jiang

Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222

• , herein, we report an asymmetric [4 + 2] annulation reaction of 5H-thiazol-4-ones with N-itaconimides. The method features excellent chemo-, enantio, and diastereoselectivities, thus leading to a series of chiral spirocyclic 1,4-sulfur-bridged piperidinone-based succinimides with excellent results

• , followed by gradient elution with DCM/MeOH mixture (500:1−200:1 ratio). Removing the solvent in vacuo, afforded product 3a. Substrate scope of the [4 + 2] annulation. Reaction conditions: 1 (0.1 mmol), 2 (0.15 mmol), V (0.01 mmol), CHCl3 (1.0 mL) at −10 °C. All drs are >20:1; ees were determined via chiral