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CuI/I2-Mediated Synthesis of Iodoisoquinoline-Fused Benzimidazoles
H.-C. Ouyang, R.-Y. Tang, P. Zhong*, X.-G. Zhang, J.-H. Li*
Wenzhou University and Hunan Normal University, Changsha, P. R. of China
16 February 2011 (online)
The iodine-mediated, CuI-catalyzed synthesis of iodoisoquinoline-fused benzimidazoles from 2-ethynylbenzaldehydes and o-benzenediamines is reported. NIS, NBS and NCS were tested as well; NIS afforded lower yields compared to I2, NBS afforded the product (single case) in 48% yield, and NCS failed to perform as a reagent. The control experiment showed that two equivalents of CuI are sufficient for effecting the cyclization step (no incorporation of iodine). The substrate scope was quite well studied, yields range from poor to good, and one of the products (R¹ = H, R² = Ph, R³ = H) was used in Sonogashira, Heck, and Suzuki coupling reactions, demonstrating further versatility.