- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
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Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
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supporting information
p. 18251 - 18265
(2020/11/02)
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- A practical total synthesis of plaunotol via highly Z-selective Wittig olefination of α-acetal ketones
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Plaunotol (1), a known antiulcer drug, is the most important component of the Thai folk medicinal plant, Plau-noi, which has remarkable antipeptic ulcer activity. Recently, it was found that plaunotol (1) has antibacterial activity against Helicobacter priori, a causative agent in gastric ulcers and gastric adenocarcinoma, for example. In our investigation of the practical synthesis of 1, we have developed an efficient method for stereoselective synthesis of trisubstituted olefins via a Z-selective Wittig reaction. The olefination of readily available aliphatic α-acetal ketones with triphenylphosphonium salts in the presence of a potassium base and 18-crown-6 ether proceeded with excellent Z-selectivity. The Z-selective olefination provides a useful method for the construction of a range of trisubstituted olefin moieties; the practical and stereoselective total synthesis of plaunotol (1) was achieved via this Wittig reaction.
- Tago, Keiko,Arai, Masami,Kogen, Hiroshi
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p. 2073 - 2078
(2007/10/03)
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