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Cooperative Catalysis of a Cationic Ruthenium Complex, Amine Base, and Na Salt: Catalytic Activation of Acetonitrile as a Nucleophile

Naoya Kumagai, Shigeki Matsunaga and Masakatsu Shibasaki*

*Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Email: mshibasamol.f.u-tokyo.ac.jp

N. Kumagai, S. Matsunaga, M. Shibasaki, J. Am. Chem. Soc., 2004, 126, 13632-13633.

DOI: 10.1021/ja0450509


Abstract

Cooperative catalysis of a cationic Ru complex, DBU, and NaPF6 enabled activation of acetonitrile as a nucleophile under mild basic conditions. The nucleophilic 1,2-addition of in situ-generated, Ru-bound, metalated nitrile to aldehydes and imines proceeded smoothly.

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Details

The document discusses a study on the catalytic activation of acetonitrile as a nucleophile using a cooperative catalytic system involving a cationic ruthenium complex, an amine base (DBU), and NaPF6. The research addresses the challenge of activating simple alkylnitriles, which have a high pKa, under mild conditions. The study found that using a soft Lewis acidic metal, specifically the cationic ruthenium complex CpRu(PPh3)(CH3CN)2PF6, in combination with DBU and NaPF6, effectively catalyzed the addition of acetonitrile to aldehydes and imines. The optimized conditions yielded high conversion rates and were applicable to various substrates, including those with electron-withdrawing or -donating groups. Mechanistic studies suggested that the ruthenium complex activates acetonitrile for deprotonation by DBU, and NaPF6 enhances the reaction by preventing the formation of inactive complexes. This catalytic system offers a milder alternative to previously reported methods, which required highly basic conditions. The study's findings contribute to the development of more efficient and selective catalytic processes in organic synthesis. Further research is ongoing to explore enantioselective variants and gain deeper mechanistic insights.


Key Words

β-Cyanohydrins, β-Aminonitriles


ID: J48-Y2004-1800