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RuPHOX-Ru-Catalyzed Asymmetric Chemoselective Hydrogenation of α-Methylene-γ/δ-carbonyl Carboxylic Acids
Jingli He1, Wenqi Xu1, Delong Liu1
1Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, Zhengzhou Industrial Technology Research Institute, School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
Abstract:
A highly efficient RuPHOX-Ru-catalyzed asymmetric chemoselective hydrogenation of the C═C bond in α-methylene-γ/δ-carbonyl carboxylic acids has been developed (46 examples), providing the desired chiral α-methyl-γ/δ-carbonyl carboxylic acids in high yields (up to 99%) with excellent enantioselectivities (almost ≥99% ee). The protocol can be performed on a gram scale with a low catalyst loading (up to 11 000 S/C) and demonstrates significant synthetic utility in the preparation of bioactive molecules, including the synthesis of anti-inflammatory and analgesic drug (S)-flobufen. Mechanistic studies revealed that H2 is the sole hydrogen source for the hydrogenation and the use of PPh3 as an additive is beneficial for the excellent enantioselectivity.
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