Diastereoselective Synthesis of an Industrially Relevant 4-Aminopentanoic Acid by Asymmetric Catalytic Hydrogenation in a Biphasic System Using Aqueous Sodium Hydroxide as Substrate Phase
Received: 17 October 2016
Accepted: 20 October 2016
22 November 2016 (online)
Dedicated to Prof. Dieter Enders on the occasion of his 70th birthday, in deep respect for his groundbreaking contributions to asymmetric catalysis.
A ’basic solution' for multiphase catalysis: The diastereoselective synthesis of a pharmaceutically relevant 4-aminopentanoic acid derivative has been studied using a chiral homogeneous catalyst in tailored biphasic reaction media. Different polar solvents were investigated as the stationary phase for the well-established Ru–Mandyphos catalyst in combination with aqueous NaOH as the substrate and product phase. Facile product isolation and effective recycling of the catalyst phase were demonstrated at gram-scale. In particular, up to 3200 turnovers have been achieved in seven repetitive batches with a diastereoselectivity of 87–96% using [EMIM][NTf2]/NaOHaq as the biphasic system.
Key wordsasymmetric hydrogenation - aqueous biphasic catalysis - ruthenium - Mandyphos - ionic liquid - catalyst immobilization
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