Asymmetric Homogeneous Hydrogenation in Flow using a Tube‐in‐Tube Reactor

Abstract

In this update, the asymmetric homogeneous hydrogenation of a number of trisubstituted olefins utilizing the recently developed tube‐in‐tube gas‐liquid flow reactor is described. A number of chiral iridium‐ and rhodium‐based catalysts and other parameters such as pressure, solvent, temperature and catalyst loading were screened. The advantage of the flow set‐up for rapid screening and optimization of reaction parameters is illustrated. Furthermore, a comparative study using batch conditions aided in the optimization of the flow reaction set‐up. The set‐up was further modified to recycle the catalyst which prolonged catalytic activity.

The Use of Gases in Flow Synthesis

“…49 It was found that a set-up consisting of two 'tube in tube' reactors separated by a mixing chip, was optimal (Scheme 15). The second 'tube in tube' reactor replenishes the hydrogen needed to increase the diastereoselectivity of 92, with the mixing chip in between to ensure turbulent mixing of substrate and catalyst which was shown to improve conversion.…”

Asymmetric Hydrogenation of Olefins Using Chiral Crabtree-type Catalysts: Scope and Limitations

“…151 Hydrogen was added by a "tube-in-tube" diffusion system. By heating the flow to 50 °C for 80 min, the product could be obtained in 75% diastereomeric excess (Scheme 27).…”

Managing Hazardous Reactions and Compounds in Process Chemistry

“…Asymmetric hydrogenations can be performed in flow (233,252,(255)(256)(257), some using a self-supported chiral catalyst (258) where the catalyst immobilizes itself (259). A trickle bed reactor has also been used (260), as has supercritical CO 2 (261,262).…”