A Palladium Wall Coated Microcapillary Reactor for Use in Continuous Flow Transfer Hydrogenations

This was an old posting on PHARMNBIOFUEL.COM dated 2010-08-08.

I decided to collect some new articles for the blog and I came across this journal by accident.  Advanced Synthesis and Catalysis.  I can’t say I read all of the journals, just the typical ones of interest, JACS, Angewandte Chemie, OPRD.   I really like this one, though.  I found some really excellent articles in it, one which I will share with you now.  I have had an interest, amongst many, mind you, in microreactors.  I have never used a microreactor, per se, it certainly is a burgeoning area of research.  The article that I found is “A Palladium Wall Coated Microcapillary Reactor for Use in Continuous Flow Transfer Hydrogenation” by Steven Ley et al, Adv. Synth. Catal., 2010, 352, p. 1736-45.  The disc-shaped microreactors are made through an extrusion process, in which microcapillaries are encased in the disc.  The polymer that is extruded is an ethylene-polyvinyl alcohol, which provides free hydroxyl groups that be functionalized after extrusion.  The paper goes into some detail to discuss how the free OH groups in the polyvinyl alcohol polymer are functionalized with Pd (0) and furthermore, what effect this has on the polymeric characteristics of the final microreactor disc.  Although the new microreactor is characterized using many different techniques, what I think is the most important part of the article is how it performs.  There are several key points to hit upon, which are that the reactor discs can be used over and over without reduced activity.  The discs are stable to water and alcohols and have a general chemical stability to many organic solvents including dichloromethane and tetrahydrofuran.  An HPLC pump is used to push the substrate in solution through the microreactor with tetraethylsilane as the hydrogen donor.  Several examples of substrates are reduced to show the utility of the technique.  I think it is fascinating that this can be done at room temperature.  The reaction time was 30 minutes at a flow rate of 0.1 mL/min.  The yields were determined by NMR.

 

Here are but a few:

 

This is a list of hydrogenation reactions performed using a disc microcapiliiary reactor.

This is a list of hydrogenation reactions performed using a disc microcapiliiary reactor.

 

 

 

 

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