Applying a continuous capillary-based process to the synthesis of 3-chloro-2-hydroxypropyl pivaloate
作者:Marc Escribà、Volker Hessel、Sonja Rothstock、Jordi Eras、Ramon Canela、Patrick Löb
DOI:10.1039/c0gc00655f
日期:——
Nowadays, continuous chemical processes (‘flow chemistry’) using micro process technology are becoming highly competitive, both for cost (better selectivity, higher productivity) and sustainability (low environmental impact) reasons. The first needs true process intensification and the second, among others, new eco-efficient starting and product materials. In this context, a new application for glycerol is reported with increasing industrial interest and tested here under highly intensified conditions. Starting from prior batch processing experience, it is reported about the transfer to a continuous process to transform dichloropropyl pivaloate, prepared from glycerol, into 3-chloro-2-hydroxypropyl ester. The continuous microreactor based process has up to three orders-of-magnitude reduced reaction times (5760×) by virtue of exploiting unusual experimental conditions in organic chemistry (Novel Process Windows), i.e. superheated pressurised processing much above the boiling point. The yields are fully comparable with the ones obtained under batch conditions, but with (expected) loss in selectivity through enhanced diproduct formation. This principally enables the new continuous process to target much higher productivities; however this also results in a more complex reaction mixture therefore the ease of separation and commercial value of the second product will decide its exploitation. Beyond such benefits for the individual reaction under investigation, this is among the very first reports about a superheated reaction with a distinct selectivity issue with two known byproduct pathways, and thus provides the first respective generic information after an upheavalled reporting on capillary- or microreactor-based superheated processing, so far mostly done for less complex reactions.
如今,出于成本(更好的选择性、更高的生产率)和可持续性(低环境影响)的原因,使用微加工技术的连续化学工艺(“流动化学”)正变得极具竞争力。第一个需要真正的工艺强化,第二个需要新的生态高效的起始材料和产品材料。在此背景下,甘油的一种新应用被报道,引起了越来越多的工业兴趣,并在高强度条件下进行了测试。据报道,从以前的间歇加工经验开始,将由甘油制备的新戊酸二氯丙酯转化为3-氯-2-羟丙酯,转而采用连续工艺。通过利用有机化学中不寻常的实验条件(新颖的工艺窗口),即远高于沸点的过热加压处理,基于连续微反应器的工艺可将反应时间缩短三个数量级(5760×)。产率与在间歇条件下获得的产率完全可比,但由于二产物形成的增强而导致选择性(预期)损失。这主要使新的连续工艺能够实现更高的生产率;然而,这也会导致更复杂的反应混合物,因此第二种产品的分离容易程度和商业价值将决定其利用。除了对所研究的单个反应的这些好处之外,这是关于具有两种已知副产物途径的明显选择性问题的过热反应的最早的报告之一,因此在毛细管或微反应器的剧烈报告之后提供了第一个相应的通用信息。基于过热的处理,到目前为止主要用于不太复杂的反应。