A Scalable Membrane Pervaporation Approach for Continuous Flow Olefin Metathesis

Organic Process Research & Development 24(10), 2298-2303, DOI: 10.1021/acs.oprd.0c00061

The translation of olefin metathesis reactions from the laboratory to process scale has been challenging with traditional batch techniques. In this contribution, we describe a continuous membrane reactor design that selectively permeates the ethylene byproduct from metathetical processes, thereby overcoming the mass-transport limitations that have negatively influenced the efficiency of this transformation in batch vessels. The membrane sheet-in-frame pervaporation module yielded turnover numbers of >7500 in the case of diethyl diallylmalonate ring-closing metathesis. The preparation of more challenging, low-effective-molarity substrates, a cyclooctene and a 14-membered macrocyclic lactone, was also effective. A comparison of optimal membrane reactor conditions to a sealed tubular reactor revealed that the benefits of ethylene removal are most apparent at low reaction concentrations.