The versatility of olefin metathesis is evident from its successful applications ranging from natural product synthesis to the valorization of renewable feedstocks. On the other side, flow chemistry has recently gained particular interest among the synthetic community, offering valuable alternatives to classic batch chemistry and paving the way to the development of new transformations. The application of continuous-flow methods to olefin metathesis represents one of the most promising evolutions in the field at the interface of industrially relevant synthesis and reactor engineering, significantly improving some of the typical problems such as undesired self-reactions and ethylene-mediated catalyst deactivation. This Minireview aims to provide a brief survey covering the major aspects of those techniques which we hope may be of interest for the chemical community as well as those interested in catalysis, continuous processing, enabling technologies and reactor design.

Angewandte Chemie International EditionVolume 61, Issue 47 e202284711 Graphical AbstractFree Access Graphical Abstract: Angew. Chem. Int. Ed. 47/2022 First published: 14 November 2022 https://doi.org/10.1002/anie.202284711AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume61, Issue47November 21, 2022e202284711 RelatedInformation

The firstcontinuous flow Z-selective olefin metathesis process is reported. Key torealizing this process was the adequate choice of stereoselective catalysts combinedwith the design of an appropriate continuous reactor setup. The designedcontinuous process permits various self-, cross- and macro-ring-closing-metathesis reactions, delivering products in high selectivity and shortresidence times. This technique is exemplified by direct application to thepreparation of a range of pheromones and macrocyclic odorant molecules andculminates in a telescoped Z-selective cross-metathesis/Dieckmann cyclisationsequence to access (Z)-Civetone, incorporating a serial array of continuallystirred tank reactors.

A manganese-catalyzed electrochemical deconstructive chlorination of cycloalkanols has been developed. This electrochemical method provides access to alkoxy radicals from alcohols and exhibits a broad substrate scope, with various cyclopropanols and cyclobutanols converted into synthetically useful β- and γ-chlorinated ketones (40 examples). Furthermore, the combination of recirculating flow electrochemistry and continuous inline purification was employed to access products on gram scale.

Continuous flow systems offer unique benefits in the generation and manipulation of sensitive reactive intermediates such as ketenes. To this end, the last decade has witnessed the development of continuous flow methods for the generation of ketenes by means of chemical, thermal, and photochemical activation modes. This perspective covers these advances and the downstream reactivity of ketenes in continuous flow technology.

The generation and use of acyl ketenes under continuous flow reaction conditions is reported. Several reaction classes of these reactive intermediates have been studied. Under zero headspace conditions, a ketone exchange process is possible between volatile ketones. The process can be readily scaled to deliver gram quantities of product.