Flow chemistry syntheses of styrenes, unsymmetrical stilbenes and branched aldehydes

• Main Authors: Bourne, Samuel L., O'Brien, Matthew, Kasinathan, Sivarajan, Koos, Peter, Tolstoy, Päivi, Hu, Dennis X., Bates, Roderick Wayland, Martin, Benjamin, Schenkel, Berthold, Ley, Steven V.
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2014
• Subjects: Science::Chemistry::Physical chemistry::Catalysis; Science::Chemistry::Organic chemistry::Organic synthesis
• Online Access: https://hdl.handle.net/10356/101703; http://hdl.handle.net/10220/19779
• Institution: Nanyang Technological University

Two tandem flow chemistry processes have been developed. A single palladium-catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi-functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium-catalysed, hydroformylation of styrene derivatives with syngas affords branched aldehydes with good selectivity. Incorporation of an in-line aqueous wash and liquid–liquid separation allowed for the ethylene Heck reaction to be telescoped into the hydroformylation step such that a single flow synthesis of branched aldehydes directly from aryl iodides was achieved. The tube-in-tube semi-permeable membrane-based gas reactor and liquid–liquid separator both play an essential role in enabling these telescoped flow processes.