Flow Ozonolysis Using a Semipermeable Teflon AF-2400 Membrane

ozonolysis - semipermeable membranes - Teflon AF-2400 - flow chemistry

Significance

<P>A simple and convenient flow chemistry device to bring about the ozonolysis of exomethylenes via gas-to-liquid transfer through semipermeable Teflon AF-2400 tubing was ­developed. Using a Teflon AF-2400 tubing (90 cm length) connected to a syringe pump (Infors AG, HT-Precidor), the flow ozonolysis of a series of ­exomethylenes was carried out in methanol with one hour of residence time to give the corresponding ketones (10 examples, 73-95% yield). A citronellol derivative (C10-OTBS) was converted into a C7-OTBS aldehyde under similar conditions in 57% yield.</P>

Comment

<P>Gas-liquid contact in a flow chemistry device usually involves the mechanical mixing of two phases. Here, more efficient, controllable, and reliable phase contact was realized using a semipermeable membrane that had high surface areas and selectively allowed O₃ to cross from outside to inside. Telfon AF-2400 consists of an amorphous copolymer of tetrafluoroethylene and a ­perfluorodimethyldioxolane.</P>