(610g) Scalable on-Demand Production of Tetrafluoroethylene for Fluoroalkylations in Continuous Flow

A two-staged continuous flow reactor was developed for the on-demand production and consumption of tetrafluoroethylene (TFE). Development of this reactor was motivated by the need for a convenient reactor to perform fluoroalkylations using TFE on intermediate-scales (1 mol/hr TFE) and enable access to bulk material. The efficiency of this reactor was demonstrated by performing the dimerization of difluorocarbene from (trifluoromethyl)trimethylsilane (TMSCF3) to form gaseous TFE (stage 1), which is subsequently reacts with 1,3-butadiene in a gas-phase, 2+2 thermal cycloaddition (stage 2) to produce 1,1,2,2-Tetrafluoro-3-vinylcyclobutane in ~60% yield by 19F-NMR. Key features of this development include (1) use of a multistage plug-flow reactor (PFR) to enable access to high temperature (120-140ºC) and high pressure (>250 psi) operation conditions to reduce the reaction time of the 2+2 thermal cycloaddition from 8 hrs to 2 hrs, (2) switching to a high-boiling solvent (diglyme) from tetrahydrofuran and acetonitrile to improve isolation and purification of the cycloalkylation product, (3) continuous distillation of the final product using a wiped film evaporator, and (4) incorporation of automation and safety controls to eliminate human exposure to carcinogenic chemicals, such as TFE. These features enabled the optimization and characterization of a simple fluoroalkylation reactor applicable for multikilogram-scale production of the desired product.