Electroreductive Borylation of Chloroalkanes and Polyvinyl Chloride Plastics
Immaculata O. Onuigbo, Jordan L. S. Zackasee, Valmuri Srivardhan, Jennifer Alina Spejcher, Christo S. Sevov
Abstract
Covalent modification of poly(vinyl chloride) (PVC) with additives that are typically mixed into PVC plastics would eliminate migration and leaching of these essential plasticizers and stabilizers. This report details an electroreductive methodology for the borylation of PVC, as well as of simple chloroalkanes, using inexpensive boron sources. Mechanistic studies implicate C–B bond formation from the reaction of a boron electrophile and an organomagnesium intermediate. While conventional Grignard formation from employing Mg 0 metals failed, Grignard intermediates were rapidly generated from chloroalkanes and highly reactive Mg deposits generated at the cathode during electrolysis. Translation of this methodology from small- to macromolecular chloroalkanes, like PVC, required the addition of surfactants that disrupt the micellar conformation of PVC in THF. This approach exposes the C–Cl bonds for activation at the cathodic surface. These operationally simple conditions enabled borylation of PVC on a multigram scale without chain scission. Finally, the borylated PVCs were further elaborated into PVCs with various functional groups using robust synthetic methods to create materials with distinct bulk properties, including improved thermal stability and increased plasticity.