Poly(β-keto enol ether) Prepared by Three-ComponentPolycondensation of Bis(diazoketone), Bis(1,3-diketone), and Tetrahydrofuran:Mild Acid-Degradable Polymers To Afford Well-Defined Low MolecularWeight Components

Rh-catalyzed three-component polycondensation of bis(diazoketone), bis(1,3-diketone), and tetrahydrofuran (THF) yielded poly(β-keto enol ether) via a simultaneous insertion of a diazo-bearing carbon atom of bis(diazoketone) with N2 elimination and a ring-opened THF into OH of an enol form of a 1,3-diketone moiety of bis(1,3-diketone). The β-keto enol ether linkage of the polymer can be efficiently cleaved under mild acidic conditions to afford a combination of two types of well-defined low molecular weight components in high yield. The degradation can indeed proceed even with trace of acid in CDCl3 solution in an NMR tube, while the polymer structure remained intact in a DMSO-d6 solution, demonstrating the high sensitivity of the β-keto enol ether linkage to acidic conditions.