Poly(β-keto enol ether) Prepared by Three-Component Polycondensation of Bis(diazoketone), Bis(1,3-diketone), and Tetrahydrofuran: Mild Acid-Degradable Polymers To Afford Well-Defined Low Molecular Weight 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.