Synthesis, Characterization, and Polymerization of 4′-Acyl(oxy) Alkenyl Azlactone Monomers Designed Using a Steglich Rearrangement Approach

Monomers and polymers containing amine-reactive azlactone functionality are useful for the design of a broad range of soft materials. The vinyl monomer 2-vinyl-4,4-dimethylazlactone (VDMA), which can be readily polymerized to poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) using free radical methods, has been widely used for these purposes, but the synthesis of other alkenyl azlactone derivatives having other substituents in the 4-position presents several challenges. Here, we report the synthesis and characterization of novel 4'-acyl(oxy) alkenyl azlactones using approaches based on the Steglich rearrangement. We report both stepwise and one-pot Steglich rearrangement approaches to the synthesis of 2-isopropenyl-4-methyl-4'-acylazlactones from 2-isopropenyl-4-methylazlactone and acyl halides using DMAP and DMAP derivatives as nucleophilic acyl transfer catalysts. This approach enables the synthesis of disubstituted alkenyl azlactone derivatives having a variety of substituted alkyl and aryl ester and ketone groups in the 4-position. The resulting alkenyl azlactones react readily through ring-opening reactions with amine-based nucleophiles and can also be polymerized by AIBN-initiated free radical polymerization to yield new amine-reactive polymers. In addition, we demonstrate an approach to the synthesis of enantioenriched alkenyl azlactone monomers using an asymmetric DMAP derivative and a novel procedure for the <i>in situ</i> activation of carboxylic acids that eliminates the need for acyl halide-based starting materials during the Steglich rearrangement. Our results provide new and useful approaches to the design of alkenyl azlactone-based monomers and polymers with novel structures that would be difficult to synthesize using conventional methods.