A Boron Scan of Ethyl Acetoacetate Leads to Versatile Building Blocks

Discovered in the 19th century, ethyl acetoacetate has been central to the development of organic chemistry, including its pedagogy and applications. In this study, we present borylated derivatives of this venerable molecule. A boron handle has been installed at either α ${{\rm \alpha }}$ ‐ or β ${\beta }$ ‐position of acetoacetate by homologation of acyl‐MIDA (N‐methyliminodiacetic acid) boronates with diazoacetates. Either alkyl or boryl groups were found to migrate with regiochemistry being a function of the steric bulk of the diazo species. Boryl β ${{\rm \beta }}$ ‐ketoesters can be further modified into borylated pyrazolones and oximes, thereby expanding the synthetic toolkit and offering opportunities for additional modifications. Discovered in the 19th century, ethyl acetoacetate has been central to the development of organic chemistry. This study presents borylated derivatives of this venerable molecule. We show how the corresponding building blocks can be converted into borylated heterocycles. The regiochemistry of homologation of acyl‐MIDA (N‐methyliminodiacetic acid) boronates with diazoacetates was found to be related to the steric bulk of the diazo species.