N-Heterocyclic Carbene Boryl Iodides Catalyze Insertion Reactions of N-Heterocyclic Carbene Boranes and Diazoesters

Boron-hydrogen bond insertion reactions of N-heterocyclic carbene (NHC) boranes and diazoesters can be catalyzed by NHC-boryl iodides and produce stable alpha-NHC-boryl esters. The conditions of the reaction resemble the previous rhodium-catalyzed transformations (only the catalyst is different); however, the mechanisms of the two reactions are probably very different. The new boryl iodide catalyzed method is adept at producing alpha-substituted-alpha-NHC-boryl esters, and this has led to a family of NHC-boryl esters with amino acid and amino-acid-like side chains.