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 α-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 α-substituted-α-NHC-boryl
esters, and this has led to a family of NHC-boryl esters with amino
acid and amino-acid-like side chains.