New Entry to the Synthesis of α‑Iminonitriles by Lewis Acid Mediated Isomerization of Cyano-Substituted Iminoisobenzofurans Prepared by Palladium-Catalyzed Three-Component Coupling of Arynes, Isocyanides, and Cyanoformates

A variety
of α-iminonitriles were formed as the minor products
of three-component coupling reactions of arynes, isocyanides, and
cyanoformates in the presence of the cationic palladium complex [Pd­(NCPh)2(dppf)]­(BF4)2 as the catalyst, along
with cyano-substituted iminoisobenzofurans as the major products.
α-Iminonitriles obtained from this process are hardly accessible
by conventional methods. In addition, when the isolated iminoisobenzofurans
were treated with diisobutylaluminum hydride (DIBAL-H) or AlMe3, the transformation of cyano-substituted iminoisobenzofurans
into α-iminonitriles was observed.