Copper-Catalyzed Electrophilic Enamidation Using Dioxazolones through Hydrozirconation of Alkynes.

A copper-catalyzed electrophilic enamidation starting from alkynes is reported. Hydrozirconation of an alkyne with the Schwartz reagent forms a vinyl zirconium intermediate, which directly undergoes a copper-catalyzed electrophilic enamidation with dioxazolones. High functional group tolerance of hydrozirconation enables the use of functionalized alkynes including esters. The developed conditions are successfully applied to syntheses of partial structures found in biologically active natural products.

Copper-Catalyzed Electrophilic Amidation of Organotrifluoroborates with Use of N-Methoxyamides.

A copper-catalyzed electrophilic amidation of aryltrifluoroborates with use of N-methoxyamides is reported. The reaction shows high functional group compatibility derived from two distinct features: 1) the high stability of the N-methoxyamides and 2) the nonbasic mild conditions in the presence of LiCl. The developed method can also be applied to the synthesis of enamides, which are widely distributed in natural products. Preliminary mechanistic studies suggest that the initial step is the transmetalation of the aryltrifluoroborate by the assistance of LiCl, and the resulting aryl copper intermediate provides the anilide through non-SN 2 oxidative addition to the N-methoxyamide and subsequent reductive elimination.