Light-Induced Metal-Free Generation of Cyanocarbenes from Alkynyl Triazenes for the Synthesis of Nitrile Derivatives.

The chemistry of alkynyl triazenes is an emerging field for organic chemists and especially acid-induced nucleophilic functionalizations, either directly, or after a prior reaction towards aromatic triazenes under extrusion of nitrogen, paved the way for fruitful strategies. In contrast, the chemical behavior of alkynyl triazenes upon irradiation with light is still unknown. Herein we present the first photoactivation of alkynyl triazenes that triggers an uncommon reactivity pattern involving the cleavage of the N1-N2 bond of the triazene moiety resulting in a unique approach to cyanocarbenes from a readily available, stable, and insensitive precursor.

Gold-Catalyzed Dimerization of Diarylalkynes: Direct Access to Azulenes.

We have developed a simple gold-catalyzed procedure for the synthesis of substituted and modifiable azulenes. The azulenes are formed either by the dimerization of push-pull diarylalkynes bearing a fluorine atom in ortho or para position or by the dimerization of a symmetric electron-rich diarylalkyne. In the presence of a cationic gold catalyst, the two alkynes can form a highly reactive vinyl cation.