Gold-Catalyzed Transformation of 2-Alkynyl Arylazides: Efficient Access to the Valuable Pseudoindoxyl and Indolyl Frameworks

摘要

Gold catalysis has recently emerged as a "convenient tool for generating molecular complexity" and diversity. The majority of the synthetic chemistry that has been developed in this field is intimately linked to the π Lewis acidic property of electrophilic gold species. These catalysts have indeed proven to be particularly useful for the activation of π systems, such as alkynes or allenes, towards the addition of various nucleophiles. In addition to this acidic character, gold can also act as an electron donor thus stabilizing the intermediate cationic species and favoring reaction pathways that are not accessible with other Lewis acids. This jt acid/ electron donor dual reactivity is highlighted, for instance, in the gold(I)-catalyzed reaction of an alkyne with an azide [Scheme 1, Eq. (1)], where an a-imino gold carbene 1 can be generated by a sequence of nucleophlic azide addition followed by gold-assisted expulsion of N2.