Functionalized pyrroles are often found in natural products and pharmaceutically active compounds, and alkynes are rigid and have good electronic properties. Therefore, an alkyne attached to a pyrrole ring may offer opportunities to discover new compounds with important functions. In particular, pyrrole compounds with the alkyne group at the C3 ring position are of interest but tricky to synthesize. Although synthetic routes to C3-alkyne pyrroles are available, they often require multiple steps or pre-functionalization, or are unselective.
Feijie Song, Jingsong You, and colleagues, Sichuan University, Chengdu, China, have developed a versatile and efficient three-step cascade reaction that gives the desired compounds in moderate to good yields (typically 50 – 70 %). The cascade involves a gold-catalyzed C–H/C–H cross-coupling reaction, followed by cyclization to form the pyrrole, and finally installation of the alkyne group. A variety of readily available starting materials such as enamines and terminal alkynes can be used.
- Gold-catalyzed cascade C–H/C–H cross-coupling/cyclization/alkynylation: An efficient access to 3-alkynylpyrroles,
Shuai Zhang, Yuanhong Ma, Jingbo Lan, Feijie Song, Jingsong You,
Org. Biomol. Chem. 2015.