Rhodium(III)-Catalyzed Triple Aryl/Alkenyl C–H Bond Activation of Aryl Enaminones to Access Naphtho[1,8-<i>bc</i>]pyrans
Yunlong Li, Wenchao Jiang, Jie Lin, Juan Ma, Baohua Xu, Yong‐Gui Zhou, Zhengkun Yu
Abstract
Rhodium(III)-catalyzed triple C–H bond activation of aryl enaminones was achieved to access naphtho[1,8-bc]pyrans by oxidative annulation to internal alkynes. 1-Naphthols might be formed as the only products, depending on the steric and/or electronic environment around the aroyl moiety of the aryl enaminones or the electronic impact from the alkynes. With propargyl alcohols as the masked terminal alkynes, aryl enaminones underwent rhodium(III)- or rhodium(I)-catalyzed internal alkenyl C–H bond activation to afford functionalized but-2-ene-1,4-diones. The resultant naphtho[1,8-bc]pyrans are highly fluorescent and can be further transformed by chlorination, bromination, and difluoromethylation, demonstrating potential practicability of the synthetic protocol.