Cp*Co(III)-Catalyzed Dearomative [3 + 2] Spiroannulation of 2‑Alkenylphenols with Ynamides via C–H Activation

An
oxidative [3 + 2] C–H spiroannulation reaction of 2-alkenylphenols
with ynamides has been developed toward the synthesis of spiro­[4,5]­decane
derivatives. This dearomative reaction employs earth-abundant cobalt
as the metal catalyst and occurs under rather mild reaction conditions
(room temperature). The use of ynamides confers unique reactivity
and exclusive regioselectivity. The products bearing an all-carbon
quaternary stereogenic center were constructed in generally good yields
with good functional group tolerance being observed. Experimental
mechanistic studies were conducted, and a possible reaction mechanism
is proposed.