A facile approach to spirocyclic butenolides through cascade cyclization/oxidative cleavage reactions of (Z)-enynols catalyzed by gold under dioxygen atmosphere

Synthesis of Spirolactones via a BF3·Et2O-Promoted Cascade Annulation of α-Keto Acids and 1,3-Enynes

“…In general, the most common strategy for building spirolactones relies on Dieckmann condensation, Diels–Alder reactions, and ring-closing metathesis (RCM) . Furthermore, Liu developed a facile approach to spirocyclic butenolides through gold-catalyzed cascade cyclization/oxidative cleavage reactions of ( Z )-enynols with molecular oxygen (Scheme a) . The Patil group reported an intramolecular ipsoarylative cyclization of aryl alkynoates with ArN 2 BF 4 under merged Au/photoredox catalysis, providing an easy access to a variety of spirocarbocycles (Scheme b) .…”

Homogeneous Gold-Catalyzed Oxidation Reactions

“…Oxidative C–C double bond cleavage is also observed with alkene reaction intermediates formed during gold catalysis. Y. Liu reported a gold-catalyzed ( Z )-enynol cyclization/oxidative C–C bond cleavage cascade (Scheme A). , O 2 was used as the oxidant in that chemistry. It was proposed that dihydrofuran intermediate HI is initially formed upon gold-catalyzed cyclization, followed by oxidative C–C bond cleavage to deliver the butenolide product.…”

Synthesis of Highly Functionalized Spirobutenolides via a Nitroalkane-Mediated Ring Contraction of 2-Oxobenzo[h]chromenes through Denitration

“…N. Sucman et al prepared butenolide-functionalized spirooxindoles by the reaction of N-substituted isatin with dimethyl acetylenedicarboxylate in the presence of triphenylphosphine . A gold-catalyzed approach has been established for constructing spirobutenolides from ( Z )-enynols, having a cyclic substituent at the C-1 position . Hejmanowska et al developed a novel approach to construct spirobutanolides via a trienamine-mediated [4+2]-cycloaddition reaction of ( E )-3-alkylidene-5-arylfuran-2­(3 H )-ones and 2,4-dienals .…”

“…15 A gold-catalyzed approach has been established for constructing spirobutenolides from (Z)-enynols, having a cyclic substituent at the C-1 position. 16 Hejmanowska et al developed a novel approach to construct spirobutanolides via a trienamine-mediated [4+2]cycloaddition reaction of (E)-3-alkylidene-5-arylfuran-2(3H)ones and 2,4-dienals. 17 Langer and Albrecht have reported the synthesis of spirobutenolides through a ring closing metathesis of vinyl acrylates using Grubbs' generation I catalyst and catalytic amounts of Ti(O-i-Pr) 4 .…”