Ruthenium-Catalyzed Cyclizations of Dienylalkynes Via Vinylidene Intermediates

Alkynolendo-Cycloisomerizations and Conceptually Related Transformations

“…The first examples of this reaction were reported by Merlic and Pauly, who showed that diene-yne substrates such as 21 undergo cycloisomerization to the aromatic product 22 under ruthenium catalysis. [15] We have found that activated methylenes 23 also participate in cyclizations with terminal alkynes to afford cyclopentenes 24, [16] and phenolic nucleophiles 25 undergo cycloisomerization to afford the benzopyran product 26.…”

Metal Vinylidenes as Catalytic Species in Organic Reactions

“…McDonald further demonstrated the utility of this transformation in a synthesis of digitoxin (82). [40] In this convergent approach, the trisaccharide moiety of the natural product was constructed by iterative cycloisomerizations, [41] and then connected to digitoxigenin (83) by glycosidation (Scheme 25).…”

“…In this reaction, dienylalkynes, such as 197, underwent conversion to benzene derivatives, such as 198 (Scheme 66). [82] The catalytic cycle for this transformation is depicted in Scheme 67. Following vinylidene formation (II), the key 6π electrocyclic ring closure leads to III.…”

Ruthenium‐Catalyzed Reactions—A Treasure Trove of Atom‐Economic Transformations

“…Formal total synthesis of insect pheromone 56 by a Ru-catalyzed oxidative cyclization reaction. [57] A ruthenium vinylidene species is also invoked as an intermediate in the cyclization of 1-alkyne-6-allyl silanes 70 to produce 1,4-dienes 71. Echavarren demonstrated that enyne 70 cyclized smoothly to diene 71 in the presence of the [CpRu(PPh 3 ) 2 Cl] precatalyst and NaPF 6 .…”