title: Dissecting alkynes: full cleavage of polarized C≡C moiety via sequential bis-Michael addition/retro-Mannich cascade.
abstract: The reaction of diaryl ketoalkynes with 1,2-diamino ethane leads to the full scission of the triple bond with the formation of acetophenone and imidazoline fragments. In this transformation, one of the alkyne carbons undergoes formal reduction with the formation of three C-H bonds, whereas the other carbon undergoes formal oxidation via the formation of three C-N bonds (one π and two σ). Computational analysis confirmed that the key fragmentation step proceeds via a six-membered TS in a concerted manner. Both amines are involved in the fragmentation: the N-H moiety of one amine transfers a proton to the developing negative charge at the enolate oxygen, while the other amine provides direct stereoelectronic assistance to the C-C bond cleavage via a hyperconjugative n(N) → σ*(C-C) interaction.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA.
authors.forename: Saumya
authors.initials: S
authors.lastname: Roy
authors.forename: Maria P
authors.initials: MP
authors.lastname: Davydova
authors.forename: Runa
authors.initials: R
authors.lastname: Pal
authors.forename: Kerry
authors.initials: K
authors.lastname: Gilmore
authors.forename: Genrikh A
authors.initials: GA
authors.lastname: Tolstikov
authors.forename: Sergei F
authors.initials: SF
authors.lastname: Vasilevsky
authors.forename: Igor V
authors.initials: IV
authors.lastname: Alabugin