title: Free-radical-mediated [2 + 2 + 1] cycloaddition of acetylenes, amidines, and CO leading to five-membered α,β-unsaturated lactams.
abstract: A free-radical-mediated [2 + 2 + 1] cycloaddition reaction comprising acetylenes, amidines, and CO was achieved by radical chain reaction to give five-membered α,β-unsaturated lactams in good yields. Both acyclic and cyclic amidines reacted with a variety of terminal acetylenes to afford monocyclic, bicyclic, and tricyclic lactams. We propose that vinyl radical carbonylation and nucleophilic addition of the amidine onto the resulting α-ketenyl radical give stable intermediates that are ready to undergo five-membered ring closure with elimination of tin radical.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
authors.forename: Takahide
authors.initials: T
authors.lastname: Fukuyama
authors.forename: Nao
authors.initials: N
authors.lastname: Nakashima
authors.forename: Takuma
authors.initials: T
authors.lastname: Okada
authors.forename: Ilhyong
authors.initials: I
authors.lastname: Ryu
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D000578:Amidines / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry*; D003500:Cyclization; D007769:Lactams / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D000578:Amidines; D007769:Lactams; D002248:Carbon Monoxide