title: Platinum-catalyzed dehydroalkoxylation-cyclization cascade via N-O bond cleavage.
abstract: ortho-Alkynylphenylureas and -acetamides 1, with an alkoxy and aryl group on the nitrogen atom, were subjected to platinum-catalyzed cyclization reactions to afford the corresponding tetracyclic compounds 2, via N-O bond cleavage, in good to excellent yields. For example, N-methoxy-N'-methyl-N'-(2-(pent-1-ynyl)phenyl)-N-phenylurea (1a) was reacted for 12 h in the presence of PtI(4) (10 mol%) in 1,4-dioxane at 100 degrees C to afford 5-methyl-12-propylindolo[1,2-c]quinazolin-6(5H)-one (2a) in 93% yield, via an iminium-bound platinum carbenoid intermediate, followed by an aromatic C-H insertion.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan. itaru-n@mail.tains.tohoku.ac.jp
authors.forename: Itaru
authors.initials: I
authors.lastname: Nakamura
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sato
authors.forename: Masahiro
authors.initials: M
authors.lastname: Terada