title: Tandem insertion-cyclization reaction of isocyanides in the synthesis of 1,4-diaryl-1H-imidazoles: presence of N-arylformimidate intermediate.
abstract: A straightforward and high-yielding synthesis of 1,4-diaryl-1H-imidazoles is reported. 1,4-Diaryl-1H-imidazoles have been difficult to access in ambient conditions, but our method utilizes two different facets of isocyanide reactivity to achieve it. The reaction is believed to involve (1) NHC-copper-catalyzed isocyanide insertion into alcohol to form an N-arylformimidate intermediate and (2) subsequent base-promoted cycloaddition with benzyl isocyanide derivatives. There is cooperation between these two processes through the deprotonation of benzyl isocyanide by KOtBu. The deprotonation gives tert-butyl alcohol and the benzyl isocyanide anion, which are used for the first and second steps of the reaction, respectively. Various control and kinetic experiments were carried out to gain an in-depth understanding of the reaction mechanism and isocyanide reactivity. The reaction mechanism determined by density functional theory calculations was consistent with the experimental data and provided detailed explanations for the reactivity trends.
authors.affiliation: Department of Chemistry, College of Natural Sciences, Seoul National University , Seoul 151-747, Republic of Korea.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pooi
authors.forename: Jeongbin
authors.initials: J
authors.lastname: Lee
authors.forename: Kyujin
authors.initials: K
authors.lastname: Choi
authors.forename: Hajime
authors.initials: H
authors.lastname: Hirao
authors.forename: Soon Hyeok
authors.initials: SH
authors.lastname: Hong