title: Synthesis of Carbazoles and Carbazole-Containing Heterocycles via Rhodium-Catalyzed Tandem Carbonylative Benzannulations.
abstract: Polycyclic aromatic compounds are important constituents of pharmaceuticals and other materials. We have developed a series of Rh-catalyzed tandem carbonylative benzannulations for the synthesis of tri-, tetra-, and pentacyclic heterocycles from different types of aryl propargylic alcohols. These tandem reactions provide efficient access to highly substituted carbazoles, furocarbazoles, pyrrolocarbazoles, thiophenocarbazoles, and indolocarbazoles. While tricyclic heterocycles could be derived from vinyl aryl propargylic alcohols, tetra- and pentacyclic heterocycles were synthesized from diaryl propargylic alcohols. The tandem carbonylative benzannulation is initiated by a π-acidic rhodium(I) catalyst-mediated nucleophilic addition to alkyne to generate a key metal-carbene intermediate, which is then trapped by carbon monoxide to form a ketene species for 6π electrocyclization. Overall, three bonds and two rings are formed in all of these tandem carbonylative benzannulation reactions.
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Wangze
authors.initials: W
authors.lastname: Song
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Xiaoxun
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Ka
authors.initials: K
authors.lastname: Yang
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Xian-liang
authors.initials: XL
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Glazier
authors.affiliation: Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University , Guangzhou, Guangdong Province 510515, P.R. China.
authors.forename: Bao-min
authors.initials: BM
authors.lastname: Xi
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.|Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Weiping
authors.initials: W
authors.lastname: Tang