Iridium-Catalyzed Formal [4 1] Cycloaddition of Biphenylenes with Alkenes Initiated by C–C Bond Cleavage for the Synthesis of 9,9-Disubstituted Fluorenes - Organic Letters (ACS Publications)

Iridium-Catalyzed Formal [4 1] Cycloaddition of Biphenylenes with Alkenes Initiated by C–C Bond Cleavage for the Synthesis of 9,9-Disubstituted Fluorenes - Organic Letters (ACS Publications)

Iridium-Catalyzed
Formal [4 + 1] Cycloaddition of Biphenylenes with Alkenes Initiated by
C–C Bond Cleavage for the Synthesis of 9,9-Disubstituted Fluorenes

Hideaki Takano^†, Kyalo Stephen Kanyiva^‡, and Takanori Shibata^*†§

^† Department
of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan

^‡ International
Center for Science and Engineering Programs (ICSEP), Waseda University, 3-4-1
Okubo, Shinjuku, Tokyo 169-8555, Japan

^§ JST, ACT-C, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan

Org. Lett., Article ASAP

DOI: 10.1021/acs.orglett.6b00619

Publication Date (Web): March 31, 2016

Copyright © 2016 American Chemical Society

*E-mail: tshibata@waseda.jp.

Abstract

An
Ir-catalyzed intermolecular reaction of biphenylenes as a C4 unit with
various alkenes as a C1 unit gave 9,9-disubstituted fluorenes in
moderate to high yields. Preliminary mechanistic studies revealed that
this formal [4 + 1] cycloaddition probably proceeds via C–C bond
cleavage, alkene insertion, β-hydrogen elimination, intramolecular
alkene insertion, and then reductive elimination. An example of
enantioselective reaction was also disclosed.