Cyclohepta[ b]indole Synthesis through [5 + 2] Cycloaddition: Bifunctional Indium(III)-Catalyzed Stereoselective Construction of 7-Membered Ring Fused Indoles

Takuya Takeda; Shinji Harada; Akito Okabe; Atsushi Nishida

doi:10.1021/acs.joc.8b01407

Cyclohepta[ b]indole Synthesis through [5 + 2] Cycloaddition: Bifunctional Indium(III)-Catalyzed Stereoselective Construction of 7-Membered Ring Fused Indoles

J Org Chem. 2018 Oct 5;83(19):11541-11551. doi: 10.1021/acs.joc.8b01407. Epub 2018 Sep 11.

Authors

Takuya Takeda¹, Shinji Harada^{1

2}, Akito Okabe¹, Atsushi Nishida^{1

2}

Affiliations

¹ Graduate School of Pharmaceutical Sciences , Chiba University , 1-8-1 Inohana, Chuo-ku , 263-8522 Chiba , Japan.
² Molecular Chirality Research Center , Chiba University , 1-33 Yayoi-cho, Inage-ku , 263-8522 Chiba , Japan.

PMID: 30179462
DOI: 10.1021/acs.joc.8b01407

Abstract

A new approach for the synthesis of highly functionalized tetrahydrocyclohepta[ b]indoles through [5 + 2] cycloaddition was developed. Two carbon-carbon bonds were formed by the simple addition of an indium catalyst, which acted as both a π-Lewis acid and σ-Lewis acid to activate the alkyne and unsaturated ester, respectively. The reaction could be applied to various substrates and proceeded regio- and diastereoselectively in all cases.