Synthesis 2007(18): 2913-2919  
DOI: 10.1055/s-2007-983798
PSP
© Georg Thieme Verlag Stuttgart · New York

Regioselective Bipyrrole Coupling of Pyrroles and 3-Substituted Pyrroles Using Phenyliodine(III) Bis(trifluoroacetate)

Toshifumi Dohi, Koji Morimoto, Motoki Ito, Yasuyuki Kita*
Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka, 565-0871, Japan
Fax: +81(6)68798229; e-Mail: kita@phs.osaka-u.ac.jp;
Further Information

Publication History

Received 27 February 2007
Publication Date:
12 July 2007 (online)

Abstract

A series of electron-rich bipyrroles were prepared by the regioselective, phenyliodine(III) bis(trifluoroacetate) (PIFA) induced oxidative coupling of pyrroles in the presence of bromotrimethylsilane. Using pyrrole and 3,4-disubstituted pyrroles gave exclusively 2,2′-linked bipyrroles without the formation of other bipyrrole regioisomers. The 3-alkyl- or 3-aryl-substituted pyrroles gave unsymmetrical H-T dimers in high yields as the major isolable α-linked bipyrrole products over the symmetrical H-H dimers. The nature of the N-substituent significantly influences the regioselectivity of the reaction, thus regiocontrolled bipyrrole coupling of N-phenyl- and N-benzyl-substituted pyrroles gave 2,3′-bipyrroles.