One-Pot Approach to 1,2-Disubstituted Indoles via Cu(II)-Catalyzed Coupling/Cyclization under Aerobic Conditions and Its Application for the Synthesis of Polycyclic Indoles

Abstract

A straightforward assembly of 1,2-disubstituted indoles has been developed through a Cu(II)-catalyzed domino coupling/cyclization process. Under aerobic conditions, a wide range of 1,2-disubstituted indole derivatives were efficiently and facilely synthesized from 2-alkynylanilines and boronic acids. 2-(2-Bromoaryl)-1-aryl-1H-indoles, which were selectively generated in one pot under the Cu catalysis, afforded the indolo[1,2-f]phenanthridines via Pd-catalyzed intramolecular direct C(sp(2))-H arylation. The one-pot tandem approaches to the polycyclic indole derivatives were also successfully achieved.

Nonplanar Butterfly‐Shaped π‐Expanded Pyrrolopyrroles

“…[56] With aldehydes 3a-c in hand, we readily prepared as eries of tetraarylpyrrolopyrroles (TAPPs; 4a-c)i ny ields of 35 to 45 %b yapplying ap rocedure previously developed in our group. [52][53] The substrate designs afford TAPPs 4a-c with brominea toms in the ortho position with respect to the pyrrolopyrrole core, which allowed as mooth Pd-catalyzed intramolecular direct arylation [57] to give Chem. Eur.J.…”

A practical Cu(I)-catalyzed domino approach to 1,2-disubstituted indoles and its application for the assembly of indolophenanthridines

“…Furthermore, a one-pot approach to indolo[1,2-f]-phenanthridines from o-alkynylanilines and 1,2-dihaloarenes has not been achieved until now. As part of our ongoing research efforts toward the domino synthesis of heterocycles under copper catalysis, 27,[37][38][39][40] we became interested in applying the one-pot protocol to the assembly of 1,2-disubstituted indoles and the tandem synthesis of indolo[1,2-f]phenanthridines. The findings are reported herein.…”

“…4), indicating that the copper catalyst was indispensable for the domino reaction. Notably, we also synthesized the intermediate 5a 27 and then subjected it to the standard copper(I)-catalyzed conditions (Eq. 5).…”

“…26 Our group has developed a Cu(II)-catalyzed domino synthesis of 1,2-disubstituted indoles using coupling/cyclization of o-alkynylanilines with aryl boronic acids. 27 Compared with aryl boronic acids, aryl halides are relatively cheap and more easily accessible. So replacing the arylating reagents by aryl halides for the transformation may prove to be both practical and economic.…”

“…29,30 However, there are only a few reports of convenient syntheses of these useful polycyclic heteroarenes. [27][28][29][30][31][32] The previously reported methods may have the limitations such as the use of special materials (e.g. arynes, 2-arylindoles, N-(o-bromophenyl)indoles, or 2-(obromoaryl)-1-arylindoles), the requirements of harsh conditions (high temperatures) and/or the restricted scopes (Scheme 1).…”