A visible light photocatalytic cross-dehydrogenative coupling/dehydrogenation/6π-cyclization/oxidation cascade: synthesis of 12-nitroindoloisoquinolines from 2-aryltetrahydroisoquinolines

Fabian Rusch; Lisa-Natascha Unkel; Dirk Alpers; Frank Hoffmann; Malte Brasholz

doi:10.1002/chem.201500612

A visible light photocatalytic cross-dehydrogenative coupling/dehydrogenation/6π-cyclization/oxidation cascade: synthesis of 12-nitroindoloisoquinolines from 2-aryltetrahydroisoquinolines

Chemistry. 2015 Jun 1;21(23):8336-40. doi: 10.1002/chem.201500612. Epub 2015 Apr 27.

Authors

Fabian Rusch¹, Lisa-Natascha Unkel¹, Dirk Alpers¹, Frank Hoffmann², Malte Brasholz³

Affiliations

¹ Department of Chemistry, Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany).
² Department of Chemistry, Institute of Inorganic Chemistry, University of Hamburg, 20146 Hamburg (Germany).
³ Department of Chemistry, Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany). [email protected].

PMID: 25917406
DOI: 10.1002/chem.201500612

Abstract

A visible light-induced photocatalytic dehydrogenation/6π-cyclization/oxidation cascade converts 1-(nitromethyl)-2-aryl-1,2,3,4-tetrahydroisoquinolines into novel 12-nitro-substituted tetracyclic indolo[2,1-a]isoquinoline derivatives. Various photocatalysts promote the reaction in the presence of air and a base, the most efficient being 1-aminoanthraquinone in combination with K3 PO4 . Further, the 12-nitroindoloisoquinoline products can be accessed directly from C1-unfunctionalized 2-aryl-1,2,3,4-tetrahydroisoquinolines by extending the one-pot protocol with a foregoing photocatalytic cross-dehydrogenative coupling reaction, resulting in a quadruple cascade transformation.

Keywords: cascade reactions; heterocycles; organocatalysis; photocatalysis.