An unprecedented benzannulation of oxindoles with enalcarbenoids: a regioselective approach to functionalized carbazoles

Abstract

A novel Rh(ii)/Brønsted acid catalyzed tandem benzannulation of oxindoles with enaldiazo carbonyls led to the formation of valuable 1-hydroxy-2-acylcarbazoles. This reaction is proposed to involve a formal insertion of a rhodium enalcarbenoid into an oxindole sp(2) C-O bond, an oxa-Michael addition, Friedel-Crafts reaction and a semipinacol type 1,2-carbonyl migration.

Selective Synthesis of Six Products from a Single Indolyl α‐Diazocarbonyl Precursor

“…Next, the palladium(II)‐ and copper(II)‐catalyzed reactions were optimized, thus allowing selective formation of the C2‐annulated product 5 a and carbazole 6 a using Pd(MeCN) 4 (BF 4 ) 2 (5 mol %) and Cu(OTf) 2 (20 mol %), respectively (Scheme ) . A key difference between these reactions is that it is necessary to perform the carbazole‐forming reaction under oxygen at 50 °C.…”

Selective Synthesis of Six Products from a Single Indolyl α‐Diazocarbonyl Precursor

“…[14] Next, the palladium(II)-and copper(II)-catalyzed reactions were optimized, thus allowing selective formation of the C2-annulated product 5aand carbazole 6ausing Pd(MeCN) 4 -(BF 4 ) 2 (5 mol %) and Cu(OTf) 2 (20 mol %), respectively (Scheme 4). [18,19] Ak ey difference between these reactions is that it is necessary to perform the carbazole-forming reaction under oxygen at 50 8 8C. It is difficult to unambiguously determine whether these reactions proceed by direct nucleophilic attack from the indole C2 or by initial C3 attack followed by a1 ,2-migration.…”

Polynuclear ampyrone based 3d coordination clusters

“…These materials find applications in biological systems, 2,3 magnetism, [4][5][6][7][8][9] material science, 10-15 photochemistry 16,17 and as components in catalytic procedures. [18][19][20] The synthesis of such finite molecules is mainly based on serendipity, 21 however the employment of an organic ligand, that bears numerous coordination sites, facilitates their synthesis. Schiff base ligands are of particular interest due to their ease of synthesis and multiple coordination sites, thus have been extensively used for the synthesis of polynuclear CCs.…”