Diels–Alder reactions of five-membered heterocycles containing one heteroatom

Abstract

Diels-Alder reactions of five-membered heterocycles containing one heteroatom with an N-arylmaleimide were studied. Cycloaddition of 2,5-dimethylfuran (4) with 2-(4-methylphenyl)maleimide (3) in toluene at 60 °C gave bicyclic adduct 5. Cycloadditions of 3 with 2,5-dimethylthiophene (11) and 1,2,5-trimethylpyrrole (14) were also studied. Interestingly, the bicyclic compound 5 cleanly rearranged, with loss of water, when treated with p-toluenesulfonic acid in toluene at 80 °C to give 4,7-dimethyl-2-p-tolylisoindoline-1,3-dione (6).

Transition‐Metal‐Free Synthesis of Carbazoles and Indoles by an SNAr‐Based “Aromatic Metamorphosis” of Thiaarenes

“…[7] Studer and coworkers invented an interesting approach, that is,reactions of arynes with nitrosoarenes, [8] but the yields were moderate and the regioselectivity was not as well controlled as is typically observed in aryne chemistry.T okuyama and co-workers developed ab ase-mediated cyclization of 2-amino-2'-bromobiphenyls via arynes. [12][13][14] Along these lines,h erein we report transition-metal-free S N Ar-based aromatic metamorphosis of dibenzothiophenes to carbazoles via dibenzothiophene dioxides.Our strategy begins with smooth oxidation of dibenzothiophenes with aqueous hydrogen peroxide (see the Supporting Information;Scheme 1). [10] Kürti and co-workers disclosed facile reductive cyclization of 2-nitrobiaryls by means of PhMgBr.…”

“…[12][13][14] Along these lines,h erein we report transition-metal-free S N Ar-based aromatic metamorphosis of dibenzothiophenes to carbazoles via dibenzothiophene dioxides. [12][13][14] Along these lines,h erein we report transition-metal-free S N Ar-based aromatic metamorphosis of dibenzothiophenes to carbazoles via dibenzothiophene dioxides.…”

Transition‐Metal‐Free Synthesis of Carbazoles and Indoles by an SNAr‐Based “Aromatic Metamorphosis” of Thiaarenes

“…[11] Regardless of these elegant protocols,t here still remains ample room to develop novel strategies to prepare carbazoles without recourse to transition-metal catalysts.Recently,o ur group has been interested in developing "aromatic metamorphosis", which represents at ransformation of an aromatic system into adifferent one through partial disassembly of the starting aromatic ring. [12][13][14] Along these lines,h erein we report transition-metal-free S N Ar-based aromatic metamorphosis of dibenzothiophenes to carbazoles via dibenzothiophene dioxides.Our strategy begins with smooth oxidation of dibenzothiophenes with aqueous hydrogen peroxide (see the Supporting Information;Scheme 1). [15] This conventional process is useful as the first step for the aromatic metamorphosis.…”

“…Recently,o ur group has been interested in developing "aromatic metamorphosis", which represents at ransformation of an aromatic system into adifferent one through partial disassembly of the starting aromatic ring. [12][13][14] Along these lines,h erein we report transition-metal-free S N Ar-based aromatic metamorphosis of dibenzothiophenes to carbazoles via dibenzothiophene dioxides.…”

A Diels–Alder/Ene Cascade Leading to 5‐(Pyrrolidin‐3‐yl)thieno[3,2‐e]isoindoles from Ketone‐derived 2‐Vinylthiophenes and N‐Phenylmaleimide

“…Because of its high resonance energy, thiophene itself performs poorly as a Diels–Alder diene , requiring high temperature, pressure, and concentration and strong dienophiles to give good results. Thiophenes with pairs of fused polycyclic aromatic substituents, such as compound 4 (Fig.…”