Diels–Alder reactions of nitrobenzofurans: a simple dibenzofuran Synthesis. Theoretical studies using DFT methods

Dearomatization of Nitro(hetero)arenes through Annulation

“…After that, the same group further extended dearomatization/rearomatization Diels‐Alder reaction between nitrobenzofurans and dienes, such as isoprene, 1‐trimethylsilyloxy‐1,3‐butadiene, 1‐methoxy‐3‐trimethylsilyloxy‐1,3‐butadiene (Danishefsky's diene) (Scheme 59). [82a] When nitrobenzofurans were reacted with isoprene at 200 °C for 72 h, mixtures of aromatic regioisomeric methyldibenzofurans and dihydrodibenzofurans were produced in reasonable yields. On the other hand, reactions of nitrobenzofurans with 1‐trimethylsilyloxy‐1,3‐butadiene yielded dibenzofuran with loss of trimethylsilyloxy and nitro groups.…”

A Base‐Mediated Approach Towards Dihydrofuro[2,3‐b]Benzofurans from 2‐Nitrobenzofurans and 1,3‐Dicarbonyls

“…In fact, 2‐nitrobenzofurans have been explored majorly in dearomative‐[3+2]‐cycloaddition reactions to access anuulated dihydrobenzofuran derivatives with interesting structural diversity [12] . Apart from cycloaddition reactions, 2‐nitrobenzofurans have also been utilized for the synthesis of dibenzofurans [13] and other 2,3‐substituted benzo[ b ]furan derivatives [14] . However, to the best of our knowledge, 2‐nitrobenzofurans have not been utilized yet for the synthesis of dihydrofuro[2,3‐ b ]benzofuran derivatives.…”

Synthesis of Dibenzofurans Derivatives via Benzannulation of 2‐Nitrobenzofurans and Alkylidene Malononitriles

“…Another complementary strategy is de novo formation of a benzene ring starting from benzofurans. To date, several benzofuran derivatives such as 2‐(tri‐ n ‐butylstannyl)benzofuran, 2, 3‐dibromobenzofuran, 2‐nitrobenzofuran, benzofuran‐3(2 H )‐one derived silyl enol ether, euparin and benzofuranyl enamines have been used to synthesize dibenzofurans. However, these synthetic methodologies suffer from narrow substrate scope, high reaction temperature, use of transition metals and/or lengthy synthesis of starting materials.…”

“…First, a variety of 2‐nitrobenzofurans can be readily prepared from the corresponding salicylaldehydes . Second, 2‐nitrobenzofurans have been used to synthesize benzofuran‐ or dihydrobenzofuran‐fused compounds. To our knowledge, there is only one example that four dibenzofuran derivatives are obtained by Diels‐Alder reactions of 2‐nitrobenzofuran with the substituted dienes at high reaction temperature (Scheme B, eq.…”