Benzo[1,4]diazocinone/Pyrrole Ensembles via the Catalyst‐Free Insertion of Pyrrolylacetylenic Ketones into Benzimidazoles

Abstract

Early unknown pharmaceutically oriented heterocyclic systems of benzo[1,4]diazocinone/pyrrole ensembles have been synthesized in up to 93 % yields by the catalyst‐free mild insertion of pyrrolylacetylenic ketones into benzimidazoles. The reaction represents an extraordinary easy expansion of the aromatic five‐membered heterocyclic ring up to pyrrole‐ringed, highly unsaturated eight‐membered heterocyclic system. The proposed mechanism of the reaction proceeding through dipole and ylide intermediates is confirmed by quantum chemical calculations (DFT).

Eco-friendly, in-water, and catalyst-free assembly of acylethenylpyrroloimidazoindoles from 3H-indoles and acylpyrrolylacetylenes

“…DFT analysis was already applied by us 24,25 to the initial step of the interaction between N-nucleophilic center and electrondeficient acetylenes. According to this approach, the interaction of 1a and 2a was initiated by the formation of Hbonded pre-reaction complex A (Scheme 3).…”

Catalyst-free nucleophilic substitution of hydrogen in quinoline rings by acylethynylpyrroles: stereoselective synthesis of 2-(E-2-acylethenylpyrrolyl)quinolines

“…Further A′ undergoes a rapid cascade transformation ( A′ → … → B → C → D ), initiated by the water molecule at the stage of proton transfer A → B (as previously considered). 23 This results in the formation of intermediate cycloadduct D . This step is preceded by the Z → E isomerization of the methylidene moiety via TS C-D with ΔΔ G ≠ = 14.3 kcal mol −1 (Fig.…”