Benzimidazol‐Derivate und verwandte Heterocyclen V. Die Kondensation von o‐Phenylendiamin mit aliphatischen und alicyclischen β‐Ketoestern

Abstract

The products of the condensation of o‐phenylenediamine with ethyl acetoacetate were re‐investigated. Depending on the reaction conditions, 2‐methylbenzimidazole (II), 2‐isopropenyl‐benzimidazole‐2‐one (VI) and 4,7‐dihydro‐5‐methyl‐1H‐2,3‐benzo‐1,4‐diazepin‐7‐one (IV) were obtained. 2‐Acetonylbenzimidazole, which had erroneously been described in the literature, could not be isolated from the above mentioned reaction; it was prepared by condensing o‐phenylenediamine with the ketal of ethyl acetoacetate followed by hydrolysis of the ketal group. The investigation was extended to the reaction of o‐phenylenediamine with 2‐carbethoxycyclohexanone and 2‐carbethoxycyclopentanone as well as with N‐substituted 3‐carbethoxy‐4‐piperidones.

Etazene (N,N-diethyl-2-{[(4-ethoxyphenyl)methyl]-1H-benzimidazol-1-yl}-ethan-1-amine (dihydrochloride)): a novel benzimidazole opioid NPS identified in seized material: crystal structure and spectroscopic characterization

“…The first papers on the synthesis and properties of benzimidazole opioids (Fig. 1) were published in 1957 and 1960 [16][17][18][19][20][21][22][23]. Already then it was signaled that these compounds could be used as painkillers.…”

Microwave‐Assisted Domino Benzannulation of α‐Oxo Ketenes: Preparation of 1,3‐Dihydro‐2H‐1,5‐benzodiazepin‐2‐ones

“…Compound 9d: 11c,11f A solution of 2‐diazocycloheptane‐1,3‐dione ( 1d ; 102 mg, 0.67 mmol) and o ‐phenylenediamine ( 8a ; 77 mg, 0.71 mmol) in anhydrous toluene (2 mL) was subjected to microwave irradiation at 130 °C for 2 min (ramp up time: 2 min), after which the reaction mixture was cooled to 50 °C with an air flow. After removal of the volatiles under vacuum, the resulting crude product was directly purified by flash chromatography eluting with EtOAc/petroleum ether to afford compound 9d (88 mg, 62 %) as a pale‐yellow solid.…”

N-Paranitrophénylhydrazono-α-(2-méthylbenzimidazol-1-yl)glyoxylate d'éthyle

“…L′évolution de la réaction a été suivie par la chromatographie sous couche mince (CCM). La formation du composé 2 s'explique vraisemblablement par un réarrangement sigmatropique-1,3 du cycle à sept éléments (Rossi et al, 1960), suivie de la perte du styrène aboutissant à un intermédiaire très instable qui se transpose à son tour pour conduire au produit réarrangé 2.…”