Synthesis ofo-(Dimethylamino)aryl Ketones, Acridones, Acridinium Salts, and 1H-Indazoles by the Reaction of Hydrazones and Arynes

Abstract

A novel, efficient route to biologically and pharmaceutically important o-(dimethylamino)aryl ketones, acridones, acridinium salts, and 1H-indazoles has been developed starting from readily available hydrazones of aldehydes and o-(trimethylsilyl)aryl triflates. The reaction proceeds through arynes under mild conditions, tolerates a wide range of functional groups, and provides the final products in good to excellent yields.

Intra- versus Intermolecular Carbon-to-Carbon Proton Transfers in the Reactions of Arynes with Nitrogen Nucleophiles: A DFT Study

“…Tremendous efforts have been devoted to the development of new synthetic methodologies utilizing arynes as reaction partners . Among them, the reactions of arynes with nitrogen nucleophiles, such as amines and imines, have been widely used in the synthesis of aniline derivatives and benzannulated N -heterocycles. − Mechanistically, these reactions usually start with the nucleophilic addition of a nitrogen nucleophile to aryne, generating an aryl anion intermediate (Scheme ). Then the intramolecular carbon-to-carbon proton transfers (PTs) may take place.…”

A Synthesis of 1H-Indazoles via a Cu(OAc)2-Catalyzed N–N Bond Formation

“…As shown in Scheme , these syntheses rely on the selective activation of the oxime in the presence of the amino group followed by an intramolecular displacement reaction to form the indazole ring. In this approach, the oximes were derived from o -aminoaryl ketones 4 , which, in turn, were prepared from o -aminobenzonitriles 1 and organometallic reagents through the hydrolysis of the ketimine intermediates 2 . , Taking into account atom and step economy, we envisioned that a direct N–N bond formation from the ketimine species 2 should be a viable and attractive approach to this important class of compounds. We further anticipated that such transformations could be facilitated via a metal-catalyzed N–N bond formation using oxygen as the terminal oxidant.…”

Transition-Metal-Free Synthesis of Benzo-Fused Five- and Six-Membered Heterocycles Employing Arynes

“…Moreover, SCHEME 60 Reaction of aryne with salicylaldehydes [84]. Furthermore, Dubrovskiy and Larock reported the reaction of arynes and hydrazones derived from aldehydes, resulting in the formation of o- (N,N-dimethylamino)aryl ketimines [91,92]. SCHEME 62 Synthesis of 9-functionalized xanthenes/acridines [85,86].…”

“…This reaction proceeds via S E Ar process and subsequent dehydration, furnished acridines in good yields. SCHEME 66 Synthesis of acridones by the reaction of 1,1-dialkylhydrazones with arynes [91,92]. The reaction can be considered as a formal [4 + 2] annulation reaction.…”