Cobalt salt-catalyzed carbocyclization reactions of α-bromo-N-phenylacetamide derivatives

Abstract

An efficient and low-cost method for the synthesis of 4-substituted quinolin-2-(1H)-ones has been developed. In the presence of TBHP, the cobalt(ii)-catalyzed carbocyclization reactions of arylethenyl substituted α-bromo-N-phenylacetamides, involving sequential 6-exo-trig radical cyclization, t-butylperoxy radical cross-coupling reaction and the base-promoted ionic Kornblum-DeLaMare reaction, produced 4-benzoylquinolin-2-(1H)-ones. A variety of useful functional groups such as methoxy, fluoro, chloro, bromo, methoxycarbonyl, and cyano groups, are compatible with the reaction conditions. This strategy was further applied to arylethynyl substituted α-bromo-N-phenylacetamides, and 4-benzylquinolin-2-(1H)-ones were formed effectively.

Developments in the Chemistry of α‐Carbonyl Alkyl Bromides

“…Carbocyclization reactions of arylethenyl-substituted abromo-N-phenylacetamides was reported by the group of Chuang in 2017 for the synthesis of 4-benzoylquinolin-2(1 H)-ones (Scheme 26). [26] In the work of Chuang and co-workers,C o(acac) 2 wasu sed as the catalyst for the sequential 6-exo-trig radical cyclization, tertbutylperoxyr adical cross-coupling reaction, and the base-promoted ionic Kornblum-DeLaMare reaction. Av ariety of useful functional groups such as MeO, F, Cl, Br,a nd CN groups, are compatible with the reaction conditions.…”

4-Aminoalkyl Quinolin-2-one Derivatives via Knorr Cyclisation of ω-Amino-β-Keto Anilides

“…In addition to this classical method, the scope of which is limited in the presence of acid-sensitive functionalities, there have been many recent developments. The modern approaches include Pd-catalysed formation of C-C or C-N bonds in the ring system [19][20][21], Pd-catalyzed synthesis from quinoline N-oxides and azodicarboxylates [22], Co-catalyzed cyclization of α-bromo-Nphenylacetamides [23], Intermolecular addition/cyclization of carbamoyl radicals under photoredox [24] or Ag [25] catalysis, hypervalent iodine(III)-mediated decarboxylative cyclization [26] and chemoenzymatic approaches [27,28].…”

Copper-Catalyzed Bifunctionalization/Annulation of Unactivated Alkene with Alkyl Bromides

“…Alkyl bromides, especially α-carbonyl alkyl bromides, have been widely employed as attractive alkyl radical precursors because of their rich reactivity, low toxicity, ease of synthesis, and high compatibility of sensitive functional groups. In recent years, intermolecular cyclization of alkenes or alkynes with alkyl bromides has surged for the construction of cyclic compounds, mostly containing a 5–7 heterocyclic skeleton. To the best of our knowledge, however, alkyl bromides serving as alkyl sources through the inter-/intramolecular annulation of alkene for constructing 4-membered rings is underdeveloped …”