Iron-acetic acid: A versatile reductive cyclizing agent

Abstract

(A) Baldwin and co-workers have reported the reductive cyclization of substituted dinitrostyrene to indole derivatives with iron powder in acetic acid. They noticed some improvement in yield over the standard conditions. (Figure Presented). (B) A convenient, operationally simple, one-pot synthesis of various substituted γ-lactams using an SN2′ reaction of acetates of Baylis-Hillman adducts with nitroalkanes followed by reductive cyclization with iron-acetic acid was reported by Basavaiah and co-workers. (Figure Presented). (C) Basavaiah et al. have reported an easy, convenient, and operationally simple one-pot procedure for the synthesis of 3-benzoylquinoline derivatives from Baylis-Hillman alcohols using iron-acetic acid. (Figure Presented). (D) Warnmark and co-workers have presented the synthesis of 2-pyridone fused 2,2′-bipyridine derivatives by reductive cyclization of 2,2′-bipyridine derivatives using iron-acetic acid. Initially, 2,2′-bipyridine derivative were derived via Ullman coupling. (Figure Presented). (E) The Baylis-Hillman acetates have been conveniently transformed into tri- or tetracyclic heterocyclic frameworks containing an important azocine moiety via a one-pot multistep protocol involving alkylation followed by subsequent reductive cyclization using iron-acetic acid. (Figure Presented). (F) Yadav and co-workers have reported the synthesis of aziridine derivatives by reductive cyclization of 1,2-acetoxysulfenyl nitroalkanes using iron-acetic acid. (Figure Presented). (G) Panda and Mishra have described an efficient method to synthesize a diverse range of [1,4]benzodiazepine skeletons in only two synthetic steps: coupling of 2-nitrobenzyl bromide with a diverse range of chiral amino acids and reductive cyclization with iron-acetic acid. (Figure Presented). (H) Kim and co-workers disclosed the synthesis of the cyclic nitrone and pyrroline derivatives by the use of iron-acetic acid to give the pyrroline derivative as the major product. (Figure Presented). (J) Recently, C.-F. Yao and co-workers reported the synthesis of novel indolylquinoline derivatives via reductive cyclization of (E)-3-[(1H-indol-3-yl)methyl]-4-(2-nitrophenyl)but-3- en-2-one derivatives in the presence of iron-acetic acid. (Figure Presented). (K) More recently, Basavaiah et al. have reported a simple, facile and one-pot procedure for the synthesis of tri- and tetracyclic heterocyclic systems containing a [1,8]naphthyridin-2-one framework from the Baylis-Hillman alcohols using iron-acetic acid. (Figure Presented). © Georg Thieme Verlag Stuttgart New York.