Recent Developments on the Synthesis of Oxygen- and Sulfur-containing Heterocycles and their Derivatives under Visible Light Induced Reactions.

Visible-light-mediated reactions have recently emerged as a powerful strategy for the synthesis of diverse organic molecules under mild reaction conditions. Usually, the reactions are performed at room temperature and thus sensitive functional groups remain unaffected. Thus, this protocol has received intense interest from academia as well as industries. The heterocycles, in general, are of much interest because of their biological activities and application in therapeutics. The Oxygen- and Sulfur-containing heterocyclic compounds have recently attracted attention as these compounds showed promising activities as anti-cancer drugs, antibiotics, antifungal and anti-inflammatory agents among other applications. The synthesis of this class of compounds by efficient and greener routes has become an important target. This review highlights the various procedures for the synthesis of these compounds and their derivatives under visible light-induced reactions. The green aspects and mechanism of each procedure have been discussed.

Iron-Catalyzed Synthesis of 13-Aryl-13H-indeno[1,2-l]phenanthrene via Double Annulations of 2-Alkynyl Biaryls.

An Fe(III)-catalyzed expedient synthesis of 13-aryl-13H-indeno[1,2-l]phenanthrene is described by a double annulations of 2-alkynyl biaryls, initiated by the activation of acetal. This strategy provides a simple, efficient and regioselective synthesis of varieties of indenophenanthrene derivatives from easily available starting materials under mild conditions in high to excellent yields. A plausible reaction mechanism is proposed.

Cu(OAc)2-Promoted Ortho C(sp2)-H Amidation of 8-Aminoquinoline Benzamide with Acyl Azide: Selective Formation of Aroyl or Acetyl Amide Based on Catalyst Loading.

An efficient method for the C(sp2) amidation of 8-aminoquinoline benzamide by acyl azide in the presence of copper acetate has been achieved via C-H activation. Interestingly, the loading of copper acetate has a strong influence on the outcome of the reaction. The use of 1 equiv of copper acetate produces the corresponding aroyl amide, whereas the use of 2 equiv led to acetyl amide. A series of substituted benzoyl and acetyl amides has been obtained.

Cobalt-Catalyzed Remote C-4 Functionalization of 8-Aminoquinoline Amides with Ethers via C-H Activation under Visible-Light Irradiation. Access to α-Heteroarylated Ether Derivatives.

A cobalt-catalyzed selective remote C-4 alkylation of 8-aminoquinoline amides via C-H activation under irradiation with a CFL lamp in the presence of eosin Y at room temperature has been achieved. A series of pharmaceutically important C-4 quinoline amide-substituted ether derivatives has been obtained by this procedure. The C-4 functionalization of quinoline amides with inert ether is of much significance and was not reported earlier.

Transition Metal- and Oxidant-Free Base-Mediated Selenation of Bicyclic Arenes at Room Temperature.

Bicyclic arenyl selenides are of much importance because of their pharmaceutical applications. A simple method for their synthesis has been developed by a reaction of 2-naphthol and styrenyl selenocyanate/diaryl diselenide in the presence of a base at room temperature. The selenation occurs exclusively at the 1-position of 2-naphthol unit. The reactions are relatively fast (2-4 h) and high yielding. A library of substituted naphthyl styrenyl and naphthyl aryl selenides are obtained by this procedure.

Aromatic fused heterocyclic [22] macrocycles with NIR absorption.

Three related aromatic [22] heteroporphyrins have been synthesized and characterized, with the target of achieving NIR absorption. The propensity of these smallest π-conjugated macrocycles to absorb in the NIR region is benefitted from the fusion/annelation of the precursor heterocycles.