Mechanochemical Ruthenium-Catalyzed Ortho-Alkenylation of N-Heteroaryl Arenes with Alkynes under Ball-Milling Conditions

Ru(II)-catalyzed oxidative (4+3) C-H/C-H annulation of 2-aryl-4H-pyrido[1,2-a]pyrimidin-4-ones with allyl alcohol

A ruthenium(II)-catalyzed direct oxidative (4+3) C-H/C-H annulation of 2-aryl-4H-pyrido[1,2-a]pyrimidin-4-ones with allyl alcohol has been described. The developed method yielded the corresponding annulated products in moderate to good yields. In addition, based on the control experimental results, a possible reaction mechanism has been proposed for the (4+3) C-H/C-H annulation reaction.

Rh(III)-catalyzed C(sp2)-H functionalization/[4+2] annulation of oxadiazolones with iodonium ylides to access diverse fused-isoquinolines and fused-pyridines

In this study, a Rh(III)-catalyzed C-H/N-H [4+2] annulation of oxadiazolones with iodonium ylides has been developed, which afforded a series of diverse fused-isoquinolines and fused-pyridines in moderate to high yields. These divergent synthesis protocols featured mild conditions, broad substrate scope, and functional-group compatibility. In addition, scale-up synthesis, related applications and preliminary mechanistic explorations were also accomplished.

Rh(III)-catalyzed oxidative [4+2] annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols

Synthesis of functionalized benzo[a]phenazines and indazolo[2,3-a]quinolines has been developed through Rh(III)-catalyzed oxidative annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols, respectively. The method features a broad substrate scope, excellent functional group tolerance, good to high yields of annulated products, and scaled-up synthesis capability. Based on a preliminary mechanistic investigation, a tentative mechanism of annulation reaction has been proposed.

Urea Hydrogen Peroxide and Ethyl Lactate, an Eco-Friendly Combo System in the Direct C(sp2)-H Bond Selenylation of Imidazo[2,1-b]thiazole and Related Structures

Herein, we describe a urea hydrogen peroxide-mediated sustainable protocol for the synthesis of selenylated imidazo[2,1-b]thiazole by using half molar equivalent diorganyl diselenides in ethyl lactate as a greener solvent. The reaction features high yields, easy performance on gram scale, metal-free conditions, as well as applicability to imidazopyridine and imidazopyrimidine.

Synthesis and site selective C-H functionalization of imidazo-[1,2-a]pyridines

Imidazo[1,2-a]pyridine has attracted much interest in drug development because of its potent medicinal properties, therefore the discovery of novel methods for its synthesis and functionalization continues to be an exciting area of research. Although transition metal catalysis has fuelled the most significant developments, extremely beneficial metal-free approaches have also been identified. Even though pertinent reviews focused on imidazo[1,2-a]pyridine synthesis, properties (physicochemical and medicinal), and functionalization at the C3 position have been published, none of these reviews has focused on the outcomes obtained in the field of global ring functionalization. We wish here to describe a brief synthesis and an overview of all the functionalization reactions at each carbon atom, viz, C2, C3, C5, C6, C7 and C8 of this scaffold, divided into sections based on site-selectivity and the type of functionalization methods used.

Direct Regioselective Hydro(hetero)arylation/Cyclocondensation Reactions of β-(2-Aminophenyl)-α,β-ynones by Means of Transition-Metal Catalysis/Brønsted Acid Synergism: Experimental Results and Computational Insights

Experimental results and computational insights explain the key role of transition-metal catalysis/Brønsted acid synergism in the achievement of the sequential regioselective direct heteroarylation/cyclocondensation reactions of β-(2-aminophenyl)-α,β-ynones with a variety of electron-rich aromatic heterocyclic/arenes to afford quinoline-(hetero)aromatic hybrids. The first approach to the synthesis of 4-(1H-pyrrol-2-yl)quinolines is described. The effectiveness of various transition metals is compared.

Ball-Milling-Enabled Zn(OTf)2-Catalyzed Friedel-Crafts Hydroxyalkylation of Imidazo[1,2-a]pyridines and Indoles

A facile and efficient synthetic method for the construction of C3-hydroxyalkylated imidazo[1,2-a]pyridines and indoles by a Zn(OTf)₂-catalyzed Friedel-Crafts hydroxyalkylation of imidazo[1,2-a]pyridines and indoles with carbonyl compounds under mechanochemical conditions is reported. Good product selectivity, shorter reaction time, ambient reaction temperature, tolerance of a wide range of functional groups, broad substrate scope, moderate to good yield of products, and scalability are the salient features of the developed methodology.