Transition Metal Free α −C−H Functionalization of Six Membered Heteroaromatic‐ N ‐Oxides

Ts2O mediated deoxygenative C2-dithiocarbamation of quinoline N-oxides with CS2 and amines

A general, efficient and practical protocol for Ts2O promoted deoxygenative dithiocarbamation of quinoline N-oxides with in situ generated dithiocarbamic acids from CS2 and amines is reported. The reaction proceeded well under transition-metal free conditions to obtain a variety of novel quinoline-dithiocarbamate compounds with wide functional group tolerance and good to high yields.

Ts2O Promoted Deoxygenative C-H Dithiocarbonation of Quinoline N-Oxides with Potassium O-Alkyl Xanthates

A simple, efficient, and practical method for the synthesis of S-quinolyl xanthates was developed via Ts2O-promoted deoxygenative C-H dithiocarbonation of quinoline N-oxides with various potassium O-alkyl xanthates. The reaction performed well under transition-metal-free, base-free, and room-temperature conditions with wide substrate tolerance. Employing potassium O-tert-butyl xanthate (tBuOCS2K) as a nucleophile, some valuable quinoline-2-thiones were unexpectedly obtained in a one-pot reaction without any additional base.

TsCl promoted deoxygenative phosphorothiolation of quinoline N-oxides towards S-quinolyl phosphorothioates

A convenient, efficient and practical approach for the synthesis of S-quinolyl phosphorothioates via cheap TsCl promoted deoxygenative C2-H phosphorothiolation of quinoline N-oxides with readily available triethylammonium O,O-dialkylphosphorothioates was developed. The reaction performed well under transition-metal-free conditions at room temperature with a very short reaction time (10-20 min). Preliminary studies showed that the current transformation underwent a nucleophilic substitution process.

Iodine-Catalyzed Radical C-H Amination of Nonaromatic Imidazole Oxides: Access to Cyclic α-Aminonitrones

A straightforward cross-dehydrogenative coupling approach to incorporate alicyclic amino residues into the structure of model cyclic aldonitrones, 2H-imidazole oxides, is reported. The elaborated C(sp2)-H functionalization is achieved by employing cyclic amines in the presence of the I2-tert-butyl hydroperoxide (TBHP) reagent system. As a result, a series of 19 novel heterocyclic derivatives were obtained in yields of up to 97%. A mechanistic study involving electron paramagnetic resonance spectroscopic experiments allowed the radical nature of the reaction to be confirmed. In particular, the envisioned mechanistic rationale comprises N-iodination of a cyclic amine, followed by N-I bond homolysis of the resulting intermediate and subsequent amination of the nitrone moiety via the newly generated nitrogen-centered radical.

Synthesis of Quinoline-2-thiones by Selective Deoxygenative C-H/C-S Functionalization of Quinoline N-Oxides with Thiourea

Quinoline-2-thiones valuable for synthetic and medicinal chemistry applications were obtained with excellent regioselectivity employing a deoxygenative C-H functionalization of readily available quinoline-N-oxides with thiourea upon activation with triflic anhydride. Unlike the current methods, this approach provides general access to diverse quinoline-2-thiones functionalized with groups of different electronic natures. Experimental simplicity and good to high yields are advantages of this protocol. Given the high reactivity of quinoline-2-thiones, this method provides an entry point for the synthesis of diverse organosulfur quinoline scaffolds.

Copper-catalyzed redox neutral ketoalkylation of Csp2–H bonds via C–C bond cleavage

An efficient copper-catalyzed ketoalkylation of Csp2–H bonds with cycloalkyl silyl peroxides under mild conditions is presented. A series of Csp2–H bonds in quinoxalin-2(1H)-ones, heteroaromatic N-oxides and quinones were amenable to this protocol.