Base-mediated denitrative C3-alkylation of quinoxaline derivatives.

We have developed a novel base-mediated method for the selective C3-alkylation of quinoxalin-2(1)-one and -protected quinoxalin-2(1)-one using inexpensive, unactivated nitroalkanes. This approach tolerates a wide range of functional groups and supports the synthesis of various bioactive compounds. Gram-scale reactions demonstrate the scalability of the method.

Depolymerization of Waste Polycarbonates to Value-Added Products.

Additive free aminolysis method developed for the depolymerization/upcycling of polycarbonates. We report here chemical recycling of polycarbonate under ambient conditions to get its monomer bisphenol A, monoaminocarbamate and biscarbamates in 1 : 2 : 1 ratio respectively. By employing the secondary amine as the aminating reagent, facilitates the depolymerization to work under additive/catalyst free conditions.

Room-temperature C-H bond alkynylation by merging cobalt and photocatalysts.

A new protocol is developed for the mono- and bis--C-H alkynylation of easily accessible benzamide derivatives using alkynyl bromides at room temperature by merging cobalt and photocatalysts. The diverse reactivity of various alkynyl bromides towards the C-H alkynylation and competing C-H/N-H bond annulation reactions has been demonstrated to give the corresponding products in good yields with excellent functional group tolerance.

Ruthenium-Catalyzed -Hydroalkynylation and -Chloroalkynylation of Internal Alkynes.

[Cp*RuCl] catalyzes the addition of PrSiC≡CX (X = H, Cl) across internal alkynes with formation of 1,3-enyne or 1-chloro-1,3-enyne derivatives, respectively; the reaction follows an unorthodox -addition mode. The well-balanced affinities of the different reaction partners to the ruthenium catalyst ensure that crossed addition prevails over homodimerization of the individual components, as can be deduced from spectroscopic and crystallographic data of various intermediates; this includes a dinuclear complex in which an internal alkyne bridges two [Cp*RuCl] fragments.

C-H and N-H bond annulation of aryl amides with unactivated olefins by merging cobalt(iii) and photoredox catalysis.

A mild, environment-friendly protocol has been developed to carry out the [4+2] annulation of aryl amides with unactivated olefins. A range of sterically and electronically diverse aryl amides and unactivated olefins were successfully employed under the developed conditions to get a variety of dihydroisoquinolinones in good-to-excellent yields.

Co -Catalyzed Isonitrile Insertion/Acyl Group Migration Between C-H and N-H bonds of Arylamides.

A general efficient and site-selective cobalt-catalyzed insertion of isonitrile into C-H and N-H bonds of arylamides through C-H bond activation and alcohol assisted intramolecular trans-amidation is demonstrated. This straightforward approach overcomes the limitation by the presence of strongly chelating groups. Isolation of Co -isonitrile complex B has been achieved for the first time to understand the reaction mechanism.

Cobalt catalyzed carbonylation of unactivated C(sp)-H bonds.

A general efficient regioselective cobalt catalyzed carbonylation of unactivated C(sp)-H bonds of aliphatic amides was demonstrated using atmospheric (1-2 atm) carbon monoxide as a C1 source. This straightforward approach provides access to α-spiral succinimide regioselectively in a good yield. Cobalt catalyzed sp C-H bond carbonylation is reported for the first time including the functionalization of (β)-C-H bonds of α-1°, 2°, 3° carbons and even internal (β)-C-H bonds.

C-8-Selective Allylation of Quinoline: A Case Study of β-Hydride vs β-Hydroxy Elimination.

An unprecedented C(8)-H bond allylation of quinoline with allyl carbonate and allyl alcohol catalyzed by Cp*Co(III) using a traceless directing group via β-oxygen and β-hydroxy elimination is described. This site-selective allylation reaction proceeds smoothly with various functional group tolerance including quinoxaline and phenanthridine. Under the nonoxidative reaction conditions, the difference in selectivity between Rh(III) and Co(III), which proceeds through β-hydride and β-hydroxy elimination using allyl alcohol, is shown for the first time.

Cp*Co(III) -Catalyzed C(sp(3) )-H Bond Amidation of 8-Methylquinoline.

An efficient and external oxidant-free, Cp*Co(III) -catalyzed C(sp(3) )-H bond amidation of 8-methylquinoline, using oxazolone as an efficient amidating agent, is reported for the first time under mild conditions. The reaction is selective and tolerates a variety of functional groups. Based on previous reports and experimental results, the deprotonation pathway proceeds through an external base-assisted concerted metalation and deprotonation process.

Cobalt(iii) catalyzed C-8 selective C-H and C-O coupling of quinoline N-oxide with internal alkynes via C-H activation and oxygen atom transfer.

An efficient, scalable, atom-economical, regio-selective air stable Cp*Co(iii) catalyzed C-H and C-O coupling via a C-H activation/oxygen atom transfer reaction of quinoline N-oxide and an internal alkyne is reported. Such a catalytic transformation is witnessed for the first time with a cobalt catalyst and using N-oxide as a traceless directing group, in contrast to the existing literature. The developed synthetic methodology is straightforward and possesses various functional group tolerances, including heterocycles.

Carboxylate Assisted Ni-Catalyzed C-H Bond Allylation of Benzamides.

A one-step synthetic method was developed for allylation of benzamides using Ni(COD)2/RCO2 H and [Ni(μ-H2O)(OOCCMe3)2 (HOOCCMe3)2]2 (A') catalytic system. Efficient, well-defined, air and moisture-stable Ni-pivalate complex was isolated and employed in catalytic allylation. The influence of solvent on product selectivity was also investigated.