Cobalt(III)-Catalyzed C-6 Alkenylation of 2-Pyridones by Using Terminal Alkyne with High Regioselectivity.

Co(III)-catalyzed alkenylation of 2-pyridones by using terminal alkyne as a reaction partner with high regioselectivity has been demonstrated for the first time. The reaction conditions are mild and compatible with a wide range of substrate combinations. It also shows good functional group tolerance.

Ruthenium-Catalyzed Regioselective C(sp)-H Activation/Annulation of -(7-Azaindole)amides with 1,3-Diynes Using -Amino-7-azaindole as the ,-Bidentate Directing Group.

The ruthenium(II)-catalyzed regioselective annulation of -(7-azaindole)amides with 1,3-diynes has been demonstrated. Bioactive -amino-7-azaindole has been used as a new bidentate directing group to furnish an array of 3-alkynylated isoquinolones. Furthermore, the developed protocol works efficiently for both aryl- and heteroaryl-substituted amides producing a range of pharmacologically useful 7-azaindole-based isoquinolones with a wide range of functionality.

Ruthenium-Catalyzed Cross Dehydrogenative Annulation of -(7-Azaindole)benzamides with Maleimides: One-Step Access to Highly Functionalized Pyrroloisoquinoline.

A ruthenium(II)-catalyzed cross dehydrogenative annulation of -(7-azaindole)benzamides with maleimides has been demonstrated. Herein, we have explored the use of -amino-7-azaindole as a new bidentate directing group for dehydrogenative [4 + 2] annulation. This method works efficiently, affording a variety of pharmacologically useful 7-azaindole-based isoquinolones and showing a wide functional group tolerance.

O-Directed C-H functionalization via cobaltacycles: a sustainable approach for C-C and C-heteroatom bond formations.

This review focuses on providing comprehensive highlights of the recent advances in the field of cobalt-catalysed C-H functionalization and related synthetic concepts, relying on these through oxygen atom coordination. In recent years, 3d transition metal (Fe, Co, Cu & Ni) catalysed C-H functionalization reactions have received immense attention on account of its higher abundance and low cost, as compared to noble metals such as Ir, Rh, Ru and Pd. Among the first-row transition metals, cobalt is one of the extensively used metals for sustainable synthesis due to its unique reactivity towards the functionalization of inert C-H bonds.

Palladium-Catalyzed C-C Bond Activation of Cyclopropenone: Modular Access to Trisubstituted -Unsaturated Esters and Amides.

Strain-driven palladium/-heterocyclic carbene-catalyzed C-C bond activation of diphenylcyclopropenone (DPC) has been explored for one-step access to trisubstituted α,β-unsaturated esters and amides. The designed transformation works under mild conditions providing exclusively a single stereoisomer. Mechanistic studies support the oxidative addition of the C-C bond of cyclopropenone to in-situ-generated Pd(0) intermediate.

Bismuth(iii)-catalyzed regioselective alkylation of tetrahydroquinolines and indolines towards the synthesis of bioactive core-biaryl oxindoles and CYP19 inhibitors.

Bismuth(iii)-catalyzed regioselective functionalization at the C-6 position of tetrahydroquinolines and the C-5 position of indolines has been demonstrated. For the first time, one pot symmetrical and unsymmetrical arylation of isatins with tetrahydroquinolines was accomplished giving a completely new product skeleton in good to excellent yields. Most importantly, this protocol leads to the formation of a highly strained quaternary carbon stereogenic center, which is a challenging task.

Redox-Neutral Cobalt(III)-Catalyzed C-H Activation/Annulation of α,β-Unsaturated Oxime Ether with Alkyne: One-Step Access to Multisubstituted Pyridine.

A redox neutral Co(III)-catalyzed annulation of α,β-unsaturated oxime ether with alkyne has been reported. Multisubstituted pyridines were synthesized in good yields without the use of any heavy metal oxidants. The developed methodology tolerates a variety of functional groups.

Rhodium-Catalyzed One-Pot Access to N-Polycyclic Aromatic Hydrocarbons from Aryl Ketones through Triple C-H Bond Activations.

A Rh-catalyzed pot and step economic synthesis of aza-polycyclic aromatic hydrocarbons (N-PAHs) from readily available aryl ketones and alkynes has been disclosed. Additionally, a novel synthetic application of the well-known aminating reagent hydroxylamine--sulfonic acid (HOSA) has been explored as an in situ redox-neutral directing group for the formation of N-PAHs via isoquinoline. Multiple bond formation in a single operation through a cascade of triple C-H bond activations is the beauty of this protocol.

Regio- and Stereoselective Synthesis of the Core Structure of Hexahydrobenzo[]phenanthridine Alkaloids via Redox-Neutral Cp*Rh(III)-Catalyzed C-H/N-H Annulation of Cyclic Alkenes with Benzamides.

A highly stereo- and regioselective synthesis of the core skeleton of hexahydrobenzo[]phenanthridine-type alkaloids is reported herein for the first time. A wide range of substrate scope, excellent functional group tolerance, and good to excellent yields were observed. This protocol gives very concise and efficient access to the core skeleton of chelidonine alkaloids as compared to the earlier approaches.

Cobalt-Catalyzed One-Step Access to Pyroquilon and C-7 Alkenylation of Indoline with Activated Alkenes Using Weakly Coordinating Functional Groups.

A new strategy for the C(7)-H functionalization of indoline derivatives using first-row transition-metal cobalt has been demonstrated wherein the pivaloyl group acts as a weakly coordinating directing group. Biologically important pyroquilon (tetrahydropyroquinolinone) derivatives have been synthesized in a one-pot manner through selective C(7)-H functionalization and concomitant cyclization. In this process, aromatic C-H and amidic C-N bonds are cleaved, and new C-C and C-N bonds are formed in a step-economical fashion.

-Amino-7-azaindole as the ,'-Bidentate Directing Group: Ruthenium-Catalyzed Oxidative Annulation of -(7-Azaindole)benzamides with Alkynes via C-H Bond Activation.

We report a new application of -amino-7-azaindole as a new bidentate-directing group for [Ru(-cymene)Cl]-catalyzed C(sp)-H alkenylation/annulation of -(1-pyrrolo[2,3-]pyridin-1-yl)benzamides with internal alkynes to afford -isoquinolono-7-azaindole via the formation of C-C and C-N bonds. The reaction shows a wide range of substrate scope with different symmetrical and unsymmetrical alkynes, affording the desired product in good to excellent yields. In the case of unsymmetrical alkynes, a highly regioselective product was obtained, which was confirmed by single-crystal X-ray crystallography.