Hydroxy Group-Enabled Regio- and Stereoselective Hydroalkylation of Alkynyl Cyclobutanol via Palladium-Catalyzed C-C Bond Activation of Cyclopropanol: A One-Step Access to Vinyl Cyclobutanols.

The regio-/stereoselective synthesis of vinyl cyclobutanols from alkynyl cyclobutanols is demonstrated. Here, selective C-C bond activation of the cyclopropyl alcohol ring has been achieved in the presence of the cyclobutanol ring. The KIE experiments indicated the noninvolvement of the O-H oxidative addition step in the rate-determining step. Further, the applicability of these vinyl cyclobutanols for the synthesis of 1,4-diketones and 1,6-diketone is demonstrated.

Cobalt-Catalyzed Deacylative Ipso-C-C Bond Functionalization: An Approach toward Indole-Acyloins and Its Photophysical Studies.

Selective functionalization of the indole-C3-C bond with aromatic/heteroaromatic 1,2-diketones has been uncovered for the first time. Cobalt catalyst was found to be an effective catalyst for this unusual transformation. This ipso-C-C bond functionalization occurred in the presence of easily available weakly coordinating groups such as ketone and ester. One of the salient features of this methodology is the in situ generation of water from hexafluoro-2-propanol which acts as a reactant for the removal of the pivaloyl/ester group in a deacylative manner. The plausible mechanism has been supported by DFT calculations. Moreover, photophysical studies show the potential utility of indole-C3-acyloin and indolo-fused carbazole, which could be used in photovoltaic and optoelectronic application.

Carboamination and olefination: ortho C-H functionalization of phenoxyacetamide.

Herein, we have demonstrated a rhodium-catalyzed carboamination of olefin with the double bond intact. For the first time, deacylative carboamination of the maleimide has been achieved wherein phenoxyacetamide has behaved as the aminating source. In addition to carboamination, we have also disclosed the C-H olefination protocol where the maleimide group has been installed successfully in the ortho-position of phenoxyacetamide. In this protocol, phenoxyacetamide behaved as a traceless directing group with the in situ release of acetamide. The base-assisted E2-elimination is the key to the success of the olefination reaction.

Annulation of Indole-2-Carboxamides with Bicycloalkenes Catalyzed by Ru(II) at Room Temperature: An Easy Access to ß-Carboline-1-one Derivatives under Mild Conditions.

Herein, we report the annulation of indole-2-carboxamides with bicycloalkenes, to synthesize ß-carboline-1-one derivatives under mild conditions. The commercially available ruthenium catalyst was used for the reaction. This reaction tolerates a wide range of functional groups and affords a good yield of ß-carboline-1-one derivatives. A reversible cyclometalation pathway was found to be operative in the mechanistic study.

Rhodium-Catalyzed Selective C(sp2)-H Activation/Annulation of tert-Butyl Benzoyloxycarbamates with 1,3-Diynes: A One Step Access to Alkynylated Isocoumarins and Bis-Isocoumarins.

We report here a Rh(III) catalyzed regio- and stereoselective synthesis of alkynylated and bis-isocoumarin from 1,3-dialkyne. Exclusive one-pot formation of 3,3-bis-isocoumarin isomers has been achieved by eliminating several other possibilities. This is the first example of transition metal catalyzed synthesis of alkynylated and bis-isocoumarin scaffolds. The protocol is compatible with a wide range of functional groups affording good to excellent yields. Several mechanistic investigations, including deuterium labeling experiments and kinetic isotope effect studies, have been carried out.

Co(II)-Catalyzed C-H/N-H Annulation of Cyclic Alkenes with Indole-2-carboxamides at Room Temperature: One-Step Access to ß-Carboline-1-one Derivatives.

We report herein a cobalt-catalyzed 8-aminoquinoline-directed highly regio- and stereoselective C-H/N-H activation annulation of indole-2-carboxamides with 1,2-dihydronaphthalene for the synthesis of ß-carboline-1-one derivatives at room temperature. A cheaper and commercially available cobalt catalyst has been used for this transformation. The protocol tolerates a wide range of functionalities, affording ß-carboline-1-one derivatives in good yields. An initial mechanistic study revealed a reversible cyclometalation to be operative.

Ruthenium-Catalyzed Regioselective C(sp2)-H Activation/Annulation of N-(7-Azaindole)amides with 1,3-Diynes Using N-Amino-7-azaindole as the N,N-Bidentate Directing Group.

The ruthenium(II)-catalyzed regioselective annulation of N-(7-azaindole)amides with 1,3-diynes has been demonstrated. Bioactive N-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.

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

A redox neutral Co(III)-catalyzed annulation of α,ß-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. Notably, this transformation has been applied to the late-stage modification of the bioactive molecule dehydropregnenolone.

Regio- and Stereoselective Synthesis of the Core Structure of Hexahydrobenzo[c]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[c]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.