Rhodium-catalyzed denitrogenative transannulation of 1,2,3-triazolyl-carbamates: efficient access to 4-aminooxazolidinones

Herein we describe a novel Rh(II)-catalyzed intramolecular transannulation reaction of 1,2,3-triazolyl carbamates to access functionalized 4-aminooxazolidinones under operationally simple conditions with low catalyst loadings. A one-pot tandem Cu(I)-catalyzed synthesis of 1,2,3-triazolyl-carbamates from propargyl carbamates followed by their rearrangement/cyclization with Rh(II)-carboxylates was also presented

Cu-catalyzed Cascade Cyclization of Isothiocyanates, Alkynes, and Diaryliodonium Salts: Access to Diversely Functionalized Quinolines

Herein, we report a copper-catalyzed novel, highly efficient, and modular cascade annulation reaction for the synthesis of quinoline derivatives starting from easily available alkynes, isothiocyanates, and diaryliodonium salts. The reaction displayed excellent regioselectivities, when unsymmetrical alkynes were employed as partners, giving access to diversely functionalized quinolines in good to excellent yields for a wide range of functional groups

Cobalt(III)-Catalyzed [4+2] Annulation of Heterobicyclic Alkenes by sp(2) C-H Activation

An efficient and convenient cobalt(III)-catalyzed highly diastereoselective strategy was demonstrated for the synthesis of epoxybenzophenanthridinone derivatives. The sp(2) C-H activation of N-methoxybenzamides and their annulation reaction with 7-oxa/aza benzonorbornadienes proceeds under mild conditions and exhibits excellent functional group tolerance. In addition, the products were transformed to biologically relevant phenanthridinones by an acid-catalyzed ring opening/aromatization sequence

Rh-Catalyzed Denitrogenative Reaction of N-Sulfonyl-1,2,3-triazoles with Isatoic Anhydrides and Oxadiazolones

A convenient and simple, Rh-II-catalyzed denitrogenative method for the synthesis of biologically interesting 2-amino-benzoxazinones and 5-amino-oxadiazoles from readily available isatoic anhydrides and oxadiazolones has been developed. These reactions proceed via an O-H insertion onto alpha-imino Rh-II-carbenoid species followed by a rearrangement. The scope of the reaction can also be extended to benzoxazinones to access amino-substituted benzoxazines

Cobalt-Catalyzed Diastereoselective [4+2] Annulation of Phosphinamides with Heterobicyclic Alkenes at Room Temperature

Cobalt-catalyzed sp(2) C-H bond functionalization of diarylphosphinamides with heterobicyclic alkenes was demonstrated at room temperature employing commercially available cobalt(II)-salts. The effectiveness of this strategy was illustrated with the reaction of various 8-aminoquinoline derived phosphinic amides and 7-oxa/azabenzonorbornadienes. The reaction conditions exhibited excellent functional group tolerance and high diastereoselectivities. Furthermore, extension of this approach to the preparation of polyaryl cyclic phosphinamides was achieved through the dehydrative ring opening/aromatization sequence

Rh(II)-Catalyzed Denitrogenative Reaction of N-Sulfonyl-1,2,3-triazoles with lsatins for the Construction of Indigoids

A convenient, Rh(II)-catalyzed, denitrogenative reaction of N-sulfonyl-1,2,3-triazoles and isatins to access (E)-2-(1-amino-2-oxo2-phenylethylidene)indolin-3-ones, the core structure of indigo dyes, was achieved under operationally simple conditions with high levels of diastereoselectivity. Moreover, photophysical and electrochemical studies were conducted to understand their applicability in optoelectronic applications

Pd-II-Catalyzed Cascade Synthesis of Chromane Derivatives Initiated by cis-Chloropalladation or trans-Acetoxypalladation

A highly regio- and stereoselective Pd-II-catalyzed cascade synthesis of biologically relevant chromane derivatives from easily available enynes was developed under operationally simple conditions. The cascade reaction consists of nucleopalladation of alkynes, insertion of the alkene and protonation. When CuCl2 was employed as nucleophile, a cis-chloropalladation initiates the cascade. Whereas in the case of AcOH, a trans-acetoxypalladation takes place

Cobalt-catalyzed aryl C-H activation and highly regioselective intermolecular annulation of sulfonamides with allenes

Herein we describe a cobalt-catalyzed C-H activation of aryl and heteroaryl sulfonamides and their intermolecular heteroannulation reaction with allenes, providing a convergent strategy for the synthesis of biologically interesting heterocyclic scaffolds. Carbometallation of allenes proceeds selectively through a Co-alkenyl pathway for a wide range of electron-poor and electron-rich allenes

Cobalt-Catalyzed sp(2)-C-H Activation: Intermolecular Heterocyclization with Allenes at Room Temperature

The reactivity of allenes in transition-metal-catalyzed C-H activation chemistry is governed by the formation of either alkenyl-metal (M-alkenyl) or metal-pi-allyl intermediates. Although either protonation or a beta-hydride elimination is feasible with a M-alkenyl intermediate, cyclization has remained unexplored to date. Furthermore, due to the increased steric hindrance, the regioselectivity for the intramolecular cyclization of the metal-pi-allyl intermediate was hampered towards the more substituted side. To address these issues, a unified approach to synthesize a diverse array of biologically and pharmaceutically relevant heterocyclic moieties by cobalt-catalyzed directed C-H functionalization was envisioned. Upon successful implementation, the present strategy led to the regioselective formation of dihydroisoquinolin- 1(2H)-ones, isoquinolin-1(2H)-ones, dihydropyridones, and pyridones