Rh(III)-Catalyzed C–H Bond Activation for the Construction of Heterocycles with sp3-Carbon Centers

Abstract

Rh(III)-catalyzed C–H activation features mild reaction conditions, good functional group tolerance, high reaction efficiency, and regioselectivity. Recently, it has attracted tremendous attention and has been employed to synthesize various heterocycles, such as indoles, isoquinolines, isoquinolones, pyrroles, pyridines, and polyheterocycles, which are important privileged structures in biological molecules, natural products, and agrochemicals. In this short review, we attempt to present an overview of recent advances in Rh(III)-mediated C–H bond activation to generate diverse heterocyclic scaffolds with sp3 carbon centers.

1,3,5‐Triaza‐7‐phosphaadamantane (PTA) Derived Caged Phosphines for Palladium‐Catalyzed Selective Functionalization of Nucleosides and Heteroarenes

“…[57] The functionalization of substrates is facilitated by the presence of mildly acidic CÀ H protons and therefore heteroarenes as substrates have found more applications than simple arenes as the later present a synthetic challenge due to the nonavailability of Brønsted acidity. [58] 1,3,4-Oxadiazole is one such heteroarene that has attracted a lot of attention due to its unique properties and diverse range of applications. [59] High catalyst loadings, poor conversions and reaction temperature in excess of 140°C are some of the pertinent issues that are associated with the functionalization methodologies available in the literature.…”

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…Incidentally, some admirable reviews commencing transition metal‐catalyzed C−H amination in the synthesis of N ‐heterocycles by Jipan Yu in 2015 and rhodium‐catalyzed asymmetric synthesis of heterocycles by Wen‐Wen Chen in 2016 have been published [6a,b] . In addition reviews dedicating Rh(III)‐catalyzed C‐H bond activation for the construction of heterocycles with sp 3 ‐carbon centers by wang group, [6c] and synthesis of fused five membered N‐ heterocycles by Kaur group have gained a significant attention [6d] . Other reports discussed in this area includes synthesis of bi‐ or tri‐cyclic N ‐Heterocycle by [3+3] cycloaddition of azomethine imine by Das and co‐workers, [6e] Microwave assisted synthesis of five membered nitrogen heterocycles by Meera and co‐workers, [6f] and synthesis of indoles from alkynes and nitrogen sources by Neto and co‐workers [6g] .…”

A Zinc-Mediated Deprotective Annulation Approach to New Polycyclic Heterocycles

“…The development of efficient methods for the synthesis of high value added polycyclic heterocyclic derivatives by metal-promoted annulation of acyclic precursors is one of the most important area of research in heterocyclic chemistry [ 1 , 2 , 3 , 4 , 5 ]. Polycyclic heterocyclic systems, in fact, are largely present as fundamental cores in natural products and in biologically active compounds [ 6 , 7 , 8 , 9 , 10 , 11 ], and the possibility to obtain them by a simple cyclization process starting from readily available substrates is particularly attractive [ 1 , 2 , 3 , 4 , 5 ].…”

“…Among acyclic substrates able to undergo a metal-promoted cyclization to give a polycyclic heterocycle, functionalized alkynes bearing a suitably placed heteronucleophile play a major role, as the triple bond can be easily electrophilically activated by a suitable metal species thus promoting the cyclization by intramolecular nucleophilic attack [ 1 , 2 , 3 , 4 , 5 ]. Usually, processes like these are promoted by costly metals (mainly gold [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ], palladium [ 20 , 21 , 22 , 23 ], rhodium [ 24 , 25 , 26 ], platinum [ 27 , 28 , 29 ], and, occasionally, ruthenium [ 30 ]), while the use of less expensive metal species, such as cobalt [ 31 ], nickel [ 32 ], copper [ 33 , 34 , 35 , 36 ], zinc [ 37 , 38 , 39 , 40 ], and silver [ 41 , 42 ] compounds, has been scantly reported in the literature, and applied to a limited number of examples.…”