Rhodium‐Catalyzed Cascade Reactions using Diazo Compounds as a Carbene Precursor to Construct Diverse Heterocycles

Abstract

Diazo compounds being used as a precursor of carbenes in synthetic chemistry by reacting them in different manners like photochemically, thermally or with metal catalysts. Further, the use of metals as a catalyst generates metallocarbenes in the reaction medium which has similar reactivity like free carbenes. In this context, a number of transition metal catalysts like Rh, Pd, Cu, Ru, Ir, Fe etc. have been employed to generate metal bound carbenes in the reaction medium. Among various metal catalyst, rhodium being used extensively in industry as well as in academia to catalyze a number of cascade transformations containing carbene insertion/transfer. In this review, we are covering the efforts made in the last five years toward the synthesis of highly important heterocyclic compounds such as isoquinoline, indoles, isocoumines, oxazoles, carbazoles etc. through rhodium catalysed cascade reactions containing carbene transfer as the vital step.

Graphene oxide-catalysed carbene-transfer reaction in water: a highly “green” and selective approach to access 3,3′,3′′-trisindoles

“…4 In particular, rhodium-based catalysts have been explored in comparison with other metal catalysts. 5 Recently, Kapur et al reported the Ir(III)-catalysed C-H alkylation of N-acetyl-1,2-dihydroisoquinolines with α-diazomalonates. 6 Development of a Rh(III)-catalysed oxidative [4 + 1] spiroannulation method for the synthesis of isoindole N-oxide and isobenzofuranones involving the C-H activation of oximes in the presence of 1-diazonapthalen-2-(1H)ones as the coupling reagent was reported by Li et al 7 Furthermore, Wang and colleagues used a rhodium(III)-based catalyst in the reaction of 4-diazoisochroman-3-imines and benzimidates, which afforded 8-alkoxy-5Hisochromeno[3,4-c]isoquinolines as products.…”

Rhodium-catalyzed migrative annulation and olefination of 2-aroylpyrroles with diazoesters

“…α-Diazocarbonyl compounds (DCCs) have a long history of practical application in organic synthesis and still remain the subject of intense and comprehensive research. 1 The reactions of DCCs with multiple bonds and lone pairs of heteroatoms catalyzed by transition metal compounds or promoted by either Lewis acids or light irradiation are the basis of reliable methods for the formation of carbon–carbon and carbon–heteroatom bonds in the synthesis of both acyclic and carbo- and heterocyclic molecules. In particular, DCCs can be efficiently olefinated using various compounds including carbonyl compounds, 2 sulfoxonium ylides, 3 allyl carbonates, 4 vinylethylene carbonates, 5 and other DCCs (Scheme 1, reactions (a)–(e)).…”

Synthesis of dihydroindazolo[2,3-f]phenanthridin-5(6H)-onesviaRh(iii)-catalyzed C–H activation of 2-aryl indazoles and annulation with iodonium ylides

“…Recently, carbene precursors such as diazo compounds, 4 hydrazones, 5 sulfoxonium ylides, 6 and others, 7 have been extensively used as efficient coupling partners in transition-metal-catalyzed C–H activation/annulation reactions for the construction of various of complex heterocyclic skeletons. Compared to dangerous and explosive diazonium compounds, iodonium ylides are inexpensive and readily available hypervalent iodine reagents which show good thermal stability, safety, solubility in common organic solvents, and have been widely used in organic synthesis.…”