Rh(III)-Catalyzed Synthesis of N-Unprotected Indoles from Imidamides and Diazo Ketoesters via C–H Activation and C–C/C–N Bond Cleavage

RhIII -Catalyzed Direct C8-Arylation of Quinoline N-Oxides using Diazonaphthalen-2(1H)-ones: A Practical Approach towards 8-aza BINOL

An efficient Rh^III -catalyzed redox-neutral method for the direct C8-arylation of quinoline N-oxides using diazonaphthalen-2(1H)-one as coupling partner has been demonstrated. The developed method is simple, scalable and straightforward with a wide range of substrate scope. The applicative potential was extended with a late-stage functionalization and straightforward synthesis of 8-azaBINOL derivative. A plausible reaction pathway was proposed after carrying out preliminary control studies.

Iridium-catalyzed [4 + 2] annulation of 1-arylindazolones with α-diazo carbonyl compounds: access to indazolone-fused cinnolines

An Ir-catalyzed tandem strategy for the synthesis of indazolone-fused cinnolines by [4 + 2] annulation of 1-arylindazolones with α-diazo carbonyl compounds.

KI-catalyzed oxidative cyclization of α-keto acids and 2-hydrazinopyridines: efficient one-pot synthesis of 1,2,4-triazolo[4,3-a]pyridines

A one-pot approach to 1,2,4-triazolo[4,3-a]pyridines via KI-catalyzed oxidative cyclization was developed with good economical and environmental advantages.

Divergent synthesis of α-aryl ketones/esters via rhodium-catalyzed selective deesterification and decarbonylation of diazo compounds

A rhodium-catalyzed selective deesterification, decarbonylation and dual C–H activation of diazo compounds is presented.

A Rh(iii)-catalyzed cascade C–H functionalization/cyclization reaction of salicylaldehydes with diazomalonates for the synthesis of 4-hydroxycoumarin derivatives

A cascade C–H functionalization/cyclization reaction of salicylaldehydes with α-diazomalonates has been developed for the synthesis of 4-hydroxycoumarin derivatives under rhodium(iii) catalysis.

Iridium-catalysed direct sulfamidation of quinazolinones

Ir-catalysed direct sulfamidation of quinazolinones has been achieved. A series of ortho-diamided quinazolinones were obtained in up to 96% yields. This transformation could proceed smoothly with a low catalyst loading under mild conditions with nitrogen released as the sole byproduct. This approach potentially provides an environmentally benign sulfamidation process for atom/step economic syntheses of useful pharmaceutical molecules or important building blocks.

An Ir-catalysed direct sulfamidation of quinazolinones has been achieved to construct a series of ortho-diamided quinazolinones in excellent yields, and nitrogen was released as the sole byproduct.

Transition-Metal-Catalyzed Cross-Couplings through Carbene Migratory Insertion

Transition-metal-catalyzed cross-coupling reactions have been well-established as indispensable tools in modern organic synthesis. One of the major research goals in cross-coupling area is expanding the scope of the coupling partners. In the past decade, diazo compounds (or their precursors N-tosylhydrazones) have emerged as nucleophilic cross-coupling partners in C-C single bond or C═C double bond formations in transition-metal-catalyzed reactions. This type of coupling reaction involves the following general steps. First, the organometallic species is generated by various processes, including oxidative addition, transmetalation, cyclization, C-C bond cleavage, and C-H bond activation. Subsequently, the organometallic species reacts with the diazo substrate to generate metal carbene intermediate, which undergoes rapid migratory insertion to form a C-C bond. The new organometallic species generated from migratory insertion may undergo various transformations. This type of carbene-based coupling has proven to be general: various transition metals including Pd, Cu, Rh, Ni, Co, and Ir are effective catalysts; the scope of the reaction has also been extended to substrates other than diazo compounds; and various cascade processes have also been devised based on the carbene migratory insertion. This review will summarize the achievements made in this field since 2001.

One-pot synthesis of 2,3-difunctionalized indoles via Rh(iii)-catalyzed carbenoid insertion C–H activation/cyclization

A new and versatile Rh(iii)-catalyzed carbenoid insertion C–H activation/cyclization for one-pot synthesis of 2,3-difunctionalized indoles has been developed.

Facile synthesis of 1-aminoindoles via Rh(iii)-catalysed intramolecular three-component annulation

A simple and efficient procedure to 1-aminoindoles starting from easily available aryl hydrazines, diazo compounds and ketones via a rhodium-catalyzed [3 + 2] annulative coupling reaction.

Regio-selective synthesis of diversely substituted benzo[a]carbazoles through Rh(iii)-catalyzed annulation of 2-arylindoles with α-diazo carbonyl compounds

A novel synthetic approach toward benzo[a]carbazoles and 6-aminobenzo[a]carbazoles containing an unprotected NH unit through Rh(iii)-catalyzed cascade reactions of 2-arylindoles or 2-arylindole-3-carbonitriles with α-diazo carbonyl compounds is presented.

Rh(iii)-catalyzed sequential C–H activation and annulation: access to N-fused heterocycles from arylazoles and α-diazocarbonyl compounds

Valuable N-fused heterocycles were successfully obtained via Rh(iii)-catalyzed sequential C–H activation and annulation.

Synthesis of 2-Arylimino-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-ones via Rh2(OAc)4-Catalyzed Reactions of Cyclic 2-Diazo-1,3-diketones with Aryl Isothiocyanates

A convenient and efficient synthesis of 2-arylimino-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-ones was developed via a Rh₂(OAc)₄-catalyzed reaction of cyclic 2-diazo-1,3-diketones and aryl isothiocyanates in acetone at 60 °C. This reaction uses readily available stable cyclic 2-diazo-1,3-diketones as a starting material and generates the desired products in good to excellent yields (78-93%). The reaction proceeds under mild reaction conditions, produces only N₂ as the byproduct, and features a broad substrate scope. A plausible mechanism for this reaction is also discussed.

Functionalizing the γ-Position of α-Diazo-β-ketoesters

Although α-diazo-β-ketoesters are synthetically versatile intermediates, methodology for introducing this functionality into complex molecules is still limited, most frequently involving a carboxylic acid precursor, which is then activated and transformed into a β-ketoester, with the diazo group being subsequently added with a diazo transfer reagent. While introducing this highly functional moiety in a convergent one step process would be ideal, such an objective is limited by the relatively few studies which address functionalization of the α-diazo-β-ketoester at the γ-position. In the present investigation, we evaluate strategies, both new and established, for functionalizing α-diazo-β-ketoesters, particularly with regard to generating compounds prospectively useful in the synthesis of C1-substituted carbapenems. We report the first δ-aldehydo-α-diazo-β-ketoester as well as a method for its oxidation to the corresponding methyl ester, and the formation of a new substituted pyrazole under basic conditions.