Expeditious Synthesis of Spiroindoline Derivatives via Tandem C(sp2)-H and C(sp3)-H Bond Functionalization of N-Methyl-N-nitrosoanilines

Presented herein is a novel synthesis of pharmaceutically privileged spiroindoline derivatives via cascade reactions of N-methyl-N-nitrosoanilines with diazo homophthalimides. A group of mechanistic studies disclosed that the formation of product involves an unusual reaction mode of N-methyl-N-nitrosoaniline featuring an initial C(sp2)-H bond activation/alkylation followed by a C(sp3)-H bond activation/spiroannulation. To our knowledge, this is the first example in which N-methyl-N-nitrosoaniline acts as a C3N1 synthon to accomplish formal [4+1] spiroannulation with the participation of the N-methyl unit rather than the previously reported C2N1 synthon to undergo formal [3+2] annulation without the participation of the N-methyl unit. In general, this newly developed synthetic protocol features simple and readily accessible starting materials, valuable products, unique reaction mechanism, high efficiency and atom-economy, excellent compatibility with diverse functional groups, and ready scalability.

Regioselective ortho C-H insertion of N-nitrosoanilines with naphthoquinone carbenes

A Rh(III)-catalyzed ortho C-H migratory insertion of N-nitrosoanilines with naphthoquinone carbenes has been developed. The products were obtained in good yields under mild reaction conditions. Diverse elaborations of the products were explored. This method is valuable for the synthesis of biarylamines and their derivatives.

Modular construction of functionalized anilines via switchable C–H and N-alkylations of traceless N-nitroso anilines with olefins

Switchable C–H or N-alkylations of N-nitroso anilines with olefins.

RhIII-Catalyzed heteroarylation of N-2,6-difluorophenyl arylamides with heteroaryl boronate esters

An efficient strategy to aryl-heteroaryl formation via RhIII-catalyzed C–H heteroarylation of arenes with N-heterocyclic boronates has been disclosed.

Recent advances in transition-metal catalyzed directed C–H functionalization with fluorinated building blocks

This review focuses on the advances in transition-metal catalyzed reactions with fluorinated building blocks via directed C–H bond activation for the construction of diverse organic molecules with an insight into the probable mechanistic pathway.

Recent advances in rhodium-catalysed cross-dehydrogenative-coupling between two C(sp2)-H bonds

Rhodium-catalysed cross-dehydrogenative coupling (CDC) has received considerable attention in recent years. This modern technology has been considered as an attractive synthetic tool for selective C−C bond formation due to (1)...

The synthesis of aryl-heteroaryl derivatives via the RhIII-catalyzed heteroarylation of arenes and heteroaromatic boronates

An efficient Rh^III-catalyzed strategy for constructing aryl-heteroaryl derivatives with removable ketoxime ether auxiliaries via direct C-H heteroarylation based on arenes and heteroaromatic boronates has been disclosed. This protocol could tolerate various pyridine, pyrimidine, pyrazole, thiophene, and furan heteroaromatic boronates well, providing the desired products with high reactivities and excellent regioselectivity. The easy synthetic accessibility may offer potential for application in the synthesis of heterocyclic drug molecules containing aryl-heteroaryl motifs.

Recent advances in rhodium-catalyzed C(sp2)-H (hetero)arylation

Arylation is a common behaviour in organic synthesis for the construction of complex structures, especially the biaryls. Among those reported arylation procedures, transition-metal-catalyzed direct C(sp²)-H arylation has been rapidly developed in recent decades and has become a reliable alternative to traditional cross-coupling procedures using organometallic reagents. Great achievements in rhodium-catalyzed C(sp²)-H arylation have been witnessed during the last decade. Aryl halides, simple arenes, aryl boronic acids, arylsilanes, aryl aldehyde, aryl carboxylic acid, diazides, etc. were successfully utilized as arylating reagents under rhodium-catalyzed conditions. In this review, recent achievements in rhodium-catalyzed arylations through C(sp²)-H bond activation were summarized together with the mechanism discussions.

RhIII -Catalyzed C6-Selective Oxidative C-H/C-H Crosscoupling of 2-Pyridones with Thiophenes

A rhodium(III)-catalyzed C6-selective dehydrogenative cross-coupling of 2-pyridones with thiophenes was developed for the synthesis of 6-thiophenyl pyridin-2(1H)-one derivatives. In this reaction, the excellent site selectivity was controlled by the 2-pyridyl directing group on the nitrogen of the pyridone ring. Control experiments indicated that the N-pyridyl was essential for the transformation. To the best of our knowledge, this procedure is the first successful example of the direct C6 heteroarylation of 2-pyridones with electron-rich thiophene derivatives. 4-Pyridone was also used as substrate to generate the corresponding C2 heteroarylated product. Moreover, this pyridyl directing group was readily removable to generate the biheteroaryl structures with a free N-H group.

Rh(III)-Catalyzed Olefination and Alkylation of Arenes with Maleimides: A Tunable Strategy for C(sp2)–H Functionalization

We herein report a new nitrogen-directed Rh(III)-catalyzed C(sp2)–H bond functionalization of N-nitrosoanilines and azoxybenzenes with maleimides as a coupling partner, in which the olefination/alkylation process can be finely controlled at room temperature by variation of the reaction conditions. This method shows excellent functional group tolerance, and presents a mild access to the resulting olefination/alkylation products in moderate to good yields.

Rh(III)-Catalyzed N-Nitroso Directed C-H Arylation for Facile Construction of Diverse N-Hetero Biaryl Compounds

A Rh(III)-catalyzed C-H arylation reaction of N-nitrosoanilines has been developed in which arylboronic acids were used as arylation reagents. It provides an efficient strategy for the synthesis of N-nitroso-[1,1'-biphenyl]-2-amine, which is an important starting material for the synthesis of N-hetero biaryl compounds, such as 2-amine-1,1'-biphenyl, carbazole, phenanthridone. This protocol can be applied to various N-alkyl substituted N-nitrosoanilines and N-nitrosoanilines with substituents on the phenyl ring. Arylboronic acids with both electron-donating and electron-withdrawing groups are tolerated.

Rhodium-catalyzed tandem acylmethylation/annulation of N-nitrosoanilines with sulfoxonium ylides for the synthesis of substituted indazole N-oxides

An atom-economical protocol for synthesizing indazole N-oxides from readily available N-nitrosoanilines and sulfoxonium ylides through the rhodium(iii)-catalyzed C–H activation and cyclization reaction is described here.

Molecular mechanism of azoxy bond formation for azoxymycins biosynthesis

Azoxy bond is an important chemical bond and plays a crucial role in high energy density materials. However, the biosynthetic mechanism of azoxy bond remains enigmatic. Here we report that the azoxy bond biosynthesis of azoxymycins is an enzymatic and non-enzymatic coupling cascade reaction. In the first step, nonheme diiron N-oxygenase AzoC catalyzes the oxidization of amine to its nitroso analogue. Redox coenzyme pairs then facilitate the mutual conversion between nitroso group and hydroxylamine via the radical transient intermediates, which efficiently dimerize to azoxy bond. The deficiency of nucleophilic reactivity in AzoC is proposed to account for the enzyme's non-canonical oxidization of amine to nitroso product. Free nitrogen radicals induced by coenzyme pairs are proposed to be responsible for the efficient non-enzymatic azoxy bond formation. This mechanism study will provide molecular basis for the biosynthesis of azoxy high energy density materials and other valuable azoxy chemicals.

Rhodium(iii)-catalyzed [3 + 3] annulation reactions of N-nitrosoanilines and cyclopropenones: an approach to functionalized 4-quinolones

We report Rh(iii)-catalyzed [3 + 3] annulation reactions for the preparation of functionalized 4-quinolones from available N-nitrosoanilines and cyclopropenones.

Rhodium-catalyzed biheteroaryl-2-carbonitrile synthesis via double C–H activation

Rhodium(iii)-catalyzed double C–H activation and in situ dealcoholization to generate biheteroaryl-2-carbonitriles have been developed via a CDC mechanism, in which benzimidates act as both directing groups and the precursors of nitrile groups.

Rh(iii)-Catalyzed α-fluoroalkenylation of N-nitrosoanilines with 2,2-difluorovinyl tosylates via C–H bond activation

Rh(iii)-Catalyzed α-fluoroalkenylation of N-nitrosoanilines with 2,2-difluorovinyl tosylates has been realized, leading to the synthesis of monofluoroalkenes with high Z-selectivity with respect to the olefin.