Merging C-H Activation and Strain-Release in Ruthenium-Catalyzed Isoindolinone Synthesis

Practical synthesis of isocoumarins via Rh(III)-catalyzed C-H activation/annulation cascade

Herein, we report an unprecedented Rh(III)-catalyzed C-H activation/annulation cascade of readily available enaminones with iodonium ylides towards the convenient synthesis of isocoumarins. This coupling system proceeds in useful chemical yields (up to 93%) via a cascade C-H activation, Rh-carbenoid migratory insertion and acid-promoted intramolecular annulation. The success of gram-scale reaction and diverse functionalization of isocoumarins demonstrated the synthetic utility of this protocol.

Organo-cyanamides: convenient reagents for catalytic amidation of carboxylic acids

An unprecedented DMAP-catalysed amidation of aryl and alkyl carboxylic acids with organo-cyanamides has been developed. Unlike the use of N-cyano-N-phenyl-p-methylbenzenesulfonamide (NCTS) as an electrophilic cyanating reagent, an unusual desulfonylation/decyanation reaction model has been disclosed for the first time. Remarkable features of this reaction include readily available substrates, simple operation and broad scope, enabling the efficient synthesis of structurally diverse amides. The synthetic utility of this protocol was demonstrated by the late-stage amidation of bioactive carboxylic acids and a scale-up reaction.

Synthesis of Unsymmetrical Ketones Using Chelation-Controlled Sequential Substitution of N-Triazinylamide/Weinreb Amide by Organometallic Reagents

N-(2,4-Dimethoxy-1,3,5-triazinyl)amide was found to exhibit similar behavior to N-methoxy-N-methylamide (Weinreb amide) but higher reactivity for nucleophilic substitution by organometallic reagents. Triazinylamide suppresses overaddition, leading to the formation of a tertiary alcohol by the chelating ability of the triazinyl and carbonyl groups. Ureas possessing both triazinylamino and methoxy(methyl)amino groups underwent sequential nucleophilic substitution with different organometallic reagents, which furnished unsymmetrical ketones without any detectable tertiary alcohols.

Access to quinolinones via DMAP-catalysed cascade reaction of 2-substituted benzoic acids with organic azides

Herein, we report a DMAP-catalysed Curtius rearrangement and intramolecular cyclisation cascade reaction of 2-substituted aryl carboxylic acids with organic azides for the first time. This protocol features simple operation, broad scope and metal-free conditions, furnishing a broad spectrum of biologically attractive heterocycles. The synthetic virtue of this reaction was demonstrated by gram-scale synthesis and applicability toward drug-like molecules.

Synthesis of 1,2-oxazetidines with a free -NH group via photoredox catalysis

A photoredox approach enabling one-step synthesis of oxazetidines with a free -NH group via the combined use of alkyne, thiophenol, and azide has been reported. The synthesized oxazetidine with the free -NH group was stable enough for various late-stage transformations such as methylation, acetylation, tosylation, and ring-opening reaction to afford synthetically useful α-aminoketones.

Merging strain-release and copper catalysis: the selective ring-opening cross-coupling of 1,2-oxazetidines with boronic acids

An unprecedented ring-opening cross-coupling of 1,2-oxazetidines with readily available arylboronic acids is achieved for the first time by copper catalysis. Unlike the known electrophilic oxygen reactivity in coupling with organometallic reagents, 1,2-oxazetidines were utilized as formaldimine precursors in this protocol. Remarkable features of this reaction include simple operation, inexpensive catalyst, broad scope and high regioselectivity, delivering a wide array of aminomethylation products. The practicality of this reaction was validated in the one-step downstream transformation of the obtained products into synthetically important molecules and late-stage modification of bioactive acids.

Divergent synthesis of fused N-heterocycles via rhodium-catalysed [4+2] cyclization of pyrazolidinones with iodonium ylides

A catalytic system-controlled divergent strategy is developed for the precise synthesis of cinnolines and pyrazolo[1,2-a]cinnolines via rhodium-catalysed [4+2] cyclization of readily available pyrazolidinones and iodonium ylides. A range of cinnolines...

Transition metal-free advanced synthetic approaches for isoindolinones and their fused analogues

The transition metal-free synthetic protocols of isoindolinone and its fused analogues are highlighted in this review since 2007 to 2021.

Strain-release enabled [3 + 2] annulation of 3-aminooxetanes with simple CN bonds: facile synthesis of imidazolidines

An unprecedented [3+2] annulation of readily available 1,3,5-triazinanes and 3-aminooxetanes is accomplished for the first time, enabling the convenient synthesis of a range of structurally diverse 4-hydroxymethyl imidazolidines.