Rh(iii)-Catalyzed acylation of heteroarenes with cyclobutenones via C-H/C-C bond activation

Engaging vinylene carbonate in ruthenium-catalyzed regioselective C-4 methylenation and C-8 formylmethylation of isoquinolinones

Herein, we disclose the first reports on the utilization of vinylene carbonate as a C1 methylene source in ruthenium-catalyzed additive controlled regioselective C4-methylenation and weak chelation-assisted C8-formylmethylation of isoquinolinones. Adopting vinylene carbonate as both a C2 and C1 synthon is an important highlight of this work. Amide carbonyl acts as the traceless directing group in C8-formylmethylation. Remarkably, in this reaction, two C-C bonds form in one-pot producing dimeric isoquinolinones by employing vinylene carbonate as a methylene surrogate in the presence of copper acetate as an additive. Importantly, unsymmetrical dimers were achievable, albeit in low yield. Extensive control experiments are conducted to decipher the reaction mechanism. It is evident from the mechanistic studies, that the formation of a formylmethyl group in situ at the C4-carbon undergoes dimerization, oxidation and subsequent decarboxylation to produce methylene-bridged isoquinolinone dimers. This protocol is scalable and compatible with a repertoire of substrates and shows high functional group tolerance. Harnessing vinylene carbonate as both a C2 and C1 synthon is an important highlight of this work.

Inherent directing group-enabled Co(III)-catalyzed C-H allylation/vinylation of isoquinolones

Co(III)-catalysed site-selective C8-allylation and vinylation of isoquinolones with allyl acetate and vinyl acetates has been accomplished. The oxo group of isoquinolone has been utilised as an inherent directing group. Based on preliminary mechanistic studies, a plausible mechanism for the developed reaction has also been delineated. Broad substrate scope with good to excellent yields and post-synthetic transformations of allylated and vinylated isoquinolines highlight the importance of the reaction.

Carbene-Catalyzed [4+2] Cycloaddition of Cyclobutenones and Isatins for Quick Access to Chiral Chlorine-Containing Spirocyclic δ-Lactones

Here we report a carbene-catalyzed enantio- and diastereoselective [4+2] cycloaddition reaction of cyclobutenones with isatins for the quick and efficient synthesis of spirocyclic δ-lactones bearing a chiral chlorine. A broad range of substrates with various substitution patterns proceed smoothly in this reaction, with the spirooxindole δ-lactone products afforded in generally good to excellent yields and optical purities under mild reaction conditions.

Regiocontrol via Electronics: Insights into a Ru-Catalyzed, Cu-Mediated Site-Selective Alkylation of Isoquinolones via a C-C Bond Activation of Cyclopropanols

A site-selective C(3)/C(4)-alkylation of N-pyridylisoquinolones is achieved by employing C-C bond activation of cyclopropanols under Ru(II)-catalyzed/Cu(II)-mediated conditions. The regioisomeric ratios of the products follow directly from the electronic nature of the cyclopropanols and isoquinolones used, with electron-withdrawing groups yielding predominantly the C(3)-alkylated products, whereas the electron-donating groups primarily generate the C(4)-alkylated isomers. Density functional theory calculations and detailed mechanistic investigations suggest the simultaneous existence of the singlet and triplet pathways for the C(3)- and C(4)-product formation. Further transformations of the products evolve the utility of the methodology thereby yielding scaffolds of synthetic relevance.

Diastereoselective formation of β-lactams via a three-component reaction

A highly diastereoselective three-component reaction of N-hydroxyanilines, diazo compounds and cyclobutenones to form densely functionalized β-lactams has been realized.

[4+3]-Cycloaddition Reaction of Sulfilimines with Cyclobutenones: Access to Benzazepinones

A catalyst-free [4+3]-cycloaddition reaction of N-aryl sulfilimines with cyclobutenones is described, which provides a straightforward protocol for synthesizing 1,5-dihydro-2H-benzo[b]azepin-2-ones under mild reaction conditions. This reaction features a broad substrate scope and good functional group tolerance and does not require catalysts or additives. Moreover, using N-pyridinyl sulfilimine as the substrate, a series of pyridoazepinones have also been prepared.

Co(III)-catalysed regioselective linear C(8)-H olefination of isoquinolone with terminal aromatic and aliphatic alkynes

A regioselective C8 linear olefination of isoquinoline-1H-2-one with terminal (aromatic and aliphatic) alkynes is reported under Co(III) catalysis. This is an exclusive report on the C8 functionalization of isoquinolone using non-noble transition metal complexes. Experimental and computational mechanistic studies have also been performed to depict the reaction pathway.

Alternative and Uncommon Acylating Agents - An Alive and Kicking Methodology

Functionalizing and derivatising organic molecules is a centerpiece in organic synthesis. Succinctly manipulating and installing acyl moieties in organic molecules spurred the interest of chemists owing to its occurrence in natural products, bioactive molecules, pharmaceuticals, and advanced materials. Traditionally, access to acylation reaction was achieved by Friedel-Crafts reaction, Schotten-Baumann, and Vilsmeier-Haack acylation, however, these protocols own pitfalls. Further to make the acylation process attractive and environmentally friendly, toluene, aldehydes, alcohols, α-keto acids, amines, amides, esters, ethers, nitriles, alkynes, alkenes, ketenes, N-acylbenzotriazoles, ketones, thioacids, oximes, thiazolium carbinols, PIDA, diacyl disulfides and acyl salts were used as an acyl surrogates/reagents. Amusingly, these acylating reagents are considered uncommon and alternative to carboxylic acids, acid chlorides and acetic anhydrides. This short review aims to encompass the usage of acylating agents in transition-metal, metal-free, light-driven and other demanding conditions, and thus reveals their practicality.

Access to the C2 C–H olefination, alkylation and deuteration of indoles by rhodium(iii) catalysis: an opportunity for diverse syntheses

A concise approach for a diversity-oriented synthesis via regioselective C2 C–H olefination, alkylation, and deuteration of indoles by Rh(iii) catalysis is described.

Rh(iii)-Catalyzed C–H allylation/annulative Markovnikov addition with 5-methylene-1,3-dioxan-2-one: formation of isoquinolinones containing a C3 quaternary centre

Rh(iii)-Catalyzed C–H allylation/annulative Markovnikov addition reaction was disclosed, offering isoquinolinones containing a C3 quaternary centre. By using this method as the key step, the US28 inverse agonist analogs were synthesized.

Transition metal-catalyzed C–H functionalizations of indoles

This review summarises a wide range of transformations on the indole skeleton, including arylation, alkenylation, alkynylation, acylation, nitration, borylation, and amidation, using transition-metal catalyzed C–H functionalization as the key step.