Mn(i)-Catalyzed nucleophilic addition/ring expansion via C–H activation and C–C cleavage

Rh(II)-Catalyzed Selective C(sp3)-H/C(sp2)-H Bonds Cascade Insertion to Construct [6-8-6] Benzo-Fused Scaffold

The fused eight-membered carbocycles (EMCs) play vital roles in the medicinal and biological investigations of many natural products and marketed drugs. The traditional synthesis of [6-8-6] benzo-fused derivatives involves multistep reactions and low yields, making the development of a one-step synthesis method a more challenging work. Here, we present a novel strategy for one-step construction of [6-8-6] benzo-fused scaffold from propargyl diazoacetates substituted with benzyl-nitrogen heterocyclic ring via Rh(ll)-catalyzed carbene/alkyne metathesis (CAM) and selective C-H bond insertion. This method exhibits a specific substrate scope, simple operation, mild reaction conditions, and high atom efficiency. Mechanistically, the process involves sequential CAM, 1,3-H-shift, intramolecular nucleophilic attack, and selective C(sp3)-H/C(sp2)-H bonds cascade insertion. Notably, the unique spirocyclic zwitterionic intermediate generated in this sequence contributes to N-heterocycle migration and fused eight-membered carbocycle formation. Additionally, the C(sp3)-H bond insertion connected to the oxygen atom rather than the nitrogen atom has been unexpectedly confirmed with the assistance of the spirocyclic zwitterionic intermediate. Overall, our findings open up a new avenue for the construction of [6-8-6] benzo-fused scaffold.

A Water-Soluble Rhenium(I) Catalyst for the Regio- and Stereoselective C(sp2)-H Alkenylation of N-Pyridyl-/N-Pyrimidylindole and the N-H Alkenylation of N-Pyrimidylaniline Derivatives with Ynamides

A water-soluble and low-valent rhenium(I) catalyst for the C2 alkenylation of N-pyridyl/N-pyrimidylindole derivatives with ynamides under mild conditions using water as the solvent has been described. The reaction of N-pyridyl/N-pyrimidyl indole with the ynamide afforded the C2-Z-selective alkenylation derivative as the sole product, and the reactions of N-pyrimidylanilines delivered the corresponding N-alkenylated product rather than the expected C-H alkenylation products in high yields under the same conditions.

Recent advances and perspectives in manganese-catalyzed C–H activation

Manganese-catalyzed C–H activation has become an emerging area in organic chemistry. These efficient and eco-friendly manganese catalysed reactions provides new opportunities in the field of synthetic organic chemistry.

Regioselective cascade annulation of indoles with alkynediones for construction of functionalized tetrahydrocarbazoles triggered by Cp*RhIII-catalyzed C–H activation

An efficient regioselective and stereoselective cascade annulation of indoles with alkynediones has been developed for construction of free (NH) tetrahydrocarbazoles with continuous quaternary carbons via Cp*Rh^III-catalyzed indole C2–H activation.

Recent Advances on Synthetic Methodology Merging C-H Functionalization and C-C Cleavage

The functionalization of C-H bonds has become a major thread of research in organic synthesis that can be assessed from different angles, for instance depending on the type of catalyst employed or the overall transformation that is carried out. This review compiles recent progress in synthetic methodology that merges the functionalization of C-H bonds along with the cleavage of C-C bonds, either in intra- or intermolecular fashion. The manuscript is organized in two main sections according to the type of substrate in which the cleavage of the C-C bond takes place, basically attending to the scission of strained or unstrained C-C bonds. Furthermore, the related research works have been grouped on the basis of the mechanistic aspects of the different transformations that are carried out, i.e.,: (a) classic transition metal catalysis where organometallic intermediates are involved; (b) processes occurring via radical intermediates generated through the use of radical initiators or photochemically; and (c) reactions that are catalyzed or mediated by suitable Lewis or Brønsted acid or bases, where molecular rearrangements take place. Thus, throughout the review a wide range of synthetic approaches show that the combination of C-H and C-C cleavage in single synthetic operations can serve as a platform to achieve complex molecular skeletons in a straightforward manner, among them interesting carbo- and heterocyclic scaffolds.

On-surface synthesis of planar acenes via regioselective aryl-aryl coupling

The reaction of 2,2'-dibromo-biphenyl on a Ag(111) surface leads to the formation of planar acenes with a high-regioselectivity rather than nonplanar saddle-shaped tetraphenylene as the typical product in solution chemistry. The regioselective aryl-aryl coupling reaction is attributed to the hydrogen repulsion between the reactants on the confined two-dimensional surface.

A Zn(II)-Coordination Polymer for the Instantaneous Cleavage of Csp3-Csp3 Bond and Simultaneous Reduction of Ketone to Alcohol

Two coordination polymers of Zn(II) and Cu(II) with n-butylmalonic acid have been achieved in this work. The crystallographic structural descriptions along with the sedimentary rock-type microstructural morphology of these two coordination polymers (CPs) have been explored. The reactivity of β-hydroxy ketones with these two CPs has also been investigated. The Zn(II)-CP shows a specific reactivity with β-hydroxy ketone at room temperature and in open air conditions. Through a microcolumn-based filtration technique, the Zn(II)-CP shows the capability to break the C_sp³-C_sp³ σ bonds of β-hydroxy ketone and simultaneously reduce the associated ketone to alcohol. Such conversion has been progressed without the use of any additional external reducing agent and any chemical workup or column chromatographic purification protocol. Other similar type CPs of Cu(II) and Mn(II) with n-butylmalonic acid completely failed to show similar reactivity with β-hydroxy ketone. On the basis of much experimental evidence, the most possible mechanistic pathway of the reactivity between β-hydroxy ketone and Zn(II)-CP has also been proposed through this work.