A new and selective C-N bond oxidative cleavage method to 3-acylated indoles by Pd-catalyzed oxidative cross coupling of indoles with α-amino carbonyl compounds has been developed; moreover, one-pot synthesis of 3-acylated indoles from 2-ethynylanilines and α-amino carbonyl compounds has also been established. Importantly, the products 3-acylated indoles can be used to construct polyheterocyclic compound, which can be employed as efficient probes for Hg(2+) and Fe(3+).
A polyoxometalate-templated silver thiolate nanocluster, [Ag62(S(t)Bu)40(Mo20O66)(Mo6O19)3(CH3CN)2]·(CF3SO3)4 (1), has been isolated, in which a giant peanut-like silver(i)-thiolate cluster [Ag62(S(t)Bu)40](22+) encapsulates an unprecedented [Mo20O66](12-) polyoxoanion core. It opens a new approach for the synthesis of both elusive polyoxometalates and high-nuclearity silver(i)-thiolate nanoclusters.
In recent years, the N-protonated chiral oxazaborolidine has been utilized as the Lewis acid catalyst for the asymmetric insertion reaction, which is one of the most challenging topics in current organic chemistry. Nevertheless, the reaction mechanism, stereoselectivity, and regioselectivity of this novel insertion reaction are still unsettled to date. In this present work, the density functional theory (DFT) investigation has been performed to interrogate the mechanisms and stereoselectivities of the formal C-C/H insertion reaction between benzaldehyde and methyl α-benzyl diazoester catalyzed by the N-protonated chiral oxazaborolidine. For the reaction channel to produce the R-configured C-C insertion product as the predominant isomer, the catalytic cycle can be characterized by four steps: (i) the complexation of the aldehyde with catalyst, (ii) addition of the other reactant methyl α-benzyl diazoester, (iii) the removal of nitrogen concerted with the migration of phenyl group or hydrogen, and (iv) the dissociation of catalyst from the products. Our computational results show that the carbon-carbon bond formation step is the stereoselectivity determining step, and the reaction pathways associated with [1, 2]-phenyl group migration occur preferentially to those pathways associated with [1, 2]-hydrogen migration. The pathway leading to the R-configured product is the most favorable pathway among the possible stereoselective pathways. All these calculated outcomes align well with the experimental observations. The novel mechanistic insights should be valuable for understanding this kind of reaction.
The multiple possible pathways of high‐valent cobalt catalyzed C−H activation/annulation of 2‐benzamidopyridine 1‐oxide with terminal alkyne were investigated in this combined theoretical and experimental study. The calculated results indicated that CoIII catalyzed C−H activation occurs via a concerted‐metalation deprotonation (CMD) process and that the subsequent annulation involves the CoIV intermediate generated through a proton‐coupled electron transfer (PCET) process in DMSO solvent or through an intermolecular single electron transfer (SET) process in trifluoroethanol (TFE) solvent. Moreover, the theoretical calculations also revealed that CoIII is the actual catalyst, and the solvent controls the chemoselectivity in the annulation stage, triggering a switch between five‐ and six‐membered ring products. Kinetic isotope effect (KIE), electron paramagnetic resonance (EPR), and TEMPO inhibition experiments were performed to confirm the computational results. The mechanistic insights should be valuable for understanding the PCET and SET processes involved in transition metal‐catalyzed C−H functionalizations.magnified image
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