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Beyond previously described carbo‐naphthalene and carbo‐biphenyl, a novel type of bis‐carbo‐benzenic molecules is envisaged from the stilbene parent. The synthesis, structure, spectroscopic and electrochemical properties of two such carbo‐stilbenes are described at complementary experimental and computational DFT levels. In the selected targets, the bare skeletal carbo‐mer of carbo‐stilbene is decorated by 8 or 10 phenyl groups, 0 or 2 tert‐butyl groups, and 2 n‐octyl chains, the later substituents being introduced to compensate anticipated solubility issues. As in the parent stilbene series, isomers of the phenylated carbo‐stilbenes are characterized. The cis‐ and trans‐isomers are, however, formed in almost equal amounts and could not be separated by either chromatography or crystallization. Nevertheless, due to a slow interconversion at the NMR time scale (up to 55 °C) the 1H NMR signals of both isomers of the two carbo‐stilbenes could be tentatively assigned. The calculated structure of the cis‐isomer exhibits a helical shape, consistent with the observed magnetic shielding of phenyl p‐CH nuclei residing inside the shielding cone of the facing C18 ring. The presence of the two isomers in solution also gives rise to quite broad UV‐vis absorption spectra with main bands at ca 460, 560 and 710 nm, and a significant bathochromic shift for the decaphenylated carbo‐stilbene vs the di‐tert‐butyl‐octaphenylated counterpart. Square wave voltammograms do not show any resolution of the two isomers, giving a reversible reduction wave at −0.65 or −0.58 V/SCE, and an irreversible oxidation peak at 1.11 V/SCE, those values being classical for most carbo‐benzene derivatives. Calculated NICS values (NICS(1)=−12.5±0.2 ppm) also indicate that the aromatic nature of the C18 rings is not markedly affected by the dialkynylbutatriene (DAB) connector between them. [ABSTRACT FROM AUTHOR]

An efficient rhodium(III)‐catalysed C−H activation of 3‐aryl‐1‐H‐indazoles with easily available vinylethylene carbonate has been reported. A series of allyl alcohol substituted 3‐aryl‐1‐H‐indazoles were obtained with broad functional groups tolerance and favourable stereoselectivity. Notably, C−H and C−O bonds were selectively activated in "one pot" manner, releasing CO2 as the sole by‐product and avoiding external oxidant. This protocol provides a powerful approach for the post stage C−H allylation of indazole‐based substrates. [ABSTRACT FROM AUTHOR]

Pd(II) catalysts, particularly the acetate salt in acetic acid, tended to favor regioselective C–H activation of quinoline N-oxides (QOs) at the C2 position. However, Pd(II)Cl2 was shown to catalyze their C–H activation at C8 and, in the presence of water, C8–H activation was accompanied by the formation of 2-quinolinones. The aim of the DFT study described in this work was to shed light on the complete mechanism of these competing catalytic reactions, when PdCl2 reacts with QO and benzaldehyde in dichloroethane. C–H activation of QO was the first step of the reaction and involved either a metallacycle, with a CQO–Pd(II) σ-bond and a C(8)–H–Pd(II) agostic bond, or an η3-QO complex, with three carbon atoms of the heteroring of QO binding PdCl2. The first situation led to the unusual C8 activation and the second to C2 activation. The σ-metallacycle undergoes C8–H activation and the energy of the TOF determining the transition state to form the product is ∼17 kcal mol−1, while for the reaction through the π-metallacycle (C2–H activation) the corresponding energy is higher (∼29 kcal mol−1) and thus is not competitive under the same conditions. The reaction proceeding through the σ-complex, activating the C8 position, is preferred, in agreement with experimental results. Both reactions involve oxidation of Pd(II) to Pd(IV) and the catalyst is regenerated. When small amounts of water are added to the reaction mixture, C8–H activation (acylation) results from the same σ-metallacycle with the same barrier, but the simultaneous formation of 2-quinolinones is more complicated. It starts with OH− attack at the C2 position, and is followed by the migration of two hydrogen atoms, and the final reductive elimination step ends with Pd(0). The higher barriers for the migration and reoxidation of Pd(0) are associated with the more demanding reaction conditions. The different reactivity of Pd(II)(OAc)2 under analogous conditions is clarified, as it is only capable of forming the above mentioned π-complex and thus of activating the C2 position of QO. This catalyst can preferentially activate the C8–H bond under rather different conditions, including in particular acetic acid medium, as shown by other authors. [ABSTRACT FROM AUTHOR]

TBAI‐catalysed [4+4]‐cyclization reaction of anthranils with hydrazones to deliver oxa‐bridged eight‐membered heterocycles in accepted yields was developed. Preliminary mechanistic studies indicated that the reaction involved the in situ generation of vinyldiazenes from readily available hydrazones followed by an aza‐Michael addition of the anthranil substrates onto the vinyldiazenes and subsequent annulation. This transformation involved the formation of two new C−N bonds and C−O bond in one pot, overcoming the synthetic limitations of anthranils in organic chemistry. This strategy benefits from high efficiency and atomic economy with mild reaction conditions. [ABSTRACT FROM AUTHOR]

A highly efficient strategy to construct benzo[d][1,3]diazepines via selective C−H bond activation of N‐aryl amidines and coupling with alkynyl cyclobutyl acetates was achieved successfully by RuII‐catalyzed [5+2] cyclization. This protocol features excellent regioselectivity, wide substrate tolerance, mild reaction conditions, which might be potentially applied in the discovery of lead compounds for the developing new drugs. [ABSTRACT FROM AUTHOR]