It has been established that reductive complexation of functionalized benzofulvenes, which are readily prepared from commercially available indene and 2-methylindene, with RhCl in ethanol affords the corresponding indenyl-rhodium(III) dichlorides bearing substituents at the 1- (H or CO Et), 2- (H or Me), and 3- [CH Ph or CH (2-MeOC H )] positions. The indenyl-rhodium(III) complexes bearing one ethoxycarbonyl group showed higher thermal stability and regioselectivity than our previously reported Cp Rh complex toward the oxidative [3+2] annulation of acetanilides with internal alkynes.

It has been established that a cationic cyclopentadienyl (Cp) rhodium(III) complex with a pendant Nphenylcarbamoyl moiety (Cp A1 Rh III ) showed high catalytic activity towards the oxidative [3 + 2] annulation of acetanilides with internal alkynes to produce substituted indoles. Catalytic activity of the Cp A1 Rh III complex in the reactions of symmetric internal alkynes (diphenylacetylene and 6-dodecyne) was higher than that of the Cp*-rhodium(III) complex and comparable to that of a Cp-rhodium(III) complex with two ethoxycarbonyl groups (Cp E Rh III ). On the other hand, the Cp A1 Rh III complex showed significantly higher catalytic activity than the Cp E Rh III complex in the reactions of unsymmetric internal alkynes (1-phenyl-1-propyne and 1-phenyl-1-hexyne). Additionally, the catalytic activity of the Cp A1 Rh III complex in the oxidative tandem [2 + 2 + 2] annulation-lactamization of acetanilides with two unsymmetric electron-deficient internal alkynes (ethtyl 2-butynoate) was also comparable to that of the Cp E Rh III complex.

It has been established that an ewly developed cyclopentadienylr hodium(III) [Cp A Rh III ]c omplex,b earing an acidic secondary amide moiety on the Cp ring, is able to catalyzet he ortho-bromination of O-phenyl carbamates with N-bromosuccinimide (NBS) at room temperature. The presence of the acidic secondary amide moiety on the Cp A ligand accelerates the bromination by the hydrogen bond between the acidic NH group of the Cp A ligand and the carbonyl group of NBS.[a] J.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.1002/chem.202000253.Scheme1.Electrophilic and transition-metal-catalyzed bromination of protected phenols. Ts OH = p-toluenesulfonic acid. TfOH = trifluoromethanesulfonic acid.

It has been established that an electron-deficient cationic CpE-rhodium(III) complex catalyzes the non-oxidative [2+2+2] annulation of N-(1-naphthyl)acetamide with two alkynoates via cleavage of the adjacent C–H and C–N bonds to give densely substituted phenanthrenes under mild conditions (at 40 °C under air). In this reaction, a dearomatized spiro compound was isolated, which may support the formation of a cationic spiro rhodacycle intermediate in the catalytic cycle. The use of N-(1-naphthyl)acetamide in place of acetanilide switched the reaction pathway from the oxidative [2+2+2] annulation-lactamization via C–H/C–H cleavage to the non-oxidative [2+2+2] annulation via C–H/C–N cleavage. This chemoselectivity switch may arise from stabilization of the carbocation in the above cationic spiro rhodacycle by the neighboring phenyl and acetylamino groups, resulting in the nucleophilic C–C bond formation followed by β-nitrogen elimination.

A newly developed cyclopentadienyl rhodium(III) [CpARhIII] complex, bearing an acidic secondary amide moiety on the Cp ring, is able to catalyze the ortho‐bromination of O‐phenyl carbamates with NBS at room temperature. The presence of the acidic secondary amide moiety on the CpA ligand accelerates bromination by the hydrogen bond between the acidic NH group of the CpA ligand and the carbonyl group of NBS. This cover feature illustrates the activation of NBS by the above hydrogen bond. The background forest is inspired by the green chemistry aspect of this reaction. More information can be found in the Communication by K. Tanaka et al. on page 5774.

Reductive complexation of functionalized benzofulvenes, which are readily prepared from commercially available indenes, with RhCl3 in ethanol affords the corresponding indenyl‐rhodium(III) dichlorides bearing various substituents. Thus, the new gate to functionalized indenyl‐rhodium(III) complexes, as well as Cp‐rhodium(III), is now opened. Furthermore, the thus obtained indenyl‐rhodium(III) complexes bearing one ethoxycarbonyl group showed high catalytic activity and regioselectivity toward the oxidative [3+2] annulation of acetanilides with internal alkynes. More information can be found in the Communication by Yu Shibata, Ken Tanaka et al. on page 505 in Issue 5, 2018 (DOI:10.1002/asia.201701716).

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It has been established that reductive complexation of functionalized benzofulvenes, which are readily prepared from commercially available indene and 2‐methylindene, with RhCl3 in ethanol affords the corresponding indenyl–rhodium(III) dichlorides bearing substituents at the 1‐ (H or CO2Et), 2‐ (H or Me), and 3‐ [CH2Ph or CH2(2‐MeOC6H4)] positions. The indenyl–rhodium(III) complexes bearing one ethoxycarbonyl group showed higher thermal stability and regioselectivity than our previously reported CpERhIII complex toward the oxidative [3+2] annulation of acetanilides with internal alkynes.