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Dibenzo[b,g]phosphindolizine oxide and three types of benzo[e]naphthophosphindolizine oxides have been synthesized by the ring-closing metathesis of benzo[b]phosphole oxide and naphthophosphole oxides with two olefin tethers. Their molecular structures and properties were revealed by X-ray crystallographic analysis, UV-vis spectroscopy, and electrochemical analysis. The number and position of the benzene rings were found to alter the structural geometry and the HOMO/LUMO energy levels, and their effects were investigated by theoretical calculations. Among the phosphindolizine oxide derivatives investigated, only benzo[e]naphtho[2,3-b]phosphindolizine oxide with the naphthalene ring fused at 2,3-positions showed weak yellow fluorescence with a large Stokes shift., (© 2022 Wiley-VCH GmbH.)

A broad variety of unactivated acyclic and alicyclic substrates cleanly undergo site-selective alkenylation of unactivated C(sp 3 )-H bonds with 1,2-bis(phenylsulfonyl)ethene in the presence of persulfate. This simple transformation furnishes (E)-2-alkylvinylphenylsulfones in up to 88 % yield. In contrast with the previously reported decatungstate protocol, the current method is applicable to alkenylation of sterically hindered C-H bonds. This important advantage significantly broadens the substrate scope, and is attributed to the compact size of the sulfate radical employed in the C-H activation and cleavage., (© 2020 Wiley-VCH GmbH.)

An S-shaped double azahelicene (1) was synthesized in excellent yield by a palladium-catalyzed double dehydrogenative C-H coupling reaction. The stereochemistry of 1 was confirmed to be dl by single-crystal X-ray diffraction analysis. Selective formation of dl-1 was attributed to the isomerization of the kinetically controlled product (meso-1) into the more thermodynamically stable dl-1 under the applied reaction conditions. dl-1 can coordinate to palladium(II) in a bidentate trans-chelating fashion, which was confirmed by X-ray absorption fine structure (XAFS) as well as by X-ray photoelectron spectroscopy (XPS), diffuse reflectance (DR) UV/Vis, and far-infrared (FIR) absorption spectroscopy. Theoretical calculations of palladium complex 16 revealed a weak attractive interaction between palladium and carbon atoms on the central dimethoxynaphthalene core, which could facilitate a disproportionation between a trans-chelating (dl-1)⋅PdCl 2 complex and PdCl 2 to form 16., (© 2020 Wiley-VCH GmbH.)

Invited for the cover of this issue is Ken Kamikawa and co-workers at Osaka Prefecture University and RIKEN Center for Sustainable Resource Science. The image depicts an S-shaped double azahelicene capturing the palladium in a trans-chelating fashion. Read the full text of the article at 10.1002/chem.202002405., (© 2020 Wiley-VCH GmbH.)

The nickel(0)-catalyzed carbonylative cycloaddition of 1,5- and 1,6-ene-imines with carbon monoxide (CO) is reported. Key to this reaction is the efficient regeneration of the catalytically active nickel(0) species from nickel carbonyl complexes such as [Ni(CO) 3 L]. A variety of tri- and tetracyclic γ-lactams were thus prepared in excellent yields with 100 % atom efficiency. Preliminary results on asymmetric derivatives promise potential in the synthesis of enantioenriched polycyclic γ-lactams., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

For this study, twisted π-extended helicene 1 and double helicene 2 with a helicene framework were synthesized through palladium-catalyzed C-H arylation or Suzuki-Miyaura coupling reaction. X-ray crystallography revealed grossly twisted structures that were soluble in various conventional organic solvents. Optical properties based on UV/Vis and fluorescence spectra were measured. Electrochemical properties were also studied by measurements of cyclic voltammetry in 1 and 2, which revealed their HOMO and the LUMO energies. Theoretical calculation supports their HOMO and LUMO energies and molecular orbitals. Furthermore, a racemization process of 2 predicted that the activation free energy at 300 K would be 31.8 kcal mol(-1) by DFT calculation, which indicated the static helicity at 300 K., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The molybdenum-catalyzed asymmetric ring-closing metathesis of the various Cs -symmetric (π-arene)chromium substrates provides the corresponding bridged planar-chiral (π-arene)chromium complexes in excellent yields with up to >99 % ee. With a bulky and unsymmetrical substituent, such as N-indolyl or 1-naphthyl, at the 2-positions of the η(6) -1,3-diisopropenylbenzene ligands, both biaryl-based axial chirality and π-arene-based planar chirality are simultaneously induced in the products. The axial chirality is retained even after the removal of the dicarbonylchromium fragment, and the chiral biaryl/heterobiaryl compounds are obtained with complete retention of the enantiopurity., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Driving benzene round the twist: Azahelicene derivatives were synthesized in high yields by utilizing palladium-catalyzed C-H annulation reactions. Functionalization at the C5 position in 6-azahelicene by using palladium-catalyzed C-H arylation also gave coupling products in good yields. A tandem intra- and intermolecular double C-H coupling reaction was performed to give a functionalized helicene in a one-pot procedure., (Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.)