Yuji Nishii

Transition-metal-catalyzed C–H activation followed by oxidative cyclization with unsaturated coupling partners has been a valuable synthetic tool for the multiring molecular scaffolds. This Perspective introduces the recent progress on the Cp*M-catalyzed (M = Co, Rh, and Ir) oxidative direct annulation of functionalized arenes with terminal alkynes and their equivalents through C–H bond cleavage. The highlighted examples are categorized according to the 10 different types of reagents used in the

A Lewis base catalyst Trip-SMe (Trip = triptycenyl) for electrophilic aromatic halogenation using <i>N</i>-halosuccinimides (NXS) is introduced. In the presence of an appropriate activator (as a noncoordinating-anion source), a series of unactivated aromatic compounds were halogenated at ambient temperature using NXS. This catalytic system was applicable to transformations that are currently unachievable except for the use of Br₂ or Cl₂: e.g., multihalogenation of naphthale

Transition-metal-catalyzed C–H activation and subsequent oxidative cyclization with alkynes has been a powerful tool for the synthesis of polycyclic aromatic compounds. Despite the substantial progress in this field, it is still a significant challenge to establish synthetic methodologies for the construction of nonsubstituted vinylene-fused aromatics. We herein report a Rh(III)-catalyzed C–H/N–H annulation with vinylene carbonate as an acetylene surrogate. Vinylene carbonate also acts as an int

Transition-metal-catalyzed activation of inert C-H bonds and subsequent C-C bond formation have emerged as powerful synthetic tools for the synthesis of elaborate cyclic molecules. In this report, we introduce an efficient synthetic method of 3,4-unsubstituted isocoumarins adopting an electron-deficient Cp^ERh complex as the catalyst. The use of vinylene carbonate as a vinylene transfer reagent enables the direct construction of isocoumarins from readily available benzoic acids, withou

Transition-metal-catalyzed C-H activation followed by oxidative annulation with alkynes has been an efficient synthetic tool for the assembly of various polyaromatic scaffolds. Despite the substantial progress in this field, it is still a significant challenge to achieve the synthesis of nonsubstituted vinylene-fused compounds. In this contribution, we report a Rh-catalyzed C-H/C-H vinylene cyclization adopting vinylene carbonate as a "vinylene transfer" agent. This protocol achieves the direct

Abstract Indoles and their analogues have been one of the most ubiquitous heterocycles during the past century, and extensive studies have been conducted to establish practical synthetic methods for their derivatives. In particular, selective functionalization of the poorly reactive benzenoid core over the pyrrole ring has been a great challenge. Reported herein is an iridium‐catalyzed direct alkynylation of the indole C4‐ and C7‐positions with the assistance of sulfur directing groups. This tra

Site-selective direct functionalization of an indole benzenoid core has been a great challenge due to its inherently poor reactivity. We herein demonstrate an iridium-catalyzed C4-selective acylmethylation of indoles using α-carbonyl sulfoxonium ylides as carbene precursors. This method exhibits high efficiency and broad functional group compatibility. The directing group was easily removed or converted to other functionalities after the catalysis. The potential synthetic utility of the coupling

Abstract A benzo[ b ]thiophene synthesis by Rh‐catalyzed three‐component coupling reaction of arylboronic acids, alkynes, and elemental sulfur (S 8 ) is developed. A notable feature of this protocol is that the thienannulation (thiophene annulation) proceeds with high regioselectivity via the sequential alkyne insertion, C−H activation, and then sulfur atom transfer to the metallacycle intermediate. In a similar manner, dibenzothiophenes can be synthesized from the parent biarylboronic acids and

A rhodium-catalysed direct formylmethylation adopting vinylene carbonate as an ethynol equivalent is reported. The developed catalytic system is further utilised for the oxidant-free production of esters with the liberation of hydrogen gas. Some control experiments are conducted to elucidate the reaction mechanism.

Amide transformations involving C–N bond cleavage are recognized as difficult reactions owing to the inert nature of amides resulting from resonance. Accordingly, a strong inductive effect and geometrical distortion reasonably decrease the resonance stabilization to attenuate the C–N linkage. Although the conversion of such activated amides has been studied intensively, reaction systems for “unactivated” amides are underdeveloped. We herein report that a zinc(II) trifluoromethanesulfonate [Zn(OT

A rhodium-catalyzed oxidative annulation of benzimidates with elemental sulfur for the direct construction of isothiazole rings is reported. The proposed reaction mechanism involving Rh(I)/Rh(III) redox is supported by a stoichiometric reaction of metallacycle species as well as DFT calculations. This method is also applicable to selenium cyclization to produce isoselenazole derivatives. The alkoxy substituent at C3 can be used for further functionalization of the azole core.

Arene-fused cyclooctatetraenes (COTs) possess unique structural and electronic properties that originate from their saddle-shaped π-conjugated architectures. Considerable attention has been paid to the transition-metal-mediated synthesis of these cyclic compounds; however, there have been limited achievements to date in the efficient construction of heteroarene-fused COTs. In this contribution, we report a novel Pd-catalyzed dehydrogenative cyclodimerization of biheteroarenes through four-fold C

Benzofuran is a privileged structure in many bioactive compounds; however, the controlled synthesis of C2,C3-nonsubstituted benzofurans has been scarce. In particular, cumbersome multistep processes are inevitable for the most inaccessible C4-substituted isomers. Herein, we report a Rh-catalyzed direct vinylene annulation of readily available <i>m</i>-salicylic acid derivatives with vinylene carbonate to achieve selective construction of C4-substituted benzofurans. The Weinreb amide directing gr

Abstract Arene‐fused cyclooctatetraenes (COTs) possess unique structural and electronic properties that originate from their saddle‐shaped π‐conjugated architectures. Considerable attention has been paid to the transition‐metal‐mediated synthesis of these cyclic compounds; however, there have been limited achievements to date in the efficient construction of heteroarene‐fused COTs. In this contribution, we report a novel Pd‐catalyzed dehydrogenative cyclodimerization of biheteroarenes through fo