Formal Insertion Reaction Research Articles

Synthesis and Characterization of Stable Gold(III) PNP Pincer Complexes

The first mononuclear AuIII PNP pincer complexes [PNP = bis(2‐diisopropylphosphinophenyl)amide] are reported. The chloro complex [(PNP)Au(Cl)][OAcF] (OAcF = OCOCF3) was synthesized by microwave irradiation of a tetrachloroaurate salt and the neutral PNHP ligand. Dehalogenation with AgOAcF afforded the trifluoroacetate‐bound complex [(PNP)Au(OAcF)][OAcF]. Both complexes were characterized by NMR spectroscopy and X‐ray crystallography. Electronic absorption spectroscopy and TD‐DFT studies assigned the electronic transition that imbues the complexes with a deep royal blue color. The AuIII trifluoroacetate complex is surprisingly stable, and no alkene insertion was observed under ethylene (C2H4), even under high pressures and at high temperatures. DFT calculations suggest that the lack of reactivity is due to the high energy of the putative dicationic C2H4‐bound intermediate invoked in a formal insertion reaction.

ChemInform Abstract: Synthesis of o‐Aminophenols via a Formal Insertion Reaction of Arynes into Hydroxyindolinones.

AbstractA series of 1‐(2‐hydroxyphenyl)indolinones (V) is readily prepared by a fluoride‐mediated reaction of N‐hydroxyindolinones with benzyne precursor (II).

Synthesis of o-Aminophenols via a Formal Insertion Reaction of Arynes into Hydroxyindolinones.

A novel approach toward the synthesis of sterically hindered o-aminophenols has been achieved by a formal aryne insertion into hydroxyindolinones. This transformation offers a rapid and efficient entry to diverse o-aminophenol scaffolds under mild transition-metal-free conditions. The reaction involves the addition of hydroxyindolinones to arynes followed by a chemo- and regioselective [1,3]-rearrangement. Furthermore, the reactions of N-hydroxyindoles and arynes were found to provide the C3-aryl indole products via an alternative [3,3]-rearrangement pathway.

General Approach to Nitrogen-Bridged Bicyclic Frameworks by Rh-Catalyzed Formal Carbenoid Insertion into an Amide C–N Bond

Various nitrogen-bridged bicyclic skeletons are found in bioactive natural products and pharmaceuticals. The development of a new reaction to construct these molecular frameworks has attracted considerable attention in synthetic organic chemistry. We developed a novel synthetic method for obtaining a wide variety of nitrogen-bridged bicyclic compounds with a catalytic process, Rh-catalyzed formal carbenoid insertion into an amide C-N bond. Using 0.1-0.4 mol % Rh2(NHCO(t)Bu)4 catalyst, various azabicyclo[X.Y.Z]alkane derivatives were obtained in good to excellent yield, successfully demonstrating the broad substrate scope of the developed process. Experimental and computational studies to elucidate the reaction mechanism revealed that the formal insertion reaction of a carbenoid into an amide C-N bond proceeded via the formation of Rh-associated N-ylides, followed by an acyl group-selective Stevens [1,2]-shift through a concerted addition/elimination process on the sp(2)-hybridized carbon.

Novel silacyclohexadienyl chromium and iron complexes bearing a bulky substituent on the central silicon atom

Novel hydrido(silacyclohexadienyl)chromium complexes bearing a bulky substituent, Tbt (2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), were synthesized using formal insertion reactions of Cr(0) into C–H or Si–H bond. When the reactions of 1-silacyclohexa-2,4-dienes bearing a hydroxy or chloro group on the silicon atom with [Cr(CH3CN)3(CO)3] were performed, the corresponding hydrido(1-silacyclohexa-2,4-dienyl) complexes were obtained as the sole product. A similar reaction of a hydrosilane having a similar skeleton with [Cr(CH3CN)3(CO)3] gave an unprecedented type of silacyclohexadienyl complex, hydrido(1-silacyclohexa-1,3-dienyl)chromium bearing a three-center bonding interaction among the silicon, hydrogen, and chromium atoms. These are the first syntheses of silacyclohexadienyl complexes by the formal insertion reaction toward the corresponding silacyclohexadienes. Furthermore, the isolation of the silacyclohexadienyl anion was achieved; it was applied to synthesis of the corresponding sandwich-type iron complex. Structures of the newly obtained complexes were revealed based on their NMR and IR spectroscopic data and X-ray diffraction study.

Copper-Catalyzed 2:1 Coupling Reaction of Arynes with Alkynes

A formal insertion reaction of two molar amounts of arynes into a C-H bond of terminal alkynes is efficaciously catalyzed by copper(I) chloride, giving 2-alkynylbiaryls in one step.

Formation of Palladium- and Platinum-Substituted Fulvenes by Cyclopentadienyl Activation in a Formal Insertion Reaction

Stepwise, low-temperature reaction of {Pd[CH(SiMe3)2](PMe3)(μ-Cl)}2 with CNBu-t and NaCp‘ (Cp‘ = C5H5, C5H4Me) affords metal-substituted fulvenes of composition {Pd[C(NHBu-t)C(C4H3R)][CH(SiMe3)2](CNBu-t)(PMe3)}, of which the C5H4Me-derived complex 2b (R = Me) has been characterized by X-ray crystallography. The formation of related complexes of Pt is also reported.