Synthesis of Heteroaryl Compounds through Cross-Coupling Reaction of Aryl Bromides or Benzyl Halides with Thienyl and Pyridyl Aluminum Reagents

An efficient method for synthesis of useful biaryl building blocks containing 2-thienyl, 3-thienyl, 2-pyridyl, and 3-pyridyl moieties was provided through cross-coupling reactions of aryl bromides or benzyl halides with heteroaryl aluminum reagents in the presence of Pd­(OAc)₂ and (<i>o</i>-tolyl)₃P. The coupling reaction also worked efficiently with heteroaryl bromides affording series of heterobiaryl compounds. The reaction of phenylbromide with in situ prepared 3-pyridyl aluminum was demonstrated to afford the product <b>8a</b> in high yield. Additionally, the catalytic system was also suited well for the coupling reaction of benzyl halides with pyridyl aluminum reagents to afford series of pyridyl-arylmethane

Unusual selective reactivity of the rare-earth metal complexes bearing a ligand with multiple functionalities

International audienceLigands play a key role in controlling activity of organometallic complexes so that development of new ligands to overcome the challenge is the main topic of modern chemistry. The first example of 1,1-hydride migratory insertion and intramolecular redox reaction has been realized in this work by applying a new ligand in rare-earth metal chemistry. The novel rare-earth metal complexes LMesRECH2TMS(THF) (RE = Y (1a), Dy (1b), Er (1c), Yb (1d), LMes = 1-(3-(2,6-iPr2C6H3N=CH)C8H4N)-CH2CH2-3-(2-CH2—4,6-Me2C6H2)-(N(CH)2NC), THF = tetrahydrofuran) bearing a ligand with imino, indolyl, NHC (N-heterocyclic carbene) multiple functionalities were synthesized and characterized. Treatment of complexes 1 with silanes (PhSiH3 or PhSiH2Me or PhSiD3) selectively produced the unprecedented 1,1-hydride (or deuterated H) migratory insertion of the indolyl moiety of the novel unsymmetrical dinuclear rare-earth metal complexes 2. The complex 2a reacts with Ph2C-O to give the selective C-O double bond insertion to the RE-Co-methylene-Mes bond product 3a which further reacts with another Ph2C-O (or DMAP, 4-N, N-dimethylaminopyridine) affording the novel μ-η2:η3-dianionic 3-iminoindolyl dinuclear rare-earth metal complex 4a. The latter is formed through an unusual intramolecular redox reaction (through electron migration from the 2-carbanion of the indolyl ring to the imino motif) resulting in the re-aromatization of the indolyl ring

Experimental and Theoretical Evidence for the First Example of an Organolanthanide(II) Compound Having an Indenyl Ligand Bonded to the Metal through the Benzo Ring in η4 Hapticity

International audienceThe reaction of 2 equiv of C9H6-1-SiMe3-3-CH2CH2NC5H10 (2) with the ytterbium(III) amide [(Me3Si)2N]3Yb-(μ-Cl)Li(THF)3 produced a novel ytterbium(II) complex with an indenyl ligand bonded to the metal via the benzo ring with η4 hapticity, [η4:η2:η1-(C5H10NCH2CH2C9H5SiMe3)Li(μ-Cl)]Yb-(η5:η1-C5H10NCH2CH2C9H5SiMe3) (1), as verified by a solid-state structure determination and theoretical calculations

Coordination and Reactivity Diversity of N-Piperidineethyl-Functionalized Indenyl Ligands: Synthesis, Structure, Theoretical Calculation, and Catalytic Activity of Organolanthanide Complexes with the Ligands

International audienceThe interactions of N-piperidineethyl-functionalized indene compounds 1-R-3-C5H10NCH2CH2C9H6 (R = H− (1), Me3Si− (2)) with lanthanide(III) amides [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Yb, Eu, Sm, Nd) were studied. The results indicated that the ligands and reductive potentials of Ln3+/Ln2+ have an influence on the reaction patterns and the coordination mode of the indenyl ligands with the central metals. Reactions of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Yb, Eu) with 2 equiv of corresponding indene compounds 1-R-3-C5H10NCH2CH2C9H6 (R = H− (1), Me3Si− (2)) produced organolanthanide(II) complexes [η5:η1-C5H10NCH2CH2C9H6]2LnII (Ln = Yb (3), Eu (5)) and novel organolanthanide(II) complexes with general formula [η4:η2:η1-(C5H10NCH2CH2C9H5SiMe3)Li(μ-Cl)]LnII(η5:η1-C5H10NCH2CH2C9H5SiMe3) (Ln = Yb (4), Eu (6)), and a new highly conjugated bis(N-piperidineethyl)dibenzofulvalene, (C5H10NCH2CH2C9H5)2 (9), was unexpectedly isolated as a byproduct in the preparation of 6, indicating the ligands' effects on the coordination and reactivity patterns. Theoretical calculations on ytterbium(II) complexes having indenyl ligands indicated that the indenyl hapticity depends on the strain, steric, and electronic effects. Treatment of lanthanide(III) amides [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Sm, Nd) with 2 equiv of C5H10NCH2CH2C9H7 (1) afforded indenyl lanthanide(III) complexes with general formula [η3-C5H10NCH2CH2C9H6]2LnIII[η3:η1-C5H10NCH2CH2C9H6] (Ln = Sm (7), Nd (8)). The shortest distances involving the nonbridging atoms of the C5 portions of the indenyl groups indicated an allyl-like nature of the ligand-to-metal coordination. The interaction of [(Me3Si)2N]3SmIII(μ-Cl)Li(THF)3 with 2 equiv of 1-Me3Si-3-C5H10NCH2CH2C9H6 (2) produced an unexpected bis(N-piperidineethyl)dibenzofulvalene (C5H10NCH2CH2C9H5)2 (9) and other unidentified solids, suggesting the ligands' influence on the reactivity patterns. All the compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of compounds 4, 7, 8, and 9 were additionally determined by X-ray diffraction study. The catalytic activity of the organolanthanide complexes 3−8 on MMA polymerization was examined. It was found that the π-bonded tris(N-piperidineethylindenyl)lanthanide(III) complexes 7 and 8 exhibit unexpected good catalytic activity on MMA polymerization, and complex 7 also showed an unexpected high catalytic activity on ε-caprolactone polymerization. It was found that the catalytic activity of the complexes depended on the polymerization conditions. The solvents, temperatures, substituted groups, and lanthanide ionic radii effects on the catalytic activity of the complexes were examined

Lewis Acid Catalyzed Cascade Reaction to Carbazoles and Naphthalenes via Dehydrative [3 + 3]-Annulation

A novel Lewis acid catalyzed dehydrative [3 + 3]-annulation of readily available benzylic alcohols and propargylic alcohols was developed to give polysubstituted carbazoles and naphthalenes in moderate to good yields with water as the only byproduct. The reaction was presumed to proceed via a cascade process involving Friedel–Crafts-type allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner–Meerwein rearrangement

A Novel Lewis Acid Catalyzed [3 + 3]-Annulation Strategy for the Syntheses of Tetrahydro-β-Carbolines and Tetrahydroisoquinolines

A novel Lewis acid catalyzed [3 + 3]-annulation process for the efficient syntheses of both tetrahydro-β-carbolines and tetrahydroisoquinolines from readily available benzylic alcohols and aziridines was developed, which would be a highly valuable complement to the widely used Pictet–Spengler reaction. A probable mechanism was proposed based on the isolation and characterization of two key intermediates. This strategy enables facile access to important alkaloid frameworks not easily available with other known methods

Reactivity of 3‑Imino-Functionalized Indoles with Rare-Earth-Metal Amides: Unexpected Substituent Effects on C–H Activation Pathways and Assembly of Rare-Earth-Metal Complexes

The reactivities of different 3-imino-functionalized indoles with rare-earth-metal amides [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ were studied to reveal unexpected substituent effects on C–H bond activation pathways, leading to the formation of unusual rare-earth-metal complexes. The reactions of 3-(<i>tert-</i>butylimino)­indole with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ produced tetranuclear rare-earth-metal complexes {[η¹:(μ₂-η¹:η¹):η¹-3-(<i>t</i>BuNCH)­C₈H₄N]­RE₂­(μ₂-Cl)₂(THF)­[N­(SiMe₃)₂]­(η¹:η¹-[μ-η⁵:η²<i>-</i>3-(<i>t</i>BuNCH)­C₈H₅N]₂Li)}₂ (RE = Ho (<b>1a</b>), Er (<b>1b</b>)), incorporating a unique indolyl-1,2-dianion through sp² C–H activation bonded with the central metal in η¹:(μ₂-η¹:η¹) mode. The reactions of 3-(phenylimino)­indole with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ afforded novel binuclear complexes formulated as {3-[PhNCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NRE­(THF)­(μ₂-Cl)­Li­(THF)₂}₂ (RE = Y (<b>2a</b>), Sm (<b>2b</b>), Dy (<b>2c</b>), Yb (<b>2d</b>)) through an unexpected sp³ C–H bond activation with subsequent C–C bond coupling reactions. Treatment of 3-(2-methylphenylimino)­indole or 3-(4-methylphenylimino)­indole with [(Me₃Si)₂N]₃­Yb­(μ-Cl)­Li­(THF)₃ generated the corresponding dinuclear rare-earth-metal amido complexes {3-[(2-MePh)­NCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NYb­(THF)­(μ₂-Cl)­Li­(THF)₂}₂ (<b>3</b>) and {3-[(4-MePh)­NCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NYb­(THF)­(μ₂-Cl)­Li­(THF)₂}₂ (<b>4</b>), following the same pathway for the formation of complexes <b>2a</b>–<b>d</b>. Treatment of 3-(4-<i>tert</i>-butylphenylimino)­indole with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ afforded new hexanuclear rare-earth-metal complexes {3-[(4-^<i>t</i>Bu-Ph)­NHCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NREN­(SiMe₃)₂}₆ (RE = Dy (<b>5a</b>), Ho (<b>5b</b>), Er (<b>5c</b>)) via sp³ C–H bond activation followed by C–C bond coupling reactions. In contrast, under the same conditions as those for the preparation of <b>5</b>, the reaction with the corresponding yttrium complex provided the new heterohexayttrium complex {3-[(4-<i>t</i>Bu-Ph)­NCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NYN­(SiMe₃)₂­Li­(THF)}₆ (<b>6</b>), having a 4-<i>t</i>Bu-anilido moiety. All of these complexes were fully characterized by elemental analysis, spectroscopic methods, and X-ray structure analysis. Plausible pathways for the formation of these different rare-earth-metal complexes were proposed

Reactivity of 1,3-Disubstituted Indoles with Lithium Compounds: Substituents and Solvents Effects on Coordination and Reactivity of Resulting 1,3-Disubstituted-2-Indolyl Lithium Complexes

Reactivity of 1,3-disubstituted indolyl compounds with lithium reagents was studied to reveal the substituents and solvent effects on coordination modes and reactivities resulting in different indolyl lithium complexes. Treatment of 1-alkyl-3-imino functionalized compounds 1-R-3-(R′NCH)­C₈H₅N [R = Bn, R′ = Dipp (<b>HL</b>^<b>1</b>); R = Bn, R′ = ^<i>t</i>Bu (<b>HL</b>^<b>2</b>); R = CH₃OCH₂, R′ = Dipp (<b>HL</b>^<b>3</b>); Dipp = ^<i>i</i>Pr₂C₆H₃] with Me₃SiCH₂Li or ^<i>n</i>BuLi in hydrocarbon solvents (toluene or <i>n</i>-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippNCH)­C₈H₄NLi]₂ (<b>1</b>), {[η¹:(μ₃-η¹:η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­[η²:η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­[η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­Li₃} (<b>2</b>), and [η¹:η¹:(μ₂-η¹:η¹)-1-CH₃OCH₂-3-(DippNCH)­C₈H₄NLi]₂ (<b>3</b>), respectively. The bonding modes of the indolyl ligand were kept in <b>1</b> by coordination with donor solvent, affording [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippNCH)­C₈H₄NLi­(THF)]₂ (<b>4</b>). The trinuclear complex <b>2</b> was converted to dinuclear form with a change of bonding modes of the indolyl ligand by treatment of <b>2</b> with donor solvent THF, producing [η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄NLi­(THF)]₂ (<b>5</b>). X-ray diffraction established that compounds <b>1</b>, <b>3</b>, <b>4</b>, and <b>5</b> crystallized as dinuclear structures with the carbanionic sp² carbon atoms of the indolyl ligands coordinated to lithium ions in a μ₂-η¹:η¹ manner, while compound <b>2</b> crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ₂-η¹:η¹ and μ₃-η¹:η¹:η¹ manners. When the lithiation reaction of <b>HL</b>^<b>1</b> with 1 equiv of ^<i>n</i>BuLi was carried out in THF, the monomeric lithium complex {η¹:η¹-1-Bn-3-(DippNCH)-2-[1′-Bn-3′-(DippNCH)­C₈H₅N]­C₈H₄NLi­(THF)} (<b>6</b>) having coupled indolyl moieties was obtained. The compound <b>6</b> can also be prepared by the reaction of <b>1</b> with 0.5 equiv of <b>HL</b>^<b>1</b> with a higher isolated yield. Accordingly, the lithium complexes [η¹:η⁴-1-Bn-3-^<i>t</i>BuNCH-2-(1′-Bn-3′-^<i>t</i>BuNCHC₈H₅N)­C₈H₄NLi­(L)] (L = THF, <b>7a</b>; L = Et₂O, <b>7b</b>) with the coupled indolyl moieties in η⁴ mode were isolated by treatment of <b>HL</b>^<b>2</b> with <b>2</b> in THF or Et₂O. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study