Total Synthesis and Absolute Configuration of Raputindole A

The first total synthesis of the bisindole alkaloid raputindole A from the rutaceous plant <i>Raputia simulans</i> is reported. The key step is a Au­(I)-catalyzed cyclization that assembles the cyclopenta­[<i>f</i>]­indole tricycle from a 6-alkynylated indoline precursor. The isobutenyl side chain was installed by Suzuki–Miyaura cross-coupling, followed by a regioselective reduction employing LiDBB. Starting from 6-iodoindole, the sequence needs nine steps and provided (±)-raputindole A in 6.6% overall yield. The absolute configuration of the natural product (+)-raputindole A was determined by quantum chemical calculation of the ECD spectrum

Synthesis and Photophysical Properties of Cyclometalated Platinum(II) 1,2-Benzenedithiolate Complexes and Heterometallic Derivatives Obtained from the Addition of [Au(PCy₃)]⁺ Units

The cyclometalated compounds [Pt­(C^N)­(HC^N)­Cl] [HC^N = 2-phenylpyridine (Hppy; <b>1a</b>), 1-(4-<i>tert</i>-butylphenyl)­isoquinoline (Htbpiq; <b>1b</b>)] react with 1,2-benzenedithiol, <i>t</i>-BuOK, and Bu₄NCl in a 1:1:2:1 molar ratio in CH₂Cl₂/MeOH to give the complexes Bu₄N­[Pt­(C^N)­(bdt)] [bdt = 1,2-benzenedithiolate; C^N = ppy (Bu₄N<b>2a</b>), tbpiq (Bu₄N<b>2b</b>)]. In the absence of Bu₄NCl, the same reactions afford solutions of K<b>2a</b> and K<b>2b</b>, which react with [AuCl­(PCy₃)] to give the neutral heterometallic derivatives [Pt­(C^N)­(bdt)­{Au­(PCy₃)}] [C^N = ppy (<b>3a</b>), tbpiq (<b>3b</b>)]. The cationic derivatives [Pt­(C^N)­(bdt)­{Au­(PCy₃)}₂]­ClO₄ [C^N = ppy (<b>4a</b>), tbpiq (<b>4b</b>)] are obtained by reacting <b>3a</b> and <b>3b</b> with acetone solutions of [Au­(OClO₃)­(PCy₃)]. The crystal structures of <b>3b</b> and <b>4b</b> reveal the formation of short Pt···Au metallophilic contacts in the range 2.929–3.149 Å. Complexes <b>3b</b>, <b>4a</b>, and <b>4b</b> undergo dynamic processes in solution that involve the migration of the [Au­(PCy₃)]⁺ units between the S atoms of the dithiolate. Complexes Bu₄N<b>2a</b> and <b>2b</b> display a moderately solvatochromic band in their electronic absorption spectra that can be ascribed to a transition of mixed ML′CT/LL′CT character (M= metal; L = bdt; L′ = C^N; CT = charge transfer), while their emissions are assignable to transitions of the same orbital parentage but from triplet excited states. The successive addition of [Au­(PCy₃)]⁺ units to the anions <b>2a</b> and <b>2b</b> results in an increase in the absorption and emission energies attributable to lower highest occupied molecular orbital energies. Additionally, the characteristics of the absorption and emission spectra of the heterometallic derivatives indicate a gradual loss of LL′CT character in the involved electronic transitions, with a concomitant increase of the L′C and ML′CT contributions

Reacting Cyclopropenones with Arynes: Access to Spirocyclic Xanthene–Cyclopropene Motifs

A formal insertion of two aryne moieties into the carbon–oxygen double bond of cyclopropenone has been realized. Spirocyclic xanthene–cyclopropene scaffolds were obtained. Mechanistically, a sequence of a formal [2 + 2]-cycloaddition followed by electrocyclic ring opening and a terminating [4 + 2]-type cycloaddition is postulated. The use of an electron-rich aryne precursor led to ring cleavage of the cyclopropene to afford an unprecedented xanthylium salt

Synthesis and Photophysical Properties of Cyclometalated Platinum(II) 1,2-Benzenedithiolate Complexes and Heterometallic Derivatives Obtained from the Addition of [Au(PCy₃)]⁺ Units

The cyclometalated compounds [Pt­(C^N)­(HC^N)­Cl] [HC^N = 2-phenylpyridine (Hppy; <b>1a</b>), 1-(4-<i>tert</i>-butylphenyl)­isoquinoline (Htbpiq; <b>1b</b>)] react with 1,2-benzenedithiol, <i>t</i>-BuOK, and Bu₄NCl in a 1:1:2:1 molar ratio in CH₂Cl₂/MeOH to give the complexes Bu₄N­[Pt­(C^N)­(bdt)] [bdt = 1,2-benzenedithiolate; C^N = ppy (Bu₄N<b>2a</b>), tbpiq (Bu₄N<b>2b</b>)]. In the absence of Bu₄NCl, the same reactions afford solutions of K<b>2a</b> and K<b>2b</b>, which react with [AuCl­(PCy₃)] to give the neutral heterometallic derivatives [Pt­(C^N)­(bdt)­{Au­(PCy₃)}] [C^N = ppy (<b>3a</b>), tbpiq (<b>3b</b>)]. The cationic derivatives [Pt­(C^N)­(bdt)­{Au­(PCy₃)}₂]­ClO₄ [C^N = ppy (<b>4a</b>), tbpiq (<b>4b</b>)] are obtained by reacting <b>3a</b> and <b>3b</b> with acetone solutions of [Au­(OClO₃)­(PCy₃)]. The crystal structures of <b>3b</b> and <b>4b</b> reveal the formation of short Pt···Au metallophilic contacts in the range 2.929–3.149 Å. Complexes <b>3b</b>, <b>4a</b>, and <b>4b</b> undergo dynamic processes in solution that involve the migration of the [Au­(PCy₃)]⁺ units between the S atoms of the dithiolate. Complexes Bu₄N<b>2a</b> and <b>2b</b> display a moderately solvatochromic band in their electronic absorption spectra that can be ascribed to a transition of mixed ML′CT/LL′CT character (M= metal; L = bdt; L′ = C^N; CT = charge transfer), while their emissions are assignable to transitions of the same orbital parentage but from triplet excited states. The successive addition of [Au­(PCy₃)]⁺ units to the anions <b>2a</b> and <b>2b</b> results in an increase in the absorption and emission energies attributable to lower highest occupied molecular orbital energies. Additionally, the characteristics of the absorption and emission spectra of the heterometallic derivatives indicate a gradual loss of LL′CT character in the involved electronic transitions, with a concomitant increase of the L′C and ML′CT contributions

Synthesis of 5‑<i>C</i>‑Methylated d‑Mannose, d‑Galactose, l‑Gulose, and l‑Altrose and Their Structural Elucidation by NMR Spectroscopy

C5/C6-Spirocyclopropanation of exocyclic enol esters followed by alkali ring-opening of the three-membered ring was used for the diastereoselective preparation of 5-<i>C</i>-methylated d-mannose, d-galactose, l-gulose, and l-altrose. Extensive NMR studies demonstrated an increase of furanose form by 5-<i>C</i>-methylation in almost all cases

Half-Open Ferrocenes and Ruthenocenes Containing an Edge-Bridged Open Indenyl Ligand

Potassium 1,1-dimethyl-1,2-dihydronaphthalenide, K­(eboInd) (<b>1</b>), was synthesized in three steps from 4,4-dimethyl-1-tetralone and used for the synthesis of half-open metallocenes containing an edge-bridged open indenyl ligand (eboInd). Successive treatment of [(THF)­FeI₂] with Li­(C₅Me₅) and <b>1</b> at low temperatures afforded [(η⁵-C₅Me₅)­Fe­(η⁵-eboInd)] (<b>2</b>), whereas [(η⁵-C₅Me₅)­Ru­(η⁵-eboInd)] (<b>3</b>) was synthesized by reaction of <b>1</b> with [(C₅Me₅)­RuCl]₄. Both compounds reacted with CO and 2,6-dimethylphenyl isocyanide (CN-<i>o</i>-Xy) to form [(η⁵-C₅Me₅)­M­(η³-eboInd)­L] (<b>4</b>: M = Fe, L = CO; <b>5</b>: M = Ru, L = CO; <b>6</b>: M = Fe, L = CN-<i>o</i>-Xy; <b>7</b>: M = Ru, L = CN-<i>o</i>-Xy), in which the eboInd ligand has undergone an η⁵-to-η³ hapticity conversion. In contrast, the N<i>-</i>heterocyclic carbene 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe) only reacted with the ruthenocene derivative <b>3</b> to give [(η⁵-C₅Me₅)­Ru­(η³-eboInd)­(IMe)] (<b>8</b>). The molecular structures of <b>2</b>–<b>7</b> were determined by X-ray diffraction analysis. None of the iron–ruthenium pairs are isotypic

Formal Insertion of Thioketenes into Donor–Acceptor Cyclopropanes by Lewis Acid Catalysis

Donor–acceptor cyclopropanes were reacted under Lewis acid catalysis with 3-thioxocyclobutanones as surrogates for disubstituted thioketenes. A broad scope of 2-substituted tetrahydrothiophenes with a semicyclic double bond was obtained under mild conditions with high functional group tolerance and in excellent yield. A sequence of a formal [3 + 2]-cycloaddition followed by the subsequent release of disubstituted ketene is postulated as the mechanism

Directed Selenium–Iodine Halogen Bonding and Se···H–C Contacts in Solid Iododiisopropylphosphane Selenide

Solid iododiisopropylphosphane selenide crystallizes in the space group <i>P</i>2₁/<i>n</i> with one molecule <i>i</i>Pr₂P­(I)Se in the asymmetric unit. Halogen bonds of the type Se···I–P (Se···I, 3.612 Å; Se···I–P, 171°) connect the molecules to form polymeric chains (-Se···I–P-)_<i>x</i>. These are further connected by Se···H contacts (2.98 Å) involving the tertiary H atom from one isopropyl group. The extended structure thus formed is a layer parallel to 101̅, and a substructure thereof consists of 10-membered (···Se···I–P–C–H···)₂ rings

Directed Selenium–Iodine Halogen Bonding and Se···H–C Contacts in Solid Iododiisopropylphosphane Selenide

Solid iododiisopropylphosphane selenide crystallizes in the space group <i>P</i>2₁/<i>n</i> with one molecule <i>i</i>Pr₂P­(I)Se in the asymmetric unit. Halogen bonds of the type Se···I–P (Se···I, 3.612 Å; Se···I–P, 171°) connect the molecules to form polymeric chains (-Se···I–P-)_<i>x</i>. These are further connected by Se···H contacts (2.98 Å) involving the tertiary H atom from one isopropyl group. The extended structure thus formed is a layer parallel to 101̅, and a substructure thereof consists of 10-membered (···Se···I–P–C–H···)₂ rings

The First Complexes with Two Metallacycles Fused Around a Common Aryl Substituent: “Akimbo” Complexes

Following the reaction sequence i) oxidative addition of RNHC­(O)­C₆H₃I₂-2,6 (R = Me, Tol) to [Pd₂(dba)₃]·dba in the presence of chelating ligands N^∧N or XyNC (Xy = C₆H₃Me₂-2,6), ii) treatment of the resulting complexes with TlTfO or Tl­(acac) (acac = acetylacetonato), and iii) insertion of unsaturated molecules (CO, XyNC, MeO₂CCCCO₂Me, MeC­(O)­CHCH₂) into one of the Pd–C_aryl bonds of the resulting complexes allowed the synthesis of aryldipalladated complexes containing the ligands L1 = μ-<i>C,C-</i>{C₆H₃C­(O)­NHR}-2,6, L2 = μ-<i>C,C-</i>{C₆H₃C­(O)­NHMe}­(CNXy)₂-2,6, L3 = μ-<i>C,O,C</i>-{C₆H₃C­(O)­NHMe}-2,6, L4 = μ-<i>C,O,C,N</i>-{C₆H₃C­(O)­NR}-2,6, L6 = μ-<i>C,N,C,O</i>-{C₆H₃C­(O)­NR}-2-(CO)-6, L7 = μ-<i>C,N,C,O</i>-{C₆H₃C­(O)­NR}-2-{C­(CO₂Me)C­(CO₂Me)}-6, L8 = μ-<i>C,N,C,O</i>-{C₆H₃C­(O)­NR}-2-(CNXy)-6 and two arylmonopalladated complexes with the ligands L5 = <i>C,O</i>-{C₆H₄C­(O)­NHMe}-2 and L9 = <i>C,N</i>-{C₆H₃C­(O)­NTol}-2-{CHCHC­(O)­Me}-6. The complex with the ligand L7 inserted CO into the second Pd–C_aryl bond to give an L10-Pd₂ complex (L10 = μ-<i>C,N,C,O</i>-{C₆H₃C­(O)­NTol}­(CO)-2-{C­(CO₂Me)C­(CO₂Me)}-6. The dipalladated species display a different environment for each palladium atom and represent the first systems containing two 5 + 5, 5 + 6, 5 + 7, or 6 + 7-membered palladacycles condensed over the central benzamide group. The two arms of the ligands L4 and L6-L8 and L10 are “akimbo”, and we coin this name both for the ligands and for the dimetallic complexes bearing them. The crystal structure of a [{Pd­(N^∧N)}₂L6]⁺ complex has been determined