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Highly active catalysts for the ring-opening metathesis polymerization (ROMP) of cyclic olefins (norbornene, cyclopentene, cycloheptene) can be generated in situ by premixing V(CHSiMe3)(NC6F5)(O-2,6-iPr2C6H3)(PMe3)2 (1) with 1.0 equiv. of C6F5OH or C6Cl5OH via the immediate phenoxy exchange; the activity was affected by the kind of phenol added [activity (TOF) in the ROMPs of norbornene: 46 200 min−1 (upon addition of C6F5OH) vs. 37.3 min−1 (by 1)]. [ABSTRACT FROM AUTHOR]

Ring-closing metathesis was monitored using real-time NMR of 1H hyperpolarized olefins at room temperature. By applying a selective saturation to an observable intermediate, its protons were found to transfer to ethylene. The intermediate was thus identified as a Ru-alkylidene species, which appears in the ethylene formation pathway. [ABSTRACT FROM AUTHOR]

A stereospecific three-component domino reaction between glycals, alkylidene malonate and aldehydes catalyzed by Yb(OTf)3 is described. Multi-substituted cis-fused perhydropyrano[2,3-b]pyran derivatives were obtained with high diastereoselectivity. [ABSTRACT FROM AUTHOR]

A stereospecific three-component domino reaction between glycals, alkylidene malonate and aldehydes catalyzed by Yb(OTf)3 is described. Multi-substituted cis-fused perhydropyrano[2,3-b]pyran derivatives were obtained with high diastereoselectivity. [ABSTRACT FROM AUTHOR]

Metal-free and environmentally friendly synthesis highly controlled by natural sources like visible light and air (or oxygen) is always a pursuit of green chemistry. In this paper, an atmosphere and light tuned highly diastereoselective synthesis of two important polyheterocyclic skeletons: cyclobuta/penta[b]indoles from aniline-tethered alkylidenecyclopropanes with alkynes, has been developed. The chiral cyclobuta/penta[b]indoles have also been obtained by optical resolution. [ABSTRACT FROM AUTHOR]

The reaction of [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(OTf)2(DME)] (DME = 1,2-dimethoxyethane, OTf = CF3SO3) with the N-heterocyclic carbene (NHC) 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene (IMesH2) leads to DME activation followed by transmethylation and in due consequence to the formation of the N-heterocyclic olefin complex [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(OTf)2(IMesH2CH2)] along with [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(OTf)(IMesH2)(κ2-O(CH2)2OMe)], [1,3-bis(2,4,6-trimethylphenyl)-2-methylimidazolidinium+ (OTf−)] and [1,3-bis(2,4,6-trimethylphenyl)-2-H-imidazolidinium+ (OTf−)]. A reaction pathway is proposed and confirmed by the use of 13C-labelled compounds; structures of the products were verified by NMR and/or single-crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

An efficient and expedient route to the synthesis of dicarba peptides from protecting group-free sequences is reported using Ru-alkylidene catalysed olefin metathesis. A range of cyclic peptides was prepared from linear peptides containing two Z-crotyl glycine residues. Free amine groups were masked as salts with Brønsted acids preventing in situ catalyst decomposition. Excellent RCM conversion was obtained in both DMF and methanol. [ABSTRACT FROM AUTHOR]

A novel palladium-catalyzed oxidative cyclization of aniline-tethered alkylidenecyclopropanes using molecular oxygen as the terminal oxidant through β-carbon elimination of aminopalladation intermediates is disclosed. The reaction opens up an effective way to obtain a series of 2- and 3-vinylindoles which are important synthetic intermediates in many natural indole derivatives. [ABSTRACT FROM AUTHOR]

A strategy to achieve the efficient synthesis of alkylidene carbonates from CO2 at atmospheric pressure by tuning the basicity of ionic liquids was developed. Excellent yields were obtained due to basic ionic liquids’ dual roles both as absorbents and as activators. The reaction mechanism was investigated through a combination of NMR spectroscopy, controlled experiments and quantum calculations, indicating the importance of a moderate basicity. [ABSTRACT FROM AUTHOR]

The synthesis, single crystal X-ray structure and activity in olefin metathesis of novel anionic tungsten imido alkylidene complexes [1,3-bis-(2,4,6-trimethylphenyl)imidazolinium]+ [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2,5-Me2Pyr)2Cl]−, [1,3-bis-(2,4,6-trimethylphenyl)imidazolinium]+ [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2,5Me2Pyr)2(OC6F5)]−, and [1,3-bis-(2,6-diisopropylphenyl)imidazolinium]+ [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2,5-Me2Pyr)Cl2]− are reported. Additionally, the first example of a bis(N-heterocyclic olefinium) alkylidene tungstate, W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2-methylene-1,3,4,5-tetramethyl-imidazoline)2(OTf)2, is described, including preparation, crystal structure and catalytic activity. [ABSTRACT FROM AUTHOR]

A Cu-catalyzed regio- and enantioselective aminoboration of alkylidenecyclopropanes (ACPs) with bis(pinacolato)-diboron (B2pin2) and hydroxylamines has been described in this paper, affording the corresponding cyclopropane-containing β-aminoalkylboranes in good yields under mild conditions. Moreover, a catalytic asymmetric variant of this transformation has also been realized by using a copper complex with a (S)-BINAP ligand along with further transformation of the product to give cyclopropane-containing 1,2-aminoalcohols. [ABSTRACT FROM AUTHOR]

Neutral, formally Fe(iv) alkylidene species are sought as plausible olefin metathesis catalysts, and the synthesis of several is described herein. The complexes are prepared via nucleophilic attack (Nu = MeLi, PhCH2K, 2-picolyllithium, Me2PCH2Li, MePhPCH2Li, Ph2PCH2Li) at the imine of cationic [mer-{κ-C,N,C-(C6H4-yl)-2-CH=N(2-C6H4-C(iPr)=)}Fe(PMe3)3][B(3,5-CF3-C6H3)4]. In contrast, MeMgCl and mesityllithium displaced and deprotonated bound PMe3, respectively. Structural details are provided for mer-{κ-C,N,C-(C6H4-yl)-2-CH(Bn)N(2-C6H4-C(iPr)=)}Fe{trans-(PMe3)2}N2 and {κ-C,N,C,P-(C6H4-yl)-2-CH(CH2PMe2)N(2-C6H4-C(iPr)=)}Fe(PMe3)2. [ABSTRACT FROM AUTHOR]

A highly enantioselective organocatalytic vinylogous aldol-cyclization cascade reaction of 3-alkylidene oxindoles to isatins has been achieved by using bifunctional organocatalysts. The unexpected intramolecular lactonization which follows the initial aldol reaction, leading to the cleavage of the oxindole ring and generation of enantioenriched spirooxindole dihydropyranones in good to excellent yields with high enantioselectivities. [ABSTRACT FROM AUTHOR]

An efficient asymmetric allylic alkylation reaction with respect to 3-alkylidene oxindoles and racemic Morita–Baylis–Hillman carbonate has been achieved by using a chiral biscinchona alkaloid catalyst, which delivers the γ-substituted alkylideneoxindoles with a chiral tertiary center in moderate to good yields (up to 92%) and very good enantioselectivities (up to ＞99% ee). [ABSTRACT FROM AUTHOR]

A chiral ytterbium(iii)-N,N'-dioxide catalyst system has been developed for the catalytic direct asymmetric vinylogous Michael addition of 3-alkylidene oxindoles to chalcones, delivering the γ-substituted alkylideneoxindoles in high yields, enantioselectivities and good Z/E selectivities under mild reaction conditions. [ABSTRACT FROM AUTHOR]

We reveal here the unique reactivity of α-(alkylideneamino)nitriles toward molecular oxygen. Thus, α-(alkylideneamino)nitriles can serve as the imide building block for the efficient synthesis of imides in the absence of transition metals under extremely mild conditions. [ABSTRACT FROM AUTHOR]

A simple and efficient metal-free methodology for the regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles has been developed by applying a novel inverse electron-demand-1,3-dipolar cycloaddition approach. The practical one-pot metal-free strategy can be accomplished with various alkylidene malononitriles and aromatic azides in the presence of base. [ABSTRACT FROM AUTHOR]

Several regioselectively π-extended, pyrrole fused porphyrinoids have been synthesized by the 1,3-dipolar cycloaddition of meso-alkylidene-(benzi)porphyrins. Pd(II) complexes gave oxidation resistant, bis-pyrrole fused adducts. The repeated 1,3-dipolar cycloaddition followed by oxidation-reduction of pentaphyrin analogs afforded p-extended porphyrin analogs. [ABSTRACT FROM AUTHOR]

A practical RhIII-catalyzed cascade olefination/annulation of picolinamides leading to pyrrolo[3,4-b]pyridines has been developed. The reaction shows wide scope, complete regiocontrol and excellent stereoselectivity. [ABSTRACT FROM AUTHOR]

The first total synthesis of the indole alkaloid apparicine has been developed through a sequence that includes an indoletemplated ring-closing metathesis and a vinyl halide Heck cyclization. [ABSTRACT FROM AUTHOR]