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We report a joint experimental and theoretical study on the ultrafast excited state dynamics of allene and a series of its methylated analogues (1,2-butadiene, 1,1-dimethylallene, and tetramethylallene) in order to elucidate the conical intersection mediated dynamics that give rise to ultrafast relaxation to the ground electronic state. We use femtosecond time-resolved photoelectron spectroscopy (TRPES) to probe the coupled electronic-vibrational dynamics following UV excitation at 200 nm (6.2 eV). Ab initio multiple spawning (AIMS) simulations are employed to determine the mechanistic details of two competing dynamical pathways to the ground electronic state. In all molecules, these pathways are found to involve as follows: (i) twisting about the central allenic C-C-C axis followed by pyramidalization at one of the terminal carbon atoms and (ii) bending of allene moiety. Importantly, the AIMS trajectory data were used for ab initio simulations of the TRPES, permitting direct comparison with experiment. For each molecule, the decay of the TRPES signal is characterized by short (30 fs, 52 fs, 23 fs) and long (1.8 ps, 3.5 ps, [306 fs, 18 ps]) time constants for 1,2-butadiene, 1,1- dimethylallene, and tetramethylallene, respectively. However, AIMS simulations show that these time constants are only loosely related to the evolution of electronic character and actually more closely correlate to large amplitude motions on the electronic excited state, modulating the instantaneous vertical ionization potentials. Furthermore, the fully substituted tetramethylallene is observed to undergo qualitatively different dynamics, as displacements involving the relatively massive methyl groups impede direct access to the conical intersections which give rise to the ultrafast relaxation dynamics observed in the other species. These results show that the branching between the "twisting" and "bending" pathways can be modified via the selective methylation of the terminal carbon atoms of allene. The interplay between inertial and potential effects is a key to understanding these dynamical branching pathways. The good agreement between the simulated and measured TRPES confers additional confidence to the dynamical picture presented here. [ABSTRACT FROM AUTHOR]

A Co(III)‐catalyzed [4+1] annulation of amides with allenes to synthesize isoindolone and 1,5‐dihydro‐pyrrol‐2‐one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide‐directed C−H activation, followed by carbocobaltation of allene, β‐hydride elimination, and an intramolecular 1,2‐hydroamination. [ABSTRACT FROM AUTHOR]

A series of arylallenes react with HB(C6F5)2 in a 2:1 molar ratio to give the tail‐to‐tail 1,6‐diaryl‐2‐boryl‐hexa‐1,5‐diene coupling products. The reaction of the phenylallene substrate with HB(C6F5)2 was shown to initially give the 2‐boryl‐3,4‐diphenyl‐1,5‐hexadiene head‐to‐head coupling product which then rearranged, by a thermally induced Cope rearrangement, into the final product. Heads or tails? Monoalkylallenes are catalytically cyclotrimerized by HB(C6F5)2, whereas arylallenes react with HB(C6F5)2 to give 1,6‐diaryl‐2‐boryl‐hexa‐1,5‐diene tail‐to‐tail coupling products. The reaction of phenylallene with HB(C6F5)2 initially gives the 2‐boryl‐3,4‐diphenyl‐1,5‐hexadiene head‐to‐head coupling product, which then rearranges, by a thermally induced Cope rearrangement, into the final product. [ABSTRACT FROM AUTHOR]

Abstract: A novel reaction that provides chiral allenes by amino catalytic activation of either aldehydes or α,β‐unsaturated aldehydes for reaction with alkynyl‐substituted enones is presented. The reaction forms a variety of trisubstituted allenes in high yields and with excellent stereoselectivities. The utility of the reaction concept is demonstrated by the synthesis of chiral furan derivatives in high yields and stereoselectivities. [ABSTRACT FROM AUTHOR]

Abstract: Bora‐acylation of allenes proceeds in the presence of a copper catalyst using B2(pin)2 and carboxylic anhydrides as boron and acyl sources, respectively. The reaction selectively affords the corresponding β‐boryl‐β,γ‐unsaturated ketones in good‐to‐high yields. Bora‐alkoxyoxalylation of an allene is also achieved using oxalates. [ABSTRACT FROM AUTHOR]

Abstract: Upon exposure to a catalytic amount of [RhCl(CO)2]2 in 1,4‐dioxane, homopropargylallene‐alkynes underwent a novel cycloisomerization accompanied by the migration of the alkyne moiety of the homopropargyl functional group to produce six/five/five tricyclic compounds in good yields. A plausible mechanism was proposed on the basis of an experiment with 13C‐labeled substrate. The resulting tricyclic derivatives were further converted into the corresponding bicyclo[3.3.0] skeletons with vicinal cis dihydroxy groups. [ABSTRACT FROM AUTHOR]

We report on the growth by solid-source MBE of random-alloy Al x In 1–x As y Sb 1–y layers lattice-matched to (0 0 1)–GaSb substrates, with x Al ∈ [0.25; 0.75]. The samples quality and morphology were characterized by X-ray diffraction, Nomarski microscopy and atomic force microscopy. Layers grown at 400 °C demonstrated smooth surfaces and no sign of phase decomposition. Samples with x Al ≤ 0.60 demonstrated photoluminescence (PL) at 300 K whereas samples with higher Al content only demonstrated PL at low temperature. Samples grown at 430 °C, in contrast, exhibited PL at low temperature only, whatever their composition. Inferred bandgap energies corroborate the estimation of a non-null quaternary bowing parameter made by Donati, Kaspi and Malloy in Journal of Applied Physics 94 (2003) 5814. Upon annealing, the PL peak energies increased, getting even closer to the theoretical values. These results are in agreement with recently published results on digital AlInAsSb alloys. Our work, which reports the first evidence for PL emission from random-alloy AlInAsSb layers lattice-matched to GaSb, opens the way to their use in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The optimization of metamorphic buffers for InSb/AlInSb QWs grown on GaAs (0 0 1) substrates is presented. With increasing surface offcut angle towards [ 1 1 ¯ 0 ] direction, the interaction of spiral growth around threading dislocations (TDs) with the offcut-induced atomic steps leads to a gradual change in the morphology of the AlSb buffer from one dominated by hillocks to that exhibiting near-parallel steps, and finally to a surface with increasing number of localized depressions. With the growth conditions used, the smoothest AlSb surface morphology was obtained for the offcut angles range of 0.8–1.3°. On substrates with 0° offcut, subsequent 3 repeats of Al 0.24 In 0.76 Sb/ Al 0.12 In 0.88 Sb interlayers reduces the TD density of AlSb buffer by a factor of 10, while 70 times reduction in the surface density of TD-related hillocks is observed. The remaining hillocks have rectangular footprint and small facet angles with respect to GaAs (0 0 1) surface: 0.4° towards [ 1 1 ¯ 0 ] direction and 0.7° towards [1 1 0] direction. Their triangular-shaped sidewalls with regularly spaced atomic steps show occasional extra step insertion sites, characteristic of TD outcrops. Many of the observed sidewalls are dislocation free and offer atomically smooth areas of up to 1 μm 2 , already suitable for high-quality InSb growth and subsequent top-down fabrication of InSb nanowires. It is proposed that the sidewalls of the remaining hillocks offer local vicinal surfaces with atomic step density optimal for suppression of TD-induced spiral growth, thus providing the important information on the exact substrate offcut needed to achieve large hillock-free and atomically smooth areas on AlInSb metamorphic buffers. [ABSTRACT FROM AUTHOR]

Allene-( E)-ene-yne N-tosyl-tethered substrates 3 a- 3 h were efficiently prepared and their rhodium-catalyzed [2+2+2] cycloaddition reactions were evaluated. The cycloadditions are chemoselective as only the proximal double bond of the allene reacted to afford exocyclic double bonds in the fused-tricyclic scaffolds. The stereoselectivity depended on the catalytic system used. Reactivity between allene, alkene, and alkyne was studied for the first time by density functional theory calculations. This mechanistic study determines the order in which the unsaturated groups take part in the catalytic cycle. [ABSTRACT FROM AUTHOR]

Enantiopure alleno-acetylenic cage (AAC) receptors with a resorcin[4]arene scaffold, from which four homochiral alleno-acetylenes converge to shape a cavity closed by a four-fold OH-hydrogen-bonding array, form a highly ordered porous network in the solid state. They enable the complexation and co-crystallization of otherwise non-crystalline small molecules. This paper analyzes the axial conformers of monohalo- and (±)-trans-1,2-dihalocyclohexanes, bound in the interior cavity of the AACs, on the atomic level in the solid state and in solution, accompanied by accurate calculations. The dihedral angles ϑa,a (X-C(1)-C(2)-X/H) of the axial/diaxial conformers deviate substantially from 180°, down to 144°, accompanied by strong flattening of the ring dihedral angles. Structure optimization of the isolated guest molecules demonstrates that the non-covalent interactions with the host hardly affect the dihedral angles, validating that the host is an ideal means to study the elusive axial/diaxial conformers. X-ray co-crystal structures of AACs further allowed for a detailed investigation, both experimentally and theoretically, on the interplay between space occupancy, guest conformation, and chiral recognition based purely on dispersion forces and weak C--X···π (X = Cl, Br, I) and C--X···||| (acetylene) contacts (X = Cl, Br). The theoretical analysis of the non-covalent interactions between host and guest confirmed the high shape complementarity with fully enveloping dispersive interactions between the binding partners, rationalizing the high degree of enantioselectivity in the previously communicated complexation of (±)-trans-1,2-dimethylcyclohexane. This study also showed that (±)-trans-1,2-dihalocyclohexanes (X = Cl, Br) engage in significant halogen bonding (XB) interactions C--X···||| with the hosts. Slow host-guest exchange on the NMR time scale enabled the characterization of the encapsulated guests in solution, demonstrating that the complexes have identical geometries to those seen in the solid state, with the guests bound in axial/diaxial conformations. [ABSTRACT FROM AUTHOR]

The diastereoselective gold(I) catalysed cyclisation of highly substituted aminoallene derivatives allows the synthesis of both epi -DAB-1 and di- epi -lentiginosine. While the sense of stereoselectivity observed is in line with earlier observations on analogous piperidine-forming cyclisations, different ligands and reaction conditions are required to obtain good yields. [ABSTRACT FROM AUTHOR]

An efficient synthesis of 1,3-diarylindenes has been achieved from propargylic alcohols containing aromatic rings via gold-catalyzed dehydrative Friedel–Crafts reaction followed by gold-catalyzed Nazarov cyclization. The reaction proceeds via allene intermediates. [ABSTRACT FROM AUTHOR]

The first stable bromoallene oxides were obtained by the DMDO epoxidation of 1-bromo-1,3-di-tert-alkylallenes, producing the first crystalline allene oxide of any kind. The epoxidations are regioselective for the bromine-bearing Δ1,2 alkene, and also face selective producing single diastereomer E-olefin products. [ABSTRACT FROM AUTHOR]

The Pd-catalysed reactions of allenyl ethers and allenylamines derived from commercially available o-aminophenols and o-nitroaniline have been studied. Using a wide variety of aryl- and heteroaryl halides, carboamination of the allenes led to sequential C-C and C-N bond formation. Both carbo- and hydroamination processes resulted in the formation of nitrogen-containing benzo-fused rings. In the case of aminoallenes arising from o-phenylenediamine, the regioselectivity of the cyclization step was strongly dependent on the protecting group tethered to the nitrogen atoms, allowing the formation of five- and seven-membered rings. [ABSTRACT FROM AUTHOR]

By using allene derivatives as probes, asymmetry under point-group symmetry (denoted as asymmetry (P) ) and asymmetry under RS -permutation-group symmetry (denoted as asymmetry (RSP) ) are compared with chirality (as the first kind of handedness) and RS -stereogenicity (as the second kind of handedness) based on stereoisograms. Van’t Hoff’s asymmetric carbon atom is extended to asymmetry (H) for supporting allene and other skeletons, which is compared with stereogenicity. The term asymmetry should be adopted to connote asymmetry (P) for discussing geometric features. A consistent set of terms having a common stem, i.e., chirality , hypo-chirality , and hyper-chirality , is coined to avoid the confusion brought about by the term asymmetry . To discuss stereoisomeric features, the term asymmetry (H) may be replaced by the term stereogenicity , which supports R/S -stereodescriptors, R a / S a -descriptors, Z/E -descriptors, and so on in a rather indecisive fashion. Instead, the more decisive term RS-stereogenicity should be used to support R/S -stereodescriptors and R a / S a -descriptors selectively. The use of asymmetry (RSP) is desirable to be restricted to analytical purpose. Although the terms hypo-RS-stereogenicity and hyper-RS-stereogenicity are coined in a parallel way to hypo-chirality and hyper-chirality, the term RS -stereogenicity is found to be sufficient for the purpose of supporting the assignment of R/S -stereodescriptors and R a / S a -descriptors. [ABSTRACT FROM AUTHOR]

Treatment of α-hydroxy-substituted methoxyallene derivatives with meta-chloroperbenzoic acid provided acyloxy-substituted 1,2-diketones in moderate yields. A mechanism for the formation of these unexpected products is proposed. The configuration of the enantiopure compound (S)-1-(3-methylquinoxalin-2-yl)-1-(4- nitrobenzoyloxy)propan-2-yl 3-chlorobenzoate - determined by X-ray crystal structure analysis - indicates the intermediacy of a carbenium ion during formation of the 1,2-diketones. The functionalized 1,2-diketones are valuable starting materials for a variety of products as demonstrated by the synthesis of quinoxalines, an imidazole derivative, and electrondeficient alkenes. [ABSTRACT FROM AUTHOR]

A three-step approach to enantiomerically pure 3-aminoseptanoside derivatives by addition of lithiated methoxyallene to d-silylated aldopentose-derived nitrones, followed by Brønsted acid mediated cyclization and chemoselective N-O bond scission is presented. For the addition of the methoxyallene anion leading to 3,6-dihydro-1,2-oxazines, excellent syn-diastereoselectivities were observed in the case of D-xylose- and L-arabinose-derived nitrones, whereas the D-ribose analogue provided syn- and anti-configured products in an approximately 2:1 ratio. Subsequent proton-induced reactions provided the corresponding dimethyl ketals as kinetic products, which slowly converted into bicyclic oxepanoides formed in a highly cis-selective manner. The final reductive ring opening was performed in good yields by using an excess of samarium(II) iodide. With a selected compound it was demonstrated that this type of product is a suitable precursor for the preparation of polyfunctionalized oxepanopyrrolidine derivatives. [ABSTRACT FROM AUTHOR]

The conventional flowchart for the classification of isomers into constitutional isomers and stereoisomers and for the further classification of stereoisomers into enantiomers and diastereomers is concluded to be misleading from a viewpoint of equivalence relationships and equivalence classes. A new flowchart based on equivalence relationships and equivalence classes is proposed, where a set of isomers a set of stereoisomers, and a pair of enantiomers are recognized as equivalence classes under the respective equivalence relationships, that is, an isomeric relationship, a stereoisomeric relationship, and an enantiomeric relationship. A constitutionally-anisomeric relationship (a revisal for a constitutionally-isomeric relationship) and a diastereomeric relationship are redefined as non-equivalence relationships. After the introduction of stereoisograms, a more comprehensive flowchart is proposed, where an RS -stereoisomeric relationship is incorporated as an intermediate concept for mediating between a stereoisomeric relationship and an enantiomeric relationship. The comprehensive flowchart detects RS -stereoisomers, which are classified into five types in accord with type-I to type-V stereoisograms. The comprehensive flowchart is applied to tetrahedral derivatives, allene derivatives, ethylene derivatives, square planar complexes, and oxirane derivatives. The results are summarized in the form of isomer-classification diagrams, which are correlated to correlation diagrams of stereoisograms. The different ways taken by van’t Hoff (‘asymmetry’, ‘stereogenicity’) and Le Bel (‘dissymmetry’, ‘chirality’) at the beginning of stereochemistry are now integrated by the comprehensive flowchart. [ABSTRACT FROM AUTHOR]

A stereoselective nickel-catalyzed [2+2] cycloaddition of ene-allenes is reported. This transformation encompasses a broad range of ene-allene substrates, thus providing efficient access to fused cyclobutanes from easily accessed π-components. A simple and inexpensive first-row catalytic system comprised of [Ni(cod)2] and dppf was used in this process, thus constituting an attractive approach to synthetically challenging cyclobutane frameworks under mild reaction conditions. [ABSTRACT FROM AUTHOR]

In this paper, a selective and versatile synthesis of functionalized phenols including 2-hydroxyaryl ketones through cascade reactions of 1,2-allenic ketones with β-diketones has been developed. The synthetic procedure is not only efficient, but also easy to handle and compatible with a variety of functional groups. In addition, reactions were combined with a subsequent condensation of the in-situ-formed o-hydroxyaryl ketones with an α-bromoketone, thus resulting in a highly simple synthesis of benzofuran derivatives. [ABSTRACT FROM AUTHOR]

Cycloaddition of monosubstituted allenes with a monomeric, base free titanocene oxide resulted in isolation and crystallographic characterization of the corresponding oxatitanacyclobutanes. In solution these compounds are a mixture of ( E ) and ( Z ) isomers and interconvert by mechanisms that are dependent on the specific substitution of the allene. Facile carbonylation of the oxatitanacyclobutanes was also observed to yield rare examples of structurally characterized oxatitanacyclopentanones. Isomerization of these species was observed in the presence of proton sources. These studies highlight the new chemistry available from synthesis of base free titanocene oxide compounds enabled by appropriate cyclopentadienyl substitution. [ABSTRACT FROM AUTHOR]

Two allene derivatives, l- and d-N-(1-(octylamino)-1-oxopropan-2-yl)-4-(propa-1,2-dien-1-yloxy)benzamide(l-1and d-1), bearingchiral amide pendants were designed and synthesized. Living polymerizationsof l-1and d-1with allylnickelcomplex as a catalyst afforded poly-l-1mand poly-d-1mwith controlledmolecular weights and narrow molecular weight distributions. Thesepolymers were found to possess a stable helical conformation witha preferred handedness in aprotic solvents on the basis of their circulardichroism (CD) spectra and specific rotation as well as computer simulation.The helical conformation of the polymers was revealed to be stabilizedby elongation of the repeating unit until the degree of the polymerizationreaches 80. The slightly influence of temperature on the CD spectraof poly-l-1100in CHCl3indicated the helical conformation was quite stable at least inthe range of 0–55 °C. Although poly-l-1100showed similar CD spectra in different aprotic solvents,remarkable decrease was observed upon the addition of protic solventssuch as methanol due to the weakened hydrogen bonding interactionsbetween the adjacent repeating units. The poly-l-1100behaves as a pH-responsive property; the helical structureof the main chain can be transformed to random coil by addition oftrifluoroacetic acid to the THF solution which again switches backto helical conformation by neutralization with triethylamine. It wasconfirmed that the copolymerization of l-1and d-1obeyed the majority rule as supported by thenonlinear correlation between the enantiomeric excess of monomer 1with the CD intensities of the generated copolymers. Atomicforce microscope (AFM) and scanning electron microscope (SEM) studiesrevealed poly-l-1100self-assembledinto well-defined helical fibrils with distinct handedness. [ABSTRACT FROM AUTHOR]

A new scheme of the domino reactions of diphenyl dichalcogenides with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH was suggested, which included nucleophilic substitution of the allylic chlorine atom in dichloropropene, dehydrochlorination of the product obtained with the formation of an allene derivative, addition of a nucleophile to the allene system, allene-acetylene rearrangement, addition of a nucleophile to the triple bond with the formation of a Z-adduct, isomerization of a 2,3-dichalcogenide product to Z-1,2-dichalcogenylprop-1-enes, and isomerization of Z-adducts to E-isomers. The most plausible mechanisms of individual steps, involving carbanions stabilized by the α-chalcogen atom, were considered. [ABSTRACT FROM AUTHOR]

The present review is focused on the application of computational/theoretical methods to the wide and rich chemistry of allenes. Special emphasis is made on the interplay and synergy between experimental and computational methodologies, rather than on recent developments in methods and algorithms. Therefore, this review covers the state-of-the-art applications of computational chemistry to understand and rationalize the bonding situation and vast reactivity of allenes. Thus, the contents of this review span from the most fundamental studies on the equilibrium structure and chirality of allenes to recent advances in the study of complex reaction mechanisms involving allene derivatives in organic and organometallic chemistry. [ABSTRACT FROM AUTHOR]

This Tutorial Review summarizes recent examples of electrophilic activation of allenes with particular focus on analogies and differences between Lewis and Brønsted acid activation of these versatile substrates. The aim of this article is to present a general overview of the possibilities offered to chemists using complementary modes of catalysis and to emphasize advantages and limitations of each approach, thereby providing a means to expand the scope of this powerful synthetic methodology. [ABSTRACT FROM AUTHOR]

Transition-metal catalysed nucleophile addition to allenes is a very powerful tool for the synthesis of functionalised molecules containing heteroatoms, heterocycles in the intramolecular version, or allyl derivatives in the intermolecular version. The reaction has been explored with a wide variety of metals, silver being one of the most effective. Although platinum has somehow been less explored, different reactivities have been observed with this metal, showing the great potential and versatility of this methodology. This review will highlight the reactions with these two metals, silver and platinum, when oxygen or nitrogen nucleophiles are employed. Although most of the examples describe the intramolecular version, some intermolecular reactions with platinum have been described, and will also be covered. [ABSTRACT FROM AUTHOR]

Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene-containing natural products isolated from the red alga Laurencia sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated. [ABSTRACT FROM AUTHOR]

Eine solide Grundlage: 2 ‐ Boryl ‐ 1,3 ‐ butadiene mit verschiedenen Substitutionsmustern wurden in guten bis hohen Ausbeuten in einer Kupfer ‐ katalysierten Borylierung von α ‐ Alkoxyallenen mit Bis(pinakolato)dibor gebildet (siehe Schema; Bn=Benzyl, pin=Pinakolat, L ist ein N ‐ heterocyclisches Carben). Die Produkte sind nützliche Zwischenstufen für die Synthese von cyclischen Vinylboranen, α,β ‐ ungesättigten Ketonen und funktionalisierten mehrfach substituierten Dienen. [ABSTRACT FROM AUTHOR]

A highly regioselective synthesis of 15-20-membered macrocycles via Pd(0)-catalyzed coupling cyclization of allenes bearing a carbon or nitrogen nucleophilic functionality and organic iodides is reported. After oxidative addition and carbopalladation, anti-π-allyl palladium intermediates were formed, which was followed by the exclusive intramolecular nucleophilic attack at the terminal carbon atom of the allene moiety to afford products with yields ranging from 44-92% and E/Z ratios of up to 97/3. [ABSTRACT FROM AUTHOR]

The cyclic alkyl(amino) carbene (cAAC:)-stabilized acyclic germylones (Me2-cAAC:)2Ge (1) and (Cy2-cAAC:)2Ge (2) were prepared utilizing a one-pot synthesis of GeCl2(dioxane), cAAC:, and KC8 in a 1:2:2.1 molar ratio. Dark green crystals of compounds 1 and 2 were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of 1 and 2 feature the C-Ge-C bent backbone, which possesses a three-center two-electron p-bond system. Compounds 1 and 2 are the first acyclic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds 1 and 2 confirmed the singlet spin ground state. DFT calculations on 1/2 revealed that the singlet ground state is more stable by ~16 to 18 kcal mol-1 than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (1)/267.1 (2) and 180.4 (1)/183.8 (2) kcal mol-1, respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of 1 and 2. The TD-DFT calculations exhibit an absorption band at ~655 nm in n-hexane solution that originates from the diradicaloid character of germylones 1 and 2. [ABSTRACT FROM AUTHOR]

An 8-quinolinolato rhodium catalyst was found to be effective for head-to-tail selective dimerization of arylacetylenes. Formation of substituted cyclopentene and allene derivatives via alkyne dimerization and subsequent addition of malonates was also catalyzed by the 8-quinolinolato rhodium catalyst in the presence of cesium fluoride. One-pot reaction using palladium-catalyzed alkyne dimerization in conjunction with rhodium-catalyzed addition of malonates was also possible. [ABSTRACT FROM AUTHOR]

2-Pyridyliminopropadienone 6 is formed together with 2-aminopyridine on flash vacuum thermolysis (FVT) of 2-pyridylamino-pyridopyrimidinone 16a and observed by Ar matrix IR spectroscopy, but the two products recombine on warming to room temperature to regenerate the starting material. FVT of the picolinylamino-pyridopyrimidinones 16b and 16c generated mixtures of pyridyliminopropadienone 6 and picolinyliminopropadienones 19b and 19c, respectively. These reactions can be understood in terms of fragmentation of the open-chain bis(2-pyridylamino)methyleneketene intermediates 20 or the thermal interconversion of pyridopyrimidinones 16 and mesoionic pyridopyrimidinium olates 21. 2-Thiazoyliminopropadienone 28 was obtained in an analogous manner by FVT of the 2-(methylthio)thiazolopyrimidinone 24. However, the corresponding dihydro derivative 31 yielded cyanoketene 36 as the major product. [ABSTRACT FROM AUTHOR]

A correlation was found between the group dipole moments of substituents determined from the dipole moments of ethylene derivatives and the second ionization potentials of allene derivatives corresponding to the π′-MO of the C(β)-C(γ) bond. It was shown that the concept of the effect of the substituent field cannot completely explain the observed phenomena, and the energies of the second ionic states of bromoallene and alkoxyallenes are lowered because of the interaction between nonbonded fragments through the σ systems of the compounds. It has been found that, in terms of orbital approximation, this interaction causes electronic destabilization of the anti-planar ( trans) conformers of methoxyallene and methyl vinyl ether compared to their sin-planar ( cis) forms. [ABSTRACT FROM AUTHOR]

The article offers information on intermolecular hydroamination of monosubstituted allenes with secondary alkylamines catalyzed by platinum (II) and silver derivative. It mentions the effective diastereoselectivity of reactants with catalyst. It further mentions the use of nuclear magnetic resonance spectroscopy analysis for determining the stereochemistry of the purified reaction mixture.

An abstract of the article “Efficient Trapping of 1,2-Cyclohexadienes with 1,3-Dipoles" is presented.

On page 861 (DOI: 10.1002/jcc.23871), Alex Domingo, Celestino Angeli, Coen de Graaf, and Vincent Robert report the intervalence charge transfer (IVCT) between the metal centers of a bi‐iron complex induces a response of the whole electronic structure of the compound. The response effects consist of an electronic reorganization that affects each molecular orbital of the complex differently. The π‐ and n‐type orbitals localized on coordinating atoms undergo the largest polarization, being even larger than that of the Fe 3d‐like orbitals involved in the transfer. The electronic reorganization follows the induced dipole moment by the IVCT, but having a weaker effect on the orbitals close to the Fe center accepting the transferring electron. [ABSTRACT FROM AUTHOR]

An abstract of the article "Cascade Copper-Catalyzed 1,2,3-Trifunctionalization of Terminal Allenes" by W. Zhao and J. Montgomery is presented.

The article focuses on a study related to the domino synthesis of fluorine-substituted polycyclic aromatic hydrocarbons. It informs that CF2 cations formed from 1,1-difluoroallenes undergo a sequence of Friedel-Crafts-type cyclization in the presence of an indium(III) catalyst. It also presents schemical equations related to the synthesis of polycyclic aromatic hydrocarbons.

The allenic ester (I) reacts with (S)-benzylmorpholine (BMP) to generate a chiral diene intermediate which readily undergoes Diels-Alder reactions with acrylic nitriles (II) to offer functionalized cyclohexenes (III) after hydrolytic cleavage of the chiral secondary amine auxiliary. [ABSTRACT FROM AUTHOR]

About 20 target ring structures are prepared from 3-olefinic oxindoles. [ABSTRACT FROM AUTHOR]

The title reaction goes through an intramolecular exo-hydroamination to afford five, six, or seven-membered 1,3-diaza- or 1,3-oxaza-heterocycles. [ABSTRACT FROM AUTHOR]

Oxidation of readily prepared allenols with PCC affords α′-hydroxydienones rather than simple oxidation products. [ABSTRACT FROM AUTHOR]

Difluoroallenes of type (III) undergo InBr3-catalyzed ring closure reactions to give 1-fluoronaphthalenes of type (IV). [ABSTRACT FROM AUTHOR]

Chemical equations for the article "Zinc Salt Promoted Diastereoselective Synthesis of Chiral Propargylamines Using Chiral Piperazines & Their Enantioselective Conversion into Chiral Allenes." by M. Dalai and others, published in the "European Journal of Organic Chemistry" in 2014, are presented.

Review: 53 refs. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Mild-Condition Synthesis of Allenes from Alkynes and Aldehydes Mediated by Tetrahydroisoquinoline (THIQ)" by M. Dou and others, published in the "Journal of Organic Chemistry" in 2013.

The article presents chemical equations related to the article "Bisphosphine-Triggered One-Pot Sequential [3 + 2]/[3 + 2] Annulation of Allenoates with Cyclic Ketimines" by S. Wang, and others, published in the "Organic Letters" in 2013.

The article presents chemical equations related to the nitration of silyl allenes for the synthesis of functionalized nitroalkenes published in the journal "Organic Letters" in 2013.

Review: < 80 refs. [ABSTRACT FROM AUTHOR]

Different substituted axially chiral allene derivatives are converted to bicyclic ring systems via a Pauson-Khand reaction. [ABSTRACT FROM AUTHOR]