- Highly active molybdenum-alkylidyne catalysts for alkyne metathesis: Synthesis from the nitrides by metathesis with alkynes
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Terminal nitrido complexes N≡Mo(OC(CF3)2Me)3 (4), N≡Mo(OC(CF3)2Me)3(NCMe) (4-NCMe), and NMo(OC(CF3)3)3(NCMe) (5-NCMe) react irreversibly with 3-hexyne at elevated temperature in hydrocarbon solution to form the corresponding propylidyne complexes EtC≡Mo(OC(CF3)2Me)3 (3) and EtC≡Mo(OC(CF3)3)3 (6), long known as exceptionally active catalysts for alkyne metathesis. The propylidyne complexes are isolated as the more readily crystallized 1,2-dimethoxyethane (DME) adducts for convenience; 3-DME is isolated in 61% yield on a multigram scale. Copyright
- Gdula, Robyn L.,Johnson, Marc J. A.
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- The reaction of 1,2,3-selenadiazole with olefins
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When 1,2,3-selenadiazoles synthesized from cyclic ketones were treated with an excess amount of olefins at 130°C, the addition of a vinyl radical, which was generated in situ by the denitrogenation of 1,2,3-selenadiazoles, to a carbon-carbon double bond followed by intramolecular cyclization proceeded efficiently giving the corresponding dihydroselenophenenes in moderate to good yields along with the formation of the corresponding 1,4-diselenins and selenophenes as by-products. In this reaction, the number of carbon atoms on the cyclic ring of the ketones used as the starting materials in the synthesis of the 1,2,3-selenadiazoles plays an important role in the selectivity of the products. In contrast to the reaction of the 1,2,3-selenadiazoles prepared from the cyclic ketones, in the reaction of 1,2,3-selenadiazoles derived from aromatic and linear ketones, the dihydroselenophenene and 1,4-diselenins derivatives were not obtained and the corresponding alkynes were formed as the sole product.
- Nishiyama, Yutaka,Hada, Yasunobu,Iwase, Kuniko,Sonoda, Noboru
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- Polylithiumorganic compounds. Part 28. The reaction of allene and alkyl substituted allenes with lithium metal
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The reaction of allene (3a) and alkyl substituted allenes 1,2-hexadiene (3b), cyclopropylallene (3c), and vinylidene cyclopropane (3d) with lithium metal was investigated in order to access 2,3-dilithioalkenes 4a-d. These dilithioalkenes 4a-d are very reactive in polar solvents like THF and act as strong bases, either metalation of the starting allene 3a-d, the solvent, or sufficiently acidic intermediates like 8 a-d is observed. The metalation products 5-7 show follow-up reactions like 1,3-H shift to the corresponding 1-lithio-1-alkynes 8 and subsequent metalation to the dilithioalkynes 9. Additionally, lithium hydride elimination and ring-chain rearrangement (for 5c) are observed. 1,2-Hexadiene (3b) can be brought to reaction with lithium metal in the apolar solvent pentane, here the follow-up reactions are much slower due to the insolubility of 4b. In all cases the elucidation of the reaction pathways is hampered by the formation of complex mixtures of, amongst others, regio- and stereoisomeric products upon quenching with simple electrophiles.
- Maercker, Adalbert,Tatai, Andrea,Grebe, Burkhard,Girreser, Ulrich
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- Mn(I)-Induced 1,6-Demethanation across the CC Triple Bond of Linear Alkynes in the Gas Phase. A Case for the Generation of Manganese Cycloalkynes?
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Complexes of Mn(alkynes)+ were generated in the gas phase and found to exhibit a reactivity which is even richer than that of the analogous Fe(alkyne)+ species.Among the many unimolecular dissociations, the Mn+-induced demethanation of 4-octyne is of particular interest.The study of isotopomers and the effects of alkyl chain lengths reveals the operation of an unprecedented 1,6-elimination mode across the CC triple bond, and the experimental results may be explained by invoking the intermediate generation of the as yet unknown metallacycloalkynes.The implications of the unexpected, rich gas-phase ion chemistry of Mn+ with regard to theoretical models are discussed.
- Schulze, Christian,Schwarz, Helmut
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