Bildung und Kristallstruktur eines dimeren sauerstoffverbrückten Titanaminobisphenoxides

Formation and Crystal Structure of an Oxygen Bridged Titanium Amino Bisphenoxide Di‐(μ‐oxo)‐titan‐bis[aminobisphenoxide] ( 3 ) was obtained by reaction of (i‐Prop)₂TiL* ( 2 ) {L* = O‐4, 6‐(t‐Bu)₂C₆H₂‐2‐CH₂‐[1, 4‐N₂C₅H₁₀]‐2'‐CH₂‐4', 6'‐(t‐Bu)₂C₆H₂O] with water in a molar ratio 1:1 in diethylether. Both i‐Propyl moieties are substituted yielding the dimeric oxygen bridged amino bisphenoxide complex. The six coordinate Ti atoms are a result of Ti—N and Ti—O interactions of the corresponding atoms of the amino bisphenoxide ligand and the bridging O atoms. The central planar Ti₂O₂ ring may be considered as the general structural feature of the title compound: Space group P1¯, Z = 1, lattice dimensions at —60°C: a = 11.6899(4), b = 11.7873(4), c = 12.6462(4) Å, α = 98.070(1), β = 99.660(1), γ = 95.343(1)°, R₁ = 0.0469, wR₂ = 0.1049, GooF = 0.939.     

Synthesen und Thermolysen von 1-Alkinyl-2-methyl-1,2-epoxy-cycloalkanen. - Versuche zur Ringerweiterung um drei Kohlenstoffatome

Syntheses and Thermolyses of 1-Alkynyl-2-methyl-1,2-epoxy-cycloalkanes. - Attempts at Ring Enlargement by Three Carbon Atoms The 1-alkynyl-2-methyl-1,2-epoxy-alkene 2 and -cycloalkenes 9, 28 and 29 were obtained by epoxidation of the conjugated en-ynes 1, 7, 26 and 27 . The 12-membered ring en-ynes 26 and 27 were synthesized by ethynylation or propynylation of 2-methylcyclododecanone ( 19 ) to the 1-ethynyl- or 1-(1′-propynyl)-cyclododecanols 20 A/B and 21 A/B , respectively, followed by dehydration to give separable mixtures of the regio- and stereoisomeric en-ynes 22, 24, 26 and 23, 25, 27 , respectively. Gas-phase thermolyses of the epoxides 2, 9, 28 and 29 were carried out under reduced pressure through a quartz tube at 550–600°. The formation of 5-hexine-2-one ( 3 ) and 4,5-hexadien-2-one ( 4 ) from 2 can be explained by [1, 5]- and [1, 3]- hydrogen shifts, respectively, and subsequent Claisen-type rearrangements. Thermolysis of the six-membered carbocyclic epoxide 9 induced the expected ring expansion by three carbon atoms to give 14% 4-cyclononynone ( 12 ), along with the ketones 13, 14 and 15 as by-products, which probably arose from surface induced heterolytic C, O-bond fission and Wagner-Meerwein-type rearrangement processes. Preliminary experiments with the thermolysis of the 12-membered carbocyclic ethynyl-epoxide 28 , yielded a mixture, which contained 4-cyclopentadecynone ( 30 ) and afforded, after hydrogenation, cyclopentadecanone ( 31 , exaltone®) in 36% yield as the semicarbazone. Traces of 3-methylcyclopentadecanone ( 32 , rac, -muscone) were identified after thermolysis and hydrogenation of the propynyl-epoxide 29 .     

Bildung eines hochexplosiven Valenzisomeren des Indens aus Dilithiopentalen und Chlorcarben

Formation of a Highly Explosive Valence Isomer of Indene from Dilithiopentalene and Chlorocarbene The principal product of the reaction of dilithiopentalene ( 3 ) with methyllithium and methylene chloride is shown by difference-FT-NMR, spectroscopy to be tetracyclo[4.3.0.0^3,5.0^4,6]nona-1,7-diene ( 8 ). This laterally bridged benzvalene derivative explodes violently at temperatures as low as ?40° when concentrated. Controlled rearrangement in diluted solution gives indene ( 4 ). The key step in the formation of the tetracyclic C₉H₈-compound 8 is suggested to be an intramolecular 1,4-carbene addition.     

Ringerweiterung bei der Reaktion eines 1,3-Cyclohexandions mit Diphenylcyclopropenon

Ring Expansion during the Reaction of a 1,3-Cyclohexanedione with Diphenylcyclopropenone The reaction of 5,5-dimethyl-1,3-cyclohexanedione ( 1 ) in form of its Na-salt with diphenylcyclopropenone ( 2 ) in DMF yielded the bicyclic triketone 3 (58 %), the structure of which was deduced as an enolizeable bicyclo[5.2.0]nonane-β-diketone from spectral data and from the following reactions: hydrolysis or methanolysis of 3 cleaved the β-dicarbonyl moiety, thereby opening the 4-membered ring to yield the keto acid 9 or its methyl ester 10 . Methylation of 3 afforded the two enol ethers 4 and 5 . The ether 5 readily underwent a thermal electrocyclic ring opening to the monocyclic enol ether 8 , whereas the ether 4 was thermally stable. The same electrocylic ring opening (in boiling benzene) converted 3 (probably via 3b ) to the monocyclic triketone 7 , which was also the hydrolysis product of the ring-opened enol ether 8 . By heating 3 in DMF/H₂O, a partial (56 %) conversion to the lactone 6 took place. The tricyclic intermediate 11 was found useful to rationalize the ring expansion during the formation of 3 from 1 and 2 as well as the corresponding ring contraction during the conversion of 3 into 6 .