5602-48-2Relevant academic research and scientific papers
Hydroalumination of alkenes by the LiAlH4*3AlBr3 system
Gorobets, E. V.,Shitikova, O. V.,Lomakina, S. I.,Tolstikov, G. A.,Kuchin, A. V.
, p. 1573 - 1578 (2007/10/02)
The hydroalumination of a series of alkenes and some fused aromatic hydrocarbons by the LiAlH4*3AlBr3 system in low-polar solvents was studied.Alkenes with mono-, di-, tri-, and tetraalkyl substituted, mono- and diaryl substituted double bonds and anthracene react at room temperature to give the corresponding dibromoaluminoalkanes in high yields.Benzylidenefluorene, tetraphenylethylene, naphthalene, and phenanthrene do not undergo hydroalumination under these conditions.Camphene, bicyclooct-2-ene, and norbornene afford the corresponding organoaluminum compounds with high stereoselectivity.Oxidation and halo- and acyldemetallation of the resulting alkyl- and arylalanes were carried out.
Differential Bridging in the Solvolysis of Epimeric Bicyclic Sulfonates. Norbornanes, Part 17
Grob, Cyril A.,Waldner, Adrian,Zutter, Ulrich
, p. 717 - 729 (2007/10/02)
The solvolysis rates and products of the 2-exo- and 2-endo-norbornyl, bicyclooct-8-yl, bicyclonon-2-yl, bicyclooct-6-yl, bicyclooct-2-yl and bicyclonon-6-yl p-toluenesulfonates 10-15, respectively, are reported.The exo/endo rate ratios for these epimeric secondary tosylates in 80percent EtOH varied from 1125 for 11 to 1.6 for 15.The relative rates varied between 2278 for exo-10 and 4E-3 for endo-11.The hydrolysis products were mainly rearrenged alcohols and olefins.The unrearrenged alcohols from the exo-tosylates were formed with complete or predominant retention of configuration, whereas those derived from the endo-tosylates were mostly inverted.These results confirm the hypothesis that relative rates, as well as products, are largely determined by the degree of bridging between the cationic center and a dorsal C-atom in the transition state and in the resulting ion pairs.Since bridging is a directed bonding interaction, it is subject to the same angle and conformational strains as ordinary covalent bonds.But bridging requires less geometrical change than the formation of normal bonds and of nonclassical ions.
DEAMINATION OF BICYCLOOCTAN-2-YL- AND BICYCLOOCTAN-2-YL-AMINES. EVIDENCE FOR CLASSICAL PRECURSORS OF NON-CLASSICAL CARBONIUM IONS
Maskill, Howard,Wilson, Alan A.
, p. 119 - 128 (2007/10/02)
Bicyclo octan-2-yl- and exo-bicyclooctan-2-yl-amines have been deaminated in acetic acid by nitrous acid and via their N-phenyltriazenes; their ethyl N-nitrosocarbamates have also been solvolysed in ethanol.Product distributions by a given method from the structurally isomeric starting materials are similar to each other and to common product distribution obtained from bicyclooctan-2-yl and exo-bicyclooctan-2-yl toluene-p-sulphonates.Each amine gives, however, a small but unmistakable excess of the structurally unrearranged product compared (in the case of subtitution) with the distribution obtained from the solvolysis of the corresponding bicyclo-octyl toluene-p-sulphonates. endo-Bicyclooctan-2-ylamine has also been deaminated in acetic acid by nitrous acid and via its ethyl N-nitrosocarbamate in ethanol.The prouct ratios of these reactions are characteristically different from those of the isomric amines but, as far as substitution is concerned, are similar to what is obtained from endo-bicyclooctan-2-yl toluene -p-sulphonate.A common mechanism describes all the deaminative reactions.We propose that classical carbonium ions are the initial products of fragmentation of diazo-intermediates.These are intercepted to only a small extent to give products structurally and stereochemically characteristic of the original amines; to an even smaller extent they rearrange to isomeric classical carbonium ions, which in turn may be intercepted.The predominant reaction of the initially formed classical carbonium ions is rearrangement to non-classical isomers.From both becyclooctan-2-yl- and exo-bicyclooctan-2-yl-amines, the same unsymmetrical nonclassical carbonium ion is produced as has been implicated in the solvolysis of the corresponding toluene-p-sulphonates. endo-Bicyclooctan-2-ylamine deamination gives rise to an isomeric symmetrical non-classical carbonium ion, the same one that intervenes in the solvolysis of endo-bicyclo-octan-2-yl toluene-p-sulphonate.Symmetrical and unsymmetrical non-classical carbonium ions once formed give product ratios largely independent of their origins or modes of formation although the symmetrical one appears to undergo a small extent of isomerization to the (more stable) unsymmetrical species.These results are contrasted with those obtained from simple carbocyclic systems (without branching at the β-carbon) in which deamination and toluene-p-sulphonate solvolysis give characteristically different and unrelated product distributions.
BRIDGING STRAIN IN THE SOLVOLYSIS OF EPIMERIC BICYCLIC TOLUENESULFONATES
Grob, Cyril A.,Waldner, Adrian
, p. 3235 - 3238 (2007/10/02)
The large variations in the rate ratios for the epimeric bicyclic p-toluenesulfonates 1 to 5 are ascribed to differential bridging strain accompanying the formation of intermediate cations.
