Cooligomerization of trans-piperylene with ethylene

Conclusions The cooligomerization of trans-piperylene with C₂H₄ in the presence of NiCl₂·[P(C₄H₉)₃]₂ and (C₄H₉)₂AlCl gave the new cooligomers, 3-methyl-2,4-hexadiene and 3-methyl-3,7-octadiene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 214–216, January, 1974.     

Linear dimerization of 1-phenylbutadiene by acid catalysts

This article describes the linear dimerization of 1-phenylbutadiene by three catalysts (CF₃SO₃H, CH₃COCIO₄, and BF₃OEt₂) under a variety of conditions. With CF₃SO₃H catalyst the unsaturated linear dimer was formed selectively (75–85%) in a high yield by the proper choice of conditions; for example, at 70°C in benzene at low monomer concentrations (0.05–0.10 mole/liter). The dimerization was promoted in less polar solvents, at lower monomer concentrations, and at higher temperatures. In contrast, BF₃OET₂ gave only high-molecular-weight oligomers at 50°C in benzene. The structure of the dimer obtained with CF₃SO₃H was analyzed by infrared (IR) and ¹H-NMR spectroscopy and was concluded to be which may be formed via 3,4-and 1,4-addition, respectively. Nuclear magnetic resonance (NMR) spectra also showed that the oligomers produced by BF₃OEt₂ carry cyclic groups—one at the chain end and the other(s) attached to the main chain. Thus it was revealed that the nature of catalysts could control not only the molecular weight but the structure of oligomerization products.     

Noncovalent dimerization of ubiquitin

Another kind of dynamics: Ubiquitin noncovalently dimerizes with a dissociation constant of approximately 5?mM. The two subunits adopt an array of relative orientations, utilizing an interface also for binding to other proteins (see picture). Quaternary fluctuation among members of the dimer ensemble constitutes a different kind of dynamics that complements the tertiary dynamics of each ubiquitin subunit.     

Reversible dimerization of decaniobate

Three different solvates of TBA₆[Nb₁₀O₂₈] (TBA = tetra-n-butylammonium) were structurally characterized. The results revealed that two water molecules are hydrogen-bonded to the terminal oxygens of the [Nb₁₀O₂₈]⁶⁻ anion in the same manner in all of the solvates. Decaniobate [Nb₁₀O₂₈]⁶⁻ dimerizes by the action of HCl to form icosaniobate [Nb₂₀O₅₄]⁸⁻, while icosaniobate breaks up into decaniobate [Nb₁₀O₂₈]⁶⁻ by the action of TBAOH. Decaniobate also dimerizes spontaneously to form icosaniobate [Nb₂₀O₅₄]⁸⁻ in CH₂Cl₂ even if no acid is added to the solution. The reaction was followed by IR spectroscopy, and the results suggested the reaction is second order with respect to the concentration of [Nb₁₀O₂₈]⁶⁻.     

Cobalt-catalyzed dimerization of alkenes

In the presence of CoX₂(PPh₃)₂/3 PPh₃ and zinc metal conjugated alkenes (CH₂CHCOOR, CH₂CHCN, CH₂CHSO₂Ph and CH₂CHCONEt₂) undergo reductive tail-to-tail dimerization to yield the corresponding saturated linear products. Under similar reaction conditions, vinylarenes (ArCHCH₂) give stereoselective head-to-tail dimerization products, trans-1,3-diarylbut-1-ene, in good to excellent yields.     

Thermodynamics of dye dimerization

The thermodynamic parameters for dimerization has been obtained for fluorescein and halo-fluorescein dyes. Results indicate an increasing contribution of hydrophobic bonding for more aggregating dyes.     

Electrochemical dimerization of 9-acetylanthracene

Conclusions It was shown that the main product of the one-electron electrochemical reduction of 9-acetylanthracene in an aprotic solvent is a tail-tail-type 9,9-diacetyl-9,9,10,10-tetrahydrobianthryl dimer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2812–2814, December, 1987.     

Reductive dimerization of pyridine N-oxide

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 133–134, January, 1988.     

DNA-templated dimerization of hairpin polyamides

Double-helical DNA accelerates the rate of ligation of two six-ring hairpin polyamides which bind adjacent sites in the minor groove via a 1,3-dipolar cycloaddition to form a tandem dimer. The rate of the templated reaction is dependent on DNA sequence as well as on the distance between the hairpin-binding sites. The tandem dimer product of the DNA-templated reaction has improved binding properties with respect to the smaller hairpin fragments. Since cell and nuclear uptake of DNA-binding polyamides will likely be dependent on size, this is a minimum first step toward the design of self-assembling small gene-regulating fragments to produce molecules of increasing complexity with more specific genomic targeting capabilities.     

Slow dimerization of isopropoxyberyllium tetraisopropoxyaluminate

An interesting dimerization behaviour has been observed in the freshly distilled monomeric isopropoxy beryllium tetra-isopropoxyaluminate on standing.