67529-90-2Relevant academic research and scientific papers
Transient Phenomena in the Pulse Radiolysis of Retinyl Polyenes. 3. Radical Cations1,2
Bobrowski, K.,Das, P. K.
, p. 5079 - 5085 (1985)
Results are presented concerning transient absorption phenomena observed upon pulse radiolysis of several retinyl polyenes at submillimolar concentrations in acetone, n-hexane, and 1,2-dichloroethane under conditions favorable for radical cation formation.Oxygen insensitive, the polyene radical cations are characterized by intense absorption maxima (575-635 nm) with locations that show little or no dependence on functional groups.In acetone, they undergo decay predominantly by first-order kinetics with lifetimes 4-11 μs.The biomolecular rate constants for radical cation quenching by water, triethylamine, and bromide ion in acetone are in the ranges (0.8-2) X 105, (0.3-2) X 108, and (3-5) X 1010 M-1 s-1, respectively.
Vinyltin acetals in terpenic and nor-terpenic synthesis
Launay, Valerie,Beaudet, Isabelle,Quintard, Jean-Paul
, p. 937 - 946 (2007/10/03)
Vinyltin acetals obtained by stannylmetallation of homopropargyl acetals with Bu3SnMgMe/CuCN (E configuration) or by titanation of the corresponding alkyltin acetals (Z configuration) have been proved to be efficient storable precursors for the stereoselective synthesis of terpenoids, under mild experimental conditions.Due to the presence of a nucleophilic centre (Csp2-Sn bond) and of a protected electrophilic centre, they are also useful intermediates for an iterative synthesis of retinal and nor-retinoids. - Keywords: vinyltin; acetal; vinyllithium; monoterpenoid; retinal; nor-retinoid
A new prenylation method using the lithium enolate of prenal. Reaction with polyunsaturated aldehydes. A short access to retinal
Duhamel, Lucette,Guillemont, Jerome,Poirier, Jean-Marie,Chabardes, Pierre
, p. 4499 - 4500 (2007/10/02)
The enolate of prenal 1 prepared from the corresponding silyl enol ether 2 or enol acetate 3 led to a γ-regiospecific reaction with polyunsaturated aldehydes 4 yielding dihydropyrans 5 leading after hydrolysis to polyenals 7. This process allows the introduction of the isoprenyl skeleton. A synthesis of retinal, from β-ionylidenacetaldehyde is reported.
Transient Phenomena in the Pulse Radiolysis of Retinyl Polyenes. 4. Environmental Effects on Absorption Maximum of Retinal Radical Anion
Bobrowski, K.,Das, P. K.
, p. 5733 - 5738 (2007/10/02)
The absorption-spectral and kinetic behaviors of radical ions of all-trans-retinal in various solvents have been studied by spectrophotometric pulse radiolysis at room temperature.Upon going from nonpolar and polar-nonprotic solvents to polar-protic ones (alcohols), large hypsochromic shifts occur in the absorption maximum (λmax) of retinal radical anion.The anion absorption maxima in the alcohols correlate well with solvent dielectric constants.In a number of solvents, parallelism is noted between the energies corresponding to λmax's of retinal anion and of solvated electron (the latter at 77 K and room temperature).Transient phenomena associated with the radical anion (λmax's = 448-460 nm) and the retinyl alcohol radical (λmax = 405 nm) are observed in the course of the pulse radiolysis of retinal in several normal micelles (aqueous).The blue-shifted locations of the anion λmax's strongly suggest a polar-protic, alcohol-like nature of the micellar region where the polyenal resides.
Transient Phenomena in the Pulse Radiolysis of Retinyl Polyenes. 1. Radical Anions
Raghavan, N.V.,Das, P.K.,Bobrowski, K.
, p. 4569 - 4573 (2007/10/02)
The spectra and kinetics of formation and decay of radical anions of a number of retinyl polyenes have been studied in methanol and 2-propanol at room temperature, using pulse radiolysis and kinetic spectrophotometry.The bimolecular rate constants for the attachment of solvated electrons, e-MeOH, to the retinyl polyenes are in the diffusion-controlled limit (8.6 x 109-1.6 x 1010 M-1 s-1).The radical anions of retinol and retinol acetate have their spectral maxima at 370-390 nm, and undergo decay very slowly with second-order kinetics.On the other hand, the radical anions of retinal, retinal n-butylamine Schiff base, and retinoic acid/ester have spectral maxima at 430-510 nm, and decay by first-order kinetics in methanol with rate constants in the range 1 x 104-1 x 106 s-1.The decay rates of radical anions of retinal and retinoic acid/ester become considerably longer on going from methanol to less acidic alcohol, 2-propanol, suggesting that protonation by solvent is the major mode of their decay in protic media.In the case of retinal Schiff base, an additional slow process with bimolecular rate constant 9.0 x 107 M-1 s-1 im methanol is observed for the formation of radical anion and is ascribed to the electron-transfer reaction from the methanol radical, .CH2OH.
