1713-41-3Relevant articles and documents
Phenyliodine diacetate-mediated oxidative cleavage of cyclobutanols leading to γ-hydroxy ketones
Fujioka, Hiromichi,Komatsu, Hideyuki,Miyoshi, Akihito,Murai, Kenichi,Kita, Yasuyuki
supporting information; experimental part, p. 973 - 975 (2011/03/21)
Oxidative cleavage of cyclobutanols using PIDA, which leads to efficient entry of γ-hydroxy ketones, is described. When using 2-substituted cyclobutanols, γ-substituted γ-hydroxy ketones are obtained through regioselective C-C bond cleavage.
Influence of cyclodextrin encapsulation on Norrish-Yang photoreaction of valerophenone
Annalakshmi, Subramanian,Pitchumani, Kasi
, p. 2000 - 2006 (2007/10/03)
In the solid-state Norrish-Yang photoreaction of valerophenone, studied in presence of various cyclodextrins, not only was elimination suppressed, but a remarkable diastereoselectivity was also observed. The predominant formation of one cyclobutanol (C1-trans) is rationalized as being due to a restricted rotational motion of the 1,4-biradical, and also stabilization of the same by hydroxyl groups present in the rim of the cyclodextrin cavity. Additional supports for the coinclusion of a side chain into the γ-CD cavity from molecular minimization calculations and 1H-1H NOESY spectra are also presented.
Photoreaction of valerophenone in aqueous solution
Zepp,Gumz,Miller,Gao
, p. 5716 - 5723 (2007/10/03)
Kinetics and products of the photoreaction of the phenyl ketone valerophenone were investigated as a function of temperature, pH, and wavelength in aqueous solution. Under these conditions (-4M), the photoreactions are pseudo-first-order with respect to valerophenone concentration. Type II quantum yields for photoreaction were close to unity throughout the 290-330 nm spectral region and in the temperature range from 10 to 40 °C. The quantum yields for the photoproducts were 0.65 ± 0.04 for cleavage to acetophenone and propene and an overall yield of 0.32 ± 0.03 for cyclization to two cyclobutanols at 20 °C. A small amount of 1-phenylcyclopentanol (2% yield) also was formed. These photoreactions were quenchable by additions of the triplet quenchers sorbic alcohol or sorbic acid, and Stern-Volmer plots were linear up to at least 80% quenching of the photoreactions. On the basis of quenching studies with steady-state irradiations, the triplet lifetime of valerophenone at 20 °C was estimated to be 52 ns, 7 times longer than that observed in hydrocarbon solvents. Since the triplet lifetime is controlled by intramolecular hydrogen abstraction, these results indicate that the rate constant for H abstraction is significantly lowered in aqueous media. The slower H abstraction in aqueous solution is attributed to stabilization of the excited π,π* state by water and vibronic mixing and slight inversion of the reactive n,π* triplet and the unreactive π,π* triplet states. This interpretation also is supported by changes in the UV absorption spectra of phenyl ketones in water compared to organic solvents. Red shifts, compared to the polar organic solvent acetonitrile, were observed in the π-π* transitions of valerophenone and acetophenone, reflecting stabilization of the excited π,π* state by water. Other results indicated that the quantum yields for valerophenone photoreaction are pH-independent from pH 9 to pH 2 but decrease significantly below pH 2. The decrease at low pH is attributed to quenching of triplet reactivity via protonation of the excited triplet state. The use of valerophenone as a convenient actinometer for studies in water is discussed; its half-lives during midday exposure to summer sunlight in temperate latitudes are 30 min.
A Comparsion between Zeolite-Solvent Slurry and Dry Solid Photolyses
Ramamurthy, V.,Corbin, D. R.,Turro, N. J.,Zhang, Z.,Garcia-Garibay, M. A.
, p. 255 - 261 (2007/10/02)
The use of zeolite-solvent slurry as a convenient medium to carry out photoreactions is illustrated with four examples, namely Norrish type I reaction of dibenzyl ketones, Norrish type I and type II reactions of α-alkylbenzyl benzyl ketones, Norrish type II reaction of aryl alkyl ketones, and photodimerization of acenaphthylene.Solvent present within the supercages of zeolites X and Y provides constraint on the mobility of the included guest molecules.Such restrictions are reflected in the product distributions.The difference in the product distribution obtained between the zeolite-solvent slurry and a homogeneous solution is often higher than that between the dry powder zeolites and a homogeneous solution.
Organic reactions in liquid crystalline solvents. 10. Studies of the ordering and mobilities of simple alkanophenones in CCH-n liquid crystals by2H NMR spectroscopy and norrish II photoreactivity
Workentin,Leigh,Jeffrey
, p. 7329 - 7336 (2007/10/02)
The Norrish II reactions of butyrophenone (BP), valerophenone (VP), and hexanophenone (HP) have been carried out at 30°C as 0.6, 5.0, and 40 mol % solutions in the isotropic, smectic (crystal-B), and nematic liquid crystalline phases of trans,trans-4′ alkyl[1,1′-bicyclohexyl]-4-carbonitrile (CCH-n) liquid crystals. In each case, the distribution of fragmentation and stereoisomeric cyclobutanols from photolysis of the ketones in the nematic phase is similar to that obtained from photolysis in a model isotropic solvent. The product distribution from photolysis of 0.6 mol % BP in the crystal-B phase is also similar to that in the isotropic phase, but both the fragmentation/cyclization and trans/cis-cyclobutanol product ratios from photolysis of VP and HP are affected significantly by smectic liquid crystalline order. The magnitude of the effect correlates with the size of the γ-substituent and inversely with concentration. Deuterium NMR spectra of the a- and ring-deuterated analogues of the three ketones, along with those of acetophenone (AP) and propiophenone (PP), have been measured as a function of temperature and concentration in CCH-4. Homogeneous smectic solutions of α-deuterated AP, PP, and BP exhibit distinctive 2H NMR spectra with regular differences throughout the series, but VP and HP show no detectable spectral features within 100 kHz of center spectrum. These results afford a qualitative correlation of the motional behavior of the solutes in the smectic phase as a function of alkanoyl chain length, which parallels that manifested in Norrish II reactivity. The ring-deuterated derivatives of all five ketones in the smectic phase show spectra consistent with solubilization of the probe in a highly ordered, oriented environment. Order parameters for the five ketones in the nematic phase at 52°C have been calculated from the spectra of the ring-deuterated derivatives. Solubility limits of the ketones in the crystal-B phase of CCH-4 have been determined from the concentration dependence of the spectra of the ring-deuterated derivatives.
Modification of photochemical reactivity through the use of clathrates: the Norrish type I and type II reactions in Dianin's compound
Goswami, P. C.,Mayo, Paul de,Ramnath, N.,Bernard, G.,Omkaram, N.,et al.
, p. 2719 - 2725 (2007/10/02)
Dianin's compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) serves as host in a series of well-defined clathrate inclusion complexes with eleven linear, as well as branched chain, phenyl alkyl ketone guest molecules, chosen for their ability to undergo the Norrish type I and type II photochemical reactions in solution.The photochemical reactivity of the guest ketones within the clathrate cavity was determined by irradiation of the inclusion complexes in the solid state.The results were compared to the photoreactivity of the ketones in polar as well as nonpolar liquid media.In general, the inclusion complex medium brings about an enhancement of type I over type II reactivity and causes an increase in type II fragmentation compared to type II cyclization.This change in reactivity is interpreted as resulting from the relatively restricted environment of the clathrate cavity coupled with the greater motion required for the type II process (γ-hydrogen abstraction) compared to the type I reaction (α-cleavage), as well as from the greater steric requirements for type II cyclization (cyclobutanol formation) as compared to type II cleavage (1,4-hydroxybiradical scission).
CIDNP from a 1,4-Biradical in the Norrish Type II Photoreaction of Valerophenone
Kaptein, Robert,Kanter, Frans J. J. de,Rist, Guenther H.
, p. 499 - 501 (2007/10/02)
Biradical CIDNP observed in the title reaction indicates that two intersystem-crossing mechanisms are operative in the intermediate 1,4-biradical, one involving hyperfine coupling of the odd electrons with protons and the other, which is product selective, involving spin-orbit coupling.