Light-induced conversion

Water-soluble sdanols such as (1) were found to undergo successive oxidative demethylations with tropospheric ultraviolet irradiation in the presence of suitable chromophores, such as nitrogen oxides (516). The water-soluble methylated sdicones did not promote diatom (Nap cu/apelliculosd) growth but the demethylated photo products did. The sequence of sod-induced degradation of sdicones to water-soluble species such as (1), followed by light-induced conversion to sdicate, suggests a pathway, conceptually at least, for the mineralization of sdicones. 

Hager, A. (1980). The reversible, light-induced conversion of xanthophylls in the chloroplast. In Pigments in Plants, ed. F.C. Czygan, pp. 57-79. Stuttgart Gustav Fischer-Verlag. 

In both light and high energy irradiation induced reactions, phenyl-thiol, 2-mercaptomesitylene, and their sulfides inhibit nonchain processes,201202 e.g., the light-induced conversion of benzophenone in 2-propanol to benzopinacol and acetone.99 217 The reaction converts compounds into radicals by removal or addition of hydrogen atoms. The sulfur compounds in rapid hydrogen transfer processes convert the free radicals to stable molecules and may do so repeatedly.46 46... 

Geller, A. 1985. Light-induced conversion of refractory, high molecular weight lake water constituents. Schweizerische Zeitschrift fiir Hydrologie 47 21-26. 

The change in chirality obtained by irradiation of 11 was sufficient to provoke the light-induced conversion of cholesteric to nematic phases in liquid crystals of 4/-(pentyloxy)-4-biphenylcarbonitrile doped with 1% w/w... 

One of the most frequently exploited photochromic processes is the cis trans isomerization of azobenzene. Irradiation of the more stable trans configuration with 360 nm ultraviolet light induces conversion to the cLs isomer, which is stable for long periods in the absence of heat or light. Exposure to moderate heat or irradiation in the visible spectrum induces the transformation back to the trans species. 

The light-induced conversion of acyclic divinylmethane reactants 1 to vinylcyclopropanes 2 (cf. Houben-Weyl, Vol. 4/5a, pp 413-433), also termed the Zimmerman rearrangement, usually occurs from the excited singlet state of the diene.The resulting vinylcyclopropane is often prone to undergo consecutive photoreactions and therefore these transformations are usually run to about 50% conversion. Under these conditions the material balance (1 - -2) is still > 95%. 

Table 1. Vinylcyclopropanes by Light-Induced Conversion of Acyclic Divinylmethane Reactants R2 r2...

Table 2. Arylcyclopropanes by Light-Induced Conversion of 3-Arylprop-l-enes...

Indeed, the formation of 2-alkenyl-thietan-3-ones represents the typical photochemical behavior for 2//,6//-thiin-3-ones and bicyclic compounds containing this ring system. Depending on the substitution pattern and on the wavelength chosen, these 2-alkenyl-3-thiacyclobutanones are stable [13, 33] or undergo further light induced conversions, e.g. a 1,3-acyl shift, to the final product(s) [34-36] as illustrated in Scheme 7. 

FIGURE 6.19 Self-assembly of achiral azobenzene-containing bent-core compound 10 and a melamine derivative to an achiral propeller-lifce complex 11 via intermolecular hydrogen bonding and light-induced conversion of supermolecular chirality in Coh phases using right and left CPL. Reproduced from [176] with permission from John Wiley Sons, Inc. 

Katsuro, H., Matsuishi, S., Kamiya, T., Hirano, M., Hosono, H., (2002). "Light-induced conversion of an insulating refractory oxide into a persistent electronic conductor" Nature, 419, pp. 462-465. 

In the majority of photocatalytic reactions both transition metal complexes and organometallic compounds play an important role in the light-induced conversion of inorganic as well as organic substrates. 

This ring contraction is not restricted to monocyclic thiinones but is also observed [37] for bicyclic compounds containing this type of ring system, for example, in the light induced conversion of (41) to (42) (Scheme 15). 

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