191750-82-0Relevant articles and documents
Slow release of fragrant compounds in perfumery using a keto esters
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, (2008/06/13)
The present invention describes a fragrance delivery system which releases fragrant aldehydes or ketones and/or fragrant compounds containing an olefin function upon exposure to light. This system comprises α-keto esters of formula in which R′*
Controlled release of perfumery aldehydes and ketones by Norrish type-II photofragmentation of α-keto esters in undegassed solution
Rochat, Sabine,Minardi, Caroline,De Saint Laumer, Jean-Yves,Herrmann, Andreas
, p. 1645 - 1671 (2007/10/03)
Alkyl or aryl α-keto esters of primary or secondary alcohols decompose upon irradiation at 350-370 nm from the intermediate triplet state into aldehydes or ketones in polar, as well as apolar solvents. The use of these keto esters as delivery systems for the controlled release of perfumery aldehydes and ketones was investigated by photoirradiation in the presence of oxygen with a Xe or UV lamp, as well as outdoor sunlight. Systematic GC/MS analysis of the irradiated solutions showed that, under these conditions, the desired Norrish type-II fragmentation of the ester side chain is the predominant reaction pathway in most of the cases. γ-H Abstraction from the alkyl side chain of alkyl keto esters, as well as an intramolecular Paterno- Buchi reaction or epoxidation of the alkene function in different citronellyl α-keto esters were identified as the most important side reactions. Some of the experimental findings have been rationalized on the basis of ab initio and density-functional calculations. (Cyclohexyl)oxoacetates and oxo(phenyl)acetates were found to be the most suitable precursors for the desired perfumery applications.
Photochemical Reactions of Alkenyl Phenylglyoxylates
Hu, Shengkui,Neckers, Douglas C.
, p. 6820 - 6826 (2007/10/03)
The photochemical reactions of alkyl phenylglyoxylate esters whose ester function contains double bonds of differing substitution, situated at varying distances from the carbonyl group, have been studied. The intramolecular Paterno-Buechi reaction is the dominating photoreaction when an electron rich alkenyl group is situated at the proper distance as in 1′,5′-dimethylhex-4′-enyl phenylglyoxylate (6). When the distance between the excited carbonyl group and the same alkenyl function is increased, as it is in 3′,7′-dimethyl-6′-octenyl phenylglyoxylate (7), intramolecular γ-hydrogen abstraction (Norrish type II) products, as well as the products of intramolecular photocycloaddition, are observed. We suggest this to be the result of a competitive distant dependent electron transfer reaction between the excited carbonyl group and the alkene. A longer distance of separation between these two reactive functions decreases the efficiency of formation of the cycloaddition product. When the separation of the same alkene from the glyoxylate is shortened as in 4′-methylpent-3′-enyl phenylglyoxylate (5), electron transfer-induced remote proton abstraction leading to cyclol formation occurs, in addition to the Paterno-Buechi reaction. Further reducing the distance as in 3′-methylbut-2′-enyl phenylglyoxylate (3) results in only the normal intramolecular (Norrish type II) and intermolecular hydrogen abstraction products. At a distance where both oxetane and cyclol formation are possible as in 5, decreasing the electron richness of the alkenyl group as in cis-3′-hexenyl phenylglyoxylate (cis-4) eliminates the oxetane product. Formation of cyclol is shown to be conformationally controlled in that a similar product is not observed to be formed from trans-3′-hexenyl phenylglyoxylate (trans-4). If both the electron richness of the alkenyl group and the distance of separation are decreased as in 2′-hexenyl phenylglyoxylate (2), only γ-hydrogen abstraction products result. Cis-trans isomerization of the olefln is not observed in either 2 or 4.
