60456-75-9Relevant academic research and scientific papers
Photoenolization as a means to release alcohols
Pika, Jana,Konosonoks, Armands,Robinson, Rachel M.,Singh, Pradeep N. D.,Gudmundsdottir, Anna D.
, p. 1964 - 1972 (2007/10/03)
We have designed molecules which release alcohols upon exposure to UV light independent of the reaction media, making it possible to liberate alcohols in a controlled manner in applications. Photolysis of 2-(2-isopropylbenzoyl)benzoate ester derivatives 4 in various solvents and in thin films results in the liberation of the alcohol moiety from the ester. The reaction mechanism for the release of the alcohol has been elucidated by time-resolved laser flash photolysis. Upon irradiation the triplet excited state of ketone, 4 is formed, and its lifetime can be estimated to be between 0.08 and 0.8 ns. The triplet excited state decays by efficient intramolecular H-atom abstraction to form a 1,4-biradical, 8, that has a lifetime of less than 17 ns and is trapped by molecular oxygen. In the absence of oxygen, biradical 8 intersystem crosses to form photoenols (Z)-9 and (E)-10 in a ratio of 5:2, respectively. Photoenol (Z)-9 has a lifetime of ～3000 ns in protic solvents and returns to the starting material through 1,5 intramolecular hydrogen transfer. The other isomer, (E)-10, is much longer lived (>1 ms) and releases the alcohol moiety through an intramolecular lactonization.
Photochemical transformation of S-aryl 2-benzoylbenzothioates to 3-phenyl-3-arylthiobenzofuranones involving aryl migration
Takahashi, Masaki,Fujita, Tsutomu,Watanabe, Shoji,Sakamoto, Masami
, p. 487 - 491 (2007/10/03)
Photochemical reactions of S-aryl 2-benzoylbenzothioates 1 in solution media have been investigated. These thioesters undergo photoinduced cyclization to 3-aryl-3-arylthioisobenzofuranones 2 in yields of 14-46% upon direct irradiation. The photocyclizatio
2-benzoylbenzoic acid: A photolabile mask for alcohols and thiols
Jones, Paul B.,Pollastri, Michael P.,Porter, Ned A.
, p. 9455 - 9461 (2007/10/03)
Photolysis of 2-benzoylbenzoate esters of primary and secondary alcohols 1 in the presence of a hydrogen donor (2-isopropanol) or an electron donor (primary amines) produces the corresponding alcohol in high yield. The fate of the benzoate is dependent on the conditions used for the photoreaction. In 2-propanol, the ketyl radical that derives from photoreduction dimerizes, to afford the benzpinacol product 3,3"-diphenylbiphthalidyl, 5. In the presence of amines the product is 3-phenylphthalide, 6, a benzhydrol derivative which is the result of simple reduction of the ketone followed by lactonization. While the photoproduct of the benzoate - 2-propanol reaction results from anticipated free radical chemistry, the amine-promoted reaction appears to result from a second, "dark", electron transfer process. We conclude that 2-benzoylbenzoic acid is an effective photolabile protecting group for primary and secondary alcohols, and preliminary studies indicate that thiols can be protected in an analogous way. Studies on the effect of benzophenone substituents and reaction solvent on the benzhydrol:benzpinacol product ratio provide mechanistic insight into the process.
Photochimie organique: photolyse de O-benzoylbenzamides secondaires et tertiaires
Gramain, Jean-Claude,Lhomme, Marie-France
, p. 141 - 146 (2007/10/02)
Intramolecular photoreduction of ketones leads to a diradical likely to undergo cleavage or cyclization to yield cyclobutanols (Norrish type II reaction).Examples of intramolecular δ- or ε-H-abstraction are known to lead to 1,5- or 1,6-diradicals, the cyclization of which gives rise to five or six-membered rings.We have prepared a series of O-benzoyl-benzamides and studied their photolysis in order to establish a pathway to phenyltetrahydroisoqoinolines.We have thus prepared N-ethyl, N-isopropyl and N-benzyl-O-benzoylbenzamides and shown that in solution these compounds have a cyclic structure (3-hydroxy-3-phenylphtalimidine) in which the ketone carbonyl is hidden.These compounds are photochemically inert.Four tertiary O-benzoylbenzamides have been prepared (N,N-diethyl, N,N-di-n-butyl, N-butyl-N-methyl, and N-benzyl-N-methyl).These compounds exhibit an n?* absorption above 300 nm.Their photolysis (λ > 300 nm) gives rise in all four cases to the 3-phenylphtalide 9 and to their dimer 10 of the 3-phenylphtalid-3-yl radical (meso and d,l) mixture.Upon irradiation below 300 nm (253.7 nm in quartz), formation of the diphtalide (dimer 10), not of the phenylphtalide 9, is observed.Finally no cyclic photoproducts derived from a 1,6-diradical are observed.In thus appears that deactivation of the excited state of tertiary O-benzolylbenzamides does not occur by intramolecular abstraction of the hydrogen α to the amide nitrogen atom, but rather by homolytic cleavage of the amide C-N bond.The radical thus formed cyclizes, giving a 3-phenylphtalid-3-yl radical which further yields, either the 3-phenylphtalide 9 by hydrogen capture, or the dimer 10 by coupling.During irradiation at 253.7 nm the optical density of the solution is very high (of the order of 1000) because of the high ε values of the starting compounds.The local concentration of 3-phenylphtalid-3-yl radicals is thus high, promoting their coupling to dimer at the expense of hydrogen capture, which would lead to the 3-phenylphtalide 9.
