54454-84-1Relevant academic research and scientific papers
Photochemistry of 1, n -Dibenzyloxy-9,10-anthraquinones
Sarma, Saurav J.,Jones, Paul B.
supporting information; experimental part, p. 3806 - 3813 (2010/08/20)
Figure presented The photochemistry of a series of 9,10-anthraquinones with multiple benzyloxy substituents was investigated. In polar solvent, the expected Blankespoor oxidative cleavage reaction is the major reaction pathway, but in most cases, several minor products were observed. In nonpolar solvents, the abundance of these minor products increases dramatically. Four types of product were observed with the favored reaction pathway shifting with minor changes in substitution on the anthraquinone. Several types of product require cleavage of the C-O bond on the benzyloxy group and, apparently, follow a photo-Claisen-type mechanism. Others involve the expected 1,5-diradical but do not exhibit the single-electron transfer usually observed in the Blankespoor-type reaction. The results indicate the importance of considering the medium and photoredox behavior in anthraquinone photochemistry.
Short-lived 1,5-biradicals formed from triplet 1-alkoxy- and 1-(benzyloxy)-9,10-anthraquinones
Smart, Robert P.,Peelen, Timothy J.,Blankespoor, Ronald L.,Ward, Donald L.
, p. 461 - 465 (2007/10/03)
The cyclopropylmethyl and (trans-2-phenylcyclopropyl)methyl radical clocks were used to estimate the lifetimes of triplet state biradicals formed from substituted 1-alkoxy-9,10-anthraquinones by photoexcitation and subsequent 1,5-hydrogen atom transfer. Irradiation (350 nm) of 1-(cyclopropylmethoxy)-2-methyl-9,10-anthraquinone (1cp) in argon-purged methanol generated the primary anthrahydroquinone product (2). Upon exposure to air, 2 was rapidly converted to cyclopropanecarboxaldehyde and 1-hydroxy-2-X-9,10-anthraquinone (3). In contrast, irradiation of 1-{(trans-2-phenylcyclopropyl)methoxy}-2-benzyl-9,10-anthraquinone (1pcp) under similar conditions produced only small amounts of 3 and the corresponding aldehyde, trans-(2-phenylcyclopropyl)carboxaldehyde. In addition, products resulting from rearrangement of the 1,5-biradical to a homoallylic 1,8-biradical were also obtained. Using the known rate constant for the rearrangement of the phenylcyclopropylmethyl radical to the homoallylic radical and the observed product ratio, lifetimes of approximately 1-2 ns were estimated for 1,5-biradicals from these anthraquinones which are about an order of magnitude shorter than those reported for triplet state biradicals derived from structurally related benzophenones and acetophenones. The short lifetimes of these biradicals are attributed to the facile formation of a zwitterion which results from an intramolecular electron transfer from one radical site, which serves as electron donor, to the other radical site, which is a semianthraquinone and therefore serves as a good electron acceptor. If either the electron-donating or electron-accepting site is absent in the biradical, zwitterion formation is not observed and coupling of the biradical occurs resulting in a longer lifetime.
Photochemistry of 1-Alkoxy- and 1-(Benzyloxy)-9,10-anthraquinones in Methanol: A Facile Process for the Preparation of Aldehydes and Ketones
Blankespoor, Ronald L.,Smart, Robert P.,Batts, Eric D.,Kiste, Alan A.,Lew, Rebecca E.,Vliet, Marc E. Vander
, p. 6852 - 6859 (2007/10/03)
The facile production of acid sensitive aldehydes and ketones via photochemical intramolecular δ-hydrogen atom transfer in 1-alkoxy- and 1-(benzyloxy)-9,10-anthraquinones (1) was investigated.Irradiation of 1 in argon purged methanol generates the primary photoproducts, 1-(RCH(OMe)O)- and 1-(ArCH(OMe)O)-9,10-anthrahydroquinones (2), respectively.Upon exposure to air, the intermediate anthrahydroquinone is rapidly converted to the corresponding aldehyde and 1-hydroxy-9,10-anthraquinone (3), which can be recycled.Aldehydes containing an acetal or ketal were prepared in high yields using this photoprocess.Apparent rate constants for the photodemethylation of 1-methoxy-2-X-9,10-anthraquinones (X = H, Me, Et, Pr, i-Bu, and benzyl) were measured and found to vary by a factor of 10 separating the slowest anthraquinone (X = H) and the fastest (X = benzyl), indicating a strong dependency upon the size of the substituent at the 2-position.These rate constants are ascribed to equilibrium populations of conformers in the geometry required for the reaction in the n,?* triplet state.
Novel anthraquinone inhibitors of human leukocyte elastase and cathepsin G
Zembower,Kam,Powers,Zalkow
, p. 1597 - 1605 (2007/10/02)
A large series of variously substituted anthraquinones has been synthesized and assayed for inhibitory capacity against human leukocyte elastase (HLE) and cathepsin G (CatG), two serine proteinases implicated in diseases characterized by the abnormal degradation of connective tissue, such as pulmonary emphysema and rheumatoid arthritis. It was found that 2-alkyl- 1,8-dihydroxyanthraquinone analogues are competitive inhibitors of HLE with IC50 values ranging from 4 to 10 μM, and also inhibit CatG with IC50 values ranging from 25 to 55 μM. Consequently, analogues containing the 2- alkyl-1-hydroxy-8-methoxyanthraquinone substitution pattern inhibit HLE to the same magnitude as for the compounds above, but show very little inhibition of CatG. Anthraquinones containing long, hydrophobic n-butyl carbonate moieties in the 1- and 8-positions in conjunction with a third hydrophobic substituent in the 2- or 3-position are highly selective for HLE, with K(i) values in the range of 10-7 M. All of the inhibitors described are completely reversible, with no evidence of acyl-enzyme formation detected.
