- Acid-catalyzed cyclization of anthracenol derivatives to homotriptycenes
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10-Benzyl-9,10-dihydroanthracen-9-ols, having high electron densities in the benzene ring, exhibit in the presence of acid a transannular ring closure to the corresponding homotriptycenes in almost quantitative yields. Since the starting compounds are easily accessible from 9(10H)-anthracenone, this process represents the most facile route to such pentacyclic systems. An electron-releasing methoxy group enables the intramolecular electrophilic substitution in its para position. In the absence of such an activation, a number of alternative processes can occur, namely the acid-catalyzed dehydration to anthracene derivatives with (R ≠ H) or without (R = H) rearrangement or a disproportionation reaction of the secondary alcohol to the corresponding ketone and hydrocarbon.
- Gao, Chunmei,Cao, Derong,Xu, Sheyang,Meier, Herbert
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p. 3071 - 3076
(2007/10/03)
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- A facile synthesis of homotriptycenes from anthranol derivatives
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Substituted trans-10-benzyl-9-anthranols 5a,b and substituted 10, 10-dibenzyl-9-anthranol 8e undergo intramolecular cyclization in the presence of formic or oxalic acid to give homotriptycenes 9a,b,e. Depending on the amount of acid used, a competitive 1,
- Cao, Derong,Gao, Chunmei,Meier, Herbert
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p. 3166 - 3168
(2007/10/03)
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- Thermolysis of 2-Benzylidenebenzocyclobutenols
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The thermolysis of a series of 2-benzylidenebenzocyclobuten-1-ols has been studied.Whenever comparisons can be made, the rate of opening of the benzocyclobutene ring was slower for these compounds than the corresponding 2-ones.The intermediate vinylallenes underwent a variety of electrocyclization reactions which depended on the nature of the additional substituent at C-1. 10-Benzylideneanthrone and 4-benzylidene-1-tetralones, respectively, were obtained when this substituent was phenyl or vinyl. 1-(Alkynylphenyl)-2-benzylidenebenzocylobuten-1-ols were converted to mixtures of 4-benzylidene-1,4-naphthoquinonemethides, 2,3-dibenzylidene-1-indanones, and 10-phenylbenzofluorenone.
- Bradley, Jean-Claude,Durst, Tony,Williams, A. J.
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p. 6575 - 6579
(2007/10/02)
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- Photochemistry and photophysics of ketyl radicals containing the anthrone moiety
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The photochemistry of several ketones containing an anthrone moiety has been employed to produce the corresponding ketyl radicals 1-4 by photoreduction in the presence of suitable hydrogen donors. The excited-state behavior of these radicals has been examined with use of two-laser, two-color techniques. The lifetimes for the excited ketyl radicals, ranging from 7.9 ns for 3 to 33 ns for 2, are longer than that observed for benzophenone ketyl, thus suggesting that conformational restrictions play a key role in controlling excited radical lifetimes. In the case of 3 the dominant mode of decay involves loss of a benzyl radical from the 10-position, while for 1 and 2 the process involves the loss of a hydrogen atom from the hydroxylic position; in the case of 2 this has been confirmed by Raman spectroscopy. The quantum yields of radical photobleaching are 0.20, 0.46, and 0.75 for 1, 2, and 3, respectively, while 4 is essentially photostable. Deuterium substitution at the hydroxylic position leads to a considerable lengthening of the excited-state lifetime. In the case of dibenzylanthrone we have also detected a rather unprecedented (monophotonic) process involving triplet cleavage of a C-C bond at the 10-position, leading to PhCH2* and a 10-benzylanthranoxyl radical.
- Netto-Ferreira,Murphy,Redmond,Scaiano
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p. 4472 - 4476
(2007/10/02)
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