- Chemical Consequences of the Intramolecular Interaction between a Sulphur Atom and a Methoxycarbonyl Group in Fluorene Systems
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The intramolecular interaction between a sulphur atom and a methoxycarbonyl group was found to affect their chemical reactivity.The rates of C-S bond cleavage in methyl-9,9-bis(ethylthio)fluorene-x-carboxylate, where x is 1, 2, or 3, with sodium ethanethiolate show that the rate is minimal, though comparable with the others, when x=1, because of steric effects.In contrast, methyl 9-(ethylthio)fluorene-x-carboxylates, where x=1, 2, or 3, exhibit the maximum rate when x=1.The rates of ester exchange in the presence of toluene-p-sulphonic acid indicate that the reaction is accelerated by the presence of two ethylthio groups at the 9 position of methyl fluorene-1-carboxylate but no significant effect is detected if there is only one ethylthio group.The hydrolysis of the thioketal group in 9,9-bis(ethylthio)fluorene is also accelerated by the presence of a 1-methoxycarbonyl group.The implication of these results are discussed with the use of a model compound.
- Nakanishi, Waro,Kusuyama, Yoshiaki,Ikeda, Yoshitsugu,Oki, Michinori
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p. 799 - 804
(2007/10/02)
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- THE EFFECTS OF THE NEIGHBORING METHOXYCARBONYL GROUP AND SULFUR ATOM(S) IN THE CARBON-SULFUR BOND CLEAVAGE AND THE ESTER EXCHANGE IN FLUORENE SYSTEMS
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9,9-bis(ethylthio)fluorene (1a) reacted with sodium ethanethiolate in methanol ro give 9-ethylthiofluorene and diethyl disulfide suggesting that a C-S bond cleavage occurs by attack of a nucleophile at sulfur if a leaving group is sufficiently stable.The pseudo-first-order rate constans for the reaction of 1a and methoxycarbonyl-substituted 9-ethylthiofluorenes have suggested that the methoxycarbonyl group at 1-position exerts through space interaction eith sulfur atoms(s).The rate constants for ester exchange in 1-methoxycarbonylfluorene and its derivatives have been discussed on the ground of neighboring sulfur participation.
- Nakanishi, Waro,Nakanishi, Hitoshi,Yanagawa, Yuko,Ikeda, Yoshitsugu,Oki, Michinori
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p. 105 - 108
(2007/10/02)
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