- Synthesis of bicyclic diones and thiones. Facile methylation of the enolates of bicycloheptane-2,5-dione and bicyclooctane-2,5-dione. An AM1 computational study of bicyclic enolates
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A group of bicyclic ketones and thiones have been synthesized for homenolization studies.Bicycloheptane-2,5-dione (6) undergoes unusually rapid tetramethylation giving 3,3,6,6-tetramethylbicycloheptane-2,5-dione (1) in good yield.Treatment of 1 with P2S5 in xylene gave 3,3,6,6-tetramethylbicycloheptane-2,5-dithione (2) and 3,3,6,6-tetramethyl-5-oxo-bicycloheptane-2-thione (3), which was converted into 4 with Raney nickel.Bicyclooctane-2,5-dione (7), prepared via Diels-Alder reaction between 2-trimethylsilyloxy-1,3-cyclohexadiene and α-acetoxyacrylonitrile followed by a one-step desilylation/hydrolysis, also undergoes facile tetramethylation giving 3,3,6,6-tetramethylbicyclooctane-2,5-dione (5) in good yields.AM1 calculations were carried out on the α-enolates of bicycloheptan-2-one, 6, 5-methylidenebicycloheptan-2-one, and 4-acetylbicycloheptan-2-one in an attempt to gain information on the source of the enhanced acidity of the C-3 hydrogens of 6 and 7. Key words: bicyclic ketones, thiones, synthesis.
- Werstiuk, N. H.,Yeroushalmi, S.,Guan-Lin, Hong
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p. 974 - 980
(2007/10/02)
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- Ultraviolet photoelectron spectra of 2-norbornanone, 2,5-norbornanedione, their alkyl derivatives and thio-analogues. An investigation of transannular interactions by photoelectron spectroscopy
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HeI photoelectron spectra are reported for a series of methyl-substituted monoketones and diketones based on 2-norbornanone.The effect of methyl substitution, and the inductive effect of a second carbonyl group has been studied.The diketones show a small separation between the two ketone moieties due to a through-bond interaction.Replacement with a thiocarbonyl group permits a comparison of the relative C=S and C=O interactions.The relative merits of the semi-empirical HAM/3 and CNDO/2 methods for such molecules are assessed.
- Frost, David C.,Westwood, Nicholas P. C.,Werstiuk, Nick H.
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p. 1659 - 1665
(2007/10/02)
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