Photochemical, Photophysical, and Theoretical Studies on Cyclobutanethiones: α-Cleavage Reactions
Photophysics and photochemistry of cyclobutanethiones 1-5 have been studied with the view to generalize the α-cleavage reactions of cyclobutanethiones.The above cyclobutanethiones possess a unit intersystem crossing efficiency from S1 to T
Multistep Reversible Redox Systems. 48. 1,3-Bisquinone Methide Cyclobutanes and Related Bicyclobutanes: Syntheses and Redox Properties
A new approach to quinone methides is presented, which starts from diazides and thioketones.Together with some model compounds, 1,3-bisquinone methide cyclobutanes 23, 25, and 37 were synthesized.Reduction with sodium transforms these quinoid compounds in
Freund, Wolfgang,Huenig, Siegfried
p. 2154 - 2161
(2007/10/02)
Thermotropic Liquid Crystals Containing the Dispirotetradecane Unit
Several 3,11-disubstituted dispirotetradecane-7,14-dions were prepared and the cis/trans-isomers were separated.The trans-stereoisomers were converted into the gem-dihalide ketones and mono- and dithioketones.The phase transfer temperatures were
Calaminus, W.,Voegtle, F.,Eidenschink, R.
p. 1011 - 1014
(2007/10/02)
Oxidation of 1,3-Cyclobutanedithiones and 3-Thio-1,3-cyclobutanediones by Singlet Oxygen
Oxidation of 1,3-cyclobutanedithiones (4-6) and 3-thio-1,3-cyclobutanediones (1-3) upon direct excitation and by singlet oxygen yields the corresponding sulfines and/or ketones.Formation of ketone is believed to involve 1,2,3-dioxathietane as the intermediate.A zwitterionic peroxide resulting from the interaction of singlet oxygen with thiocarbonyl chromophore is the common intermediate for both ketone and sulfine.The variation in the product distribution among 1-6 is understood on the basis of the electronic and steric factors operating on the zwitterionic peroxide intermediate.
Sundari, B.,Ramamurthy, V.
p. 498 - 501
(2007/10/02)
Strain-Assisted α-Cleavage Reactions of Thioketones: Cyclobutanethiones
Photochemical α-cleavage from the lowest triplet state (n?*,T1), resulting in the generation of a diradical intermediate, appears to be general for cyclobutanethiones.The diradical intermediate derived from 1,3-dithione is observed to undergo ring expansion to carbene or close to either dithione or dithiolactone.The photochemical behavior reported here for cyclobutanethiones is different from that of the corresponding cyclobutanones. α-Cleavage processes in the case of cyclobutanethiones are not efficient and are often accompanied by side reactions.
Muthuramu, K.,Sundari, B.,Ramamurthy, V.
p. 4482 - 4487
(2007/10/02)
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