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Photochemical, photophysical, and theoretical studies on cyclobutanethiones..alpha.-Cleavage reactions

Rao, Bantu Nageshwer and Chandrasekhar, Jayaraman and Ramamurthy, Vaidhyanathan (1988) Photochemical, photophysical, and theoretical studies on cyclobutanethiones..alpha.-Cleavage reactions. In: Journal of Organic Chemistry, 53 (4). pp. 745-751.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jo00239a008

Abstract

Photophysics and photochemistry of cyclobutanethiones 1-5 have been studied with the view to generalize the a-cleavage reactions of cyclobutanethiones. The above cyclobutanethiones possess a unit intersystem crossing efficiency from S1 to T1, a high self-quenching rate (-4 X lo9 M-' s-'), and a short triplet lifetime (<0.50 ws). Photolysis of 1-5 yields in benzene a product resulting from 1,3-transposition and in methanol two cyclic thioacetals.The origin of these products is traced to the triplet excited state. A mechanistic scheme involving a-cleavage as the primary photoprocess and diradicals and thiacarbenes as intermediates has been formulated to rationalize the formation of thioacetals and rearranged products. The proposed mechanistic scheme is supported by UHF MIND013 calculations performed on four model systems, cyclobutanethiones and 1,3-cyclobutanedithiones 18-21. These calculations indicate that formation of diradical is favored thermodynamically and kinetically for systems analogous to 19 and 21, while rearrangement to thiacarbene is likely only for those similar to 21.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 25 Sep 2010 06:40
Last Modified: 25 Sep 2010 06:40
URI: http://eprints.iisc.ernet.in/id/eprint/32448

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