Synthesis of some select benzo-annelated and/or methano-bridged sulfur heterocyclics: Mechanistic and theoretical study of their sulfur extrusion.
Item
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Title
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Synthesis of some select benzo-annelated and/or methano-bridged sulfur heterocyclics: Mechanistic and theoretical study of their sulfur extrusion.
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Identifier
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AAI9630437
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identifier
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9630437
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Creator
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Benshafrut, Ronnie.
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Contributor
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Adviser: Klaus G. Grohmann
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Date
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1996
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Organic
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Abstract
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The studies of thiepins and 1,2-dithiocins have seen only limited success due to their great instabilities and tendencies of valence isomerization leading to sulfur extrusion. This still unknown mechanism of sulfur extrusion may be controlled by various methods such as selective substitution and annelation. Benzannelation allowed the synthesis of various thiepins and 1,2-dithiocins which were found sensitive and difficult to study. Benzannelation is traditionally believed to increase the barrier for extrusion of sulfur units as an o-quinoid is formed en route to extrusion. We thus attempted the synthesis of such thiepins where sulfur extrusion is minimized and controlled. Increased stability of the thiepin skeleton was found when methano-bridging was present. Thiepin IV has been synthesized and determined to be resistant of sulfur extrusion. The effects of benzannelation are further examined in regards to reduction in paramagnetic/diamagnetic ring currents.;The effects of benzannelation have been extensively investigated in various systems and were shown to result in bond fixation and reduction in ring currents. Benzannelation of methano-bridged annulenes, however, has been studied only rarely due to the unavailability of simple precursors. The new, one-pot synthesis of 3,4-benzcycloheptatriene-1,6-dicarboxaldehyde opens the door to such investigations. Successful synthesis of benzannelated, non-aromatic and 4n antiaromatic annulenes has been achieved providing insight as to the stability, chemistry and ring currents as compared with known parent non-annelated systems. In the 4n systems, reduction in paratropicity is evident with annelation sites determining the degree of reduction. With 4n+2 systems, however, such reductions were not obvious.;This dissertation as a whole describes and discusses the synthesis and study of benzannelation of methano-bridged annulenes. Complete experimental discussions and results are presented, supported by relevant spectroscopical data.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
