An approach toward the synthesis and investigation of di- and tri-benzo-13-methylphenalene.
Item
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Title
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An approach toward the synthesis and investigation of di- and tri-benzo-13-methylphenalene.
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Identifier
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AAI9530896
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identifier
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9530896
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Creator
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Levison, Derek Warren Keith.
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Contributor
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Adviser: Klaus Grohmann
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Date
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1995
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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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Theoretical and synthetic investigations have been undertaken on 13-Methylphenalene, a long-sought bridged (12) -annulene, and its mono-, di-, and tri-benzannelated derivatives (1-7) *. Using AM1 calculation methodology, the bond-dissociation energies of the central sp{dollar}\sp3{dollar} carbon/methyl bond have been found to range from a high of 33.37 kcal/mole for (7), to a low of 1.03 kcal/mole for (3). A trend of increasing stability of these anti-aromatic systems with respect to increasing benzannelation has been observed. Exceptions noted are only for those derivatives which are benzannelated in an anthracene-like fashion (3, 5 and 6), whereby no resonance structure can exist in which all external benzenoid rings simultaneously contain a closed sextet of {dollar}\pi{dollar}-electrons. Transition state calculations suggest an inherent minimum barrier to dissociation of 24.36 kcal/mole for (3), and increase as high as 40.30 kcal/mole. Comparative studies of a corresponding (10) -annulene series, 7b-methyl-7bH-cyclopent- (c,d) -indene (13) and its mono-, di- and tri-benzannelated derivatives, suggest an opposite trend, with decreasing stability of the central sp{dollar}\sp3{dollar} carbon/methyl bond upon increasing benzannelation.;Synthetic investigation of three benzannelated derivatives of 13-methylphenalene, (3), (4) and (7), have been pursued. The first approach is toward (7), the most stable derivative of the 13-methylphenalene series. This involves a simultaneous functionalization of the benzylic positions of tribenzylcarbinol, the key step being a three-fold ring-closing intramolecular Friedel-Crafts acylation. The second approach, towards (4), the second most stable derivative of this series, is based on an intramolecular Diels-Alder approach to the formation of its carbon skeleton. A novel and exciting third approach towards the synthesis of (3), the least stable and therefore the most interesting of the entire series, has been conceived, using Hart's elegant synthesis of meta-terphenyls. Several attempts at modification and cyclization of meta-terphenyls to form the as yet unknown dibenz-metacyclophane-1,3,4,6-tetraene have been undertaken. In a key step, the low-temperature (0{dollar}\sp\circ{dollar}C) Ramberg-Backlund rearrangement of 8H,10H-tribenzo- (c, ef,h) - (1) -thiecine-9,9-dioxide to dibenz-6-metacyclophane-3-ene has resulted in the formation of benz (e) acephenathrylene only, with no observable trace of the alkene. Presumably the alkene undergoes immediate Cope-rearrangement, followed by oxidization and aromatization. This promising result suggests that the last cyclophane-allene will also be able to undergo Cope-rearrangement to form (7). Alternate routes toward dibenz-metacyclophane-1,3,4,6-tetraene, avoiding the formation of the alkene, are proposed. ftn*Please refer to dissertation for diagram.
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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.
