Titanium tetrachloride catalyzed cyanation of benzylic chlorides with trimethylsilyl cyanide and mechanistic and synthetic studies on substituted tetraphenylethanes.
Item
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Title
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Titanium tetrachloride catalyzed cyanation of benzylic chlorides with trimethylsilyl cyanide and mechanistic and synthetic studies on substituted tetraphenylethanes.
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Identifier
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AAI9521322
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identifier
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9521322
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Creator
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Wo, Shiming.
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Contributor
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Adviser: Herman E. Zieger
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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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Six sterically hindered benzylic chlorides have been substituted with cyano groups in excellent yields with trimethylsilyl cyanide and titanium tetrachloride in methylene chloride. Both monochloro substrates such as diphenylmethyl chloride and triphenylmethyl chloride and dichloro substrates such as dichlorodiphenylmethane and symtetraphenylethylene dichloride were studied. Because isonitriles are plausible reaction intermediates, the isomerization of trityl isonitrile by titanium tetrachloride and by trityl tetrafluoroborate was studied at 0{dollar}\sp\circ{dollar}C and {dollar}-{dollar}78{dollar}\sp\circ{dollar}C. Both reagents catalyze conversion to triphenylacetonitrile at 0{dollar}\sp\circ{dollar}C while only trityl tetrafluoroborate is effective at {dollar}-{dollar}78{dollar}\sp\circ{dollar}C. It was also found that trityl tetrafluoroborate reacts with trimethylsilyl cyanide in the absence of titanium tetrachloride to give triphenylacetonitrile in 96% yield.;A first example of a long-lived substituted tetraphenylethyl cation: 2-cyano-1,1,2,2-tetraphenylethyl cation (18) has been synthesized from the reaction of 3-chloro-2,2,3,3-tetraphenylpropanenitrile (4) with silver salts as well as with SbCl{dollar}\sb5{dollar}. It has been shown that cation 18 is stable at {dollar}-75\sp\circ{dollar}C and starts to decompose at a temperature between {dollar}-55\sp\circ{dollar}C and {dollar}-35\sp\circ{dollar}C. It was also found that cation 18 generated with AlCl{dollar}\sb3{dollar} undergoes reaction intramolecularly to give 9-(cyanodiphenylmethyl)fluorene. The solvolysis of symtetraphenylethylene dichloride with CF{dollar}\sb3{dollar}CO{dollar}\sb2{dollar}Ag was studied. In the presence of phenol, the reaction gave a cyclic ortho ester 31. Similar results were obtained with allyl alcohol and 2-propanol. In the presence of methanol, however, the reaction afforded a sterically hindered ketal, benzopinacolone dimethyl ketal (39), which could not be synthesized directly from benzopinacolone. Finally, the reactions of cation 18 and ketal 39 with organosilane reagents and aromatic substrates were carried out and the results are discussed.
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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.
