| Research Abstract |
Rotamers of 2-(substituted 9-triptycyl)-2-methylpropylamines were diazotized with isopentyl nitrite and acetic acid in boiling benzene and the products were identified and analyzed by ^1H NMR spectra. For identification expected products were independently sythesized.
Triptycenes that carry a C4 olefinic substituent at the 9-position were sythesized by benzyne addition to 9-C4-olefinic anthracene which were prepared by dehydration of 2-(9-anthryl)-2-butanol followed by separtion by chromatography and recrystallization. 1,1-Dimethyl-1,2,6,10b-tetrahydro-6,10b-o-benzenoaceanthrylenes were prepared by benzyne addition to 1,1-dimethyl-1,2-dihydroaceanthrylene which was prepared by dimethylation of 1,2-dihydroaceanthrylen-2-one followed by forced Wolff-Kishner reduction. 9-(2-Hydroxy-1,1-dimethylethyl)triptycenes were prepared by benzyne addition to either 9-(2-acetoxy-1,1-dimethylethyl)anthrancene or 9-(2-trimethylsiloxy-1,1-dimethylethyl)anthrancene which was made from 9-(2-hydroxy-1,1-dim
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ethylethyl)-anthracene that was the product of borane reduction of 2-(9-anthryl)-2-methylpropanoic acid. These products were purified as alcohols which were acetylated to give the corresponding aetoxy compounnd.
Diazotization of the ap forms of substituted 2-methyl-2-(9-triptycyl)propylamine exhibited a similar tendency. The main product was 9-[(E)-1-methyl-1-propenyl]-triptycene together with other C4-olefin isomers. 1,1-Dimethyl-1,2,6,10b-tetrahydro-6,10b-o-benzennoaceanthrylene and ap-9-(2-acetoxy-1,1-dimethylethyl)triptycenes were formed as minor products. By contrast, the sc isomers showed remarkable differences according to the substituent at the 1-position, except for the fluorine case in which the product distribution was similar with that of the ap case. However, even for the fluorine case, sc-9-(2-acetoxy-1,1-dimethylethyl)-1,2,3,4-tetrafluorotriptycene increased significantly in its yield with respect to the ap case, indicating that a fluoro group can participate in stabilizing a carbocation. A chloro substituent, as expected, stabilizes the carbocation more efficiently than a fluoro group and consequently sc-9-(2-acetoxy-1,1-dimethylethyl)-1,2,3,4-tetrachlorotriptycene was the main product of diazotization of the corresponding amine. Unfortunately, we encoutered various difficulties in the study of the corresponding tetrabromo compound, and a onclusion has not been drawn so far. Diazotization of sc-2-(1,2-dimethoxy-9-triptycyl)-2-methylpropylamine afforded a cyclized compound, which was the product derived by the attack of the intervening cation to the oxygen atom of the substituent, and the 9-(2-acetoxy-1,1-dimethyl)-compound to indicate that the methoxy participation is even more effective than the chlorine case. When the 1-substituent was a methyl, insertion of the cation to the C-H bond of the methyl group took place with a significant increase in the yield of the acetoxy compound to indicate that the methyl group can participate in stabilizing the cation. Ionization of 9-(2-chloro-1,1-dimethylethyl)-1,4-dimethyltriptycene with silver tetrafluoroborate gave a similar result with the diazotization in the case of sc, whereas the ap form reacted very slowly. Less
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