The work in this thesis was undertaken in order to determine the kinetic factors responsible for the regioselectivity in enol ether formation in 2—vinylcyclopropyl cyclohexyl ketone systems.
Conversion of commercially available 4-carbethoxy-3-methyl-2-cyclo-hexen-l-one (106) into 3,3-dimethylcyclohexanecarboxylic acid chloride (.105) was accomplished via a straightforward sequence of reactions. Treatment of (105) with lithium (phenylthio)(cis-2-vinylcyclopropyl)cuprate (33) afforded the ketone (101). Alternatively, reaction of (105) with a mixture of the cuprate reagent (33) and the isomeric reagent (34), followed by base-catalyzed equilibration of the resultant mixture of ketones, provided the ketone (103). Hydrogenation of c_is-2-vinylcyclopropyl cyclohexyl ketone (89) with diimide provided the ketone (104).
Treatment of the ketone (101) with lithium diisopropylamide in tetrahydrofuran at -78°C, followed by trapping of the resultant mixture of enolate anions with tert-butyldimethylsilyl chloride, gave a mixture of the enol silyl ethers (120) and (121) , in a ratio of 12 : 88. Thermolysis of the latter mixture (160°C, neat) afforded a mixture of the annulated materials (122) and (123) (ratio ~14 : 86), which, upon acid hydrolysis under mild conditions, gave the cycloheptenone (127) and compound (123). The latter two substances could be separated by column chromatography.
Subjection of the ketone (103) to a sequence of reactions similar to that described above (lithium diisopropylamide, tetrahydrofuran; tert-butyldimethylsilyl chloride; thermolysis, 240°C, neat; acid hydrolysis) gave the final products (127) and (123) in a ratio of 87 : 13, respectively.
Treatment of cis-2-ethylcyclopropyl cyclohexyl ketone (104) with lithium diisopropylamide in tetrahydrofuran, followed by trapping of the resultant mixture of enolate anions with tert-butyldimethylsilyl chloride afforded the two enol silyl ethers (125) and (126) in a ratio of 1:1.
The results summarized above are discussed in terms of the factors which might be affecting the regioselectivity of kinetic deprotonation of 2-vinylcyclopropyl cyclohexyl ketone systems. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/22400 |
| Date | January 1981 |
| Creators | Burmeister, Max Stewart |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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