This thesis describes the preparation of 4-chloro-2-trimethyl-stannyl-1-butene (8̲4̲) and its conversion into a number of structurally interesting and synthetically useful donor-acceptor reagents. Thus, transmetalation of (8̲4̲) with methyllithium produced 4-chloro-2-lithio-1-butene (9̲5̲), which reacted smoothly at -78°C in tetrahydrofuran with aldehydes, ketones and α,β-unsaturated N,N',N'-trimethylcarboxhydrazides to provide the addition products (1̲0̲8̲)-(̲1̲1̲3̲) and (̲1̲2̲8̲)-(̲1̲3̲0̲). When the reaction mixtures were treated with hexamethylphosphoramide and were then allowed to warm to room temperature, the 3-methylenetetrahydro-furan derivatives (̲1̲1̲4̲)-(̲1̲1̲9̲) and the 3-methylenecyclopentanecarboxylic acid derivatives (̲1̲3̲1̲)-(̲1̲3̲3̲) were produced in good yields.
Treatment of reagent (̲9̲5̲) with 1 equiv of phenylthiocopper or cuprous cyanide provided solutions of the corresponding cuprate reagents (̲1̲7̲9̲) and (̲1̲8̲0̲). Conjugate addition of the latter species to the cyclic enones (̲1̲8̲1̲)-(̲1̲8̲6̲) afforded very good yields of the ketones (̲1̲8̲7̲)-(̲1̲9̲2̲), which, when treated with potassium hydride in tetrahydrofuran, provided the methylenecyclopentane annulation products (̲1̲̲9̲3̲)-(̲1̲9̲8̲), respectively.
This methylenecyclopentane annulation method served as a key
process in the total synthesis of two structurally interesting triquinane
sesquiterpenoids, (±)-Δ⁹⁽¹²⁾ -capnellene (̲2̲0̲5̲) and (±)-pentalenene (̲2̲5̲1̲). Thus, copper bromide - dimethylsulfide catalyzed addition of the Grignard reagent (̲2̲3̲3̲) to 2-methyl-2-cyclopenten-1-one (̲1̲8̲4̲), followed by intramolecular
alkylation of the resultant chloro ketone (̲1̲9̲0̲), gave the annulation product (̲1̲9̲6̲). This material was converted into the enone (̲2̲3̲1̲) , which was subjected to an annulation sequence identical with
that used in the conversion of (̲1̲8̲4̲) into (̲1̲9̲6̲). Removal of the
carbonyl group from the resultant product (̲2̲3̲2̲) provided (±)-Δ⁹⁽¹²⁾ capnellene (̲2̲0̲5̲).
Transformation of the readily available keto acetal (̲2̲8̲̲7̲) into the enone (̲2̲8̲4̲), followed by subjection of the latter substance to the methylenecyclopentane annulation sequence, gave the tetracyclic keto olefin (̲2̲8̲5̲). Treatment of an acetic acid solution of this material with hydrogen in the presence of platinum metal produced a mixture of the epimeric ketones (2̲9̲8̲) and (2̲9̲9̲), which was converted into a mixture of (±)-pentalenene (2̲5̲1̲) and (±)-9-e̲p̲i̲-pentalenene (2̲6̲9̲), respectively. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/25810 |
| Date | January 1985 |
| Creators | Karunaratne, Veranja |
| Publisher | University of British Columbia |
| 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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