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UBC Theses and Dissertations

Preparation and some chemistry of ethyl 2,3-bis(alkylidene)cyclobutanecarboxylates Lu, Yee-Fung


This thesis describes the preparation and some chemistry of the cyclobutanecarboxylates 9. Syntheses of larger ring homologs of 9 (compounds and 11) are also presented. Deconjugation-alkylation of ethyl (Z)- and (E)-3-trimethylstannyl-2-alkenoates 1 and 2 with alkylating agents of general structure 7 affords the (Z)-3-trimethylstannyl-3-alkenoates (see 8), respectively. The diene esters 8a efficient intramolecular palladium(0)-catalyzed cross coupling reactions of the halide and vinylstannane groups to provide the cyclobutanecarboxylates the diene esters 8b and 8c were converted into the coupled products respectively. A number of Diels-Alder reactions of the cyclobutanecarboxylates structurally related substances are described. These studies provided regarding the relative reactivities of various substrates of general structure face-, regio- and stereoselectivities of the Diels-Alder processes. The reactions led to the preparation of the bicyclic cyclobutenes 314 and Alder reactions were also performed on the diene 318 to provide cyclobutenes 319 and 321. The bicyclic cyclobutenes 322, 324 and 327 readily prepared from the keto esters 314 and 315. The stereochemistry of the thermally induced, conrotatory ring reaction of each of the bicyclic cyclobutenes 314, 315, 319, 321, 322, 327 was investigated. Thermolysis of 319, 321 and 322 gave, in each product resulting from exclusive outward rotation of the CH₂OR group. heating the substituted 3-formylcyclobutenes 324 and 327 resulted in exclusive inward rotation of the formyl group. Thermally induced resulted in the predominant outward rotation of the CO₂Et group. hand, the keto ester 315 showed no preference for the direction CO₂Et group during the thermal ring [See Thesis for Diagrams].

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