UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

An investigation of the effect of organic soil constituents on boron adsorption Gu, Baohua

Abstract

The preparation and synthetic utility of a number of structurally interesting donor-acceptor reagents is described. It has been found that protonative deconjugations of geometrically isomeric β-trimethyl-stannyl-α,β-unsaturated esters are highly stereospecific. Thus, treatment of the esters (131) and (137) with lithium diisopropylamide in THF or THF-HMPA followed, in each case, by transfer of the resultant solution to a cold (-98°C) solution of acetic acid in ether, provided exclusively the alkyl 3-trimethylstannyl-3-alkenoates (167) and (173), respectively. Ethyl (Z) and (E)-3-trimethylstannyl-3-pentenoates were converted into the chlorides (99) and (100), respectively. Transmetalation of (99) afforded (204), which was transformed into the Grignard reagent (218) . Both (204) and (218) serve effectively as conjunctive reagents which are synthetically equivalent to the (E)-d³,a⁵-2-pentene synthon (200). For example, copper(I)-catalyzed conjugate addition of (218) to enones and subsequent intramolecular alkylation of the resultant products form the basis of a new (Z)-ethylidenecyclopentane annulation process [(220) → (222)]. Interestingly, although transmetalation of (100) also occurred smoothly, the resultant lithio reagent (207) self-annihilated rapidly even at low temperatures to give ethylidene-cyclopropane. The annulation method described above played a key role in short syntheses of (±)-oplopanone (257), (±)-8-epi-oplopanone (323), and (±)-anhydro-oplopanone (258). Thus (Z)-ethylidenecyclopentane annulation of 4-isopropyl-2-cyclohexen-l-one provided the bicyclic ketone (307). Suitable functional group manipulations transformed (307) into (±)-(257), (±)-(323), and (±)-(258). Reaction of 1-alkyn-3-ols with Me₃SnCu.Me₂S-MeOH, [Me₃SnZn(t-Bu)₂]Li-CuCN, or [Me3SnZnEt2]Li-CuCN provided, in varying ratios, the vinylstannanes (109) and (339). Orthoester Claisen rearrangement of (109) and (339) afforded the esters (357) and (363), respectively. Ethyl (Z)-4-trimethylstannyl-4-hexenoate was transformed into the chloride (370). Compound (370) is a convenient precursor of reagents (371) and (374) which are synthetically equivalent to the (E)-d³,a⁶-2-hexene synthon (379). For instance, the Grignard reagent (374) served as a pivotal species in the development of a new six-membered annulation method [(101) → (380)]. [See Thesis for Diagrams]

Item Media

Item Citations and Data

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.