Oxy anion-accelerated rearrangements

oxy-Cope rearrangement, Cope rearrangement, [3,3] rearrangment, [1,3] rearrangment, alkoxide fragmentation, synthetic method

Baillargeon, David Joseph ; Evans, David A.

University:California Institute of Technology

Department:Chemistry and Chemical Engineering

关键词: oxy-Cope rearrangement, Cope rearrangement, [3,3] rearrangment, [1,3] rearrangment, alkoxide fragmentation, synthetic method;   

Others  :  https://thesis.library.caltech.edu/8842/1/Baillargeon_dj_1979.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The alkali metal salts of 1,5-hexadien-3-ols undergoaccelerated Cope rearrangements to the enolates of δ, ε-unsaturatedcarbonyl compounds. The generality of therearrangement was investigated in numerous systems,particularly acyclic cases, and the effect of changes insubstituents, counterions, solvents, and geometricalstructures were noted and discussed. Applications ofthis methodology in synthesis included the synthesis ofthe insect pheromone frontalin, the preparation ofselectively monoprotected 1,6-dicarbonyl compounds from4-methoxy- and 4-phenylthio-1,5-hexadien-3-ols, and theconstruction of complex ring structures such as a D-homo-estratetraenonederivative.

Thermochemical estimates of the energetics of anionpromotedalkoxide fragmentations were made, and in allcases heterolytic cleavage was favored over hemolyticcleavage by 8.5-53 kcal/mol. The implication of theseand other thermochemical estimates is that the anionicoxy-Cope rearrangement occurs via a concerted mechanismrather than a dissociation-recombination process. Theconcepts of anion-induced bond weakening were successfullyapplied to an accelerated [1,3]-shift of a dithiane fragmentin a cyclohexenyl system. Trapping experimentsdemonstrated that > 85% of the [1,3]-shift occurred withina solvent cage. Attempts at promoting an intramolecularene reaction using the potassium salts of 2,7-octadien-1-o1and 2,8-nonadien-1-o1 were unsuccessful. A general reviewof anion-promoted bond reorganizations and anion substituenteffects is also presented.