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Rieke magnesium-mediated transformation of conjugated dienes into novel functionalized molecules
Abstract
The preparation of Rieke magnesium by the direct reduction of a magnesium salt is described. Rieke magnesium reacts with a wide variety of substituted 1,3-dienes to give the corresponding (2-butene-1,4-diyl)magnesium complexes in excellent chemical yield. The reaction of a substituted (2-butene-1,4-diyl)magnesium complex with either an epoxide or a ketone followed by addition of carbon dioxide affords good yields of a spiro $\delta$- or $\gamma$-lactone, respectively, after lactonization. Alternatively, protonation of the initial adduct produces in high isolated yields an alcohol containing a quaternary carbon center. Fused bicyclic systems containing both primary and tertiary hydroxyl groups can be conveniently prepared by the reactions of cyclic, acyclic, and unsymmetric dienes with carboxylic esters or lactones mediated by Rieke magnesium. The reaction proceeds via a magnesium salt intermediate containing a cyclopropane ring. Quenching the intermediate at low temperature followed by warming to room temperature provides a novel pathway to the regioselective synthesis of $\beta,\gamma$-unsaturated ketones. A one-pot synthesis of secondary amines is based upon the reaction of a substituted (2-butene-1,4-diyl)magnesium complex with an imine. The initial adduct was also found to undergo further nucleophilic addition to carbon dioxide, generating, after lactamization, a $\gamma$-lactam containing both a vinyl group and a $\beta$-quaternary carbon center. The mono-functionalizations of dihaloarenes via Rieke metals has also been accomplished. This one-pot preparation of mono-organomagnesium, mono-organozinc, and mono-organocalcium intermediates could be applicable to the synthesis of conducting polymers as well as various unsymmetrical substituted aromatics. Finally, the formation of novel organometallic reagents using Rieke barium and Rieke strontium has been demonstrated. These reagents may prove to be useful in the formation of novel functionalized molecules.
Subject Area
Organic chemistry
Recommended Citation
Sell, Matthew Scott, "Rieke magnesium-mediated transformation of conjugated dienes into novel functionalized molecules" (1995). ETD collection for University of Nebraska-Lincoln. AAI9600755.
https://digitalcommons.unl.edu/dissertations/AAI9600755