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Thienyl-based organocopper and conjugated diene magnesium reagents mediated by Rieke copper and Rieke magnesium
Abstract
The preparation of Rieke copper by the direct reduction of lithium (2-thienylcyano)cuprate with preformed lithium naphthalenide is described. This active copper species oxidatively adds to carbon-halogen bonds to form organocopper reagents. The ability to directly form the organocopper reagent from organic halides and active copper allows for the incorporation of a wide variety of functionalities to be present in the organic halides and the organocopper reagents. Significantly, this formulation of active copper was able to oxidatively add to allyl chlorides and acetates at low temperatures to allow the direct formation of allylic organocopper reagents without Wurtz-type homocoupling. These functionalized organocopper compounds are able to undergo a variety of reactions such as: cross-coupling with acid chlorides, 1,4-conjugate addition with $\alpha,\beta$-unsaturated carbonyl compounds, and intermolecular and intramolecular epoxide-opening reactions. Importantly, this copper species avoids the use of phosphine ligands affording the ensuing product isolation much more convenient than with phosphine-based organocopper reagents. Higher order and "non-ate" allyl copper reagents have been prepared utilizing a formal copper anion solution generated via the low temperature reduction of Cu(I) complexes by two equivalents of lithium naphthalenide. These reagents undergo substitution, epoxide opening, and 1,4-conjugate addition reactions. The preparation of Rieke magnesium by the direct reduction of a magnesium salt with preformed lithium naphthalenide is described. Rieke magnesium reacts with a wide variety of substituted 1,3-dienes to give the corresponding (2-buten-1,4-diyl)magnesium reagents. A straightforward, one-pot synthesis of $\gamma$-lactams and secondary amines mediated by Rieke magnesium is described. This technique involves the treatment of a conjugated diene-magnesium reagent with an imine at $-$78$\sp\circ$C, affording an intermediary organomagnesium complex derived from the incorporation of the imine with the diene-magnesium complex. Upon warming, the intermediate undergoes further nucleophilic addition to carbon dioxide. Following acidic hydrolysis and subsequent warming, a $\gamma$-lactam is afforded in good chemical yield by the lactamization of the resulting $\gamma$-amino acid.
Subject Area
Organic chemistry|Chemistry
Recommended Citation
Klein, Walter Robert, "Thienyl-based organocopper and conjugated diene magnesium reagents mediated by Rieke copper and Rieke magnesium" (1994). ETD collection for University of Nebraska-Lincoln. AAI9425289.
https://digitalcommons.unl.edu/dissertations/AAI9425289