Regioselective Transition‐Metal‐Free Allyl–Allyl Cross‐Couplings |
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Authors: | Mario Ellwart Dr. Ilya S. Makarov Dr. Florian Achrainer Prof. Dr. Hendrik Zipse Prof. Dr. Paul Knochel |
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Affiliation: | Ludwig-Maximilians-Universit?t München, Department Chemie, München, Germany |
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Abstract: | Readily prepared allylic zinc halides undergo SN2‐type substitutions with allylic bromides in a 1:1 mixture of THF and DMPU providing 1,5‐dienes regioselectively. The allylic zinc species reacts at the most branched end (γ‐position) of the allylic system furnishing exclusively γ,α′‐allyl–allyl cross‐coupling products. Remarkably, the double bond stereochemistry of the allylic halide is maintained during the cross‐coupling process. Also several functional groups (ester, nitrile) are tolerated. This cross‐coupling of allylic zinc reagents can be extended to propargylic and benzylic halides. DFT calculations show the importance of lithium chloride in this substitution. |
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Keywords: | 1,5-dienes allylic compounds cross-coupling SN2 reaction zinc |
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