- An Easy Preparation of α-Allenic Ethers and Tertiary α-Allenic Amines
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α-Allenic ethers 2 are prepared by the reaction of 1,4-dialkoxy-2-butynes 1 with lithium aluminium hydride and magnesium bromide.Tertiary α-allenic amines 4 are obtained by treating 4-dialkylamino-1-methoxy-2-butynes 3 with lithium aluminium hydride and aluminium chloride.
- Barbot, Francis,Dauphin, Benoit,Miginiac, Philippe
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- Cycloaddition Reactions of Cobalt-Complexed Macrocyclic Alkynes: The Transannular Pauson-Khand Reaction
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The Pauson-Khand reaction is a powerful tool for the synthesis of cyclopentenones through the efficient [2 + 2 + 1] cycloaddition of dicobalt alkyne complexes with alkenes. While intermolecular and intramolecular variants are widely known, transannular versions of this reaction are unknown and the basis of this study. Macrocyclic enyne and dienyne complexes were readily synthesized by palladium(II)-catalyzed oxidative macrocyclizations of bis(vinyl boronate esters) or ring-closing metathesis reactions followed by complexation with dicobalt octacarbonyl. Several reaction modalities of these macrocyclic complexes were uncovered. In addition to the first successful transannular Pauson-Khand reactions, other intermolecular and transannular cycloaddition reactions included intermolecular Pauson-Khand reactions, transannular [4 + 2] cycloaddition reactions, intermolecular [2 + 2 + 2] cycloaddition reactions, and intermolecular [2 + 2 + 1 + 1] cycloaddition reactions. The structural and reaction requirements for each process are presented.
- Karabiyikoglu, Sedef,Boon, Byron A.,Merlic, Craig A.
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p. 7732 - 7744
(2017/08/14)
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- Transannular [4 + 2] Cycloaddition Reactions of Cobalt-Complexed Macrocyclic Dienynes
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The first transannular [4 + 2] cycloaddition reactions of macrocyclic dicobalt hexacarbonyl-dienyne complexes were demonstrated. Complexes were conveniently prepared through palladium(II)-catalyzed intramolecular oxidative cyclization of bis(vinylboronate esters) followed by complexation with dicobalt octacarbonyl. Transannular [4 + 2] cycloaddition reactions of the complexes occurred at lower temperatures and shorter times than transannular Diels-Alder reactions of metal-free dienynes. Intermolecular control reactions confirmed the effect of cobalt complexation on [4 + 2] cycloaddition reactions of unactivated alkynes and dienes.
- Karabiyikoglu, Sedef,Merlic, Craig A.
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supporting information
p. 4086 - 4089
(2015/09/01)
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