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Issue 5, 1991
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Tricarbonylpyridinechromium complexes: stereoselective alkylations and aldol-type reactions involving α-carbanions derived from η-tricarbonyl(2-alkylpyridine)chromium complexes

Abstract

Reaction of tricarbonyl(η-2-alkylpyridine)chromium(0) complexes with lithium diisopropylamide at –40 °C generates the resonance stabilised carbanions at the α-position which undergo completely stereoselective electrophilic quench with alkyl halides to generate the corresponding α-branched tricarbonyl(η-2-alkylpyridine)chromium (0) complexes. These complexes can then be subjected to nucleophilic additions with methyllithium followed by methyl iodide quench to afford the tricarbonyl(η-exo-6-alkyl-1,2-dimethyl-1,2-dihydropyridine)chromium (0) complexes. Treatment of the resonance stabilised α-carbanion derived from tricarbonyl(η-2-ethylpyridine)chromium (0) with the non-enolisable aldehydes benzaldehyde or pivalaldehyde affords the erythro-aldol-type products with complete control of stereochemistry at both the newly formed α-and carbinol centres. X-Ray crystal structures of SR(RS)-tricarbonyl[η-exo-1,2-dimethyl-6-(2-pent-4-enyl)-1,2-dihydropyridine)-chromium (0) and RSS(SRR)-tricarbonyl[erythro-2-η-(2-pyridyl)-1-phenylpropanol]chromium (0) are reported.

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Article type: Paper
DOI: 10.1039/P19910001009
Citation: J. Chem. Soc., Perkin Trans. 1, 1991,0, 1009-1017
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    Tricarbonylpyridinechromium complexes: stereoselective alkylations and aldol-type reactions involving α-carbanions derived from η-tricarbonyl(2-alkylpyridine)chromium complexes

    S. G. Davies, A. J. Edwards and M. R. Shipton, J. Chem. Soc., Perkin Trans. 1, 1991, 0, 1009
    DOI: 10.1039/P19910001009

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