- ACYLATION OF α-BROMINATED KETONES IN THE PRESENCE OF ZINC
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The acylation of α-bromo ketones in the presence of zinc takes place preferentially at the O-reaction center of the intermediate organozinc compound.
- Fotin, V. V.,Shchepin, V. V.,Sinani, S. V.
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p. 1744 - 1746
(2007/10/02)
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- TRAPPING REACTION OF ENOLATES FROM LITHIUM DIMETHYLCUPRATE CONJUGATED ADDITION: IMPORTANCE OF STERIC FACTORS AND, PARTICULARLY, OF β-SUBSTITUTION OF ENONE IN THE C- vs. O-ACYLATION
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Conjugated addition of lithium dimethylcuprate to α,β-unsaturated ketones gives intermediate enolates which, treated with acetyl chloride, undergo O- and/or C-acylation depending on the substitution at the enone β-carbon.Results agree with the hypothesis that C-acylation proceeds through an intramolecular metal-assisted mechanism.
- Bernasconi, Silvana,Jommi, Giancarlo,Montanari, Stefania,Sisti, Massimo
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p. 125 - 128
(2007/10/02)
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- Regio- and Stereo-selectivity of Acetoxymercuration of Acetylenes
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Acetoxymercuration of alkylphenylacetylenes (PhCCR; R = Me, Et, Prn, or Bun) (1) in acetic acid at 20 - 60 deg C proceeds completely in a trans-fashion to afford a regioisomeric mixture of two vinylmercury(II) compounds, Ph(OAc)C=C(HgCl)R (2) and Ph(HgCl)C=C(OAc)R (3), the extent of attack of Hg at the carbon α to alkyl group to form (2) being increased upon increasing the carbonyl chain length of the alkyl group .A bridged mercurinium ion intermediate in which phenyl and alkyl groups are bent toward the attacking side of acetate anion is proposed for explaining a marked dependence of the isomer ratio (2):(3) on the kind of alkyl groups.Similar treatment of diphenylacetylene at 20 - 95 deg C gives only the cis-adduct as reported previously, while that of diethyl-acetylene affords the trans-adduct and a mixture of trans- and cis-adduct at 20 deg C and at 65 deg C, respectively.The NaBH4 reduction of (2, R = Me) in neutral condition produces a mixture of (Z)- and (E)-1-acetoxy-1-phenylpropene (ca. 3-5:1) in contrast to the reduction of thallium analogue of (2) which gives only the Z-isomer.
- Uemura, Sakae,Miyoshi, Haruo,Okano, Masaya
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p. 1098 - 1103
(2007/10/02)
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