73400-23-4Relevant academic research and scientific papers
Chemistry of Dienyl Anions. IV. Geometry of Pentadienyl Anions in Solution and in the Solid State Determined by Regioselective Trimethylsilylation and NMR
Yasuda, Hajime,Yamauchi, Michihide,Ohnuma, Yasuo,Nakamura, Akira
, p. 1481 - 1491 (1981)
The configurational analysis of a series of alkyl substituted pentadienyl anions in THF was examined by trimethylsilylation and from the variable temperature 1H- and 13C-NMR spectra.Potassium pentadienide, -2-methylpentadienide or -2,4-dimethylpentadienide produced preferentially (Z)-2,4-pentadienyltrimethylsilane or its methyl substituted analogues to indicate that these compounds have the "U"-shaped structure in solution.By contrast, trimethylsilylation of potassium pentadienide and -2-methylpentadienide in the crystalline state produced the (E)- and the (E),(Z)-isomers, respectively, suggesting that the geometry is drastically changed to the "W"- or "S"-shaped by the medium effect.The W-shaped structure of potassium 3-methylpentadienide in THF and in the solid state is exceptional.Geometry of trapped products of potassium cycloheptadienide and -cyclooctadienide is also (Z) but the silylation occurred on the central carbon in contrast to the terminal silylation seen for the open-chain pentadienides.Geometry of these dienyl anions determined by NMR below -30 deg C was consistent with the result obtained from trimethylsilylation.Superficial conflict between MINDO/3 prediction and the experimental evidence was reasonably reconciled by considering contact ion pair for potassium pentadienide in THF and more strongly-solvated ion pair for the lithium analogues.
Pentadienyl type lithium and potassium species: The regioselectivity of their reactions with electrophiles
Schlosser,Zellner,Leroux
, p. 1830 - 1836 (2007/10/03)
Seven structurally distinct pentadienyl type lithium and potassium compounds were screened against a variety of electrophiles in order to assess the regioselectivity of the trapping reactions. Organoborates and analogs thereof (fluorodimethoxyborane) proved to be perfectly regioreliable attacking only unsubstituted terminal positions and thus providing, after oxidation, exclusively primary allylic alcohols. 2,4-Pentadienyllithiums or -potassiums, that carry a methyl group at the 1- or 3-position, exhibit the same extreme regioselectivity towards halotrialkylsilanes or carbon dioxide. Although the unsubstituted parent compounds combine with such electrophiles still preferentially at the terminal position, considerable proportions of branched products are concomitantly formed as well (1/3-attack ratios ranging from 2:1 to >20:1). Hydroxyalkylating and alkylating reagents such as formaldehyde, oxirane or butyl iodide invariably afford regioisomeric mixtures generally varying in composition between 3:1 and 1:3. The condensation reaction with halotrialkylsilanes appears to follow a concerted (SN2-like) rather than an addition/elimination (ate complex-mediated) mechanism.
SYNTHESE NEUER ORGANOELEMENTSUBSTITUIERTER PENTADIENE (1)
Kauffmann, Thomas,Gaydoul, Klaus-Ruediger
, p. 4067 - 4070 (2007/10/02)
By applying four different methods twelve new organoelement substituted pentadienes have been prepared.They contain one or two organoelement groups. - Pentadienyllithium (2) reacted with Cl-SPh, Br-SePh, Cl-PPh2, and Cl-AsPh2 (lone pair at the element) ex
Synthesis and Electrophilic Substitution of Some Hexa- and Penta-2,4-dienyl-silanes, -germanes and -stannanes
Jones, Martin,Kitching, William
, p. 1863 - 1879 (2007/10/02)
Penta-2,4-dienyl and hexa-2,4-dienyl derivatives of silicon, germanium and tin have been synthesized (normally as E/Z mixtures) by metalation of the corresponding pentadienyllithium reagents.The E/Z isomeric mixtures have been fully characterized by 1H and 13C nuclear magnetic resonance spectroscopy.Trifluoroacetolysis of these compounds (CF3COOD) has been studied by direct 2H n.m.r. spectroscopy, and ε-electrophilic attack is predominant.In contrast, sulfur dioxide insertion (with the stannanes) is γ-regiospecific, but these kinetic γ-sulfinates rearrange, by a presumed electrocyclic process, to the conjugated dienylmethylsulfinates.
Synthetic Implications of the Reactions of Alkali-Metal Pentadienyls with Organic Electrophiles and Comments on the Nature of "Organopotassiums" Derived Using Lochmann's Base.
Paget, Walter E.,Smith, Keith,Hutchings, Michael G.,Martin, Gary E.
, p. 327 - 341 (2007/10/02)
Pentadienyl anions derived by metallation of penta-1,4-diene with n-butyl-lithium, or of penta-1,3-diene with n-butyl-lithium - potassium tert-butoxide, react with electrophiles to produce mixtures of E- and Z-5-substituted penta-1,3-dienes and 3-substituted penta-1,4-dienes.The proportions depend, amongst other things, upon the nature of the electrophile.For simple aldehydes and ketones, for example, the proportions can vary, under otherwise identical conditions, from entirely 5-substituted product (as an E/Z mixture) with benzophenone, to predominantly (64percent) 3-substituted product with acetone.Reaction with bromocyclopentane produces almost entirely the 3-substituted product.The synthetic implications of these results are discussed.The reactions of the anions generated by the two different methods are very similar, which has prompted a discussion of the nature of the reagents, often described as organopotassiums, which are derived using Lochmann's base.
