200574-93-2Relevant academic research and scientific papers
The stereochemistry of allenic enol tautomerism - Independent generation and reactivity of the enolates
Zimmerman, Howard E.,Pushechnikov, Alexei
, p. 3491 - 3497 (2006)
A priori, allenic enolates as reaction intermediates may be protonated to afford (Z)- or (E)-α,β-unsaturated carbonyl products. The allenic enolates are tautomeric with α-vinyl-carbanions. The literature on the behavior of these species on protonation is highly varied both in stereochemical outcome and in mechanistic interpretation. The current study has provided an independent mode of generation of the allenic enolates and has investigated the reaction stereochemistry of protonation to afford the stereoisomeric α,β-unsaturated carbonyl products. Under kinetic conditions, these highly reactive species are protonated in the α,β-π plane with preference (E) to the larger β group. Under thermodynamic conditions, addition/elimination equilibrates the two product stereoisomers. The kinetic protonation stereochemistry is a function of solvent, proton donor, and donor concentration. Computations serve to clarify the reaction mechanism. It was found that the stereochemistry of ketonization of allenic enolates follows the reaction course suggested as possible some decades earlier and common to less unique enolates. Additionally, the linear versus the bent enolate structure proves to depend on the countercation. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
Siloxyallenes revisited. A useful functional intermediate for the synthesis of (Z)-β-branched Morita-Baylis-Hillman type adducts and (Z)-chalcones
Yoshizawa, Kazuhiro,Shioiri, Takayuki
, p. 6259 - 6286 (2008/02/04)
Siloxyallenes proved to be a useful functional intermediate in the preparation of (Z)-β-branched Morita-Baylis-Hillman type adducts by the reaction of aldehydes with silylacetylenes or siloxypropynes. Various (Z)-chalcones were stereoselectively synthesized from siloxypropynes via siloxyallenes.
