102776-11-4Relevant academic research and scientific papers
The influence of α-coordinating groups of aldehydes on E/Z-selectivity and the use of quaternary ammonium counter ions for enhanced E-selectivity in the Julia–Kocienski reaction
Rehman, Mintu,Surendran, Sravya,Siddavatam, Nagendra,Rajendar, Goreti
supporting information, p. 329 - 333 (2022/01/20)
Modified reaction conditions for improved E-selectivity of olefins in the Julia–Kocienski reaction of aldehydes having α-coordinating substituents are demonstrated. The chelating groups in aldehydes are expected to stabilize the syn-transition state with metal ions, whereas the weakly coordinating quaternary ammonium ions are devoid of all possible chelating interactions to enhance E-selectivity. A systematic investigation is presented to study the size of the neighbouring protecting groups of aldehydes and their chelation effect on E/Z-selectivity in the Julia–Kocienski reaction.
Facially controlled C-methylation of oxolanyl and cyclopentyl acetate enolates: Application to the total synthesis of (+)-nephromopsinic acid
Mulzer, Johann,Steffen, Ulrich,Martin, Harry J.,Zorn, Ludwig
, p. 1028 - 1043 (2007/10/03)
The stereoselectivity of the C-methylation of oxolanyl and cyclopentyl acetate enolates 5a-22a was investigated. The configuration of the C-methyl diastereomers was elucidated by a combination of crystal structure analysis, NMR spectroscopy and chemical correlations. Generally, the methylation proceeded re*-selectively, although with very different degrees of selectivity. The most important stereodirecting effect was a steric one exerted by the 5-phenethyl substituent, and this steric effect was strongly increased by the stereodirecting effect of a 3-OR group. Contrary to previous literature evidence, the endocyclic oxolanyl oxygen does not exert an effect. These findings were applied in a highly stereoselective synthesis of (+)-nephromopsinic acid (94). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
