103108-46-9Relevant academic research and scientific papers
SELECTION SIMPLE ET DIASTEREOFACIALE DE LA REACTION D' ALDOLISATION DE L' ACIDE PROPANEDITHIOIQUE
Beslin, Pierre,Houtteville, Marie-Claire
, p. 4445 - 4456 (1989)
Lithium enedithiolate, obtained by double deprotonation of propanedithioic acid with LDA, reacts at -50 deg C diastereoselectively with achiral aldehydes forming aldols with syn-anti ratios ranging from 1/5 to 9/1.The selectivity observed does not depend of time and temperature and, the aldolisation still occurs at 0 deg C with a better yield without alteration of the stereoselectivity.The selectivity variation induced by using other cation instead of lithium and the influence of a crown ether are fully explained by a classic chair like transition state.The same lithium enedithiolate reacts at -120 deg C stereoselectively with chiral aldehydes affording anti-syn aldols and syn-syn aldol in the particular case of 2-phenyl propanal.The yields are improved by increasing the reaction temperature up to 0 deg C with the same selectivity.The aldol configurations are stated by comparison of the HPLC retention time of aldol mixture with that of authentic syn or syn-syn major aldol mixture prepared by known diastereoselective aldol reactions of methyl propanedithioate.Confirmation of aldol configurations by 1H and 13C NMR spectra are given.
DIASTEREOFACIAL SELECTIVITY VIA ALDOL REACTIONS USING ETHYL DITHIOACETATE AND ETHYL DITHIOPROPIONATE ENOLATES
Meyers, A. I.,Walkup, Robert D.
, p. 5089 - 5106 (2007/10/02)
The lithium enolate of ethyl dithioacetate reacts with α-methyl aldehydes to yield the aldol products in which the syn configuration in the positions β and γ to the thiocarbonyl of the product is favored over the anti configuration.This selectivity is solvent-dependent, and is enhanced at lower temperatures.In most cases, syn:anti product ratios obtained under these conditions varied from 57:43 to >99:1, depending upon the structure of the α-methyl aldehyde.When the lithium enolate of ethyl dithiopropionate was allowed to react with α-methyl aldehydes, only two out of the four possible diastereomers were detected in the product mixtures.
