Influnce des interactions de torsion dans la reduction des cetones par les hydrures interpretation generale du deroulement sterique de la reduction des cetones acycliques et de l'addition des organomagnesiens sur les aldehydes acycliques
作者:M. Cherest、N. Prudent
DOI:10.1016/s0040-4020(01)83128-8
日期:1980.1
Reduction of ketones L-CHMe-CO-R [L=Ph and Cy(Cy = cyclohexyl) and R=Me, Et, iPr and tBu] affords pairs of diastereoisomeric alcohols L-CHMe-CHOH-R. The predominant diastereoisomer is always that predicted by Cram's rule, and the stereoselectivity of the reaction generally increases as R is made more bulky. Thus, with LiAlH4 in ether at 35°, the diastereoisomer ratios are respectively 2.8:1, 3.2:1
Stereoselectivity in the condensation reactions of 1-phenylethyl alkyl and phenyl ketones with organometallic reagents
作者:Carlos Alvarez-Ibarra、Odón Arjona、Rafael Pérez-Ossorio、Alfredo Pérez-Rubalcaba、María L. Quiroga、María J. Santesmases
DOI:10.1039/p29830001645
日期:——
Stereochemical results of the condensation reactions of a series of ketones, PhCHMeCOR (R = Me, Et, Pri, But, Ph), with various organomagnesium and organolithium derivatives in ethers as solvents are reported. Results are accounted for on the basis of competition between two transition states which may adopt either Karabatsos- or Felkin-type conformations according to the nature of R, the reagent nucleophilicity
Hydrogenation reactions of alkenes were catalyzed by zirconium–alkene complex derivatives which were prepared from Cp2ZrCl2 (Cp = η5-C5H5) and n equiv. of RR′CHCH2M (M = MgX or Li). By the use of three or more equiv. of EtMgBr relative to Cp2ZrCl2, the product yield of hydrogenation of 1-decene was remarkably improved most likely due to the stabilization of the Zr(II) species.
Reactions of zirconocene-alkene complexes with aldehydes gave alcohols as coupling products after hydrolysis. The carbon-carbonbondformation proceeded at C1 carbon of alkenes, in sharp contrast to the reactions of alkene-alkene coupling on zirconium. A similar alcohol was also obtained by the reaction of zirconacyclopentane with aldehyde after hydrolysis. Treatment of (C5Me5)2ZrEt2 with styrene gave
Reactivity of the secondary benzylic Grignard reagent from 1-phenylethyl chloride with aldehydes and ketones. More evidence for the rearrangement mechanism in benzyl Grignard reactions
作者:Claude Bernardon
DOI:10.1016/0022-328x(89)87200-6
日期:1989.5
the reaction of the Grignard reagent from benzyl chloride with aldehydes has been obtained from a study of the interaction of the Grignard reagent from 1-phenylethyl chloride with carbonyl compounds. This Grignard reagent reacts with ketones (except non-enolisable ketones) to give normal alcohols in low yields, and with aldehydes to give diols. However, in contrast to that formed in the reaction of