21589-60-6Relevant academic research and scientific papers
Fluoride-induced proto- and carbo-desilylation of S,S-, O,O- and O,S-silylated acetals: an insight into the chemical and stereochemical reaction outcome
Capperucci, Antonella,Fochi, Mariafrancesca,Mazzanti, Andrea,Pollicino, Salvatore
, p. 606 - 616 (2014/01/06)
A general overview on the chemical and stereochemical behavior of a wide range of stereodefined 2-silyl-1,3-dithianes, -1,3-dioxanes, -1,3-dioxolanes and -1,3-oxathiolanes is reported, when subjected to fluoride ion-induced proto- and carbo-desilylation. Retention of configuration or epimerization appears to depend not only on the kind of the substituents on the aromatic ring, but also on the nature of heteroatoms in the silyl acetals, leading to envisage the occurence of a free carbanion or of an hypervalent-silylated species.
On the Mechanism of Lewis Acid Mediated Nucleophilic Substitution Reactions of Acetals
Mori, Ichiro,Ishihara, Kazuaki,Flippin, Lee A.,Nozaki, Kyoko,Yamamoto, Hisashi,et al.
, p. 6107 - 6115 (2007/10/02)
Lewis acid mediated nucleophilic substitution of acetals can occur by direct displacement (SN2) or oxocarbenium ion (SN1) mechanisms.With acyclic acetals, stereoselectivity increases with increasing steric bulk of the alkoxy group and with increasing polarity of the reaction medium.The enhanced stereoselectivity observed with acetals of secondary and tertiary alcohols is explained by perturbation of the approach trajectory of the nucleophilic alkene as it attacks the oxocarbenium ion.Highest stereoselectivity is seen in the reaction of 2-(1-phenylethyl)-4,4,5,5-tetramethyl-1,3-dioxolane (4) with enol silane 5; only one diastereomeric product (9s) is obtained, even in the relatively nonpolar solvent CH2Cl2.The TiCl4-mediated reactions of cyclic acetals 18c, 18t, 25, and 28 with silyl enol ether 5 show that in these systems the substitution does not occur by the SN2 mechanism.
