Selective Formation of Both Enantiomerically Pure Disilanes from One Fluorosilane Antipode with Silyllithium

Abstract

Stereochemistry crossover from retention to inversion of configuration at about -20 °C was observed in the nucleophilic substitution of optically active (R)fluoromethyl(1-naphthyl)phenylsilane ((R)-2 F ; >99% ee) with the achiral silyllithium species (dimethyl(4-methoxynaphth-1-yl)silyl)lithium ( 1 ) to give optically active 1,1,2-trimethyl-2-(4-methoxy-1-naphthyl)-1-(1-naphthyl)disilane (3). It became possible to synthesize both enan-tiomerically pure stereoisomers of disilane with one chiral center from a single antipode of the fluorosilane enantiomer by using HMPA, LiClO 4 , LiBr as additives, or by changing the temperature.

On the Mechanism of the Reductive Metallation of Asymmetrically Substituted Silyl Chlorides

“…Although it has been reported that silyl chlorides racemise in THF, [25] racemisation of (SiS)-7a was marginal after 1 h and only occurred after prolonged reaction times ( Table 1, Entry 1).…”

“…Inverse as well as normal addition furnished disilane (SiR)-13a with clean inversion [8,25] of the configuration (Scheme 6). Notably, we were able to demonstrate that the substitution reaction is faster than the chloride-induced racemisation.…”

Reactions of Silicon Compounds and Development of Functional Materials Based on the Characteristics of Silicon-Containing Bonds. 1. Reactions of Silicon Compounds in Polymer Synthesis

“…They further showed that various silicon compounds could be optically resolved by liquid chromatography on cellulose or amylose based packings [23]. As shown in Figure 8, moreover, it was discovered that (1-naphthyl)phenylmethylsilyllithium could be synthesised with high stereoselectivity by converting (1-naphthyl)phenylmethylchlorosilane to the trimethyl tin derivative and then reacting with methyllithium [6].…”

“…With carbon compounds the stereochemistry is lost owing to solvolysis and racemisation occurs, but this is diffi cult with silicon compounds. We have made some interesting discoveries regarding the stereochemistry of fl uorine compounds [5,6]. Unlike carbon in a carbanion, silicon can retain its chirality in the anionic state: sp 2 hybridisation is not always stable in silicon compounds and in contrast with carbon, silicon anions can take up sp 3 hybridisation instead.…”

Catalytic synthesis and characterization of stereoregular and optically active polycarbosilanes

“…Recently, we reported the synthesis and optical properties of stereoregular and optically active polycarbosiloxanes [6 -11], polysiloxanes [12][13][14][15] and oligosilanes as model compounds of polysilanes [16][17][18][19]. For widening the class of stereoregular and optically active silicon-containing polymers, we report here the synthesis and characterization of stereoregular and optically active polycarbosilanes.…”