Phenylthiomethyl silane

Polymetalated systems of this type without phenyl substitution at the lithiated carbon centre are only accessible when solutions of LiCioHg (144a) or LiDBB (145) in THF instead of a suspension of metallic lithium in THF are reacted with bis(phenylthiomethyl)silanes of type 155. In our group, variously substituted bis(lithiomethyl)silanes 117a, 156b-e and 101 were synthesized by reductive cleavage of the carbon-sulphur bond with LiCioHg... 

As a particular example, reactions of diphenylbis(phenylthiomethyl)silane (155f) are shown. While the reaction of 155f with four equivalents of LiCioHg at —40 °C yields the dimetalated bis(lithiomethyl)diphenylsilane (101), a selective monolithiation (compound 158) can be achieved by using only two equivalents of the electron transfer reagent at —60°C. A side reaction of the monolithiated silane 158 is observed, when the reaction temperature rises above —30°C, giving [lithio(phenylthio)methyl]methyldiphenylsilane (159) (Scheme 57). This problem, also observed for other (phenylthiomethyl)element systems, can mostly be avoided by an exact control of the reaction temperature . 

By prior substitution at the a-carbon centre (deprotonation, followed by sUylation), also asymmetrically functionalized bis(lithiomethyl)silanes like compound 161 are accessible from their substituted parent compounds (e.g. compound 160). This selective reaction sequence is based on the possibility of deprotonating bis(phenylthiomethyl)silane 155f with w-butyllithium without attacking the thioether groups (Scheme 58). ... 

The (phenylthiomethyl)silanes used for reductive cleavage were produced by the reaction of (phenylthiomethyl)lithium with the corresponding chlorosilanes (Scheme 2). 

The reductive cleavage of just one C-S bond yields the mono(lithiomethyl)silanes. This transformation is well known and used in the Peterson olefmation for the preparation of (lithiomethyl)trimethylsilane (15) [5], We employed it as a method to exchange the thiophenyl-group in the (phenylthiomethyl)silanes 5-14 with lithium, thus creating the corresponding poly(lithiomethyl)silanes (see, e.g.. Scheme 3 for methylsilanes) [4]. 

Poly(lithiomethyl)silanes can be prepared by the reaction of poly(phenylthiomethyl)silanes with electron transfer reagents. The carbon analogs of some (phenylthiomethyl)silanes show a different reactivity. The new poly(lithiomethyl)silanes can be used as building blocks for organosilicon compounds. 

Phenylthiomethyl)silanes as New Bifunctional Assembling Ligands for the Construction of Heterometallic Complexes... 

Synthesis of Platinum and Rhenium Complexes with a Chelating (Phenylthiomethyl)silane Ligand... 

In order to study the ability of the (phenylthiomethyl)silanes 1 to chelate metal complexes and the associated stereochemical problems we first prepared simple model compounds using diphenylbis[(phenylthio)methyl]silane Ic. On reaction of Ic with [PtCl2(PhCN)2] the very stable square planar chelate complex 3 was isolated. NMR investigations at variable temperature show that meso- and DL-isomers coexist in a temperature-dependent equilibrium due to a facile inversion process at the sulfur atoms [2] in solution. At higher temperature (325 K) the pyramidal inversion is sufficiently fast that only one "averaged planar" conformation is observed in the H NMR spectrum... 

Summary Disilacyclopentanes containing a heteroelement have been prepared by specific routes starting from bis(lithiomethyl)silanes or bis(lithiomethyI)disilanes. The key reaction in the sequence of synthesis is the reductive cleavage of C-S bonds of bis(phenylthiomethyl)silanes and -disilanes to obtain the corresponding difunctional lithioalkyl compounds. The crystal structures of two novel l,2-disila-4-element-cyclo-pentanes and a spirocyclic disilane were obtained and show strained ring systems. Three reaction sites of l,l,2,2-tetramethyl-4,4-diphenyl-l,2,4-trisilacyclopentane could be activated selectively. 

Phenylthiomethyl)trimethylsilyl carbene (10) has been generated via two independent methods, either from the diazo compound through copper catalysis (eq 14), or from the chloro-(phenylthiomethyl)silane by base-induced o -elimination. The generation of carbene 10 was verified by [2 +1] cycloadditions with olefins affording cyclopropanes (eq 15) in low to moderate yields (12-61%). ... 

Except for silanes, other heteroatom substituted systems have been used to stabilize multiply lithiated centres, e.g. (phenylthiomethyl)germanes 173a-c, 174a-c and 175, -stannanes 176a and 176b (Figure 22), -amines and (phenylthiomethyl)phosphanes . ... 

Alkyl phenyl ketonesAlkylation of the anion of 1 followed by oxidation and rearrangement gives a mixed acetal, which is hydrolyzed by acid to a ketone (cf. Phenylthiomethyl(trimethyl)silane, this volume). 

Phenylthiocyclobutanone, 422 Phenylthiolation, 456 Phcnylthiomethyllithium, 422-423 Phenylthiomethyl(trimethyl)silane, 423-424 1 -Phenylthio-1 -trimethylsilylethylene, 83 Phenylthio(triphenylstannyl)methyllithium, 424... 

Aminomethyl)silanes (E) can be metallated by lithiumalkyls and characterized by trapping with disulfides (Scheme 3). The (phenylthiomethyl)(aminomethyl)silanes G can be metallated again in toluene or THF In reactions of (lithiomethyl)(aminomethyl)diphenylsilanes with aldehydes or ketones we observed no clear addition/deprotonation profile. The (lithiomethyl)silanes H add to ketones with de up... 

Alkylation of phenylthiomethyl(tiimethyl)silane or phenylthimhenyl(trimethylsilyl)methane with alkyl halides followed by deprotection gave aldehydes or ketones respectively. 

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