Chloromethyl silanes

Among the Friedel-Crafts alkylations of aromatic compounds with (chlorinated alkyl)silanes, the alkylation of benzene with (tt>-chloroalkyl)silanes in the presence of aluminum chloride catalyst was generally affected by two factors the spacer length between the Cl and silicon and the electronic nature of substituents on the silicon atom of (w-chloroalkyl)silanes. As the spacer length between the C—Cl and silicon increases from (chloromethyl)silane to (/i-chloroethyl)silane to (/-chloropropyl)silane, the reactivity of the silanes increases. As the number of chloro-groups on the silicon decreases from (chloromethyl)trichlorosilanes to (chloromethyl)methyldichlorosilanes to (chloromethyl)trimethylsilanes, the... 

Insertion of germanium into the a, oj-dihaloalkanes and chloromethyl-silanes provides useful germanium halogen derivatives254 ... 

Methyl dichlorosilane [75-54-7] M 115.0, m -92.5°, b 41°/748mm, 40.9°/760mm, 40-45°/atm, d j l.105. Impurities are generally other chloromethyl silanes. Distilled through a conventional Stedman column of 20 theoretical plates or more. It should be protected from H2O by storing over P2O5. [fl 52 695 1919 JACS 68 9621946]. 

Silathietanes can be readily prepared from the appropriate bis(chloromethyl)silane and KSH or by intramolecular hydrosilation in the presence of Wilkinson s catalyst (Scheme 97) (81JOM(204)13). Electron impact and photoionization mass spectrometry support the loss of silathione ions (R2Si=S) (R = Me, Et) indicating a transannular interaction, though decomposition by the loss of silenes and thioaldehyde also readily occurs (81JOM(214)145). 

The formation of the expected 2,4,6-trisilaalkanes 2 can be explained by the 2 1 reaction of (chloromethyl)silanes 1 and elemental silicon. The byproducts, 1,3-disilaalkanes 3, were obtained from the reaction of (chloromethyl)silane reactant 1 and hydrogen chloride (or chlorine) with the same silicon atom, as methyldichlorosilane (or methyltrichlorosilane) was obtained from the methyl chloride reaction. This result indicates that some of the (chloromethyl)silane reactant decomposed under the reaction conditions and acted as a chlorine or hydrogen chloride source. In the direct reaction of (chloromethyl)dimethylchlorosilane (lc), a significant amount of starting material was recovered at temperatures below 300 °C, but the reaction went to completion above 320 °C. 2,6-Dimethyl-2,4,4,6-tetra-chloro-2,4,6-trisilaheptane (2c) was obtained in much higher yields than 3-methyl-l,l,l,3-tetrachloro-l,3-disilabutane (3c) at reaction temperatures ranging from 280 to 320 °C, but the ratio of both compounds reversed above 340 °C. 

The formation of 4c can be explained by the reaction in which 1 mol of each of the two reactants reacted simultaneously with an equivalent of elemental silicon. Besides 1,3-disilaalkanes 3c and 4c, 2c was obtained in small amounts along with trichlorosilane and tetrachlorosilane. Cadmium was a good promoter for the reaction as observed in the direct reaction of reactant lc above, while zinc was found to be an inhibitor for this particular reaction. Other (chloromethyl)silanes la.b.d were also applied for this reaction.27... 

Even though 2,2-dichloro-2-silaindane was obtained from o of-dichloro-o-xylene in good yield, there was some deposition of solid materials, probably formed by the decomposition of o of-dichloro-o-xylene on the surface of the silicon. Zinc, known as a good promoter for the direct reaction of methyl chloride, was found to accelerate the decomposition of the reactant. Cadmium, known as a good promoter for the direct reaction of (chloromethyl) silanes, had no significant effect for this particular reaction, as was the case for silver.26... 

In the reaction using cadmium promoter, the selectivity for tris(chloro-silyl)methane 8b was the highest among the four tris(chlorosilyl)methanes 7b-10b and about 73% in the distribution of their four compounds. These are consistent with the results observed for the direct reactions of silicon with (chloromethyl)silanes,20,21 allyl chloride,27 methylene chloride,22 and chloroform.23... 

Cadmium was a good promoter for the reaction, and the optimum temperature for this direct synthesis was 280 °C.24 Bis(chlorosilyl)methanes 3 and 4 were the same as those obtained in the direct reaction of silicon with a mixture of (chloromethyl)silanes 1 and hydrogen chloride,21 indicating that some of the starting (dichloromethyl)silanes 6a-d decomposed to... 

Recent studies on the direct reaction of elemental silicon with alkyl chlorides such as methyl chloride, activated alkyl chlorides, polychloro-methanes, (chloromethyl)silanes, (dichloromethyl)silanes, etc. are summarized in this review. In the direct reaction of elemental silicon with activated alkyl chlorides and polychloromethanes, the decomposition of the reactants can be suppressed and the production of polymeric carbosilanes reduced by adding hydrogen chloride to the reactants. These reactions provide a variety of new organosilicon compounds containing Si-H and Si- Cl functionalities, which should find considerable application in the silicone industry. 

As in the research work of Vivet et al., new bicyclic sila-heterocycles were synthesized by Handmann et al. <2000ZNB133, 2000JOM19>. Compound rac-164 underwent a thermally induced cyclization reaction to give rac-7-ethoxy-2,2-dimethyl-2,3,5,7a-tetrahydro-177-3a,6,-sila-inden-4-one 9a (Equation 27). The crystal stmcture of 9a and kinetic studies of the cyclization reaction have also been reported. Starting from 3,6-ethoxy-2,5-dihydropyrazine 163, metallation with 1 molar equivalent of -butyllithium and subsequent treatment with 1 molar equivalent of the bis(chloromethyl)silane produced compound 164 in 50% yield. Pleating neat 164 at 120 °C gave the crystalline 9a in almost quantitative yield. 

Dimethyl- and 3,3-diethyl-l,3-thiasilacyclobutanes are obtained by intramolecular cyclization of the bis(chloromethyl)silane with hydrosulfide ion, as exemplified by the synthesis of 522 or by an intramolecular hydro-silation, as exemplified by the synthesis of 523. A chloroplatinic acid catalyst (Speiers catalyst) also has been used for the hydrosilation... 

Reaction of vinyl (chloromethyl)silanes such as 31a led to cyclopropylsilane derivatives 3Id, and intermediates such as 31b and 31c were implicated, although an understanding of the delocalization in the cationic intermediates and the cyclopropylsilanes is still under development ... 

The hydrolysis of DBU and its quaternary salts (12) in aqueous methanolic potassium hydroxide gave the corresponding lactam (10 or 11) (81HCA399). Quaternization of DBU with trimethyl(chloromethyl)silane in dimethyl-formamide at ambient temperature gave 13 (82ZOB2055). 

Most of the known 1,3-disilacyclobutanes were synthesized by [2+2] cycloaddition of the corresponding silicon-carbon double bonds or the "Kriner Reaction" of chloro(chloromethyl)silanes with magnesium or lithium [3], The 1,3-disilacyclobutanes prepared by these reactions are normally symmetrically substituted (Scheme 1). 

Oxygenated Silanes. Controlled introduction of oxygen substituents onto silicon is an interesting special case, since several syntheses are possible. For mono-oxygenated compounds, one can simply react a chloro-(chloromethyl)silane with two equivalents of triazole and then displace the labile silicon-bound triazole with water or an alcohol. However, a better alternative in practice is to introduce first an alcohol and then triazole. In this case, the hydroxy compound can be prepared by hydrolysis of the silyl ether with aqueous acid. Scheme II outlines these options. 

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