Allylchlorosilanes

Nametkin and co-workers hrst reported the alkylation of benzene derivatives with allylchlorosilanes in the presence of aluminum chloride as catalyst. " 2-(Aryl)propylsilanes were obtained from the alkylation of substituted benzenes (Ph—X X = H, CL Br) with allylsilanes such as allyldichlorosilane and allyltrichlo-rosilane.The yields ranged from 34 to 66% depending upon the substituents on the benzene ring, but information concerning reaction rates and product isomer distribution was not reported. 

Allylchlorosilanes reacted with naphthalene to give isomeric mixtures of poly-alkylated products. However, it was difficult to distill and purify the products for characterization from the reaction mixture due to the high boiling points of the products and the presence of many isomeric compounds. The alkylation of anthracene with allylchlorosilanes failed due to deactivation by complex formation w ith anthracene and the self-polymerization of anthracene to solid char. 

Jung etal. reported the Friedel-Crafts type alkylation of ferrocene with allylchlo-rosilancs. The reaction of ferrocene with allylchlorosilanes in the presence of Lewis acid afforded regiospecific alkylated ferrocenes bearing chlorosilyl groups at the /J-carbon to the ferrocene ring (Eq. (4)). 

Vinylchlorosilanes react with aromatic compounds in the presence of Lewis acid to give the alkylation products 2-(chlorosilyl)ethylarenes. In the Friedel-Crafts alkylation of aromatic compounds, the reactivity of vinylchlorosilanes is slightly lower than that of allylchlorosilanes.Friedel-Crafts alkylation of benzene derivatives with vinylsilanes to give 2-(chlorosilyl)ethylarenes was first reported by the Andrianov group (Eq. (5))." The reactivity of vinylsilanes in the... 

Allylchlorosilanes undergo Friedel-Crafts alkylation with aromatic compounds such as benzene derivatives and ferrocene to give [p-(chlorosilyl)alkyl]arene compounds in the presence of Lewis acid catalyst. Allylsilanes containing two or more chlorine atoms on silicon react smoothly with benzene under mild conditions to give alkylation products in good yields [Eq. (15)]. In alkylations of benzene, the reactivity of the allylsilanes increases as the number of chlorine atoms on the silicon increases, but decreases as the number of methyl groups increases. Because the reactivity of allylsilanes is sensitive to the electronic nature of the substituents on the silicon atom, allylsilane selection is an important factor for alkylation reactions. 

In the polyalkylation reaction of benzene with allylchlorosilanes, trialkylated compounds are the most substituted products obtained in appreciable amount due to increased steric interactions with additional allyltrichlorosilane. This is the case even when more than a four-fold excess of allyltrichlorosilane is used. In addition, multi-step alkylation reactions give the trialkylated products in higher yields than the one-step reaction. 

The reaction of ferrocene with allylchlorosilanes in the presence of Lewis acid in methylene chloride solvent affords alkylated ferrocenes bearing chlorosilyl groups... 

The reactivity of allylchlorosilanes for the alkylation of ferrocene varies depending upon the substituents on the silicon atom. Generally, the reactivity increases as the number of alkyl groups on the silicon of allylsilanes increases." Allyl(dialkyl)-chlorosilanes react with ferrocene in the presence of HfCU under mild reaction... 

Phenols have been employed as directing groups in the enantioselective allylation of aldimines and ketimines using allylchlorosilane reagents.45... 

Assessing on the whole the method of the production of alkyl- and aryl-chlorosilanes based on the interaction of alkyl- and arylchlorides with free silicon (i.e. direct synthesis), we should say that this method in comparison with metalorganic synthesis is more efficient, especially for the production of methyl- and phenylchlorosilanes. As for unsaturated chlorosi-lanes (vinyl- and allylchlorosilanes) and organochlorosilanes with higher radicals (hexyl-, heptyl-, octyl- and nonylchlorosilanes), no direct synthesis technique has yet been developed. 

Allylation of aldehydes with allylsilacyclobutanes proceeds spontaneously at 130-160 °C with regio- and stereospecificity (Equation (23)).101 Under the same conditions, allyldimethylphenylsilane is insensitive to aldehydes. The thermal allylation takes place probably via a six-membered cyclic transition state, which would be assisted by the relatively strong Lewis acidity of the strained silyl group. Allylsilacycles derived from allylchlorosilanes by treatment with 1,2-diols, /3-amino-alcohols, and 1,2-diamines are reactive enough for spontaneous allylation at or below room temperature.102 1023 10215 103... 

Allylsilanes are known as interesting and useful reagents for organic synthesis.85-88 Hurd first reported the direct reaction of elemental silicon with allyl chloride in the presence of copper catalyst to give a mixture of allylchlorosilanes and polymeric materials.15 Among the volatile compounds, allyltrichlorosilane, formed by the 1 1 1 reaction of allyl chloride, hydrogen chloride and elemental silicon, was observed as the major product instead of the normally expected diallyldichlorosilane. Since diallyldichlorosilane thermally polymerizes at temperatures above 130°C, the product mixture polymerized during the reaction or upon distillation. 

To prepare allylchlorosilanes, the problems of allyl chloride decomposition and diallyldichlorosilane polymerization must be solved.15 The hydrogen chloride addition technique was expected to work for this reaction. 

Zinc inhibited and cadmium promoted this particular reaction, consistent with the results observed for the direct reaction of elemental silicon with a mixture of alkyl chloride and hydrogen chloride, described above. In addition to allylchlorosilanes, several other compounds were also produced as minor products, including the following 2-methyl-1,1,4,4-tetrachloro-l,4-disilabutane 1,1,5,5-tetrachloro-1,5-disilapentane and 3-(dichlorosilyl)-1,1,5,5-tetrachloro-1,5-disilapentane. 

Of particular interest was the development of a one-pot enantioselective synthesis of a piperidine appended benzimidazole 147 utilizing a new chiral allylchlorosilane 148. The reaction proceeds via allylation of ketimine 149 followed by RCM in the presence of the G2 catalyst <07OL3699>. 

Preparation. Allylchlorosilanes are conveniently obtained by cross-coupling of allyl chloride with polychlorosilanes in dimethylimidazolidinone using zinc as mediator. 

A mixture of allyldichlorosilane and 0.6-0.7 mole of adiponitrile heated with distillation of the products at 70-75° during 7 >4 hrs., then distillation continued rapidly at temp, up to 119° -> allylchlorosilane (Y 77%) and allyltrichlorosilane (Y 71%).—The rate of the disproportionation depends on the character of the hydrocarbon group attached to silicon and is greatest in the case of alkenyl groups having the double bond in the y-position with respect to the Si-atom. F. e., also with pyridine as catalyst, s. A. D. Petrov and V.M. Vdovin, Izvest 1960, 519 G. A. 54, 22325i. 

There are many examples of the direct reaction of silicon with ethyl chloride, vinyl chloride and chlorobenzene. Vinyl and allylchlorosilanes were first made via a direct process in 1945 as were phenylchlorosilanes. Jung s group has recently extended the direct reaction of silicon with a variety of substrates including allyl chloride. Silicon... 

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