Bok Ryul Yoo

EFFECTS OF HYDROGEN CHLORIDE ADDITION TO THE DIRECT REACTION OF METHYLENE CHLORIDE WITH ELEMENTAL SILICON

Abstract Direct synthesis of bis(chlorosily)methanes has been reinvestigated by reacting elemental silicon simultaneously with methylene chloride and hydrogen chloride in the presence of copper catalyst using a stirred reactor equipped with a spiral band agitator at a carefully controlled temperature between 260 and 340°C. Bis(dichlorosily)methane and (dichlorosily)(trichlorosily)methane were obtained as the major products and bis(trichlorosily)methane as a minor product along with trichlorosilabe and tetrachlorosilane derived from the reaction between elemental silicon and hydrogen chloride. The decomposition of methylene chloride was suppressed and the production of polymeric carbosilanes reduced by adding hydrogen chloride to the methylene chloride reactant. The optimum mixing ratio of methylene chloride and hydrogen chloride for the direct synthesis of bis(silyl)methanes was 1:4. The deactivation problem of elemental silicon owing to decomposition of methylene chloride and polycarbosilanes was eliminated. Cadmium was a good promoter for the reaction, while zinc was found to be an inhibitor for this particular reaction.

Friedel—Crafts polyalkylation of alkylbenzenes with dichloromethylvinylsilane

Abstract The Friedel—Crafts alkylation of alkylbenzenes such as toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, o-, m-, p-xylene, and mesitylene with dichloromethylvinylsilane in the presence of aluminum chloride catalyst has been studied under mild conditions. Alkylation with dichloromethylvinylsilane at room temperature gave peralkylated products in yields ranging from 25 to 63%, depending upon the number of substituents on the benzene ring. Less alkylated compounds were also obtained as minor products along with alkyl-reoriented products or transalkylated products. The alkylations of substituted benzenes such as chlorobenzene and anisole did not give the peralkylated products under the same conditions. The molecular structure of tris(dichloromethylsilylethyl)mesitylene has been determined by X-ray diffraction studies. The two chlorosilyl group containing substituents are arranged above the benzene plane and the other one below. Peralkylated compounds were methylated or reduced to the corresponding derivatives by reacting with methyl Grignard reagent and LiAlH4.

Synthesis and biological evaluation of [1‐(1H‐1,2,4‐triazol‐1‐yl)alkyl]‐1‐silacyclopentanes

A series of 1-aryl-1-(1H-1,2,4-triazol-1-yl)alkyl-1-silacyclopentanes has been synthesized by four-step reactions starting from 1-chloroalkyltrichlorosilane and tested for fungicidal activities in vitro for ten fungi and in vivo for four fungi occurring in rice, cucumber, tomato etc. Biological activities of the title compounds are strongly dependent upon the p-substituent on the phenyl group in the following order: F > Cl > Ph > OEt > H. Especially, 1-p-fluorophenyl-1-[1-(1H-1,2,4-triazol-1-yl)alkyl]-1-silacyclopentanes (alkyl = methyl or ethyl) showed significant fungicidal activity with a broad spectrum comparable to flusilazole in in-vivo assay.

Friedel–Crafts alkylation of benzene with (polychloromethyl)silanes

Abstract (Polychloromethyl)silanes (Cl 3− m Me m SiCH 3− n Cl n : m =0–3; n =2, 3) reacted with excess benzene in the presence of aluminum chloride to give (polyphenylmethyl)silanes. Such reactions occurred at the temperatures ranging from room temperature ( m =2, 3; n =2) to 80°C ( m =0, 1; n =2, 3), indicating that the reactivity increases with increasing the number (m) of electron-donating methyl-group(s) at the silicon. In particular, (dichloromethyl)silanes with two or three methyl groups at the silicon ( m =2 or 3; n =2) underwent the alkylation and the decomposition of their products at room temperature. The reaction with (dichloromethyl)trimethylsilane occurred immediately at room temperature to give no (diphenylmethyl)trimethylsilane, but diphenylmethane and trimethylchlorosilane via the decomposition of alkylation product. (Trichloromethyl)silanes ( m =0, 1; n =3) reacted with excess benzene to give (triphenylmethyl)silanes as major products and the unusual (diphenylmethyl)silanes as minor. It was found that unusual (diphenylmethyl)silanes were formed by the decomposition of (triphenylmethyl)silanes under the reaction condition. In the alkylation to benzene, the reactivity of (polychloromethyl)silanes (Cl 3− m Me m SiCH 3− n Cl n : m =0–3; n =2, 3) decreases in the following order: m =3>2>1>0; n =3>2.

Photochemical reactions of [5,6:7,8]dibenzo-2-silabicyclo[2.2.2]octanes

Abstract The photochemical reactions of 2-R-2-phenyl[5,6: 7,8]dibenzo-2-silabicyclo[2.2.2]octanes (R = Ph, 1, R = Me, 5) in cyclohexane have been studied in the presence or absence of trapping agents such as methanol and methoxytrimethylsilane. The photolysis of 1 in the presence of methanol gave 9-(1,1-diphenylmethoxysilyl-3,3-dimethylbutyl)-9,10-dihydroanthracene as the major product and the methanol adduct of 1,1-diphenyl-2-neopentylsilene as the minor product. When trimethylmethyoxysilane was used as the trap, the silene adduct was only isolated in small quantity and no 9,10-disubstituted anthracene product was obtained. The photolysis of pure Z-5 or E-5 in the absence of trapping agent gave Z - E photoisomerization products and polymeric products. During the photolysis a constant ratio of Z-5 and E-5 was never observed because the formation of high molecular weight products was faster than isomerization. The major product of photolysis of pure E-5 or Z-5 in the presence of methanol or deuterated methanol was SS(RR), 6, and RS(SR), 6′, respectively, at early stages of the reaction but the other diastereomer was produced also as the photolysis proceeded. Photoisomerization of the diastereomers 6 and 6′ also occurred. The 1,6-biradical intermediates formed from Z- and E-5 retain their asymmetry at the silicon atom prior to the abstraction of methoxy group from methanol, but not at carbon.

Hydrosilylation of Olefins with Allyldichlorosilane: A Convenient Route to Allyl Group Containing Organodichlorosilanes

The hydrosilylation of olefins with allyldicholorosilane in the presence of chloroplatinic acid diluted with isopropanol gave allylalkyldichlorosilanes, retaining the allyl group. When the olefin was used in fivefold excess or more relative to allyldichlorosilane, allylalkyldichlorosilanes were obtained in good yields (63–89%), and the formation of double hydrosilylation products was reduced to less than 6%. The isomerization of allylsilane to 1-propenylsilane was suppressed by lowering reaction temperatures below 100°C. This hydrosilylation of olefins with allyldichlorosilane is a good synthetic route to an allyl group containing organodichlorosilanes.

Structure-Reactivity Relationship in Silacycloalkyl Diamide Complexes of Titanium(IV)

The structure-reactivity relationship of titanium complexes CySi(HNBut)2TiCl2 (1) (CySi = silacyclobutane, silacyclopentane, silacyclopentene, and silacyclohexane) stabilized by a series of cyclic silyldiamide ligands has been studied. The crystallographic results establish that steric interactions between the silacycloalkyl and tert-butyl groups influence the C(But)-N-Ti angles and, hence, the steric environment at titanium. The compounds 1 were further investigated as potential catalysts for the polymerization of ethylene. While sterically less demanding silacyclobutyl and -pentyl diamide complexes (1a and 1b) exhibit low ethylene polymerization activity (3.9 ∼5.8 kg PE molcat −1h−1) in the presence of methylalumoxane, highly puckered silacyclohexyl diamide complex 1e shows better activity (10 kg PE molcat −1 h−1) for the ethylene polymerization when it is activated with MAO.