Aryl dimethylsilanes

The course of this reaction is analogous to that of the corresponding reactions with simple silanes such as (chloromethyl)aryl dimethylsilanes (16) and (chloro- or iodomethyl) dimethylsilanes (93), although in these it is aryl or hydride migration that leads to rearrangement. 

From (trialkylstannyl)dimethylsilane and terminal alkynes this method gives 3,4-disubstituted siloles (28, R = H, R = alkyl, aryl or alkoxy groups) in moderate to good yields44. Catalysis by Pd is better than by Ni or Rh. The proposed mechanism involves a palladium-silylene species 30 as an intermediate. This reacts with an alkyne giving successively a palladasilacyclobutene (31) and a palladacyclohexadiene (32). In the final... 

Polymeric silicon alkyl compounds Polymeric compounds are often observed in the Wurtz synthesis of dihalodialkyl(aiyl)silanes with metals. The intermediate product is probably a dialkyl(aryl)silylene (see Chapter 7). A polymeric dimethylsilane was found by Burkhard68). A yellow polymeric (SiCH3) was isolated after pyrolysis of SiH4 with ethylene156). 

Four synthetic routes lead to silyl triflates (1) reaction of silyl chlorides with silver triflate (very expensive), (2) reaction of silyl chlorides with triflic acid, (3) reaction of tetraalkylsilanes with triflic acid, and (4) reaction of arylsilanes with triflic (trifluoromethane sulfonic) acid (24-26). The displacement of a chlorine atom and a phenyl group from trimethylsilyl chloride and trimethylphenylsilane indicate that these groups are much more reactive than the alkyl substituents for the synthesis of triflated silanes. We found that the aryl group is over 200 times more reactive than chloride in these reactions (14). We were able to displace two phenyl groups from diphenyl-dimethylsilane in a stepwise manner ... 

Various types of aryl and alkenyl halides can undergo cross-coupling with 1- w.oro(dimethyl)silyl-l-alkenes. Representative examples are shown by the synthesis of conjugate dienes. For example, ( -l-octenyl(fluoro)dimethylsilane reacted with (E)- or (Z)-iodoalkene by use of (j -CjHsPdCljj (2.5 mol%) catalyst and TASF (1.5 mol) in THF at 50 °C to give the corresponding E,E)- or ( ,Z)-dienes with complete retention of configuration [Eq.(9)j. 

Dihydrodisilaanthracenes 150 [Eq. (66)] were successfully prepared from the aryl di-Grignard reagents 149 synthesized using Rieke magnesium and bis(o-chlorophenyl) methylsilane or bis(o-chlorophenyl)dimethylsilane [120,121]. These aryl chlorides were unreactive toward granular or powdered magnesium. 

How did this work originate In 1965-1968, Zilkha et al. reported low molecular-weight tin polyesters formed from the reaction of a dialkyl(or aryl)dichlorotin or a tetraalkyldichlorotin with the sodium salt of bis[o-(carboxymethyl)phenyl]- or bis[p-(carboxymethyl)phenyl] dimethylsilanes.154,155,156... 

A related method is lithiation of an aryl halide with subsequent treatment by means of chloroalkylsilanes to achieve alkyl aryl silanes as can be shown by the synthesis of bis[3,4-dimethylphenyl]dimethylsilane (229) (equation 109)138. 

The diazasilole (76) was obtained by treating the pyrrolidinecarboxamide (75) with dichloro-dimethylsilane <74CB2804>. Aryl A,A-tetramethylenehydrazones (77) react with sulfur dichloride to give novel pyrrolo[2,l-h][l,3,4]thiadiazoles (78). The overall reaction can be considered as a [4- -1] cyclization, although the final step in the proposed mechanism involves a [5 - - 0] cyclization of the intermediate (79) (Scheme 12) <88JCS(P2)82i>. 

Scheme 3-175. Cross-coupling of alkenyl[2-(hydroxymethyl)phenyl]dimethylsilanes with aryl iodides.

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