Trifluoro silane

Useful stereoselective syntheses of ( )- and (Z)-2-butenyl(trifluoro)silanes have been reported. The (Z)-isomer is available by hydrosilation of butadiene, the (E)-compound being prepared by displacement of chloride from ( )-l-chloro-2-butene37. 

Allylic transposition is observed in fluoride-induced reactions of allyl(trifluoro)silanes50 and allyl(trichloro)- and allyl(trialkoxy)silanes in the presence of hydroxylic promoters, e.g., 1,2-benzenediol51,52. Pentacoordinated silicates are believed to be involved53. 

In contrast, ( )- and (Z)-2-butcnyl(trifluoro)silanes undergo stereoselective fluoride-induced reactions with aldehydes to give anti- and. sy -products, respectively37. 

Of particular interest are reactions between a-hydroxy ketones and allyl(trifluoro)silanes which proceed with participation of the hydroxy group via a pentacoordinated allylsilane, with intramolecular delivery of the allyl group to the ketone. Excellent stereoselectivity is obtained at up to three contiguous stereogenic centers66. 

A solution of 3 mmol of trifluoro(3-mcthyl-2-butenyl)silane, 2 mmol of hydroxypropanone and 3 mmol of Ft jN in 5 ml, of THF is heated under reflux for 20 h. Chromatography of the mixture on silica gel gave the product yield 71 %. 

Previously, trifluorosilyl groups have been bound to phosphorus (40) and silicon via the SiF (g), fluorine-bond insertion-mechanism (41). The new compound HgCSiFs) is readily hydrolyzed, but it can be stored for long periods of time in an inert atmosphere. It is a volatile, white solid that is stable up to at least 80°C. The preparation of bis(trifluoro-silyDmercury, of course, raises the possibility of (a) synthesis of the complete series of trifluorosilyl, "silametallic compounds, as had previously been done for bis(trifluoromethyl)mercury by using conventional syntheses, and (b) transfer reactions similar to those in Section II, as well as (c) further exploration of the metal-vapor approach. The compound Hg(SiF.,)j appears also to be a convenient source of difluoro-silane upon thermal decomposition, analogous to bis(trifluoromethyl)-mercury ... 

When double bonds are reduced by lithium in ammonia or amines, the mechanism is similar to that of the Birch reduction (15-14). ° The reduction with trifluoro-acetic acid and EtsSiH has an ionic mechanism, with H coming in from the acid and H from the silane. In accord with this mechanism, the reaction can be applied only to those alkenes that when protonated can form a tertiary carbocation or one stabilized in some other way (e.g., by a OR substitution). It has been shown, by the detection of CIDNP, that reduction of a-methylstyrene by hydridopenta-carbonylmanganese(I) HMn(CO)5 involves free-radical addition. ... 

While trifluoro and other halosilanes function by increased electrophilicity at silicon, nucleophilic reactivity of allylic silanes can be enhanced by formation of anionic adducts (silicates). Reaction of allylic silanes with aldehydes and ketones can... 

Recently, Olah and co-workers reported a new route to tributyl(trifluoro-methyl)tin via in situ formation and capture of the trifluoromethyl anion by trialkyltin oxide [106]. Reaction of trimethyl(trifluoromethyl)silane with tribu-tyltin oxide in the presence of catalytic TBAF in THF afforded the corresponding tributyl(trifluoromethyl)tin in good yield (Scheme 38). This reaction system was first reported by Warner and Buchwald [107]. 

Trichloromethyl)benzene and its derivatives are easily fluorinated with antimony(III) fluoride however, with a trifluorosilyl group in the 2-position, the use of antimony(V) chloride catalyst is required. Trifluoro[2-(trifiuoromethyl)phenyl]silane (6) can be prepared by this procedure in 87% yield.80... 

Silane Dichloro-ethyl-trifluoro-methyl- ElOb, 435 (Br - Si) c3hsf... 

Silane Pcntalluorophenyl-trifluoro-ElOa. 257 (Educt) ElOb,. 427 (Educt)... 

Silane Diethylammo-tris-[trifluoro-niethyl]- ElOb,. 403 (Br - Si-NR,)... 

Silane [(4-Mcthoxycarbonyl-phenoxy)-triethyl]-trifluoro-ElOa. 602 (3OR -> 3F)... 

Diethylaminosulfur trifluoride Sulfur, (diethylaminato)trifluoro- (38078-09-0), 69, 49 Diethylamino(trimethyl)silane Silanamine, N,N-diethyl-1,1,1-trimethyl- ... 

Heath, G. A.,L. F. Thomas, and J. Sheridan The Structure of Trifluoro-silane from Microwave Spectra. Trans Faraday Soc. 50, 779—783 (1954). 

To a suspension of KF (spray dried, 2.1 g, 36 mmol) in DMF (7.0 ml) was added 1.7 g (7.2 mmol) of (dichloro)(ethyl)(4-methoxyphenyl)silane and 4-trifluoro-1-bromobenzene (1.05 g, 6.0 mmol) at 0°C under an argon atmosphere. The resulting reaction mixture was then stirred at 60 °C for 3 h. The mixture was allowed to cool to r.t., and a solution of palladium acetate (6.7 mg, 0.030 mmol) and triphenylphosphine (7.8 mg, 0.030 mmol) in DMF was added. The reaction mixture was heated at 120 °C for 18 h and then cooled to r.t., poured into a saturated aqueous NaCl solution, and extracted with ethyl acetate (20 ml x 3). The combined organic extracts were dried over MgS04. Concentration under... 

Alkyl(trifluoro)silanes are also applicable to the cross-coupling reaction with aryl halides (Eq. 34) [41,42]. TBAF in excess is required for giving products in acceptable yields, as the coproduced Sip4 is readily converted into (SiFs) or (SiFa)2-. 

To a solution of Pd(PPh3)4 (12 mg, 0.010 mmol) and 4-bromoacetophenone (40 mg, 0.20 mmol) in THF (1 ml) placed in a screwed sealed glass tube were added sequentially hexyl(trifluoro)silane (68 mg, 0.40 mmol) and TBAF (1 M THF solution, 0.80 ml, 0.80 mmol) at r.t. The mixture was stirred for 30 min at r.t. and heated at 100 °C for 22 h. The reaction mixture was concentrated in vacuo, and the viscous residue was purified briefly by column chromatography (silica gel, CH2CI2) to remove the Pd catalyst and tetrabutylammonium salt. The residue was further purified by flash column chromatography on silica gel to afford 3-(4-acetylphenyl)-l-butene (65% yield). 

C —Br and C l bond polarization in perfluoroalkyl- and polyfluoroaryl-containing derivatives may be promoted by reagents other than phosphorus derivatives. When tetrakis-(dimethylamino)cthene is treated with bromotrifluoromethane or trifluoroiodomethane in the presence of chlorotrimethylsilane under similar conditions" only traces of trimethyl(trifluoro-methyl)silane are obtained, but dimethylbis(trifluoromethyl)silanecan be prepared from trifluoroiodomethane and dichlorodimethylsilane in 63 "/u yield. " ... 

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