Silanes trifluoromethyl

Lithium silylamides react smoothly with tiifluoronitrosomethane to give diazenes Traces ot water initiate the decomposition of the latter with liberation of a trifluoromethyl carbanion, which is trapped by carbonyl compounds [775] (equation 116) Desilylation of trialkyl(trifluoromethyl)silanes by fluoride ion produces also a trifluoromethyl carbanion, which adds to carbonyl carbon atoms [136, 137] (equations 117 and 118)... 

Silicon tetra-chloride, -bromide, or -iodide ( 5 mmol) was similarly treated with (CF3)2Hg (1-20 mmol) at temperatures that varied from 0 to 100°C. Although CaFg, SiF4, and e.g., Hgl were produced, and identified by mass spectrometry, in no case were trifluoromethyl-substituted silanes discerned under the conditions employed. 

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 ... 

The 0/7/fo-alkylation of aromatic ketones with olefins can also be achieved by using the rhodium bis-olefin complex [C5Me5Rh(C2H3SiMe3)2] 2, as shown in Equation (9).7 This reaction is applied to a series of olefins (allyltrimethyl-silane, 1-pentene, norbornene, 2,2 -dimethyl-3-butene, cyclopentene, and vinyl ethyl ether) and aromatic ketones (benzophenone, 4,4 -dimethoxybenzophenone, 3,3 -bis(trifluoromethyl)benzophenone, dibenzosuberone, acetophenone, />-chloroacetophenone, and />-(trifluoromethyl)acetophenone). 

Trifluoromethyl thioethers are produced in a fluoride-catalysed one-pot reaction of alkyl or aryl thiocyanates with trifluoromethyl silanes [37]. The reaction is initiated by fluoride ion displacement of the trifluoromethyl anion from the silane the thioether is formed from the thiocyanate by displacement by the trifluoromethyl anion of the cyanide ion, which then perpetuates the reaction. Trifluoromethyl selenoethers are obtained by an analogous route. In a similar manner, disulphides can be converted into trifluoromethyl thio- or selenoethers [38],... 

Trifluoromethyl)trimethylsilane Silane, trimethyl(trifluoromethyl)- (11) (81290-20-2) Chlorotrimethylsilane Silane, chlorotrimethyl- (8,9) (75-77-4)... 

The use of aryltrimethylsilanes as intermediates has been found to be a useful complement to direct thallation in the preparation of arylthallium intermediates. The advantages are (a) position specificity, because the thallium always replaces the silane substituent, and (b) improved ability to effect thallation of certain deactivated rings, such as those having trifluoromethyl substituents. What role does the silyl substituent play in these reactions ... 

Trifluoromethyl iodide is a poor substrate for SN2 reactions [28], The increased donativity of the methylene carbon as rendered by the fluorine atoms is reflected in its reluctance to enter a bonding relationship with a nucleophile. Similar reactivity patterns are known for chloromethyl phenyl sulfone [28] and chloromethyltrimethyl-silane. In these latter compounds the reactive center is directly linked to an acceptor group. 

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]. 

Recently, analogues of nucleosides [60], natural products Huperzine-A [61] and Hydroartemisinin [62], and inhibitors of metallo-/ -lactamases have been synthesised [63]. With acylsilane electrophiles, the initial adducts undergo Brook rearrangement which is interrupted by -Si bond fission with loss of fluoride anion (Eq. 16), leading to the formation of extremely useful difluoro-enol silanes [64]. Of the various fluoride sources employed, the tetrabutylam-monium triphenyldifluorostannate described by Gingras appears to be particularly effective. The numerous other methods for trifluoromethylation formed the subject of an exhaustive review [65]. More recently, the Olah group described a chlorodifluoromethyl trimethylsilane which is expected to have a rich chemistry [66]. 

Silane Tributyl-trifluoromethyl-ElObp 403 (Br - SiR3), 411 (Educl)... 

Silane Bis-[3-trifluoromethyl-phenylj-difluoro- ElOa. 522 [Si(OR)2 - SiFJ... 

Trifluoromethylation of aryl iodides was carried out by the fluoride ion in duced cross-coupling reaction of aromatic iodides with trifluoromethyltnalkyl-silanes in the presence of copper salts [219] (equation 147) Some pentafluoro- ethyl derivative was also formed This methodology was extended to pentafluoroethyl-and heptafluoropropyltnethylsilanes [219]... 

Fluoride ion-catalysed addition of trifluoromethyltrimethylsilane to acyl silanes occurs to give l,l-difluoro-2-trimethylsilyloxyalkenes (silyl enol ethers of difluoromethyl ketones), through nucleophilic addition of trifluoromethyl anion, Brook rearrangement and loss of fluoride. These compounds could be isolated when tetrabutylammonium difluorotriphenylstannate was used as a catalyst use of tetrabutylammonium fluoride gave the product corresponding to subsequent aldol reaction with the difluoromethyl ketone (Scheme 78)m. 

Trifluoromethyl ketones have been alkenylated, alkynylated, and phenylated in high ee using silane reagents and a chiral copper(I)-diphosphine complex.178... 

The treatment of 2,2,4,4-tetramethyl-3-thioxocyclobutanone 122a with trimethyltrifluoromethyl silane and TBAF in THF led to the formation of (4-isopropylidene-3,3-dimethyl-2-trifluoromethyl-thietan-2-yloxy)trimethyl silane 123 in high yield (Equation 36) <2002HCA1644>. 

Tetrasubstituted silanes are also sources of silylene. Suginome and coworkers reported that palladium catalyzed the transfer of dimethylsilylene, formed from silylborane 44, to alkynes [equation (7.8)], 60 Exposure of silylborane 48 and alkyne 49 to substoichiometric amounts of palladium and P(7-Bu)2(2-biphenyl) afforded 2,4-disubstituted silole 50. This process tolerates a variety of functionality including silyl ether-, dimethylamino-, and trifluoromethyl groups. In addition to aliphatic terminal acetylenes, arylacetylenes were also competent substrates. For... 

The cross-coupling reaction of alkenyl(fluoro)silanes with aryl halides sometimes produces, in addition to the desired ipso-cowpled products, small amounts of cmc-coupled products [14]. The czne-coupling is often striking in the reaction with organotin compounds. The isomer ratio of products produced by the reaction of l-fluoro(dimethyl)silyl-l-phenylethene with aryl iodides is found to depend on the electronic nature of a substituent on aryl iodides (Eq. 11) an electron-withdrawing group like trifluoromethyl and acetyl favors the formation of the ipso-coupled product. To explain the substituent effect, the mechanism depicted in Scheme 3 is proposed for the transmetalation of alkenylsilanes with palladium(ll) complexes. It is considered that an electron-donating substituent on Ar enhances... 

Triethyl(trifluoromethyl)silaneandtributyl(trifluoromethyl)silane(64% bp53-58 C/0.5 Torr) can be synthesized by the reaction of bromotrifluoromethane with chlorotrielhylsilane and... 

The method has been further improved." Trimethyl(perfluoroalkyl)silanes RpTMS (Rp = c, -C, perfluoroaliphatic groups) are prepared by reaction of perfluoroalkyl halides RpX (X = Br, I) with chlorotrimethylsilane in the presence of tris(dialkylamino)phosphanes in acetonitrile. For example, chlorotrimethylsilane was treated with bromotrifluoromethane and tris(diethylamino)phosphane in acetonitrile at — 40"C for 1 hour to give trimethyl(trifluo-romethyl)silane in 90% yield. Bis(dimethylamino)(trifluoromethyl)silane is available from the reaction of chlorobis(dimethylamino)silane with the system bromotrifluoromethane/tris-(diethylamino)phosphane, while trichloro(trifluoromethyl)silane is prepared by nucleophilic trifluoromethylation of tetrachlorosilane with bromotrifluorornethane/tris(diethylamino)phos-phane. " ... 

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. " ... 

Grobe and Hegge demonstrated that aluminum powder in fV-methylpyrrolidinone (NMP) can also be used for the reduction of bromotrifluoromethane in the presence ofchlorotrimethyl-silane to produce trimethyl(trifluoromethyl)silane, a method more convenient than the modified Ruppert procedure. The C Br bond of bromochlorodifluoromethane is selectively reduced by aluminum powder in. V-methylpyrrolidinone in the presence of ehlorotrimethylsilane giving (chlorodifluoromethyl)trimethylsilane in 80% isolated yield. The process appears to involve a two-electron reduction of the C Br bond of bromochlorodifluoromethane followed by trapping of the resulting CFjCU" anion by chlorotrimethylsilane. Aluminum powder, corresponding to a net consumption of two electrons per mole of bromochlorodifluoromethane. is needed for the reduction. 

Many new syntheses have been developed using triethyl(trifluoromethyl)silane and other per-fluoroalkylsilanes. ... 

Dichlorofluoromethyl)trimethylsilane and trimethyl(trifluoromethyl)silane react (under the conditions of nucleophilic catalysis by fluoride ions) with compounds containing halogen atoms at C = N or N = groups, e.g. formation of 6 and 7. Such halogen atoms can be easily substituted by dichlorofluoromcthyl or trifluoromethyl groups. 

On the basis of differences in electronegativity, tlie C - Si bond possesses 12% ionic character. Silicon is the positive end and carbon is the negative end of the dipole. Trimethyl(trifliioro-methyl)silane is thus a reagent for introducing the trifluoromethyl group into carbonyl compounds (aldehydes, ketones, enoncs). ... 

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