TMS halides

The ligand exchange reaction of tm halides with bis(trifluoromethyl)mer-cury has been used to prepare trifluoromethyltm halides [6 7] (equation 5)... 

Flavones are halogenated selectively in the 3-position on treatment with PhI(OAc)2 and a TMS halide <01SC2101>. The reaction of 3-halogeneochromones with amines is known to be complex the products are dependent on conditions, type of amine and the halogen. It is now reported that secondary amines react with the three 3-halogenochromones 31 in the presence of K2CO3 in DMF to give exclusively 2-aminomethylene-3(2//)-benzofuranones (Scheme 36) <01H(55)881>. 

The Michaelis-Arbuzov Rearrangement. It has been found that TMS halides, including TMS-Br, may be used to facilitate the Michaelis-Arbuzov reaction (eqs 53 and 54). This transformation is usually high yielding and substantially free from such by-products as phosphine oxides. The reaction of TMS-X with trialkyl phosphites for the preparation of phosponates is similarly efficient with regards to O to P alkyl group transfer selectivity. 

Pyrrole derivatives are prepared by the coupling and annulation of o-iodoa-nilines with internal alkynes[291]. The 4-amino-5-iodopyrimidine 428 reacts with the TMS-substituted propargyl alcohol 429 to form the heterocondensed pyrrole 430, and the TMS is removed[292]. Similarly, the tryptophane 434 is obtained by the reaction of o-iodoaniline (431) with the internal alkyne 432 and deprotection of the coupled product 433(293]. As an alternative method, the 2,3-disubstituted indole 436 is obtained directly by the coupling of the o-alky-nyltrifluoroacetanilide 435 with aryl and alkenyl halides or triflates(294]. 

Tetramethylsilane (TMS) [75-76-3] M 88.2, b 26.3, n 1.359, d 0.639. Distilled from cone H2SO4 (after shaking with it) or LiAlH4, through a 5ft vacuum-jacketted column packed with glass helices into an ice-cooled condenser, then percolated through silica gel to remove traces of halide. 

The preparation of mono- and di-tm-butylcyclopentadienes 1 and 2 starting from monomeric cyclopentadiene was reported first in 1963 [23]. It was noted that the nucleophilic attack of the cyclopentadienide anion on ferf-alkyl halide has to compete with elimination reaction giving isobutene. The yield of the di- and tri-fer/-butylcyclopentadienes 2 and 3 was therefore reported to be modest to low [23, 24], Recently an elegant improvement for this synthesis using phase transfer catalysis was presented (Eq. 1), but the availability of the tri-substituted derivative... 

A remarkable process was reported by Mori that forms aniline from dinitrogen (Equation (26)).106 Titanium nitrogen fixation complexes were generated from reactions of titanium tetrachloride or tetraisopropoxide, lithium metal, TMS chloride, and dinitrogen. These complexes generated a mixture of aryl and diarylamines in yields as high as 80% when treated with aryl halide and a palladium catalyst containing DPPF ... 

TM-catalyzed reaction between a diorganozinc or organozinc halide and an organic halide. 

Carbonylation procedures have been successfully used for C—C bond forming radical strategies. Alkyl halides could be carbonylated under moderate pressure of CO (15-30 atm) in benzene at 80 °C in the presence of (TMS)3SiH and AIBN [16], Reaction (7.8) shows the effect of the CO pressure on the carbonylation of a primary alkyl bromide. These radical chain reactions proceed by the addition of an alkyl radical onto carbon monoxide, which generates... 

A new entry for the synthesis of vinyl- and arylphosphonates has been achieved by reaction of vinyl or aryl halides with trialkyl phosphites in the presence of (TMS)3SiH under standard radical conditions [72]. An example of this intermolecular C—P bond formation is given in Reaction (7.62). Interestingly, the reaction works well either under UV irradiation at room temperature or in refluxing toluene. 

Attempts to directly iodinate quinoxaline failed, and the synthesis of 2,3-diphenyl-5,8-dibromoquinoxaline is somewhat more involved (Scheme 9) [61]. Starting from ort/zo-phenylenediamine, reaction with SOCI2 gives benzothia-diazole in high yield. Bromination in HBr furnishes 4,7-dibromobenzothiadi-azole, which can be alkynylated or directly reduced [62]. Reduction of the dibromide with sodium borohydride leaves the halide substituents unmolested but opens the ring to furnish l,4-dibromo-2,3-diaminobenzene. Reaction of this intermediate with a 1,2-dione furnishes a 2,3-disubstituted 5,8-dibromo-quinoxaline. Pd-catalyzed alkynylation finishes the sequence off and removal of the TMS groups yields the desired 5,8-diethynylquinoxaline monomers (Table 9, entries 13,14). 

In these oxyhalide complexes, the inter-halide distances between layers are smaller than the sum of the ionic radii of the halides (Table 11). In the oxybromides and ox5dodide series the M—Br (next layer) and M—I (next layer) distances increase (Table 11) with increase in parameter c (Table 10) as these distances depend solely on the dimensions of the c-axis. In the oxychloride series the M—Cl (next layer) distance, however, show a decrease along the lanthanide series. So does the parameter c (Table 10). This is the reason why the oxychlorides of Tm, Yb and Lu cannot maintain the PbFCl type structure. 

The chemical reactivities of such titanium homoenolates are similar to those of ordinary titanium alkyls (Scheme 2). Oxidation of the metal-carbon bond with bromine or oxygen occurs readily. Transmetalations with other metal halides such as SnCl4, SbClj, TeCl4, and NbCls proceed cleanly. Reaction with benzaldehyde gives a 4-chloroester as the result of carbon-carbon bond formation followed by chlorination [9]. Acetone forms an addition complex. No reaction takes place with acid chloride and tm-alkyl chlorides. 

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