Bromo trimethylsilane

In contrast to these results, bromo-trimethylsilane (527) has only ester cleaving properties referring to dialkyl phosphonates (Scheme 85). Via this reagent a great variety of substituted phosphonic acids can be prepared in hitherto unknown yields. 

ALKYL BROMIDES Bromine. Bromo-trimethylsilane. Chlorotrimethylsilane-Lithium bromide. 

The unstable triethoxyphosphoranes (2) have been generated by the reaction of oxalylcarbamates with triethyl phosphite. Reaction of (2) in situ with bromo-trimethylsilane or hydrogen bromide in acetic acid gave the corresponding phosphonates (3) in high yield and so provides a new and most convenient route to the synthetically useful amino(diethoxyphosphoryl)-acetic esters (4) (Schone... 

In the case of aromatic spacers, the synthesis was carried out in five steps with an overall yield of 56%. 4-(Bromomethyl)benzonitrile was first reduced using diisobutylaluminium hydride and followed by hydrolysis, to obtain the corresponding aldehyde. The latter was then reacted with triethyl phosphite. Subsequent reaction with methylamine and reduction with sodium borohydride of the resulting phosphonate allowed synthesis of the phosphonated secondary amine. Finally, the 4-(iV-methylaciylamido-methyl)benzylphosphonic acid monomer was obtained by an aciyloylation reaction, and hydrolysis of the phosphonated ester group with bromo-trimethylsilane and methanol finally led to the desired phosphonic acid moiety. 

Preparation of Other Trimethylsilyl Derivatives. Hexamethyldisiloxane has been used as an inexpensive starting material for the preparation of numerous synthetically useful trimethylsilyl derivatives. Examples include fluorotrimethylsilane, bromo-trimethylsilane, and iodotrimethylsilane, as well as... 

B. (3-Bromo-3,3-difluoropropyl)trimethylsilane. A 1-L, four-necked flask is equipped with a mechanical stirrer, thermometer, Claisen adapter, septum inlet, reflux condenser (the top of which is connected to a calcium chloride drying tube), and a solid addition funnel. The flask is charged with (1,3-dibromo-3,3-difluoropropyl)trimethylsilane (78.3 g, 0.25 mol), and anhydrous dimethyl sulfoxide (200 mL), and the solid addition funnel is charged with sodium borohydride (11.5 g, 0.30 mol) (Notes 7 and 8). The stirred solution is warmed to 80°C, and sodium borohydride is added at a rate sufficient to maintain a reaction temperature of 80-90°C (Note 9). Toward the end of the addition, an additional portion of dimethyl sulfoxide (200 mL) is added via syringe to lower the viscosity of the reaction mixture. After the addition is complete, the mixture is cooled in an ice-water bath, diluted with 100 mL of pentane, and cautiously quenched with 12 M hydrochloric acid until no further gas evolution occurs. The mixture is transferred to a separatory funnel and washed with three, 100-mL portions of 5% brine. The pentane extract is dried over calcium chloride and the solvent removed through a 15-cm Vigreux column. Further fractionation yields 41.5 g (72%) of 3-bromo-3,3-difluoropropyltrimethylsilane, bp 139-141 °C (Note 10). 

Copper(l) chloride Copper chloride (8,9) (7758-89-6) tert-Butyl alcohol (8) 2-Propanol, 2-methyl- (9) (75-65-0) (3-Bromo-3,3-difluoropropyl)trimethylsilane Silane, (3-bromo-3,3-difluoropropyl)-trimethyl- (12) (134134-62-6)... 

The diene is prepared by oxidative dimerization of the cuprate of (2-bromo-allyl)trimethylsilane (equation I). 

Dealkylation of phosphonates. Vigorous acid treatment is usually required for this reaction. To circumvent this difficulty, both bromo- and chloro-trimethylsilane have been used with limited success. lodotrimethylsilane is more selective the parent phosphonic acids can be obtained under very mild conditions without modification of a variety of other functional groups. However, monodealkylation is not practical with this reagent. Aryl esters are not cleaved hence selective dealkylation of alkyl aryl esters of phosphonic acids may be possible. 

I-Bromo-2.2-dichloro-l-trimelhylsilylcyclopropane A suspension of (I-bromovinyl)trimethylsilane (34.9 g, 0.195 mol) and sodium trichloroacetate (36.2 g, 0.195 mol) in DMH/2-methoxyethyl ether (10 1. 25 mL) was stirred under Nj at 80-90 C until CO, evolution ceased (ca. 10 h). The resulting dark solution was cooled to 25 C and diluted with pentane (100 mL) and H O (100 mL). After stirring for 0.5 h, the mixture was filtered through glass wool and the residue washed with pentane (200 mL). The aqueous phase from... 

Bromo-2-methylpropene 3-Bromo-2-methylpropene 2-(Bromomethyl)tetrahydrofuran (Bromomethyl)trimethylsilane... 

Several new methods for the reduction of sulphoxides to sulphides have appeared. Trifluoroacetic anhydride has been used in conjunction with dimethyl sulphide, hydrogen sulphide, " or sodium iodide. The silicon compounds bromo- and iodo-trimethylsilane, or the phenyltrimethylsilane-iodine combina-... 

Substrate for Cyclopropanation. Dichlorocar-bene adds to vinyltrimethylsilane, and the adduct is a source of 1-chlorocyclopropene, a reactive dienophile for Diels-Alder reactions. Dichlorocarbene also reacts with (l-bromovinyl)trimethylsilane to form (l-bromo-2-dichlorocyclopropyl)trimethylsilane. 8-Elimination in the presence of tetra-n-butylammonium fluoride gives l-bromo-2-chlorocyclopropene, another reactive dienophile (eq 7). 

Both (bromo- and (iodoethynyl)trimethylsilane undergo base-induced desilylation, followed by decomposition, when subjected to Cadiot-Chodkiewicz coupling conditions. Switching to the more stable (bromoethynyl)triethylsilane affords good yields of the terminal diynes after protodesilylation (eq 4). ... 

---