Trimethylsilylallyl bromide

With a catalytic amount of diisobutyi telluride method B. Chalcone (0.5 mmol), cesium carbonate (1.0 mmol), ( )-3-bromo-l-trimethylsilylprop-l-ene (0.75 mmol), diisobutyi telluride (0.1 mmol), THF (5 cm ) and water (5 mm ) were mixed in a reaction tube and stirred at 50°C for a specific period of time. After 28 h, additional trimethylsilylallyl bromide (0.25 mmol) was added and stirring continued for 20 h. When the reaction was complete (monitored by TLC), work-up as for method A and flash chromatography of the residue on silica gel afforded the product, of purity >98% (GC). 

Sulfide 2a was later employed by Tang and coworkers in the reaction of 4-chlorobenzaldehyde with 3-trimethylsilylallyl bromide for the synthesis of viny-loxiranes. In the presence of 20mol% of 2a, the trans vinyl epoxide was obtained as the major diastereoisomer in 40% yield and 37% ee (21). Higher concentrations of both aldehyde and aUyhc bromide were found to be beneficial to the yields, because the high concentration of aUyhc bromide favors the formation of the sulfonium salt and the high concentration of aldehyde could probably allow capture of the sulfur ylide before the [2,3]-sigmatropic rearrangement (Scheme 20.6). This reaction with thiolane (THT) as a catalyst could also be carried out without solvent, but the yield was lower than that in t-BuOH. 

Huang and co-workers reported the catalytic cyclopropanation of a series of p-aryl enones with an excess of trimethylsilylallyl bromide using j-Bu Te (237) as catalyst (20 mol%) in the presence of sohd Cs COj (2 equiv.) in THF/trace H O at 50°C. The proposed mechanism is shown in Scheme 7.36 [164]. In this reaction, high yields and excellent diastereoselectivities were achieved (Table 7.17). 

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See also in sourсe #XX -- [ ]

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