Dibromo methylmagnesium

To increase the stereoselectivity of the aldol reaction, successful reaction of dibromo-/3 -lactams with methylmagnesium bromide followed by addition of acetaldehyde has been studied (equation 10/ . 

Treatment of the mixture with methylmagnesium bromide regenerates the starting silole34. Reaction of two equivalents of bromine with 1,1-dimethyl-2,5-diphenylsilole led to tetrabromosilacyclopentane from which a double /J-elimination afforded (E,E)-1,4-dibromo-l,4-diphenylbutadiene (equation 48). 

Dibromo-3-dodecylthiophene (1.28 g, 3.12 mmol) is dissolved in 18 ml of dry THF. Methylmagnesium bromide (3.15 ml, 1.0 M solution in butyl ether) is added and the mixture is heated to reflux for 1 h. Ni(dppp)Cl2 (16.9 mg) is added and the solution is stirred at reflux for 2 h. The mixture is poured into 150 ml of methanol and filtered into a soxhlet thimble. Soxhlet extractions are performed with methanol (to remove monomer and salts), hexanes (to remove catalyst and oligomers), and chloroform. The chloroform fraction is reduced and dried in vacuo to afford 0.510 g (65% yield) of the title polymer as a violet film. 

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