A-Bromoisobutyryl bromide

A. Preparation of a-bromoisobutyryl bromide. To a mixture of 250 g. (2.85 moles) of isobutyric acid and 35 g. (1.13 moles) of red phosphorus in a 1-1. three-necked flask, fitted by ground-glass joints to a dropping funnel, mechanical stirrer, and reflux condenser, is added, dropwise with stirring, 880 g. (5.5 moles) of bromine. After the addition is complete, the solution is warmed to 100° over a period of 6 hours. The unreacted bromine and hydrogen bromide are removed under reduced pressure (30 mm.). The a-bromoisobutyryl bromide is decanted from the phosphorous acid and fractionated through a short helices-packed column. After a considerable fore-cut, the main fraction, 493-540 g. (75-83%), is collected at 91-98° (100 mm.). 

The preparation of ketenes has been discussed by Hanford and Sauer in Organic Reactions Dimethylketene has been prepared by the treatment of a-bromoisobutyryl bromide with zinc,3 and by the pyrolysis of isobutyrylphthalimide,4 dimethylmalonic anhydride,6 or a-carbomethoxy-a,j3-dimethyl- -butyrolactone. Dimethylketene dimer has been prepared by heating isobutyryl chloride with a tertiary amine. Pyrolysis of the dimer yields dimethylketene.7... 

Bromo-2-heptene, 38, 8 a-Bromoisobutyryl bromide, 33, 29 -Bromomandelic acid, 36,11 2-Bromo-3-methylbenzoic acid, 38,... 

Synthesis (Tull et al. (Merck Co.), 1975 1976) Friedel-Crafts reaction of fluorobenzene and a-bromoisobutyryl bromide gives 5-fluoro-2-methylindan-1-one, which is treated with 4-methylthiobenzylmagnesium chloride to yield 5-fluoro-2-methyl-1-(4-methylthiobenzyl)indene. Condensation with glyoxylic acid in the presence of N-benzyltrimethyl ammonium hydroxide (Triton B) gives 3-carboxy methylene-5-fluoro-2-methyl-1 -(4-methylthio-ben-zyl) indene, which is isomerized in acid to 5-fluoro-2-methyl-1-(4-methylthiobenzylidene)indene-3-acetic acid. Oxidation with hydrogen peroxide affords sulindac. 

Preparation, (a) From a-bromoisobutyryl bromide. The o-bromo acid bromide is added dropwise to a mixture of zinc turnings and ethyl acetate in a flask flushed with... 

Considering the activity data of the different ATRP initiators presented in Fig. 3.4, using -hydroxylethyl a-bromoisobutyrate (HEBIB) as bifunctional initiator seemed reasonable and was synthesized according to White et al. [45]. Briefly, anhydrous ethylene glycol (90 ml, 1.6 mol) was cooled to 0 °C in a flame-dried two-neck round bottom flask. a-Bromoisobutyryl bromide (8 ml, 0.06 mol) was slowly added with an addition funnel to the stirring ethylene glycol. The reaction solution was stirred at 0 °C for three hours. Thereafter, the reaction was quenched with 40 ml of deionized water and extracted with chloroform (3 x 40 ml). The chloroform/product mixture... 

Very recently, pentaalkylcorannulene derivatives were used as initiators to generate corannulene-core polymers by expansion of live pendant groups (Scheme 14) [97]. The first initiator 45-PrOH was prepared by the Fe-catalyzed Kumada coupling of 46 with (3-((triisopropylsilyl)oxy)propyl)magnesium bromide, as presented in Scheme 13, and subsequent desilylation. The second initiator 45-PrE was obtained by the reaction of 45-PrOH with a-bromoisobutyryl bromide. 

Na added in small pieces to ethyl benzoylacetate, stirred 2 hrs. at 60-70° until a soln. results, a-bromoisobutyryl bromide added with stirring below 10°, stirring continued 6 hrs. at room temp, and 24 hrs. at 50° ethyl 2,3-dihydro-2,2-di-methyl-3-oxo-5-phenylfuran-4-carboxylate. Y 36%. F. e. s. A. Takeda, S. Tsuboi, and T. Sakai, Chem. Lett. 1973, 425. 

The general procedure was outlined as follows. 6.5 g compound (TV) (21.1 nunol) and 2.6 g TEA (25.3 mmol) were dissolved in 150 mL of DCM. 11.6 g a-bromoisobutyryl bromide (50.6 mmol) dissolved in 50 mL of DCM was added into the reaction mixture under nitrogen flow at 0 °C within 0.5 h. The mixture was stirred overnight. After filtration, the mixture was diluted with 100 mL of DCM and extracted with 50 mL of saturated sodium bicarbonate aqueous solution. The organic phase was dried with anhydrous sodium sulfate. After removing the solvent by evaporation, the ande product was purified by column chromatography to give a dark-yellow oil 9.0 g (71 %). 

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