Y-Halogenocarboxylic acid esters

A soln. of diazomethyl isopropyl ketone in tetrahydrofuran added with ice-cooling below ca. 15° to a stirred soln. of tri-n-hexylborane in the same solvent, stirring continued 1 hr. at ca. 25° when Ng-evolution is quantitative, cooled to ca. 0°, N-bromosuccinimide added at once under a Na-stream, stirred 15 min. at ca. 0°, cold 3 N NaOH-soln. added, and vigorously stirred for 15 min. 4-bromo-2-methyl-3-decanone. Y 63%. F. e., also synthesis of a-halogenocarboxylic acid esters, s. J. Hooz and J. N. Bridson, Can. J. Chem. 50, 2387 (1972) review of a-diazoketones cf. A. L. Fridman et al., Russ. Chem. Rev. 41, 371 (1972) (Eng. transL). 

A soln. of borane in tetrahydrofuran added dropwise to an ice-cooled mixture of cyclopentene and tetrahydrofuran, stirred 1 hr. at 25°, the resulting tricyclo-pentylborane soln. ice-cooled, /erf-butanol followed by ethyl bromoacetate added, then K-ferf-butoxide in ferf-butanol added during 10 min. ethyl cyclo-pentylacetate. Y 75-95%. F. e. s. H. C. Brown et al.. Am. Soc. 90, 818 (1968) a-halogenocarboxylic and dialkylacetic acid esters s. Am. Soc. 90, 1911. 

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