Preparation and Structure Determination of Trimethylamine−Dibromocarboxyborane Esters
摘要:
We have developed a new method for the preparation of esters of trimethylamine-dibromocarboxyborane (Me3N.BBr2COOR), from trimethylamine-carboxyborane, in a one-pot reaction. The reaction involves the treatment of trimethylamine-carboxyborane with 2.5 equiv of Br-2 in the appropriate alcohol for 4 h at 0 degreesC, for compounds 1-5 (R = Me, Et, n-Pr, CH2CH2Cl, CH2CF3), and 5 equiv of Br-2 for 8 h under the same conditions, for compounds 6-8 (R = n-Bu, i-Bu, i-Pe). Compounds 1-5 were obtained in high purity and in essentially quantitative yields (similar to99%). Compounds 6-8 were purified from traces of monobromo product and the alcohol by column chromatography. Molecular structures for the compounds 2, 6, and 7 were determined by X-ray crystallography.