Preparation and Structure Determination of Trimethylamine−Dibromocarboxyborane Esters

We have developed a new method for the preparation of esters of trimethylamine−dibromocarboxyborane (Me 3 N·BBr 2 COOR), 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 °C, for compounds 1 − 5 (R = Me, Et, n -Pr, CH 2 CH 2 Cl, CH 2 CF 3 ), 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 (∼99%). 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.