The invention relates to new processes to prepare low odor dialkyl sulfides, the low odor dialkyl sulfides obtainable by these processes and to methods of using these low odor dialkyl sulfides. Moreover, the invention relates to a process to prepare dialkyl sulfide borane complexes of high purity, the dialkyl sulfide borane complexes obtainable by this process and to a process for enantioselective reductions employing these dialkyl sulfide borane complexes of high purity as reducing agent.