cobalt-catalyzed hetero-biaryl couplingreaction between aryl chlorides and arylmagnesium halides with unprecedented selectivity has been developed. The protocol utilizes 1 mol% of cheap Co(acac)3 as pre-catalyst and effects clean reactions of deactivated chlorostyrenes with only 1.1 equiv. of the Grignard reagent under mild conditions (30 °C, 5–30 min). Highly chemoselective reactions were realized even in