TaCl5-catalyzed reaction of 1-alkenes with n-alkyl Grignard reagents

► Unactivated alkenes react with n-alkyl Grignard reagents in the presence of TaCl5. ► [(2R′,3R)- and (2R,3R)-disubstituted]-n-butylmagnesiums are the final products. ► β,β′-Dialkyl substituted tantalacyclopentanes are proposed as key intermediates. ► Good to high product yields (up to 90%) are obtained in tetrahydrofuran.