CH H3C (9) B (10 MgB CHaCHo OMgBr Br (11)(H2CH (CH3)2CI Br(9) (10) (11) CH3 Br Br CH3 H3C C C O O O CH3 ― ―MgBr CH3 ― CH3CH2OMgBr NO2 (CH3 ) 2CH Br NO2 Br (CH3 ) 2 CH Br (B) (B) (B) (A) (A) (A) (C) (C)