Organocuprate (1) reagents are now being widely used f o r highly s e l e c t i v e s u b s t i t u t i o n reactions' with a l k y l Y 2 alkenyl,' aryl,2 and acy13 h a l i d e s and with a,a'-dihaloketones. with 1,2-dihaloalkanes i s of i n t e r e s t because two main r e a c t i o n pathways may be expected: and (b) reductive elimination of halogen t o form alkenes.' W e r e p o r t here t h a t various types of 1,2-dibromides react with lithium d i a l k y lcuprate(1) reagents under exceedingly mild conditions t o give alkenes exclusively (Eq. 1 ) . Organocopper i n t e r a c t i o n (a) replacement of both halogens by organic groups Rtf2CuLi RCH=CHR' (Eq. 1) RqH-FHR' E t 2 0 ' B r Br 'gH5 ---'gH5 meso-la R = R' = --d , l -l b R = R' -CyClO-_l~ R = R' = (CH2)4 l e R = H, R ' = (CH ) CO CH --2 11 3 -." 2 8 2 3 Id R = H, R' = (CH ) CH 1 1,2-Dibromoalkanes ;a -,le r e a c t with f i v e mole equivs of f r e s h l y prepared lithium dimethyl-or di-1-butylcuprate(1) (concentration E. 0.25 M> i n d i e t h y l e t h e r u s u a l l y a t low temperature6 during 0.5 -3.0 h r t o a f f o r d t h e
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