ALKYLIRON AND ALKYLCOBALT REAGENTS .7. ON THE SUBSTITUTION OF THE HALOGEN OF ALKENYL CHLORIDES, ALKENYL FLUORIDES, AND ALKYNYL HALIDES BY REAGENTS OF THE TYPE R4MLI2 (M = FE, CO)

Me4FeLi2 and Me4CoLi2, which are favourable reagents for the substitut ion of Br in alkenyl bromides [1-4], also proved to be favourable for the substitution of the halogen in alkenyl chlorides (yields 68-99%; n early complete retention of configuration in the case of Me4FeLi2), be ta-fluorostyrene (best yield 92%), and 1-fluoronaphthalene (best yield 47%). Me4FeLi2 differentiates between various alkenyl chlorides in 1: 1 competition experiments better than Me4CoLi2 and is the optimal reag ent for the substitution of halogen in 1-chloro-2-phenylethyne (12), 1 -bromo-2-phenylethyne (13), and 1-chloro-3-phenoxypropyne (15) by meth yl (yields 70, 46, and 80%, respectively). Substitution of the halogen in 12 by the n-butyl, n-octyl, and phenyl residue is better achieved by the catalytic systems RMgBr + 2.5 mol % FeCl2 (R = nBu, nOct, Ph; y ields 75, 63, and 96%, respectively) than by the reagents nBu4FeLi2, n Bu4Fe(MgBr)2, nOCt4Fe(MgBr)2, or Ph4Fe(MgBr)2 (yields 18-28%).