Alkyleisen‐und Alkylcobalt‐Reagenzien, VII. Über die Substitution des Halogens von Alkenylchloriden, Alkenylfluoriden und Alkinylhalogeniden durch Reagenzien des Typs R 4 MLi 2 (MFe, Co)

Alkyliron and Alkylcobalt Reagents, VII [1] . – On the Substitution of the Halogen of Alkenyl Chlorides, Alkenyl Fluorides, and Alkynyl Halides by Reagents of the Type R 4 MLi 2 (MFe, Co) Me 4 FeLi 2 and Me 4 CoLi 2 , which are favourable reagents for the substitution of Br in alkenyl bromides [1–4] , also proved to be favourable for the substitution of the halogen in alkenyl chlorides (yields 68–99%; nearly complete retention of configuration in the case of Me 4 FeLi 2 ), β1‐fluorostyrene (best yield 92%), and 1‐fluoronaphthalene (best yield 47%). Me 4 FeLi 2 differentiates between various alkenyl chlorides in 1:1 competition experiments better than Me 4 CoLi 2 and is the optimal reagent for the substitution of halogen in 1‐chloro‐2‐phenylethyne ( 12 ), 1‐bromo‐2‐phenylethyne ( 13 ), and 1‐chloro‐3‐phenoxypropyne ( 15 ) by methyl (yields 70, 46, and 80%, respectively). Substitution of the halogen in 12 by the n 1‐butyl, n 1‐octyl, and phenyl residue is better achieved by the catalytic systems RMgBr + 2.5 mol % FeCl 2 (R n Bu, n Oct, Ph; yields 75, 63, and 96%, respectively) than by the reagents n Bu 4 FeLi 2 , n Bu 4 Fe(MgBr) 2 , n Oct 4 Fe(MgBr) 2 , or Ph 4 Fe(MgBr) 2 (yields 18–28%).