The Coupling Reaction of Grignard Reagents with Unsaturated Sulfides Catalyzed by Nickel Complexes

Abstract

Aryl, 1-alkenyl and heterocyclic sulfides reacted with aryl and alkyl Grignard reagents in the presence of nickel complexes to afford the coupling products in high yields. Generally, the use of 3 mol% nickel complexes gave the best results (Table 1 and 2). T h e most effective catalysts were [NiCl₂(PPh₃)₂] [6] J for sterically hindered sulfides (run 21 in Table6) and aryl Grignard reagents and [NiCl₂(Ph₂PCH₂CH₂CH₂PPh₂)] [8] J for primary alkyl and simple aryl Grignard reagents (see Table 6). But, for secondary alkyl Grignard reagent s, this nickel catalyzed coupling reaction was impractical because of side reactions, reductive desulfurization and isomerization (run 3 and 4 in Table 6 and Fig.5). By the com petitive reaction with butylmagnesium bromide; the reactivity order C₆ > H₅I> C₆H₅SeCH₃ > C₆H₅Br > C₆H₅Cl > C₆H₅SCH₃ was observed (Table 5). The reaction me chanism and the scope and limitation of this coupling reaction are also discussed.