Ruthenium-Catalyzed Sequential Enyne Cross-Metathesis/ATRA Reactions

Sequential enyne cross-metathesis reactions of arylalkynes with ethylene followed by atom transfer radical addition (ATRA) with ethyl dichloroacetate or dichloroacetonitrile provide 1,5-dichloropent-2-ene derivatives. The second-generation Grubbs alkylidene complex [RuCl2(=CHPh)(PCy3)(NHC)] [NHC = 1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene] is used as the catalyst precursor for both reactions. Preliminary results show that the reaction products can be converted into vinylcyclopropanes by dechlorination with magnesium or manganese.