Iron-Mediated C-C Bond Formation. Preparation of (Trimethylenemethane)iron Complexes via Reaction of Weak Carbon Nucleophiles with in Situ Generated Cross-Conjugated Pentadienyl Cations. Nucleophilic Attack on (Trimethylenemethane)iron Complexes with Carbanions

Article abstract of DOI:10.1021/jo00111a019

The reaction of (2-(acetoxymethylene)-1,3-butadiene)Fe(CO)3 (8) or ((acetoxymethylene)trimethylenemethane)Fe(CO)3 (9) with weak carbon nucleophiles in the presence of BF3*Et2O gives the corresponding substituted (trimethylenemethane)Fe(CO)3 complexes as the major product.Applicable nucleophiles include trialkylaluminums, allyltrimethylsilane, and 2-((trimethylsilyl)oxy)-1-propene.This reaction proceeds in a stereospecific fashion; reaction of 1 2 gives a single (trimethylenemethane)iron product.The reaction of (1,2-bis(acetoxymethylene)-1,3-butadiene)Fe(CO)3 (20) with allyltrimethylsilane gives a (TMM(Fe(CO)3 product in which two new C-C bonds have been formed in one reaction.Reaction of TMMFe(CO)3 (1a) and substituted derivatives with carbanions, followed by workup with trifluoroacetic acid, gives the corresponding methallylated product.Applicable nucleophiles include anions derived from diphenylmethane, ethyl isobutyrate, isobutylnitrile, and 2-phenyl-1,3-dithiane.Use of allyl bromide in place of trifluoroacetic acid gives 6-substituted 5-methylene-1-hexenes as products, the result of the three-component coupling.