.eta.2 Cyclobutadienoid transition metal complexes. Generation and trapping of a cationic .eta.2-cyclobutadiene iron complex

Metal-Assisted Cycloaddition Reactions in Organotransition Metal Chemistry

“…(η 2 -Cyclobutadiene)Fp + has been inferred 529 as the reactive intermediate when (η 1 -3-chlorocyclobut-4enyl)(η 5 -cyclopentadienyl)dicarbonyliron ( 307) is treated with AgPF 6 . In the presence of cyclopentadiene and 1,3-diphenylisobenzofuran, it was trapped in the form of the respective Diels-Alder adducts 308 and 309 (eq 85).…”

Synthesis of Polyfunctional Aromatic Ring Systems (Phloroglucide Analogs) under Microwave Irradiation

“…Compounds 2l and 2m, e.g., are derived from eugenol (essential oil of clove [18]) and would be difficult to prepare by classical methods [19] in which the allyl moiety is altered. In the literature [19], electrophilic substitutions with eugenol are performed with a protected allyl group, which otherwise reacts with electrophiles, leading to loss of biological activity. Under −classical× conditions (HCl/MeOH solution), side reactions dominate, as shown in Scheme 3.…”