ALKENYLIRON COMPLEXES. CYCLOADDITION REACTIONS OF ORGANOIRON METALLOALKADIENES

Article abstract of DOI:10.1016/0022-328X(85)87473-8

The metalloalkadienes, 2-Fp-1,3-butadiene (5), 1-Fp-1,3-butadiene (6), and 1-Fp-3-methyl-1,3-butadiene (7) (Fp = η-C5H5(CO)2Fe) form Diels-Alder adducts with a variety of electrophilic dienophiles.Kinetic experiments have demostrated that 5 is at least 100 times more reactive toward dimethyl acetylene dicarboxylate than 2-trimethylsiloxy-1,3-butadiene. 5 and toluene sulfonyl isocyanate from an imino lactone that is thought to arise via a stepwise process involving ionic species.The synthetic utility of 5 is limited by its low decomposition point (110 deg C) and the formation of nearly equimolar quantities of the 1,3- and 1,4-positional isomers of cycloadducts derived from several asymmetric dienophiles.