BF3-CENTER-DOT-ET(2)O-PROMOTED ALLYLATION REACTIONS OF ALLYL(CYCLOPENTADIENYL) IRON(II) DICARBONYL COMPLEXES WITH CARBONYL-COMPOUNDS

The Lewis-acid-promoted reaction of allyl(cyclopentadienyl)iron dicarb onyl complexes with aldehydes, ketones, imines, and acetals has been i nvestigated. These additions take place under mild conditions using BF 3 . Et(2)O to afford zwitterionic iron-alkene pi-complexes as isolable yellow precipitates. The structures of the pi-adducts derived from al dehydes have been characterized fully by proton, carbon, and fluorine NMR spectroscopy, infrared spectroscopy, and fast atom bombardment (FA B) mass spectrometry. Treatment of these iron-olefin salts with CH3CN or NaI in acetone gives the demetalated homoallylic alcohols, amines, or ethers, respectively. The additions of S-substituted allyliron comp lexes to aldehydes favor the formation of the 1,2-syn adduct regardles s of the E or Z geometry of the starting reagent. Thus, the diastereof acial selectivity for these allylations is analogous to that of other allylmetal reagents (allylsilanes, allylstannanes) whose additions hav e been postulated to proceed through an open (extended) transition sta te.