Pentadienylzirconium compounds: easily accessible new reagents for selective pentadienylation reactions

2,4-Pentadienylzirconium complexes are generated from 2,4- or 2,2′-pentadienyl ethers in turn. These compounds react in situ with aldehydes and ketones in a totally γ-regioselective manner and with predominant anti stereoselectivity to produce bis(homoallylic) alcohols in good yields. Iodocyclization of one of these alcohols represents regio- and stereocontrolled short entry to functionalized tetrahydrofurans.