Total synthesis of prostaglandin F2alpha using nickel-catalyzed stereoselective cyclization of 1,3-diene and tethered aldehyde via transmetalation of nickelacycle with diisobutylaluminum acetylacetonate

Total synthesis of prostaglandin F2alpha utilizing a nickel(0)-catalyzed cyclization of 1,3-diene and tethered aldehyde was achieved. The cyclization proceeded via a transmetalation of nickelacycle with diisobutylaluminum acetylacetonate (iBu2-ALAC). Thus, the reaction of 19, having a side chain corresponding to the alpha-chain in PGF2alpha with Ni(cod)2 (10 mol %), PPh3 (20 mol %), and 1,3-cyclohexadiene (25 mol %) in the presence of iBu2-ALAC (1.5 eq) proceeded stereoselectively to give the cyclized product 26 in 54% yield. During the cyclization of 19, the Z-olefin at C-5 in the side chain completely retained its geometry, and the four contiguous chiral carbon centers in PGF2alpha were stereoselectively constructed. Transformation of the key intermediate 19 into PGF2alpha was successfully achieved.