ChemInform Abstract: Chiral Sulfur-Containing 1,2-Disubstituted Ferrocenes

Enantiopure 1 -t- butylsulfinyl-2-subsituted ferrocenes were synthesized in reactions of (SR,1S,2R)-1-t-butylsulfinyl-2-lithioferrocene (11) with various electrophiles in good yields. (SR,1S,2R)-1-t-Butylsulfinyl-2-formylferrocene (19), prepared this way, underwent complete stereoselective addition reactions with Grignard reagents under chelation controlled conditions with titanium tetraisopropoxide. 1,4-Addition reactions of selected α,β-unsaturated esters with cuprate reagents gave mixtures of two diastereomers. The lack of stereoselectivity in these 1,4-addition reactions is due presumably to the remote reactive site (C-3′) and the flexibility of the side chain of the ester. A stereoselective cationic displacement reaction of (1S,2R,1′S)-1-(t-butylsulfonyl)-2-[α-(2-propenoyl)oxybenzyl]ferrocene (44) with 1-acetoxy-1,3-butadiene was found to produce (1S,2R,1′S)-1-(t-butylsulfonyl)-2-(5′-oxo-1′-phenyl-3′-pentenyl)ferrocene (45).