Zirconium-Catalyzed Mukaiyama Aldol Reactions

A cationic zirconocene complex, [Cp2Zr(0-r-Bu) THF](BPh4) has also been investigated and found to catalyze Mukaiyama aldol reactions [6]. The regioselectivity of the catalytic reaction was not as high as that of stoichiometric reactions. 

5 Ring-Opening Aldol-Type Reaction of 2,2-Dialkoxycyclopropane-carboxylic Ester [7] 

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Group 4 Titanium and Zirconium. The titanium tetrachloride mediated aldol reaction of silyl enol ethers with aldehydes was first reported in early of 1970s (16,17). It proceeds in a highly regioselective manner for cross or direct aldol reactions in high yields (18-20). Since the pioneer contribution by Mukaiyama s group, numerous synthetically useful procedures were developed in titanium- and zirconium-catalyzed aldol reaction of broad substrates (21-23). 

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