Bisoxazolines nickel complex

Vinylogous Mukaiyama-Michael additions of 2-trimethylsilyloxyfuran to 3-alkenoyl-2-oxazolidinones to provide 7-butenolides were shown to be /7-selective. The reaction could be rendered enantioselective in the presence of a (T symmetric copper-bisoxazoline complex <1997T17015, 1997SL568> or a l,T-binaphthyl-2,2 -diamine-nickel(ii) complex as catalyst, as depicted in Equation (16) <2004CC1414>. 

Seidel et al. exploited the complex of Mg(OTf)2 and chiral bisoxazoline 50 to catalyze the cascade reaction of substrates 48 carrying a, P-unsaturated acyl oxazolidinone, which produced chiral tetrahydroquinolines 49 in good yields and high enantioselectivities (Scheme 18) [97]. The employment of nickel perchlorate in combination with ligand 50 also furnished 49 in good diastereo- and enantioselectivity. 

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