A neutral bis(imidazolidine)pyridine (PyBidine)‐CoCl2 complex showed catalytic activity for the Michael reaction of malonates with nitroalkenes. The results indicated that a weak amine base aided enolate formation from the neutral complex, in which the N−H proton of the imidazolidine ligand played a significant role.magnified image
A PyBidine-Zn(OAc)2 complex catalyzed asymmetric chlorination of β-ketoesters. With assistance of NaHCO3, a newly developed N-pentafluorobenzyl-PyBidine (N-PFB-PyBidine)-Zn(OAc)2 catalyst promoted the reaction of α-benzyl-β-ketoesters with N-chlorosuccinimide (NCS) to give the chlorinated products with up to 82% ee. Results of a mechanistic study suggested that zinc-enolate of β-ketoesters was formed on the basic (N-PFB-PyBidine)-Zn(OAc)2 catalyst. The α-chlorinated-β-ketoester was successfully transformed into the chiral epoxide through sequential asymmetric chlorination/cyano-epoxidation in a one-pot synthesis.
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