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leading to 4-fluorinated pyrazolones (II) and (IV) with moderate to good enantioselectivities

A highly efficient and practical one-pot sequential process, consisting of an organocatalytic enantioselective Friedel–Crafts-type addition of 4-nonsubstituted pyrazolones to isatin-derived N-Boc ketimines and a subsequent diastereoselective fluorination of the pyrazolone moiety, is developed. This reaction sequence delivers novel oxindole–pyrazolone adducts featuring vicinal tetrasubstituted stereocenters with a 0.5 mol % catalyst loading in high yield with excellent enantio- and diastereocontrol. Notably, chloro, bromo, and thioether functionalities can be readily incorporated, rendering a broad diversity of the product.

i-Pr-and t-Bu alkyl ketones are found to be competent reaction partners for easy trifluoromethyl ketone separation from the product mixtures.

A straightforward method for the asymmetric fluorination of 4-substituted isoxazolinones catalyzed by a bis-cinchona alkaloid catalyst was developed. A series of 4-fluoroisoxazolinone derivatives with a fluorine-containing quaternary stereocenter were obtained in good to high yields with good enantioselectivities (up to 91 % yield, 85 % ee).

Borane, generated in situ via reaction of NaBH4 with DMSO, is successfully applied to reduce prochiral ketones.

The Michael addition of 3-substituted oxindoles to nitroolefins was catalyzed by a novel tartrate-derived guanidine in high yield with excellent diastereo- and enantioselectivity. This method showed an extraordinarily broad substrate scope in terms of both reaction partners.

A novel library of chiral guanidines featuring a tartaric acid skeleton was developed from diethyl l-tartrate. These guanidines are easily accessed with tunable steric and electronic properties. The utilities of the guanidines were highlighted by their ability to catalyze the α-hydroxylation of β-ketoesters and β-diketones with remarkable efficiency and excellent enantioselectivity.

The Mo cluster efficiently promotes the reaction of dialkylanilines and indoles with allylic alcohols.

Poly-salen-Co(III) complexes were employed in the hydrolytic kinetic resolution (HKR) of terminal epoxides and ee's up to 98% were obtained. In the HKR of epichlorohydrin, the polymeric catalysts can be recovered and modified for recycling. The recovered polymer catalyst shows good activity and selectivity.

N-(α,β-Unsaturated acyl)-α-amino acids, amides and esters are structural motifs of many biologically active natural products. An alternate and advantageous approach for the synthesis of N-(α,β-unsaturated acyl)-α-amino acid derivatives is developed via acylation of unprotected α-amino acids with stable crystalline N-(α,β-unsaturated acyl)benzotriazole. The proposed methodology provides a new synthesis for compound (9) which is a precursor to a novel cytotoxic agent.

Polymeric salen-Ti(IV) complexes were employed in the enantioselective O -acetyl cyanation of aldehydes with KCN and Ac 2 O. The polymeric catalysts with appropriate crosslinking degree exhibited good activities and enantioselectivities, up to 94% yield and 91% ee were obtained at −20 °C with 1 mol % of catalyst (based on bimetallic catalytic unit). Moreover, the crosslinked polymeric catalyst could be easily recovered and reused for six consecutive runs without obvious decrease in activity and enantioselectivity.