Optically active β‐hydroxy sulfonamides and β‐hydroxy sulfones are very important building blocks for the preparation of bioactive compounds and pharmaceuticals. In this work, a highly efficient asymmetric hydrogenation of β‐keto sulfonamides and β‐keto sulfones has been developed using the phosphine‐free chiral ruthenium complex Ru(OTf)(TsDPEN)(η6‐p‐cymene) as the catalyst, to afford the corresponding β‐hydroxy sulfonamides and β‐hydroxy sulfones in high yields with excellent optical purities. In addition, a cascade asymmetric hydrogenation/dynamic kinetic resolution (DKR) of racemic cyclic β‐keto sulfonamides and β‐keto sulfones was also realized using the same catalyst, to give the corresponding chiral cyclic β‐hydroxy sulfonamides and β‐hydroxy sulfones in good yields with excellent enantio‐ and diastereoselectivities.magnified image

The tandem oxo-Michael-IED/HDA and oxo-Michael-IED/HDA-Michael-Aldol condensation transformations between (E)-2-hydroxyaryl-2-oxobut-3-enoate derivatives with enals have been developed in the presence of (S)-diphenylprolinol trimethylsilyl ether as an organocatalyst. Two types of tricyclic chroman derivatives were, respectively, obtained, by adjusting the reactant ratio and reaction temperature, in good yields (up to 96%) with excellent enantioselectivities (up to >99%) and good diastereoselectivities (up to >30/1). It should be noted that the divergent chiral chroman derivatives were obtained by successive reaction of (E)-2-hydroxyaryl-2-oxobut-3-enoate derivatives with two different enal substrates in highly catalytic results.

A formal thio [3 + 3]-cyclization catalyzed by a DPEN-derived chiral thiourea has been reported for the construction of optically active thiopyrano-indole annulated heterocyclic compounds in high yields with excellent enantioselectivities. The high reactivity between indoline-2-thione (keto-S) and 2-benzylidenemalononitrile has also been supported by density functional theory (DFT) calculations.

Thiourea-modified cinchona alkaloids as bifunctional catalysts and a base could catalyze a stepwise [5+1] cyclization of divinyl ketones with nitromethane via double Michael additions, furnishing optically active 4-nitro-cyclohexanones with good yields, excellent diastereoselectivities (>20 : 1) and high enantiomeric ratios (up to 97 : 3).

The regioselective and enantioselective Michael addition between azlactones and o-hydroxy chalcone derivatives is reported. Enantiomerically enriched N,O-aminals with two continuous stereogenic centers are exclusively obtained in moderate to good yields with excellent diastereoselectivities and good to excellent enantioselectivities. The experimental results show that an o-hydroxy group on the cinnamenyl motif of chalcone derivatives plays a crucial role at the reaction sites for the regioselective Michael addition. In addition, circular dichroism (CD) spectroscopy and density functional theory (DFT) are used to investigate the absolute configuration of N,O-aminals and the corresponding transition-state structures.