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The enantioselective aza‐Diels–Alder reaction is efficient for constructing chiral tetrahydropyridines, but the catalytic asymmetric aza‐Diels–Alder reaction of ketimines with unactivated dienes is still a challenging topic. Herein, guided by computational screening, a highly enantioselective aza‐Diels–Alder reaction of 2‐aryl‐3H‐indol‐3‐ones with unactivated dienes was realized by using a B(C6F5)3/chiral phosphoric acid catalyst system under mild conditions. The reaction has a broad scope with respect to both aza‐Diels–Alder reaction partners and hence offers rapid access to an array of tetrahydropyridine derivatives with pretty outcomes (up to 99 % yield, >20:1 dr and 98:2 er). The reaction is very efficient: lowering catalyst loadings for the model reaction to 0.1 mol %, enantioselectivity is still maintained. The synthetic utility was confirmed by transformations of the products. DFT calculations provide convincing evidence for the interpretation of stereoselection. [ABSTRACT FROM AUTHOR]

An efficient asymmetric allylation reaction of allylboronates with seven-membered cyclic imines, dibenzo[b,f][1,4]oxazepines, is described. The reaction, which is catalyzed by a Bi(OAc)3/CPA system, gives a range of chiral nitrogen-containing heterocycle structures in high yields and with good enantioselectivities. The conversion of these products to nitrogen-containing heterocycles is also demonstrated. [ABSTRACT FROM AUTHOR]

The enantioselective ketimine–ene reaction is one of the most challenging stereocontrolled reaction types in organic synthesis. In this work, catalytic enantioselective ketimine–ene reactions of 2‐aryl‐3H‐indol‐3‐ones with α‐methylstyrenes were achieved by utilizing a B(C6F5)3/chiral phosphoric acid (CPA) catalyst. These ketimine–ene reactions proceed well with low catalyst loading (B(C6F5)3/CPA=2 mol %/2 mol %) under mild conditions, providing rapid and facile access to a series of functionalized 2‐allyl‐indolin‐3‐ones with very good reactivity (up to 99 % yield) and excellent enantioselectivity (up to 99 % ee). Theoretical calculations reveal that enhancement of the acidity of the chiral phosphoric acid by B(C6F5)3 significantly reduces the activation free energy barrier. Furthermore, collective favorable hydrogen‐bonding interactions, especially the enhanced N−H⋅⋅⋅O hydrogen‐bonding interaction, differentiates the free energy of the transition states of CPA and B(C6F5)3/CPA, thereby inducing the improvement of stereoselectivity. [ABSTRACT FROM AUTHOR]

Herein, we disclosed an efficient protocol for the construction of chiral 3-allyl-3-hydroxyoxindoles via the enantioselective allylation reaction of isatins and allylboronates catalyzed by a simple binary acid Bi(OAc)3/CPA system under mild conditions. The synthetic utility of this strategy has been demonstrated through the formal synthesis of ent-CPC-1. [ABSTRACT FROM AUTHOR]

An asymmetric 1,6-conjugate addition of thioacetic acid with para-quinone methides has been developed by using chiral phosphoric acid catalysis in the presence of water. A series of sulfur-containing compounds were thus obtained in high yields with good to excellent enantioselectivities. Theoretical studies indicated that the water-bridged proton transfer is a potentially favorable reaction pathway. An unprecedented O−H⋅⋅⋅π interaction between water and the aromatic nucleus of chiral phosphoric acid was discovered to contribute significantly to the stereocontrol in the catalysis. [ABSTRACT FROM AUTHOR]

The article discusses a study on an asymmetric binary acid catalysis of hetero-Diels-Alder reaction of simple olefins with electron-deficient enones. It says that achieving a catalytic asymmetric version with simple olefins remains elusive despite the advances in Diels-Alder chemistry. It mentions the examination of Lewis acids and chiral phosphoric acids in the model reaction of styrene 2a with ketoester 3a.

A mechanistic study of the tert-aminocyclization reaction was performed by using DFT calculations and labeling experiments. The results showed that the reaction proceeded through a rate-limiting-, stereospecific-, and suprafacial 1,5-H-transfer pathway, followed by a barrier-less CC bond formation. The mode of stereocontrol for facial selection could be ruled out owing to the high activation energy of CN bond rotation. The intrinsic feature of this Lewis acid activation was found to be the activation of the LUMO, as well as an intermediate-stabilization effect. The catalytically active species was believed to be a 1:1 complex of phosphoric acid and MgCl2, which was stabilized by a H⋅⋅⋅Cl hydrogen bond. The chiral catalytic complex selectively recognizes and activates one of the two helical conformations of substrate A, required for 1,5-suprafacial H-transfer, which dictates the stereoselectivity of the forming products. [ABSTRACT FROM AUTHOR]

The addition of water is crucial for the stereocontrol of the title process providing sulfur containing products in high yields with moderate to high enantioselectivities. [ABSTRACT FROM AUTHOR]