Zinc(II)-Catalyzed Asymmetric Diels-Alder Reaction of ( E)-1-Phenyl Dienes with β,γ-Unsaturated α-Ketoesters

Conversion of Phenols and Anilines to trans-Olefins via Oxidation, Wittig Olefination, and Stereoselective Olefin Isomerization

Development of metal-free conversion of naturally abundant phenols and anilines to the corresponding olefins remains a formidable challenge. The current state of the art relies on the TM-catalyzed Heck coupling of activated phenols (triflates, tosylates, and more) with the olefins. While these advancements are promising, the reaction suffers from branch vs linear selectivity and requires an expensive TM-ligand combination, hazardous organotin reagents, and very high reaction temperature. Herein, we reported a one-pot conversion of phenol and anilines to the corresponding E-olefins, which goes via oxidation, Wittig olefination, and stereoselective olefin isomerization.

Fe-BPsalan Complex-Catalyzed Asymmetric [4 + 2] Cycloaddition of Cyclopentadiene with α,β-Unsaturated Heterocycles

An efficient iron-catalyzed asymmetric [4 + 2] cycloaddition of cyclopentadiene with α,β-unsaturated acyl imidazoles or 2-cinnamoylisoindoline-1,3-dione derivatives was developed to afford the addition products in high yield and selectivity. Interestingly, the absolute structures of the addition products were controlled by the auxiliaries via different coordination modes with the same type of catalyst.

2,2'-Bipyridine-α,α'-trifluoromethyl-diol ligand: synthesis and application in the asymmetric Et2Zn alkylation of aldehydes

A chiral 2,2'-bipyridine ligand (1) bearing α,α'-trifluoromethyl-alcohols at 6,6'-positions was designed in five steps affording either the R,R or S,S enantiomer with excellent stereoselectivities, i.e. 97% de, >99% ee and >99.5% de, >99.5% ee, respectively. The key step for reaching high levels of stereoselectivity was demonstrated to be the resolution of the α-CF₃-alcohol using (S)-ibuprofen as the resolving agent. An initial application for the 2,2'-bipyridine-α,α'-CF₃-diol ligand was highlighted in the Zn^II-catalyzed asymmetric ethylation reaction of aromatic, heteroaromatic, and aliphatic aldehydes. Synergistic electron deficiency and steric hindrance properties of the newly developed ligand afforded the corresponding alcohols in good to excellent yields (up to 99%) and enantioselectivities (up to 95% ee). As observed from single crystal diffraction analysis, the complexation of the 2,2'-bipyridine-α,α'-CF₃-diol ligand generates an unusual hexacoordinated Zn^II.

Fe-BPsalan complex catalyzed highly enantioselective Diels–Alder reaction of alkylidene β-ketoesters

A practical Fe-BPsalan-catalyzed asymmetric Diels–Alder reaction of various alkylidene β-ketoesters and dienes was developed to afford estrone analogues in excellent yields, good to high diastereoselectivities and excellent enantioselectivities.

Chiral Hydroxytetraphenylene-Boron Complex Catalyzed Asymmetric Diels-Alder Cycloaddition of 2'-Hydroxychalcones

(S)-2,15-Cl₂-DHTP-boron complex catalyst for the asymmetric Diels-Alder cycloaddition of 2'-hydroxychalcones and dienes was developed and tested. The resulting cyclohexenes with three chiral centers were obtained in high yields (up to 98%) with excellent stereoselectivities (up to >20:1 endo/exo, >99% ee). This catalytic system features high efficiency, broad substrate scopes, and mild reaction conditions. In addition, a DFT study was performed to explain the stereochemical course of the asymmetric induction.