Chirale Brønsted-Säuren in der katalytischen asymmetrischen Nazarov-Reaktion – die erste enantioselektive organokatalytische elektrocyclische Reaktion

De novo synthesis of inherently chiral heteracalix[4]aromatics from enantioselective macrocyclization enabled by chiral phosphoric acid-catalyzed intramolecular SNAr reaction

We report herein the synthesis of highly enantiopure inherently chiral N3,O-calix[2]arene[2]triazines from enantioselective macrocyclization enabled by chiral phosphoric acid-catalyzed intramolecular nucleophilic aromatic substitution reaction. In contrast to documented examples, the inherent chirality of the acquired compounds arises from one heteroatom difference in the linking positions of heteracalix[4](het)arenes.

Asymmetric Gold(I)-Catalyzed Tandem Hydroarylation-Nazarov Cyclization: Enantioselective Access to Cyclopentenones

The asymmetric synthesis of cyclopentachromenones from gold-catalyzed reaction of readily available skipped alkenynones is described. This cascade reaction involves an initial anti-Michael hydroarylation of the ynone moiety to form a gold-functionalized dialkenylketone intermediate, followed by a Nazarov cyclization that proceeds in an unprecedented enantioselective manner. Excellent enantiomeric ratios and chemical yields are obtained under mild reaction conditions.

Asymmetric Nazarov Cyclizations of Unactivated Dienones by Hydrogen-Bond-Donor/Lewis Acid Co-Catalyzed, Enantioselective Proton-Transfer

We report an enantioselective Nazarov cyclization catalyzed by chiral hydrogen-bond-donors in concert with silyl Lewis acids. The developed transformation provides access to tri-substituted cyclopentenones in high levels of enantioselectivity (up to 95% e.e.) from a variety of simple unactivated dienones. Kinetic and mechanistic studies are consistent with a reversible 4π-electrocyclization C-C bond-forming step followed by rate- and enantio-determining proton-transfer as the mode of catalysis.

Enantioselective Synthesis of Chiral Cyclopent-2-enones by Nickel-Catalyzed Desymmetrization of Malonate Esters

The enantioselective synthesis of highly functionalized chiral cyclopent‐2‐enones by the reaction of alkynyl malonate esters with arylboronic acids is described. These desymmetrizing arylative cyclizations are catalyzed by a chiral phosphinooxazoline/nickel complex, and cyclization is enabled by the reversible E/Z isomerization of alkenylnickel species. The general methodology is also applicable to the synthesis of 1,6‐dihydropyridin‐3(2H)‐ones.

Experimental and computational study of the catalytic asymmetric 4π-electrocyclization of N-heterocycles

The first asymmetric metal-catalyzed Nazarov cyclization of N-heterocycles has been developed. The use of a chiral catalyst allows the enantioselective electrocyclization of N-heterocycles under mild conditions and the corresponding products are obtained in good yields with excellent enantio- and diastereoselectivity. The reaction mechanism and the absolute configuration of the obtained products are explained by means of computational studies.