Karl Anker Jørgensen

Catalytic Enantioselective Aza Diels–Alder Reactions of Imino Dienophiles

1 mol% of catalyst is sufficient: The hetero Diels-Alder reaction of α-imino esters 1 with activated conjugated dienes 2 (R=H, Me) needs only 1 mol% of a 2,2-bis(diarylphosphanyl)-1,1-binaphthyl (BINAP) copper(I) complex as the catalyst to generate the adducts 3 in good yields and with enantioselectivities up to 96%. The reaction can also be carried out on gram scale! Tos=H3 CC6 H4 SO2 ; TMS=Me3 Si.

Solvent Effects in Asymmetric Hetero Diels-Alder and Ene Reactions

Abstract The use of polar solvents such as nitromethane or 2-nitropropane leads to a significant improvement of the catalytic properties of a cationic copper-Lewis acid in the hetero Diels-Alder reaction of alkyl glyoxylates with dienes. The scope of a newly developed copper(II)-bisoxazoline catalyst for the hetero Diels-Alder reaction is demonstrated by the reaction of different dienes with alkyl glyoxylates in nitroalkane solvents with the formation of the hetero Diels-Alder adduct in high enantiomeric excess as the major product. The synthetic application of the reaction is exemplified by an improved synthesis of a highly interesting synthon for sesquiterpene lactones.

Development of an unusually highly enantioselective hetero-Diels-Alder reaction of benzaldehyde with activated dienes catalyzed by hypercoordinating chiral aluminum complexes

The effect of Lewis acid catalysis of the hetero-Diels-Alder reaction between benzaldehyde and activated dienes (e.g. the Danishefskys diene) has been investigated. In the present work we decided to study a series of chiral aluminum complexes as potential catalysts for the hetero-Diels-Alder reaction in order to gain a better understanding of the effect on the chiral induction of varying the steric and electronic environment of the metal ion. The results of this study prompted us to conclude that steric effects in the ligand coordination sphere and hypercoordination are strongly contributing factors to the optical yield of the reaction. Optimization of the reaction culminated in the synthesis of the hetero-Diels-Alder product in 99.4% ee and 97% yield of the isolated product. Based on the experimental results the mechanism for the hetero-Diels-Alder reaction is discussed and it is postulated that hypercoordination to the chiral aluminum Lewis acid center is of importance for the reaction.

Catalytic formation of aziridines from imines and diazoacetate

A catalytic method for the preparation of aziridines from imines and diazoacetate is developed using copper complexes as catalyst; the synthetic, diastereo- and enantio-selective scope of the reaction are presented.

The first highly diastereo- and enantioselective polymeric catalyst for the 1,3-cycloaddition reaction of nitrones with alkenes

A highly diastereo- and enantioselective 1,3-dipolar cycloaddition reaction of nitrones with alkenes catalyzed by chiral polybinaphthyl Lewis acids has been developed giving isoxazolidines with up to 99% ee; the chiral polymer ligand shows almost identical stereoselectivity to its monomeric version but has the advantage of easy recovery and reuse, and this work further demonstrates that a rigid and sterically regular polymer chain can be used to preserve the catalytic properties of monomeric catalysts.

Development and Application of Catalytic Highly Enantioselective Hetero-Diels-Alder Reactions of Aldehydes and Ketones

The hetero-Diels-Alder reaction of carbonyl compounds with conjugated dienes [eq (1)] constitutes one of the cornerstone reactions in organic chemistry.1 The products formed in this reaction are of fundamental importance in chemistry, and numerous examples of the use of these compounds in academia and industry have appeared.

On the Electronic Structure of Oxo-Metalloporphyrins and Mechanistic Aspects of Oxygen-Transfer Reactions

The chemical properties of metalloporphyrins and their use as catalysts in oxidations chemistry have received considerable attention in recent years [1,2]. These compounds are interesting because of the similarity to the oxidation enzymes [1,2]. In order to learn more about the structure and catalytic properties of these systems in nature, metalloporphyrins have served as model substrates [1,2]. Another aspect of the chemistry of metalloporphyrins is their applications in modern organic synthesis as catalyst for various selective reactions [2]. The catalytic properties of metalloporphyrins is related to the formation of a high-valent oxotransitionmetal porphyrin intermediate, 1, by reaction of a transition-metal porphyrin with a terminal oxidant, XO, (Scheme 1). The formed high-valent oxotransition-metal porphyrin intermediate, 1, is thus capable of transferring the oxygen atom to various organic substrates, SO (Scheme 1). It can also catalyze the oxidation of organic substrates by electron-transfer reactions [1–3].