Enantioselective Oxidative Cyclization Research Articles

Cobalt-Catalyzed Regio-, Diastereo- and Enantioselective Reductive Coupling of 1,3-Dienes and Aldehydes.

Catalytic regio-, diastereo- and enantioselective reductive coupling of 1,3-dienes and aldehydes through regio- and enantioselective oxidative cyclization followed by regio- and diastereoselective protonation promoted by a chiral phosphine-cobalt complex is presented. Such processes represent an unprecedented reaction pathway for cobalt catalysis that enable selective transformation of the more substituted alkene in 1,3-dienes, affording a broad scope of bishomoallylic alcohols without the need of pre-formation of stoichiometric amounts of sensitive organometallic reagents in up to 98% yield, >98:2 regioselectivity, >98:2 dr and 98:2 er. Application of this method to construction of axial stereogenicity and deuterated stereogenic center provided a wide range of multifunctional chiral building blocks that are otherwise difficult to access. DFT calculations revealed the origin of regio- and stereoselectivity as well as a unique oxidative cyclization mechanism for cobalt catalysis.

Stereoselective Oxidative Cyclization of N-Allyl Benzamides to Oxaz(ol)ines.

This study presents an enantioselective oxidative cyclization of N-allyl carboxamides via a chiral triazole-substituted iodoarene catalyst. The method allows the synthesis of highly enantioenriched oxazolines and oxazines, with yields of up to 94% and enantioselectivities of up to 98% ee. Quaternary stereocenters can be constructed and, besides N-allyl amides, the corresponding thioamides and imideamides are well tolerated as substrates, giving rise to a plethora of chiral 5-membered N-heterocycles. By applying a multitude of further functionalizations, we finally demonstrate the high value of the observed chiral heterocycles as strategic intermediates for the synthesis of other enantioenriched target structures.

Cover Feature: PdII/Novel Chiral Cinchona Alkaloid Oxazoline‐Catalyzed Enantioselective Oxidative Cyclization of Aromatic Alkenyl Amides (Eur. J. Org. Chem. 24/2019)

Cover Feature: Pd^II/Novel Chiral Cinchona Alkaloid Oxazoline‐Catalyzed Enantioselective Oxidative Cyclization of Aromatic Alkenyl Amides (Eur. J. Org. Chem. 24/2019)

PdII/Novel Chiral Cinchona Alkaloid Oxazoline‐Catalyzed Enantioselective Oxidative Cyclization of Aromatic Alkenyl Amides

A highly enantioselective PdII‐catalyzed aza‐Wacker oxidation tandem cyclization of aromatic nitrogen‐containing dienes has been achieved in the presence of novel chiral cinchona alkaloid oxazoline ligands for the first time, affording chiral dihydroindole nitrogen‐containing polycyclic compounds with good yields (up to 83 %), high diastereoselectivities (> 95:5 dr), and excellent enantioselectivities (up to 97 % ee).

Oxidative Cyclization of Naphtholic Sulfonamides Mediated by a Chiral Hypervalent Iodine Reagent: Asymmetric Synthesis versus Resolution

A chiral aryl iodide promotes the enantioselective oxidative cyclization of 1-naphtholic sulfonamides, albeit in moderate ee and low yield. The products tend to crystallize as conglomerates. Recrystallization thus increases their ee to > 99% ee. This highly enantioenriched material provides seed crystals for the resolution of the racemate (prepared in high yield by oxidative cyclization with (diacetoxyiodo)benzene in trifluoroacetic acid) by coupled preferential crystallization. This enables the production of significant quantities of highly enantioenriched products, despite the low efficiency of the enantioselective reaction.

Rhodium-Catalyzed Enantioselective Oxidative Cyclization

Rhodium-Catalyzed Enantioselective Oxidative Cyclization

Enantioselective Synthesis of (+)‐Mitomycin K by a Palladium‐Catalyzed Oxidative Tandem Cyclization

AbstractThe mitomycins, a family of bioactive natural products, feature a compact 6/5/5‐fused polycyclic ring structure densely decorated with highly reactive and/or fragile quinone, amino ketal, and aziridine as well as carbamate moieties. It is this striking feature that has defeated numerous synthetic attempts towards these apparently small molecules, rendering them one of the most formidable targets for total synthesis. We herein report the first enantioselective synthesis of (+)‐mitomycin K, a representative of G series mitomycins. The key step of this synthesis is an enantioselective oxidative cyclization catalyzed by a palladium/(+)‐sparteine system that had previously been developed by our group. The robustness of this method bodes well for further applications in the asymmetric total synthesis of natural products, particularly those with characteristic 6/5/5‐fused pyrroloindole skeletons.

Enantioselective Synthesis of (+)-Mitomycin K by a Palladium-Catalyzed Oxidative Tandem Cyclization.

The mitomycins, a family of bioactive natural products, feature a compact 6/5/5-fused polycyclic ring structure densely decorated with highly reactive and/or fragile quinone, amino ketal, and aziridine as well as carbamate moieties. It is this striking feature that has defeated numerous synthetic attempts towards these apparently small molecules, rendering them one of the most formidable targets for total synthesis. We herein report the first enantioselective synthesis of (+)-mitomycin K, a representative of G series mitomycins. The key step of this synthesis is an enantioselective oxidative cyclization catalyzed by a palladium/(+)-sparteine system that had previously been developed by our group. The robustness of this method bodes well for further applications in the asymmetric total synthesis of natural products, particularly those with characteristic 6/5/5-fused pyrroloindole skeletons.

Asymmetric Oxidative Cycloetherification of Naphtholic Alcohols.

The catalytic, enantioselective oxidative cyclization of naphthol-derived carboxylic acids mediated by chiral hypervalent iodine reagents has been studied extensively in the recent past, but analogous reactions of non-carboxylic substrates are yet unknown. This paper describes a catalytic, enantioselective, hypervalent iodine-promoted oxidative cycloetherification reaction of naphtholic alcohols. The new process relies on a variant of the Uyanik-Ishihara catalyst, in which the stereogenic centers have been relocated closer to the iodine atom. The new catalyst design affords optical yields comparable to those available with Uyanik-Ishihara iodides, but chemical yields are sensibly higher, at least with the tests substrates. An even more problematic reaction is the catalytic, enantioselective oxidative cyclization of naphtholic sulfonamides. In this case, the new catalyst affords significantly higher optical inductions than Uyanik-Ishihara iodides. The kinetic resolution of particular naphtholic alcohols is demonstrated. The absolute configuration of a numver of enantioenriched compounds obtained in this study was ascertained by X-ray diffractometry.

ChemInform Abstract: A Chiral Electrophilic Selenium Catalyst for Highly Enantioselective Oxidative Cyclization.

AbstractThe first transformation of β,γ‐unsaturated carboxylic acids to γ‐butenolides according to the title reaction is elaborated.

A Chiral Electrophilic Selenium Catalyst for Highly Enantioselective Oxidative Cyclization.

Chiral electrophilic selenium catalysts have been applied to catalytic asymmetric transformations of alkenes over the past two decades. However, highly enantioselective reactions with a broad substrate scope have not yet been developed. We report the first successful example of this reaction employing a catalyst based on a rigid indanol scaffold, which can be easily synthesized from a commercially available indanone. The reaction efficiently converts β,γ-unsaturated carboxylic acids into various enantioenriched γ-butenolides under mild conditions.

ChemInform Abstract: High‐Turnover Hypoiodite Catalysis for Asymmetric Synthesis of Tocopherols.

AbstractChiral ammonium hypoiodite salts are used to catalyze highly chemo‐ and enantioselective oxidative cyclization of γ‐(2‐hydroxyphenyl)ketones to 2‐acyl chromans bearing a quaternary stereocenter, which serve as productive synthetic intermediates for tocopherols.

Asymmetric Cyclization of 4-Alkenoic Acids via Oxidative Allylic C-H Esterification

In this paper, the Pd-catalyzed enantioselective oxidative cyclization of 4-alkenoic acids is reported. The methodology is based on the SPRIX ligand, which has already shown unique reactivity in Pd-mediated asymmetric oxidative reactions. A range of products was obtained with moderate to excellent yields and enantioselectivities up to 82% ee. The use of other nucleophiles emphasized the crucial role of the carboxy group for efficient outcome.

Novel Catalyst System for Enantioselective Oxidative Cyclization

Novel Catalyst System for Enantioselective Oxidative Cyclization

Palladium-catalysed addition of chiral nucleophiles to non-conjugated dienes: enantioselective oxidative cyclization of cis-1,2-divinylcyclohexane

Download options Please wait... Article information DOI https://doi.org/10.1039/C39880001516 Article type Paper Download Citation J. Chem. Soc., Chem. Commun., 1988, 1516-1519 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Palladium-catalysed addition of chiral nucleophiles to non-conjugated dienes: enantioselective oxidative cyclization of cis-1,2-divinylcyclohexane A. Heumann and C. Moberg, J. Chem. Soc., Chem. Commun., 1988, 1516 DOI: 10.1039/C39880001516 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Andreas Heumann Christina Moberg