Chiral Copper Catalyst Research Articles

Chiral bipyrindine and biquinoline ligands: Their asymmetric synthesis and application to the synthesis of trans-whisky lactone

Chiral bipyrindine and biquinoline which have been reported to be efficient ligands for the construction of chiral copper catalysts, were synthesized enantioselectively by using Mn-salen catalyzed asymmetric epoxidation as a key step. Enantioselective synthesis of trans-whisky lactone was then achieved by way of enantiospecific ring expansion reaction of oxetane with a chiral copper catalyst bearing the bipyrindine ligand as a chiral source.

ChemInform Abstract: Chemoselectivity and Stereoselectivity of Cyclization of α‐ Diazocarbonyls Leading to Oxygen and Sulfur Heterocycles Catalyzed by Chiral Rhodium and Copper Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chemoselectivity and stereoselectivity of cyclisation of α-diazocarbonyls leading to oxygen and sulfur heterocycles catalysed by chiral rhodium and copper catalysts

Good levels of enantioselectivity have been achieved in intramolecular C–H insertion reactions of α-diazocarbonyl compounds leading to six-membered oxygen heterocycles (chromanones) through the use of chiral rhodium(II) carboxylates as catalysts. Competition between C–H insertion and sigmatropic rearrangement, the latter leading to five-membered oxygen heterocycles (furanones), was observed with precursors containing a proximal O-allyl side chain. Whereas rhodium carboxylates produced C-H insertion products predominantly, a copper catalyst produced sigmatropic rearrangement products exclusively. A precursor with an S-allyl side chain exhibited cyclisation via sigmatropic rearrangement with both copper and rhodium catalysts.

Synthese optisch aktiver 2‐Siloxycyclopropancarbonsäureester durch asymmetrische Katalyse, II [1] . Einfluß der Silylenolether‐Struktur auf die enantioselektive Cyclopropanierung mit Diazoessigsäure‐methylester

Synthesis of Optically Active Siloxycyclopropanes by Asymmetric Catalysis, II[1]. – Influence of the Silyl Enol Ether Structure on the Enantioselective Cyclopropanation with Methyl Diazoacetate On the basis of reactions of (Z)-1-phenyl-1-(trimethylsiloxy)-1-propene (1a) with methyl diazoacetate (2) in the presence of different chiral (Schiff base) copper catalysts 4-Cu we extended our study to the silyl enol ethers 1b–1j. The highest enantiomeric excesses were obtained in most cases with catalyst 4b-Cu. Whereas cyclopropanations of 1-aryl- and 1-alkenyl-substituted silyl enol ethers 1b–1h gave moderate to good enantioselectivities (up to 80%ee), alkyl-substituted olefins 1i and 1j provided less satisfactory results. By deprotonation and alkylation of 3c, 3h, and 3i it could be established that for these cyclopropanes the predominating absolute configuration of cis- and trans-cyclopropanes is equal at C-1, but consequently opposite at C-2. The influence of the silyl enol ether structure on the enantioselectivities achieved is briefly discussed.

ChemInform Abstract: Copper(II) in Organic Synthesis. Part 10. The Importance of Steric Hindrance in the Design of Chiral Tridentate Ligand Copper(II) Catalysts for Enantioselective Michael Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselectively catalyzed intramolecular cyclopropanations of unsaturated diazo carbonyl compounds

A series of unsaturated α-diazo carbonyl compounds underwent enantioselective intramolecular cyclopropanation (ee = 4–77%) when treated with an enantiomerically pure chiral copper catalyst. The nature of the diazo substrate was critical: α-diazo ketones gave the best enantioselectivities whereas α-diazo β-keto ester systems showed diminished enantioselectivities.

ChemInform Abstract: Enantioselective Synthesis of Siloxycyclopropanes and of γ‐Oxocarboxylates by Asymmetric Catalysis.

AbstractThe cyclopropanation of the silyl enol ethers (III) with methyl diazoacetate (IV) is performed in the presence of the chiral copper catalyst (I) or (II), yielding the siloxycyclopropanes (V).

ChemInform Abstract: The Chemistry of Thujone. Part 12. The Synthesis of Pyrethroid Analogues via Chiral Cyclopropanation.

AbstractThe diene (II) obtained from thujone (I) is treated with ethyl or L‐menthyl diazoacetate (III) in the presence of various chiral and achiral copper catalysts to give cyclopropanes such as (IV) and (V).

The chemistry of thujone. XII. The synthesis of pyrethroid analogues via chiral cyclopropanation

An extensive study involving achiral and chiral cyclopropanation of various isoprenoid units derived from the monoterpene thujone is presented. Carbenoid intermediates generated from ethyl and L-menthyl diazoacetates and various achiral and chiral copper catalysts are employed to achieve the desired cyclopropanation reaction. It is shown that high levels of enantiomeric excess can be achieved, particularly when L-menthyl diazoacetate and a chiral catalyst are employed. The resultant products are then converted to pyrethroid-like analogues.