Catalytic Intramolecular Cyclopropanation Research Articles

Tetrahydrothiophene‐Catalyzed Synthesis of Benzo[n.1.0] Bicycloalkanes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A Practical and Scaleable Synthesis of 1R,5S-Bicyclo[3.1.0]hexan-2-one: The Development of a Catalytic Lithium 2,2,6,6-Tetramethylpiperidide (LTMP) Mediated Intramolecular Cyclopropanation of (R)-1,2-Epoxyhex-5-ene

An efficient synthesis of 1R,5S-bicyclo[3.1.0]hexan-2-one from (R)-1,2-epoxyhex-5-ene is described. Development of a catalytic intramolecular cyclopropanation of (R)-1,2-epoxyhex-5-ene gives the key homochiral bicycle[3.1.0]hexan-1-ol, which is then oxidized to the desired ketone. This process has been successfully demonstrated on a multi-kilogram scale.

Tetrahydrothiophene-Catalyzed Synthesis of Benzo[n.1.0] Bicycloalkanes

A catalytic intramolecular cyclopropanation for the preparation of benzobicyclic compounds with [n.1.0] units has been developed. In the presence of 20 mol % of tetrahydrothiophene, the reactions of compounds 2a-2h afford versatile benzo[n.1.0]bicycloalkanes with excellent stereoselectivity in moderate to good isolated yields.

Enantioselective Catalytic Intramolecular Cyclopropanation Using Modified Cinchona Alkaloid Organocatalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform Abstract: Enantiocontrolled Macrocycle Formation by Catalytic Intramolecular Cyclopropanation.

ChemInform Abstract: Enantiocontrolled Macrocycle Formation by Catalytic Intramolecular Cyclopropanation.

Enantiocontrolled Macrocycle Formation by Catalytic Intramolecular Cyclopropanation

Stereoselectivity in intramolecular cyclopropanation reactions resulting in cyclopropane fusion with ten- and larger-membered rings has been examined using chiral copper(I) and dirhodium(II) catalysts. The influence of alkene structure and catalyst has been obtained using the 1,2-benzenedimethanol linker between the allylic double bond and diazoacetate. Control features in the addition reaction, especially those for diastereoselectivity and enantioselectivity, have been elucidated, and they are associated with the metal itself or its attendant ligands that influence the trajectory of the alkene to the carbene center. The influence of ring size, from five- to twenty-membered rings, on stereoselectivity has been determined with selected copper(I) and dirhodium(II) catalysts, and the changes in stereocontrol as a function of ring size can be understood as being due to a change in the olefin trajectory to the carbene center. Hydride abstraction from a benzylic position accompanies addition when dirhodium cata...

ChemInform Abstract: Macrocycle Formation by Catalytic Intramolecular Cyclopropanation. A New General Methodology for the Synthesis of Macrolides.

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.

Macrocycle Formation by Catalytic Intramolecular Cyclopropanation. A New General Methodology for the Synthesis of Macrolides

Catalytic intramolecular cyclopropanation by diazoacetates onto a remote carbon−carbon double bond resulting in the formation of 9- to 20-membered ring lactones is reported. When competition exists between proximal allylic and remote olefinic cyclopropanation, macrocyclization is favored by catalysts of increasing electrophilicity: Rh2(pfb)4 > Rh2(OAc)4, Cu(MeCN)4PF6 > Rh(cap)4, and Cu(acac)2. Terpene systems, cis-nerolidyl diazoacetate and related structures, malonic ester derivatives, and those with 1,2-benzenedimethanol, pentaerythritol, and cis-2-buten-1,4-diol linkers all undergo cyclopropanation onto the most remote carbon−carbon double bond in good yield. Generally, only one cyclopropane diastereoisomer is observed, but increasing ring size allows stereochemistries in macrocyclization reactions that resemble those of their intermolecular cyclopropanation counterparts. In one system (25) macrocyclic addition is accompanied by ylide formation/[2,3]-sigmatropic rearrangement resulting in the formation of a 10-membered ring lactone. Overall, few limits to macrocycle formation are evident, and the methodology appears to have general applicability.

Enantiocontrol in intramolecular cyclopropanation of diazoketones. Conformational control of metal carbene alignment

Diazo ketones with γ or δ double bonds undergo catalytic intramolecular cyclopropanation. These reactions occur with high enantiocontrol when catalyzed by copper semicorrins and bis-oxazolines, but low enantiocontrol characterizes reactions catalyzed by a broad selection of chiral dirhodium(ii) carboxamidates. The reverse stereocontrol occurs for intramolecular cyclopropanation of allylic and homoallytic diazoacetates and diazoacetamides. This divergence is explained by conformational control of carbonyl alignment (syn oranti to the metal) of the metal carbene intermediate.

ChemInform Abstract: Enhancement of Enantiocontrol/Diastereocontrol in Catalytic Intramolecular Cyclopropanation and Carbon‐Hydrogen Insertion Reactions of Diazoacetates with Rh2(4S‐MPPIM)4.

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.

Enhancement of enantiocontrol/diastereocontrol in catalytic intramolecular cyclopropanation and carbon-hydrogen insertion reactions of diazoacetates with Rh2(4S-MPPIM)4

Summary Dirhodium(II) tetrakis[methyl 1-(3-phenylpropanoyl)imidazolidin-2-one-4(S)-carboxylate], Rh 2 (4S-MPPIM) 4 , provides significant enhancement in enantiocontrol for intramolecular cyclopropanation reactions of allylic diazoacetates and optimal enantiocontrol/diastereocontrol for intramolecular C-H insertion reactions of secondary alkyl diazoacetates.

Enantioselective catalytic intramolecular cyclopropanation of allylic α-diazopropionates optimized with dirhodium(II) tetrakis[methyl 2-oxazolidinone-4(S or R)-carboxylate

Abstract High enantiocontrol, up to 85% ee, has been achieved in intramolecular cyclopropanation reactions of representative allylic α-diazopropionates with the catalytic uses of Rh 2 (4S-MEOX) 4 .