26597-09-1Relevant articles and documents
Enhanced diastereoselectivity via confinement: Diastereoselective photoisomerization of 2,3-diphenyl-1-benzoylcyclopropane derivatives within zeolites
Sivaguru,Sunoj, Raghavan B.,Wada, Takehiko,Origane, Yumi,Inoue, Yoshihisa,Ramamurthy
, p. 5528 - 5536 (2007/10/03)
Photochemistry of optically pure trans-2,3-diphenyl-1-benzoylcyclopropane has been examined in isotropic solution and within zeolites. Results suggest that it isomerizes by cleavage of either the C1-C2 or C1-C3
Catalytic cyclopropanation of electron deficient alkenes mediated by chiral and achiral sulfides: Scope and limitations in reactions involving phenyldiazomethane and ethyl diazoacetate
Aggarwal, Varinder K.,Smitha, Helen W.,Hynd, George,Jones, Ray V.H.,Fieldhouse, Robin,Spey, Sharon E.
, p. 3267 - 3276 (2007/10/03)
Phenyldiazomethane reacts with electron deficient alkenes in the presence of catalytic amounts of transition metal catalyst [Rh2(OAc)4 was better than Cu(acac)2] and catalytic amounts of sulfide to give cyclopropanes. Pentamethylene sulfide was found to be superior to tetrahydrothiophene and the optimum solvent was toluene. Under these optimised conditions a range of enones were cyclopropanated in high yields. Cyclic enones and acrylates were not successful in this process. The use of the chiral 1,3-oxathiane derived from camphorsulfonyl chloride in 2 steps in this process furnished cyclopropanes in good yield and very high enantiomeric excess (>97% ee). The absolute stereochemistry of cyclopropane 10 was proven by X-ray analysis and the origin of the stereochemical induction has been rationalised. Extension of this work to include diazoesters was partially successful. Again pentamethylene sulfide was found to be superior to tetrahydrothiophene, but this time both Rh2(OAc)4 and Cu(acac)2 were found to be equally effective. Enones, fumarates and unsaturated nitro compounds worked well but simple acrylates and unsaturated aldehydes were not effective substrates. Control experiments were conducted in which the stabilised ylide was isolated and reacted with the less successful substrates and, whilst unsaturated aldehydes still gave low yields, simple acrylates gave high yields of the corresponding cyclopropane. The use of the chiral 1,3-oxathiane was not successful with these more stable diazo compounds.
Cyclopropanation reactions of enones with lithiated sulfoximines: Application to the asymmetric synthesis of chiral cyclopropanes
Pyne, Stephen G.,Dong, Zemin,Skelton, Brian W.,White, Allan H.
, p. 2337 - 2343 (2007/10/03)
Stabilized lithiated sulfoximines 2 and 9 undergo highly diastereoselective Michael reactions with acyclic enones under kinetically controlled conditions. At rt the initially formed anionic Michael adducts undergo intramolecular displacement of the sulfonimidoyl group, with inversion of stereochemistry at the carbon bearing the nucleofuge, to give cyclopropanes. Lithiated sulfoximines derived from S-alkyl sulfoximines give mixtures of 1,2- and 1,4-adducts with enones mider kinetically controlled conditions. However, at rt the 1,2-adducts are in equilibrium with their corresponding 1,4-adducts. The 1,4-adducts are formed in a highly diastereoselective manner and are rapidly converted to diastereomerically pure cyclopropanes in good to excellent yields. Optically active versions of these sulfoximines give cyclopropanes in high enantiomeric purities.
Catalytic asymmetric cyclopropanation of electron deficient alkenes mediated by chiral sulfides
Aggarwal, Varinder K.,Smith, Helen W.,Jones, Ray V. H.,Fieldhouse, Robin
, p. 1785 - 1786 (2007/10/03)
Catalytic asymmetric cylopropanation of enones has been achieved using diazo compounds, catalytic quantities of a metal catalyst and a camphor-derived thioacetal; this sulfide shows exceptionally high levels of enantioselectivity.
Study on the reactions of telluronium ylide VIII. A facile synthesis of substituted cyclopropanes
Zhong,Shao,Liu
, p. 489 - 495 (2007/10/02)
Some telluronium salts react easily with substituted chalcones to afford derivatives of cyclopropane in 52-95% yield and with high stereoselectivity.
Generation of Diastereomeric Cyclopropanes from Benzylidenesulfuranes and Chalcones
Stahl, Ingfried,Schomburg, Sabine,Kalinowski, Hans Otto
, p. 2247 - 2260 (2007/10/02)
The reaction of the benzylidenesulfuranes 2, available by deprotonation of the benzylsulfonium bromides 1, with chalcones 3, which are substituted in the aroyl part, leads to the stereoisomeric cyclopropanes 4 and 5.The stereochemistry of 4 and 5 is elucidated by spectroscopy.A carbenic mechanism of formation of 4 and 5 is excluded experimentally.
