Enantioselective Intramolecular Cyclopropanations of Allylic and Homoallylic Diazoacetates and Diazoacetamides Using Chiral Dirhodium(II) Carboxamide Catalysts
作者:Michael P. Doyle、Richard E. Austin、A. Scott Bailey、Michael P. Dwyer、Alexey B. Dyatkin、Alexey V. Kalinin、Michelle M. Y. Kwan、Spiros Liras、Christopher J. Oalmann
DOI:10.1021/ja00126a016
日期:1995.5
counterparts, but allylicdiazoacetates are subject to greater variations in enantioselectivities with changes in substitution patterns on the carbon-carbon double bond. For example, the enantioselectivities in the intramolecularcyclopropanations of 3-allcyl/aryl-2(Z)-alken-l-y1 diazoacetates are generally 194%, whereas the cyclizations of the homologous 4-alkyl/aryl-3(Z)-alken1-yl diazoacetates are typically
Remarkably Stable Iron Porphyrins Bearing Nonheteroatom-Stabilized Carbene or (Alkoxycarbonyl)carbenes: Isolation, X-ray Crystal Structures, and Carbon Atom Transfer Reactions with Hydrocarbons
作者:Yan Li、Jie-Sheng Huang、Zhong-Yuan Zhou、Chi-Ming Che、Xiao-Zeng You
DOI:10.1021/ja020391c
日期:2002.11.1
spectrometry, and elemental analyses. X-raycrystalstructure determinations of 1.0.5C(6)H(6).0.5CH(2)Cl(2) and 4 reveal Fe=CPh(2) bond lengths of 1.767(3) (1) and 1.827(5) A (4), together with large ruffling distortions of the TPFPP macrocycle. Complexes 2 and 4 are reactive toward styrene, affording the corresponding cyclopropanes in 82 and 53% yields, respectively. Complex 1 is an active catalyst for both
α-Diazoacetates as Carbene Precursors: Metallosalen-Catalyzed Asymmetric Cyclopropanation
作者:Tsutomu Katsuki、Tatsuya Uchida
DOI:10.1055/s-2006-926448
日期:2006.5
Readily available α-diazo compounds have been shown to be efficient carbene precursors for asymmetric cyclopropanation using ruthenium(NO)-salen and cobalt-salen complexes, as catalysts. The stereoselectivity of the cyclopropanation depends on the metal ion, its valency, the structural and electronic nature of the salen ligand, and the apical ligand of the salen complex used. Both trans- and cis-selective asymmetric intermolecular cyclopropanation can be realized under mild conditions by using a suitable metallosalen complex. Furthermore, a wide range of alkenyl α-diazoacetates and the related alkenyl diazomethyl ketones undergo intramolecular cyclopropanation in a highly enantioselective manner by using various metallosalen complexes, easily prepared in a modular fashion, as catalyst.
Optically active Co(II)–salencomplexes (5 and 7) were found to catalyze highlyenantioselective intramolecular cyclopropanation of 2-alkenyl α-diazoacetates in the presence of N-methylimidazole under high substrate concentration.