- Gold-catalyzed ethylene cyclopropanation
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Ethylene can be directly converted into ethyl 1-cyclopropylcarboxylate upon reaction with ethyl diazoacetate (N2CHCO2Et, EDA) in the presence of catalytic amounts of IPrAuCl/NaBArF4 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene; BArF4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate).
- Rull, Silvia G.,Olmos, Andrea,Pérez, Pedro J.
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- Polyoxometalates: Powerful catalysts for atom-efficient cyclopropanations
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The polyoxometalate-based catalytic cyclopropanation of olefins by ethyl diazoacetate (EDA) is reported. The outstanding catalyst productivity (TONs up to 100,000) and the use of equimolar EDA/olefin ratio confer to the methodology a high sustainability. Preliminary mechanistic investigations are also discussed.
- Boldini, Irene,Guillemot, Geoffroy,Caselli, Alessandro,Proust, Anna,Gallo, Emma
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supporting information; experimental part
p. 2365 - 2370
(2010/12/25)
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- Cobalt-catalyzed asymmetric cyclopropanation of electron-deficient olefins
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The cobalt(II) complex of a D2-symmetric chiral porphyrin [Co(1)] is an effective catalyst for asymmetric cyclopropanation of electron-deficient olefins, including α,β-unsaturated esters, amides, ketones, and nitriles. Due to the absence of dimerization of diazo compounds, the catalytic reactions can be performed in one-pot protocol using olefins as the limiting reagent, forming the desired electrophilic cyclopropane derivatives in high yields and selectivities under mild conditions. In most cases, both excellent diastereo- and enantioselectivity were achieved. Copyright
- Chen, Ying,Ruppel, Joshua V.,Zhang, X. Peter
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p. 12074 - 12075
(2008/03/27)
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- 2-(Tosylamino)benzyltrimethylammonium halides as precursors of 2-substituted indoles
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The reactions of 2-(tosylamino)benzyltrimethylammonium halides (1) with dimethylsulfonium 2-oxo-2-phenylethylide (6b), dimethylsulfonium 2-ethoxy-2-oxo-ethylide (6c) and dimethylsulfonium cyanomethylide (6d) are useful synthetic routes to 2-substituted indoles (8b-d). The relationship between reaction conditions and selectivity is discussed.
- Croce, Piero Dalla,Ferraccioli, Raffaella,La Rosa, Concetta
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p. 2397 - 2407
(2007/10/03)
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- Reactions of Hexaphenylcarbodiphosphorane, IV. Reactions of Hexaphenylcarbodiphosphorane with Halogen Compounds. Diphosphaallyl Cations
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Hexaphenylcarbodiphosphorane (1) undergoes nucleophilic displacement reaction with halogen compounds 3 with formation of compounds 5 which can be regarded as salts of the diphosphaallylcation. 1 reacts with bromoacetic ester 11 as base, with proton abstraction and formation of a carbanion 12 which gives rise to formation of (E)-cyclopropantricarboxylicacid ester (13).In an analogous way, 1 attacks isothiocyanatoaceticacid ester (14) with formation of an ionpair 15 which undergoes a cycloaddition with a second molecule 14 forming 16, which can be converted into the mercaptothiazol derivative 17 by treatment with HCl. - Key words: Hexaphenylcarbodiphosphorane Diphosphaallyl Cations, 13C NMR Spectra
- Bestmann, Hans Juergen,Oechsner, Helmut
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p. 861 - 865
(2007/10/02)
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