575456-74-5Relevant academic research and scientific papers
Rhodium(II)-catalyzed inter- and intramolecular cyclopropanations with diazo compounds and phenyliodonium ylides: Synthesis and chiral analysis
Ghanem, Ashraf,Lacrampe, Fabienne,Schurig, Volker
, p. 216 - 239 (2007/10/03)
Different classes of cyclopropanes derived from Meldrum's acid (=2,2-dimethyl-1,3-dioxane-4,6-dione; 4), dimethyl malonate (5), 2-diazo-3-(silyloxy)but-3-enoate 16, 2-diazo-3,3,3-trifluoropropanoate 18, diazo(triethylsilyl)acetate 24a, and diazo(dimethylphenylsilyl)acetate 24b were prepared via dirhodium(II)-catalyzed intermolecular cyclopropanation of a set of olefins 3 (Schemes 1 and 4-6). The reactions proceeded with either diazo-free phenyliodonium ylides or diazo compounds affording the desired cyclopropane derivatives in either racemic or enantiomer-enriched forms. The intramolecular cyclopropanation, of allyl diazo(triethylsilyl)acetates 28, 30, and 33 were carried out in the presence of the chiral dirhodium(II) catalyst [Rh 2{(S)-nttl)4}] (9) in toluene to afford the corresponding cyclopropane derivatives 29, 31 and 34 with up to 37% ee (Scheme 7). An efficient enantioselective chiral separation method based on enantioselective GC and HPLC was developed. The method provides information about the chemical yields of the cyclopropane derivatives, enantioselectivity, substrate specifity, and catalytic activity of the chiral catalysts used in the inter- and intramolecular cyclopropanation reactions and avoids time-consuming workup procedures.
Diazo compounds and phenyliodonium ylides in inter- and intramolecular cyclopropanations catalyzed by dirhodium(II). Synthesis and chiral resolution by GC versus HPLC
Ghanem, Ashraf,Lacrampe, Fabienne,Aboul-Enein, Hassan Y.,Schurig, Volker
, p. 1205 - 1219 (2007/10/03)
The dirhodium(II)-catalyzed intermolecular cyclopropanation of a set of olefins with either diazo free phenyliodonium ylides or diazo compounds afforded cyclopropanes derived from Meldrum's acid, dimethyl malonate, (silanoxyvinyl)diazoacetates, 3,3,3-trifluoro-2-diazopropionate, ethyl diazo(triethyl)- and (dimethylphenyl)silylacetate with moderate to high yield in either racemic or enantio-enriched forms. The intramolecular cyclopropanation of triethylsilyl-substituted allyl diazo-acetates in the presence of the chiral rhodium(II) catalyst [Rh2(s-nttl)4] in toluene afforded the corresponding cyclopropanes with up to 37% ee. An efficient chiral separation method based on enantioselective GC and HPLC was developed. The method provides information about the chemical yields of the cyclopropane products, enantioselectivity, substrate specifity, and catalytic activity of the chiral catalysts used in the inter- and intramolecular cyclopropanation reactions and avoids time-consuming work-up procedures. Springer-Verlag 2005.
Asymmetric Cyclopropanation of Olefins with an in situ Generated Phenyliodonium Ylide
Müller, Paul,Ghanem, Ashraf
, p. 1830 - 1833 (2007/10/03)
A procedure for the in situ generation of the phenyliodonium ylide (2) derived from Meldrum's acid (1) and its Rh(II)-catalyzed decomposition to afford an intermediate metallocarbene is described. In the presence of olefins, cyclopropanes are formed with yields and enantioselectivity comparable to that resulting from cyclopropanation with the isolated ylide 2.
Rhodium(II)-catalyzed olefin cyclopropanation with the phenyliodonium ylide derived from Meldrum's acid
Mueller, Paul,Allenbach, Yves,Robert, Estelle
, p. 779 - 785 (2007/10/03)
The phenyliodonium ylide 3a derived from Meldrum's acid reacts with olefins in the presence of Rh(II) carboxylate catalysts to afford cyclopropanes. The reaction is stereospecific. Enantioselectivities of up to 63% have been observed for the cyclopropanation of pent-1-ene. No 1,3-cycloadducts are formed between 3a and polarized olefins such as furan or 2,3-dihydrofuran.
