4729-30-0Relevant academic research and scientific papers
Intermolecular cyclopropanation versus CH insertion in Rh(II)-catalyzed carbenoid reactions
Müller, Paul,Tohill, Sarah
, p. 1725 - 1731 (2007/10/03)
The product ratio of intermolecular insertion and cyclopropanation in transition metal-catalyzed diazo decompositions depends strongly upon the metal, its ligands and upon the substituents of the diazo compound. Ethyl diazoacetate (2a) reacts with cyclohexene (1) almost exclusively by cyclopropanation. However, diazomalonate (2d) and methyl 2-diazophenylacetate (2e) in the presence of Rh(II) catalysts exhibit a marked tendency towards allylic CH insertion. With 1,4-cyclohexadiene (6), methyl 2- diazophenylacetate (2e) in the presence of chiral Rh(II) catalysts affords the allylic insertion product 7 in almost quantitative yield and with up to 74% ee. (C) 2000 Elsevier Science Ltd.
Concave reagents 32: Syn- and anti-selective cyclopropanation of alkenes with diazoacetates catalyzed by copper(I) complexes of concave 1,10- phenanthrolines
L?ffler, Frank,Hagen, Martin,Lüning, Ulrich
, p. 1826 - 1828 (2007/10/03)
Two classes of concave 1,10-phenanthroline ligands 1 and 2 have been used in the copper(I) catalyzed cyclopropanation of several acyclic and cyclic alkenes 3 with three diazoacetates 4-6. The bimacrocyclic 2,9-diaryl- 1,10-phenanthrolines 1 favor the anti(trans- or exo-) cyclopropanation with anti/syn-selectivities of up to > 99:1 (8g). In contrast, with the 1,10- phenanthroline bridged calix[6]arenes 2 as ligands a rarely observed syn- selective cyclopropanation was achieved. Methyl diazoacetate (6) showed the best syn-selectivities with anti/syn-ratios of up to 14:86 (9g).
Cyclopropanation of alkenes with ethyl diazoacetate: Copper(I) complexes of concave 1,10-phenanthrolines as diastereoselective catalysts
Hagen, Martin,Liining, Ulrich
, p. 231 - 234 (2007/10/03)
Concave 1,10-phenanthrolines 1a-c have been used as ligands in the copper(I)-catalyzed cyclopropanation of alkenes 2 with ethyl diazoacetate. The complexes proved to be efficient cyclopropanation catalysts and exhibited an enhanced diastereoselectivity, particularly in the reactions of cyclic alkenes 2b-d. The preferred formation of exo-cyclopropanes 3b-d can be explained by the concave shape of these catalysts. VCH Verlagsgcsellschaft mbH.
STERICALLY CROWDED CYCLOPROPANATION CATALYSTS. SYN-SELECTIVITY USING RHODIUM(III)PORPHYRINS
Callot, H. J.,Metz, F.,Piechocki, C.
, p. 2365 - 2369 (2007/10/02)
Rhodium(III)porphyrins catalyze the decomposition of ethyl diazoacetate and the transfer of ethoxycarbonylcarbene to alkenes to form cyclopropanes in moderate to high yields.When compared with other catalysts a large syn-selectivity was observed on reaction with cis-alkenes.This selectivity increased with the size of the substituents, and suggested a preferencial direction of approach of the alkene towards a rhodium-carbene complex.
