Cyclopropanation Of Styrene Research Articles

ChemInform Abstract: Olefin Cyclopropanation with Aryl Diazocompounds upon Catalysis by a Dirhodium(II) Complex.

AbstractIn contrast to previously reported dirhodium(II) catalysts, the title complex allows the cyclopropanation of styrenes.

Chiral monooxazolines as modular copper(I)-heterocomplex building blocks: investigations on the catalytic asymmetric cyclopropanation of alkenes

Novel chiral monodentate oxazoline ligands have been synthesized in good yields. The catalytic activity of these monodentate oxazoline/Cu catalysts was evaluated in the catalytic asymmetric cyclopropanation of styrene and α-methylstyrene, giving moderate to good enantioselectivities (up to 74% ee for the trans-cyclopropane product) and full conversions (up to 100%). In an attempt to enhance the enantioselectivities of the cyclopropanations, heterocombinations of these ligands were used. Unfortunately, with the data set that was used in this study, no improvements were observed. However, to gain an insight into the nature of the active catalyst present under these circumstances, NMR, mass spectrometric and computational studies were carried out and indicated the presence of bidentate heterocomplexes in the equilibrium mixture. Analysis of the stereoselectivities (ees and des) did not prove very useful in pin-pointing the identity of the active chiral catalyst and only afforded a very weak conclusion. In order to ascertain the importance of the π–π interactions, the monodentate oxazoline ligands 3a and 3b were synthesized and screened in these reactions, and the resulting stereoselectivities were compared to the results obtained using ligands 1a and 1b. There seemed to be very weak π–π interactions at work.

ChemInform Abstract: Cobalt Carbaporphyrin‐Catalyzed Cyclopropanation.

AbstractCobalt carbaporphyrinoids catalyze the cyclopropanation of styrene with a higher trans‐selectivity than the corresponding porphyrin and phthalocyanine complexes.

Enantioselective synthesis of tranylcypromine analogues as lysine demethylase (LSD1) inhibitors

Asymmetric cyclopropanation of styrenes by tert-butyl diazoacetate followed by ester hydrolysis and Curtius rearrangement gave a series of tranylcypromine analogues as single enantiomers. The o,- m- and p-bromo analogues were all more active than tranylcypromine in a LSD1 enzyme assay. The m- and p-bromo analogues were micromolar growth inhibitors of the LNCaP prostate cancer cell line as were the corresponding biphenyl analogues prepared from the bromide by Suzuki crosscoupling.

Recyclable mesoporous silica-supported chiral ruthenium-(NHC)NN-pincer catalysts for asymmetric reactions

New stable chiral [RuHClCO((NHC)NN)] and [RuCl2(p-cymene)((NHC)NN)] pincer complexes with a pendant silyloxy group ((NHC)NN: (S)-1-((6-((3-aryl-2,3-dihydro-1H-imidazol-1-yl)methyl)pyridin-2-yl)methyl); R-N-(3-(triethoxysilyl)propyl)pyrrolidine-2-carboxamide, aryl = mesityl, 2,6-diisopropylphenyl; R = Me, Ph) were synthesized and grafted onto a mesoporous silica MCM-41 through the siloxane linkage, and the resulting supported ruthenium catalysts were highly active and recyclable catalysts for the asymmetric hydrogenation of alkenes and cyclopropanation of styrenes. The solid catalysts were characterized with a variety of methods including solid state cross-polarization magic-angle spinning (CP MAS) 13C NMR, FT-IR, and elemental analysis. Excellent activity and enantioselectivity was observed for these supported Ru-catalysts owing to readily accessible and uniform catalytic sites within the large channels of MCM-41 and short diffusion lengths for the organic compounds. The high accessibility introduced by the structure of the support allows the preparation of highly efficient immobilized catalysts which can duplicate the activity of the homogeneous analogues. No deactivation of the catalysts was observed after repeated recycling.

Cobalt carbaporphyrin-catalyzed cyclopropanation

Cobalt complexes of N-confused porphyrins and benziphthalocyanine, which both feature organometallic bonds at the macrocycle cores, catalyze the cyclopropanation of styrene with a higher trans-selectivity than the corresponding porphyrin and phthalocyanine complexes.

Cu(i) catalysed cyclopropanation with enantiopure scorpionate type ligands derived from (+)-camphor or (−)-menthone

One-pot syntheses of three new enantiopure heteroscorpionate ligands derived from (+)-camphor or (-)-menthone are described. The ligands are obtained by reacting pyrazoles derived from (+)-camphor or (-)-menthone with sodium hydride and thionyl chloride. Subsequent reactions with pyridine and various aldehydes afford the tripod ligands in multi-gram amounts. Especially the menthopyrazole based ligand 6 showed encouraging ee values up to 69% in the Cu(I) catalysed enantioselective cyclopropanation of styrene with ethyl diazoacetate.

CuI complexes containing a multidentate and conformationally flexible dibenzylidene acetone ligand (dbathiophos): Application in catalytic alkene cyclopropanation

The synthesis and characterisation of a multidentate conformationally flexible ligand based on the dibenzylidene acetone core structure, dbathiophos (1), is described. Ligand 1 has a high affinity for cationic and neutral Cu(I) species. Three unique Cu(I) complexes (4-6) are reported showing that the ligand backbone of dbathiophos is hemilabile, and able to adopt different 1,4-dien-3-one conformational geometries around Cu(I). Complexes 4 and 6 both effectively catalyse the cyclopropanation of styrene with ethyl diazoacetate at low catalyst loadings (1 mol% Cu).

Computational comparison of Rh 2(esp) 2 and Rh 2(O 2CH) 4 as catalysts in a carbenoid reaction

A computational study of Rh 2(esp) 2-catalysed cyclopropanation of styrene with ethyl bromodiazoacetate is presented. The calculated structures and the energy profile of the reaction show a high level of similarity between Rh 2(esp) 2, a catalyst with sizeable, tethered ligands, and the simplified model catalyst Rh 2(O 2CH) 4.

Versatile NewC3-Symmetric Tripodal Tetraphosphine Ligands; Structural Flexibility to Stabilize CuIand RhISpecies and Tune Their Reactivity

The high-yielding synthesis and detailed characterization of two well-defined, linkage isomeric tripodal, tetradentate all-phosphorus ligands 1-3 is described. Coordination to Cu(I) resulted in formation of complexes 4-6, for which the molecular structures indicate overall tridentate coordination to the copper atom in the solid state, with one dangling peripheral phosphine. The solution studies suggest fast exchange between the three phosphine side-arms. For these new Cu(I) complexes, preliminary catalytic activity in the cyclopropanation of styrene with ethyldiazoacetate (EDA) is disclosed. The anticipated well-defined tetradentate coordination in a C(3)-symmetric fashion was achieved with Rh(I) and Ir(I), leading to the overall five-coordinated complexes 7-12. Complex 11 has the norbornadiene (nbd) ligand coordinated in an unprecedented monodentate 2,3-eta(2) mode to Rh. Furthermore, unexpected but very interesting redox-chemistry and reactivity was displayed by the Rh(Cl)-complexes 7 and 8. Oxidation resulted in the formation of stable Rh(II) metalloradicals [7]PF(6) and [8]PF(6) that were characterized by X-ray crystallography, magnetic susceptibility measurements, cyclic voltammetry, and electron paramagnetic resonance (EPR) spectroscopy. Subsequent redox-reactivity of these metalloradicals toward molecular hydrogen is described, resulting in the formation of Rh(III) hydride compounds.

ChemInform Abstract: Optically Active Aldiminato Copper(II) Complexes as Efficient Catalysts for Enantioselective Cyclopropanation of Styrenes with Diazoacetates.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Highly Enantioselective Cyclopropanation of Styrenes with Diazoacetates Catalyzed by Optically Active β-Ketoiminato Cobalt(II) Complexes.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Fullerene Dendrimers and Lipofullerenes with an Inherently Chiral Hexaaddition Pattern.

The facile synthesis of enantiomerically pure C3-symmetrical fullerene dendrimers all-R-fA-7, all-S-fC-8, all-R-fC-9, and all-S-fA-10, as well as lipofullerenes all-S-fA-11 and all-S-fC-12 involving an octahedral [3:3] addition pattern is described. The C3 symmetrical tris[bis(4-phenyl-2-oxazoline)methano]fullerenes 1, 2, 3, and 4 with known absolute configuration were used as precursors. The completion of the octahedral addition pattern was achieved by a threefold cyclopropanation with the dendritic 3,5-dihydroxybenzylic bromomalonate 5 and the lipophilic dioctadecyl bromomalonate 6. The absolute configurations of the precursor trisadducts were retained in the inherently chiral C3-symmetrical hexakisadducts 7-12. The structure and the isomeric purity of all hexakisadducts 7-12 were unambiguously proven by NMR spectroscopy and other techniques. Preliminary experiments with the dendritic hexakisadducts all-S-fC8 and all-S-fA10 revealed that these macromolecular ligands posess catalytic properties with respect to stereoselective cyclopropanations of styrene with ethyl diazoacetate.

A Water-Soluble Ruthenium Glycosylated Porphyrin Catalyst for Carbenoid Transfer Reactions in Aqueous Media with Applications in Bioconjugation Reactions

Water-soluble [Ru(II)(4-Glc-TPP)(CO)] (1, 4-Glc-TPP = meso-tetrakis(4-(beta-D-glucosyl)phenyl)porphyrinato dianion) is an active catalyst for the following carbenoid transfer reactions in aqueous media with good selectivities and up to 100% conversions: intermolecular cyclopropanation of styrenes (up to 76% yield), intramolecular cyclopropanation of an allylic diazoacetate (68% yield), intramolecular ammonium/sulfonium ylide formation/[2,3]-sigmatroptic rearrangement reactions (up to 91% yield), and intermolecular carbenoid insertion into N-H bonds of primary arylamines (up to 83% yield). This ruthenium glycosylated porphyrin complex can selectively catalyze alkylation of the N-terminus of peptides (8 examples) and mediate N-terminal modification of proteins (four examples) using a fluorescent-tethered diazo compound (15). A fluorescent group was conjugated to ubiquitin via 1-catalyzed alkene cyclopropanation with 15 in aqueous solution in two steps: (1) incorporation of an alkenic group by the reaction of N-hydroxysuccinimide ester 19 with ubiquitin and (2) cyclopropanation of the alkene-tethered Lys(6) ubiquitin (23) with the fluorescent-labeled diazoacetate 15 in the presence of a catalytic amount of 1. The corresponding cyclopropanation product (24) was obtained with approximately 55% conversion based on MALDI-TOF mass spectrometry. The products 23, 24, and the N-terminal modified peptides and proteins were characterized by LC-MS/MS and/or SDS-PAGE analyses.

Chiral C1-symmetric 2,2′:6′,2′′-terpyridine ligands: Synthesis, characterization, complexation with copper(II), rhodium(III) and ruthenium(II) ions and use of the complexes in catalytic cyclopropanation of styrene

Three new optically pure C 1-terpyridine ligands ( L1– 3) were prepared and the copper(II) complexes, of formula [Cu( L)Cl 2], the rhodium(III) complexes, of formula [Rh( L)Cl 3], and the ruthenium(II) complexes, of formula cis- or trans-[Ru( L)(X)Cl 2] (X = DMSO or CO), were synthesized. Structures of a chiral C 1-ligand, a copper complex, a rhodium complex and a ruthenium DMSO complex were analysed using X-ray crystal structure analysis. The copper, rhodium and ruthenium complexes were shown to be precursors of catalysts for cyclopropanation. Reaction of [Cu( L)Cl 2], [Rh( L)Cl 3] or cis- or trans-[Ru( L)(X)Cl 2] with AgOTf converted the complex to catalyst, which in the case of trans-[Ru( L)(CO)Cl 2] gave enantioselectivities of up to 67% ee for the cis-isomers of styrene cyclopropanes with t-butyl diazoacetate. Comparisons with C 2-analog of copper, rhodium and ruthenium catalysts were made.

Iminophosphoranylferrocenes as New Nucleophilic Organocatalysts for Regioselective Ring-opening of Epoxides

We have further demonstrated that they are not only versatile ligands in a Cu-catalyzed cyclopropanation of styrene and Pd-/Mo- catalyzed allylic alkylation of allyl acetates to achieve a com-plete diastereoselectivity but also nucleophilic catalysts for highly regioselective ring-opening of epoxides.

Noncovalent immobilization of chiral cyclopropanation catalysts on mesoporous TUD-1: Comparison of liquid-phase and gas-phase ion-exchange

TUD-1 has been used as Brønsted acidic mesoporous support for the immobilization of a chiral cyclopropanation catalyst. Brønsted acid sites were introduced by supporting phosphotungstic acid on all alumina TUD-1 matrix (PW-TUD-Al 2O 3) or by substitution of Si by Al in all silica TUD-1 matrix (Al-TUD-1). The chiral cyclopropanation catalyst Cu(I)- 2,2′-methylenebis [(4 R,5 S)-4,5-diphenyl-4,5-dihydro-1,3-oxazole] was immobilized by different noncovalent immobilization techniques; ion-exchange in solution and solid–gas ion-exchange. The chiral cyclopropanation catalyst was adsorbed on PW-TUD-Al 2O 3 during ion-exchange in solution. This catalyst system displayed high leaching of copper reaching values of 21%. While using Al-TUD-1 as support copper was introduced as CuCl at temperatures from 550 to 850 °C subsequently followed by introduction of the ligand. Noncovalent immobilization by solid–gas ion-exchange of CuCl on Al-TUD-1 resulted in heterogenous catalyst with only 1% leaching of copper but also moderate results in the cyclopropanation of styrene in terms of yield (33%) and enantioselectivities.

The first one-pot synthesis of alkoxycyclopropanes via cyclometalation of styrene with Cl nAlEt 3−n and RCO 2R′ mediated by Cp 2ZrCl 2

The one-pot cyclopropanation of styrene using Cl n AlEt 3− n (Et 2AlCl, EtAlCl 2, AlCl 3) and carboxylic esters in the presence of Cp 2ZrCl 2 as catalyst gives rise to alkoxycyclopropanes.

Hydrotrispyrazolylborate-copper complexes as catalysts for the styrene cyclopropanation reaction with ethyl diazoacetate under homogeneous and heterogeneous conditions

A series of complexes of general formulae Tp xCu have been employed as the catalyst for the styrene cyclopropanation reaction with ethyl diazoacetate, both under homogeneous and heterogeneous conditions. Several solid supports have been tested, with silica gel being the most convenient for this transformation. A comparison of the results obtained under both conditions has shown that the catalytic pocket is affected by the support.

Bimacrocyclic concave N-heterocyclic carbenes (NHCs): Synthesis, structure and application in catalyses

Imidazolinium moieties have been incorporated into bimacrocycles to generate precursors for concave N-heterocyclic carbenes (NHCs). Starting from 2-nitroresorcinol and alkenols, symmetric concave imidazolinium salts 1 were obtained. Bimacrocyclisation was achieved via ring-closing metathesis (RCM). In an analogous fashion, axially chiral concave imidazolinium salts 2 were obtained using a naphthalene bridgehead devoid of local C2-symmetry. The concave NHCs derived from the symmetric precursors 1 were used as nucleophilic catalysts for the synthesis of γ-butyrolactones and as ligands for transition metal catalysts. Copper complex 18 was used as a catalyst for the cyclopropanation of styrene and indene with ethyl diazoacetate (EDA). Palladium complex 24 was used as a catalyst for the Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions.