Showing 1-30 of 710 results for "cyclopropanations"
Thomas Heel et al.
Chembiochem : a European journal of chemical biology, 15(17), 2556-2562 (2014-10-09)
Recent work has shown that engineered variants of cytochrome P450BM3 (CYP102A1) efficiently catalyze non-natural reactions, including carbene and nitrene transfer reactions. Given the broad substrate range of natural P450 enzymes, we set out to explore if this diversity could be...
Ramya Sambasivan et al.
Chirality, 25(9), 493-497 (2013-06-12)
Dirhodium metallopeptides have been developed as selective catalysts for asymmetric cyclopropanation reactions. A selective ligand sequence has been identified by screening on-bead metallopeptide libraries in a 96-well plate format. Efficient ligand synthesis and screening allows a 200-member library to be...
José M Concellón et al.
Chemical Society reviews, 39(11), 4103-4113 (2010-08-05)
Samarium metal and samarium diiodide have become important tools as selective cyclopropanating agents in organic synthesis due to their high chemo- and stereoselectivity. Therefore, Sm and SmI(2) are the ideal reagents to prepare cyclopropane derivatives. This tutorial review highlights C-C...
Jeremy J Clemens et al.
The Journal of organic chemistry, 78(2), 780-785 (2012-12-21)
Efforts to substitute the cyclopropane ring in a series of aryl cyclopropylnitriles led to the discovery of an operationally simple one-pot method for Knoevenagel condensation and subsequent Corey-Chaykovsky cyclopropanation giving diastereomerically pure products as a racemic mixture of enantiomers. Method...
Ming Yu et al.
Organic letters, 5(24), 4639-4640 (2003-11-25)
[reaction: see text] Direct allylation of glycal-derived donor-acceptor cyclopropanes has been achieved with TiCl(4) activation followed by addition of allyltrimethylsilane. The alpha diastereomer is the major product, with selectivities ranging from 3:1 to 10:1 and yields around 80%.
GuangRong Peh et al.
Organic letters, 14(21), 5614-5617 (2012-10-26)
Cyclopropane-substituted allylic ethers react with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to form oxocarbenium ions with no competitive ring cleavage. This reaction can be used for the preparation of cyclopropane-substituted tetrahydropyrans. The protocol was used as a key step in the total synthesis of the...
D S LEVINE et al.
Canadian Anaesthetists' Society journal, 11, 425-428 (1964-07-01)
Yoshihiro Oonishi et al.
Angewandte Chemie (International ed. in English), 51(29), 7305-7308 (2012-06-29)
Giving direction: An C sp 3-H bond activation directed by a rhodacycle intermediate has been found to occur in a Rh(I)-catalyzed reaction between an allene moiety having a tert-butyl substituent, and tethered alkynes. Cyclic compounds containing a cyclopropane ring were obtained in...
Ming Yu et al.
Organic letters, 6(6), 1057-1059 (2004-03-12)
[reaction: see text] Two new series of 2,2'-bipyrroles and 2,2'-thienylpyrroles have been prepared by trimethylsilyl trifluoromethanesulfonate (TMSOTf)-mediated reaction of donor-acceptor cyclopropanes with 2-cyanopyrroles and 2-cyanothiophene, respectively. This method opens the door toward a wide variety of unsymmetrical bipyrroles and thienylpyrroles.
Carl W Liskey et al.
Journal of the American Chemical Society, 135(9), 3375-3378 (2013-02-21)
The borylation of cyclopropanes catalyzed by the combination of (η(6)-mes)IrBpin3 or [Ir(COD)OMe]2 and a phenanthroline derivative is reported. The borylation occurs selectively at the methylene C-H bonds of the cyclopropane ring over methine or methyl C-H bonds. High diasteroselectivities were...
Masayuki Wasa et al.
Journal of the American Chemical Society, 133(49), 19598-19601 (2011-11-09)
Systematic ligand development has led to the identification of novel mono-N-protected amino acid ligands for Pd(II)-catalyzed enantioselective C-H activation of cyclopropanes. A diverse range of organoboron reagents can be used as coupling partners, and the reaction proceeds under mild conditions....
Poonam Srivastava et al.
Nature communications, 6, 7789-7789 (2015-07-25)
Artificial metalloenzymes (ArMs) formed by incorporating synthetic metal catalysts into protein scaffolds have the potential to impart to chemical reactions selectivity that would be difficult to achieve using metal catalysts alone. In this work, we covalently link an alkyne-substituted dirhodium...
Benoît Moreau et al.
Journal of the American Chemical Society, 127(51), 18014-18015 (2005-12-22)
A highly enantioselective (up to 97.5% ee) and diastereoselective (95:5 dr trans/cis) Cu(I)-catalyzed cyclopropanation of alkenes using phenyliodonium ylide generated in situ from iodosobenzene and methyl nitroacetate is reported. The cyclopropanation took place with high enantioselectivity for a wide range...
Enzymatic chemistry of cyclopropane, epoxide, and aziridine biosynthesis.
Christopher J Thibodeaux et al.
Chemical reviews, 112(3), 1681-1709 (2011-10-25)
Michael P Doyle et al.
Chirality, 15(4), 369-373 (2003-04-01)
Dirhodium(II) azetidinone-carboxylates are effective asymmetric catalysts for diazo decomposition of allyl diazoacetates and their subsequent intramolecular cyclopropanations. The effect of alkene substituents on enantiocontrol has been examined and modest selectivities have been achieved. Steric influences from substituents on the diazo...
Gülsüm Özüduru et al.
Organic letters, 14(19), 4990-4993 (2012-09-27)
The first enantioselective copper-catalyzed cyclopropanation of N-acyl indoles is described. Using carbohydrate-based bis(oxazoline) ligands (glucoBox), the products were obtained in up to 72% ee. Cyclopropanation of N-Boc 3-methyl indole yielded a product with an all-carbon quaternary stereocenter, which is a...
A Hussain K Sharba et al.
Molecules (Basel, Switzerland), 10(9), 1153-1160 (2007-11-17)
New heterocyclic derivatives of cyclopropane dicarboxylic acid comprising thiadiazole and 1,2,4-triazole moieties are reported. Reaction of 1,1-cyclopropane dicarboxylic acid (1) with thiosemicarbazide and phosphorous oxychloride resulted in 1,1-bis (2-amino-1,3,4-thiadiazol-5- yl)cyclopropane (2). Cyclopropane dicarboxylic acid thiosemicarbazide (6) was converted into 1,1-bis(3-thio-4H-1,2,4-triazol-5-yl)...
Russell J Hewitt et al.
Chemical communications (Cambridge, England), 47(1), 421-423 (2010-09-21)
gem-Dibromocyclopropane 1, prepared from tri-O-benzyl-D-glucal, undergoes thermal and silver-promoted ring expansion in the presence of alcohols to give substituted oxepines. With further heating, ring contraction to highly substituted tetrahydrofurans follows. These represent C-furanosides, potentially useful as precursors to C-nucleosides and...
L Xia et al.
Se pu = Chinese journal of chromatography, 17(1), 43-45 (2003-01-29)
The enantiomeric resolution of racemic mixtures of thirteen trans-1,2-disubstituted cyclopropane was achieved with HPLC by using Chiralcel OD and Chiralcel OJ as chiral stationary phase and hexane/2-propanol mixtures with different concentrations as eluent. The chromatographic parameters of these racemates on...
Filippo De Simone et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 17(51), 14527-14538 (2011-11-25)
The Nazarov cyclization of divinyl ketones gives access to cyclopentenones. Replacing one of the vinyl groups by a cyclopropane leads to a formal homo-Nazarov process for the synthesis of cyclohexenones. In contrast to the Nazarov reaction, the cyclization of vinyl-cyclopropyl...
Rui Zhang et al.
The Journal of organic chemistry, 73(20), 8089-8092 (2008-09-19)
A convenient and efficient synthesis of substituted dihydrofurans is developed via ring-enlargement of 1-dimethylaminopropenoyl-1-carbamoyl/benzoyl cyclopropanes catalyzed by ammonium acetate in acetic acid with high regio- and stereoselectivity. Some of the newly synthesized substituted dihydrofurans are subjected to further synthetic transformation...
Roxanne K Kunz et al.
Journal of the American Chemical Society, 127(10), 3240-3241 (2005-03-10)
A new method for enantioselective organocatalytic cyclopropanation is described. This study outlines the identification of a new class of iminium catalyst based on the concept of directed electrostatic activation (DEA). This novel organocatalytic mechanism exploits dual activation of ylide and...
Zhenjun Mao et al.
Chemical communications (Cambridge, England), 48(79), 9927-9929 (2012-08-31)
1,1-Cyclopropane aminoketones were efficiently synthesized in high yields by the tandem reaction of α-amino aryl ketones with vinyl sulfonium salts using DBU as the base in CH(2)Cl(2). This methodology was utilized to synthesize 2-benzoyl quinolines.
International anesthesiology clinics, 3, 51-76 (1964-11-01)
Thibault Ferrary et al.
Organic letters, 15(21), 5598-5601 (2013-10-22)
The synthesis of highly functionalized monofluorinated cyclopropanes based on a Michael Initiated Ring Closure (MIRC) reaction has been developed. The addition of quaternary ammonium salts derived from ethyl bromofluoroacetate on a panel of electron deficient alkenes followed by cyclization gave...
Jordi Eras et al.
Journal of agricultural and food chemistry, 56(13), 4923-4927 (2008-06-07)
The stability of the cyclopropane ring and the fatty acid composition of microbial cells were determined using chlorotrimethylsilane as reagent with three different conditions 80 degrees C for 1 h, 60 degrees C for 1 h, and 60 degrees C...
Angela M Bernard et al.
Organic letters, 7(21), 4565-4568 (2005-10-08)
[reactions: see text] Regioselective synthesis of 2,4,5- or 3,4,5-trisubstituted 2,3-dihydrofurans has been realized by using donor-acceptor cyclopropanes or by a Corey ylide reaction with alpha-sulfenyl-, alpha-sulfinyl-, or alpha-sulfonylenones. The method allowed a straightforward synthesis of the natural product calyxolane B.
R P Bell et al.
The Journal of organic chemistry, 66(7), 2350-2357 (2001-04-03)
A general and efficient route to the marasmane skeleton is described. Total syntheses of two simple marasmanes (35 and 37) in racemic form were achieved using a MgI2-catalyzed rearrangement-cyclopropanation reaction of trimethylsilyl enol ether 31 derived from naphthalenone 30. The...
Soda Chanthamath et al.
Chemical communications (Cambridge, England), 48(62), 7750-7752 (2012-07-04)
The Ru(II)-Pheox complex is an efficient catalyst for the intermolecular cyclopropanation of various terminal olefins with succinimidyl diazoacetate. This catalytic system can perform under mild conditions, and the desired cyclopropane products are obtained in high yields with excellent diastereoselectivity and...
Soda Chanthamath et al.
Organic letters, 15(4), 772-775 (2013-01-31)
The Ru(II)-Pheox-catalyzed asymmetric cyclopropanation of vinylcarbamates with diazoesters resulted in the corresponding cyclopropylamine derivatives in high yield and excellent diastereoselectivity (up to 96:4) and enantioselectivity (up to 99% ee).

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