Cyclopropanation Versus Deoxygenation in the Reactions of Halocarbenes with pre-Aromatic Ketones

The reactions of halocarbenes with pre-aromatic ketones 1, 2 resulted in cyclopropanation and deoxygenation products. The varying product ratio could be accounted for by a mechanism involving the carbonyl ylide intermediate.

Asymmetric Induction of Chiral 1,1'-Bis(oxazolinyl)ferrocenes as Ligands in Metal-Catalyzed Cyclopropanation and Diels-Alder Reactions

Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Alder reaction between 3-acryloyl-2-oxazolidinone and cyclopentadiene. Enantioselectivities up to 24% and 41%, respectively, for cyclopropanation and Diels-Alder reaction were observed.

Asymmetric Cyclopropanation Catalyzed by Four Stereoisomers of a Copper-(Schiff-base) Complex with Double Chiral Centers

Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiomeric excess of up to 91.8%. A mechanism that predicts the observed results accurately was proposed.

Cyclopropanation of 1, 1-Dichloro-4-methyl-1,3-pentadiene with Diazoacetate

Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, yield of this reaction is rather law compared with that of 2,5-dimethyl-2,4-pentadiene, Of all catalysts concerned. yield ranged from 25.1% to 47.2%.

Synthetic Studies on 1-Amino-1-Cyclopropane-Carboxylic Acid( Ⅰ )——The Cyclopropanation via Addition-Elimination Reactions

Various addition-elimination approaches have been explored for diastereoselective construction of 1-amino- 1-cyclopropane-carboxylic acid (ACPC) derivatives, and the desired product was obtained from a reaction of cyclo(NAc-L-Val-NAc-Gly) and methyl α-bro-moacrylate under protonic solvent.

Catalytic Asymmetric Cyclopropanation using a New Chiral β-Diketone Cu (Ⅱ) Complex as a Catalyst

A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on the enantioselectivity was studied. Both chendcal yield and optical yield being reduced when the steric bulky substrate was employed. The reaction mechanism and the chiral model of the transition state are under fufther investigation.

Cyclopropanation of Diazoacetate with Olefins

Nine copper compounds are used for catalyzing the cyclopropanation of 1-hexene/TME with alkyl diazoacetate.Cu(Salad)2 shows the highest yield for the reaction of TME at high temperature such as 100℃.The reaction of crude RDA with TME in 73.7% yield under the optimal condition is obtained.

Immobilization of Pd(II) Catalysts for Cyclopropanation in Ionic Liquid

Cyclopropanation of styrene with ethyl diazoacetate catalyzed by Pd(II) inionic liquid [omim][BF_4] was investigated. Palladium catalysts can be effectively immobilized inionic liquid. The catalysts PdCl_2 and cyclopalladated complex 2 contained in ionic liquid could berecycled for 6 and 7 times, respectively, without losing the efficiency.

K3PO4-Promoted Cyclopropanation of Electron-deficient Alkenes with 2-Bromo-1,3-Propanedione Compounds

An easy and efficient method for the synthesis of multisubstituted cyclopropane derivatives from electron-deficicent alkenes with 2-bromo-1,3-propanedione compounds was described.For this method,ethylα-cyanocinnamate derivatives 1 andβ,β-dicyanostyrene derivatives 4 can all smoothly reacted with 2-bromo-1,3-propanedione compounds 2 to afford the corresponding multisubstituted cyclopropane derivatives 3 and 5 in good to excellent yields(up to 100%)promoted by anhydrous K3PO4 in DMF at room temperature,respectively.A possible mechanism of this reaction was proposed.Structures of all the products were confirmed by ^1H NMR,^13C NMR and HRMS.

Cyclopropanation of active methylene compounds with β-alkoxycarbonyl vinylsulfonium salts

An efficient synthesis of β-alkoxycarbonyl vinylsulfonium salts had been developed. Their reaction with indene-1,3-diones and other active methylene compounds provided cyclopropane carboxylates in good yields. A tentative reaction mechanism was proposed.

New Chiral Substituted 8-Quinolinyl-oxazolines as Ligands for Copper(I)-catalyzed Asymmetric Cyclopropanation

New chiral substituted 8-quinolinyl-oxazoline ligands have been synthesized and applied in the copper(I)-catalyzed asymmetric cyclopropanation of styrene with alkyl diazoacetates. The steric effect in the ligands plays a significant role in the enantiocontrol in asymmetric cyclopropanation, while the electronic effect is less important.

A new class of chiral pyrrolidine ligands for homogeneous catalytic enantioselective cyclopropanation of styrene

A new class of chiral pyrrolidine ligands have been successfully synthesized and their chiral induction abilities have been examined in the homogeneous catalytic enantioselective cyclopropanation of styrene. 15–30% enantiomeric excess (ee) has been achieved.

Theoretical Exploration on Structural Stabilities and Detonation Properties of Nitrimino Substituted Derivatives of Cyclopropane

The packed density, detonation velocities, and detonation pressures of a series of cyclopropane derivatives were investigated to look for high energy density compounds. For exploring the possibility of synthesis, the bond order, heats of formation(HOF), bond dissociation energy(BDE), and characteristic height were calculated. Based on our results, A3 has the best detonation characters. Both A1 and A2 showed comparative detonation parameters and compact sensitivity with RDX, and could be regarded as the candidates of high energy density molecules.Both the heats of formation and explosive heats rose with the increase of nitrimino groups and the strain energy of three-membered ring. For A1 compound, pyrolysis mechanism might be a mix one(breakages of C–C and N–NO2 bonds). However, for A2 and A3 compounds, the N–NO2 is the trigger bond in explosive reactions. Our results may provide the basic information for further study of this kind of compounds.

Facile and Convenient One-pot Synthesis of 1,1-Disubstituted Cyclopropanes in Water

A facile and convenient one-pot synthesis method of substituted cyclopropanes in water has been developed. A series of 1,1-disubstituted cyclopropanes 3 were synthesized from the reaction of β-dicarbonyl compounds 1 with 1,2-dibromoethane 2, in very high yields catalyzed by tetrabutylammonium bromide（TBAB） at 50 ℃ in the presence of K2CO3 in water. The catalyst TBAB in the aqueous phase can be reused after the separation of organic products.

Synthesis, Crystal Structure and Biological Activity of a New 1,2,4-Triazole Derivative

A new 1,2,4-triazole containing cyclopropane moiety was synthesized and characterized by 1H NMR, MS and elemental analyses. The crystal structure of the title compound （C13H14FN3S, Mr= 263.33） has been determined by single-crystal X-ray diffraction. The crystal is of monoclinic, space group P21/c with a = 12.614（3）, b = 7.0202（14）, c = 15.556（3）A, β = 110.92（3）°, V = 1286.7（4） A3, Z = 4, F（000） = 552, D,. = 1.359 g/cm3,μ = 0.25 mm-1, the final R = 0.0336 and wR = 0.0898 for 2568 observed reflections with 1 〉 2σ（/）. A total of 10093 reflections were collected, of which 3045 were independent （Rint = 0.0268）. The herbicidal activity of the title compound was determined, and this compound displays excellent herbicidal activity against Brassica campestris.

Synthesis and Structure of trans-1,2-Bisaromatic Heterocycle Substituted Cyclopropanes

Trans-1,2-bis(2 ' -(5 ' -phenyl-1 ' , 3 ' , 4 '-oxadiazolyl ) ) cyclopropane (BDCP) and its eleven substituted novel derivatives were synthesized. Besides four derivatives of l,2-bis(2'-(5'-phenyl-l ' , 3 ' , 4 ' -ox-adiazo1yl))ethane (BPDS) were also synthesized as model compounds. The crystal structure of ethyl BDCP was determined and the cyclopropane ring was found to be able to transmit conjugation between the aromatic groups directly bonding with it by studying the ultraviolet and fluorescent spectra of the above compounds.

Stereoselective Synthesis of Polysubstituted Cyclopropanes from Poly(ethylene glycol) Supported Pyridinium Ylide

Polysubstituted cyclopropanes were efficiently prepared with poly（ethylene glycol）（PEG） as soluble support. The reaction of PEG-supported pyridinium ylide with arylidenemalononitrile（R=CN） or ethyl arylidenecyanoa-cetate（R=COOEt） in the presence of triethylamine（TEA） afforded PEG-supported cyclopropanecarboxylates, which were cleaved by 1% KCN/EtOH to obtain polysubstituted cyclopropanes with exclusive trans-selectivity and good yields.