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The reduction of 2-cyclopropylcarbonyl-, 2-(thiophen-2-yl)carbonyl-, and 2-arylcarbonylbenzonitriles with sodium tetrahydridoborate afforded 3-cyclopropyl-, 3-(2-thiophen-2-yl)-, and 3-arylphthalides, respectively, in high yields. Under analogous conditions, 3-cyanobenzophenones were converted to the corresponding 3-cyanobenzhydrols. [ABSTRACT FROM AUTHOR]

A simple and efficient method to prepare 1-(1-chlorocyclopropyl)-2-(1,2,4-triazol-1-yl)ethan-1-one via nucleophilic substitution of 2-chloro-1-(1-chlorocyclopropyl)ethanone and 1,2,4-triazole is described. The title compound is the key intermediate required for the synthesis of prothioconazole, a promising agricultural fungicide. By exploring changes in the reaction time, temperature, ratio of starting reagents, acid binding agent, and the nature of phase transfer catalyst, the reaction conditions could be optimized to afford the desired N-alkylated material in nearquantitative yield. The ultimate yield of the product after recrystallization was 93%, with a purity of 99% based on its characterization by Gas Chromatography-Mass Spectrometer (GC-MS), Fourier Transform infrared spectroscopy (IR), Proton Magnetic Resonance (¹H NMR), and Carbon-13 Nuclear Magnetic Resonance (13C NMR). The synthetic process is suitable for industrial application, with the advantages of high yield and facile preparation under mild operating conditions. [ABSTRACT FROM AUTHOR]

1-Benzoyl-1-( o-alkoxyphenyl)cyclopropanes undergo Yang photocyclization to form dihydrobenzo-pyranols in a stereospecific manner. The cyclopropyl group at alpha position to carbonyls gives not only a bias in the most stable geometries of the starting ketones but also conformational restriction on geometries of biradical intermediates. More importantly, intramolecular hydrogen bonds seem to give an additional effect on conformational control of the biradical reactivity. [ABSTRACT FROM AUTHOR]

Oxidative ring-opening reactions of benzene-fused bicyclic cyclopropyl silyl ethers, promoted by copper(II) tetrafluoroborate, were investigated. The regioselectivity of cyclopropane ring-opening as well as product distributions were found to be highly dependent on the nature of the solvent. In alcohols, dimeric substances arising from external bond cleavage are major products. Radical rearrangement products are also formed in solvents such as ether and ethyl acetate. On the contrary, nucleophile addition to carbocation intermediates, generated by internal bond cleavage, occurs mainly in reactions taking place in acetonitrile. It is proposed that the observed solvent effects that govern the reaction pathways followed are a consequence of varying solvation of copper intermediates, which governs their reactivity and redox properties. In addition, the influence of counteranions of the copper salts, organonitriles, cyclic dienes, and substrate structures on the pathways followed in these reactions was also examined. [ABSTRACT FROM AUTHOR]

A new series of 4-cyclopropyl-5-(2-fluorophenyl)arylhydrazono-2,3-dihydrothiazole derivatives was synthesized via the reaction of prepared thiosemicarbazones with 2-bromo-1-cyclopropyl-2-(2-fluorophenyl)ethanone in the presence of Et3N as a catalyst through a semi Hantzsch cyclization. The optimized reaction conditions for this one-pot reaction were achieved. The products were obtained in short reaction times, high yields and high purities. Antioxidant activity of products was evaluated using DPPH (2,2-diphenyl-2-picrylhydrazyl) and ABTS 2,2-azinobis(3-ethylbenzothiazoline-sulfonate) assays. Products showed higher antioxidant activity using the ABTS method. Compounds5cand5gshowed lower IC50values compared with ascorbic acid as a standard. Compounds5a–5hpossessed moderate to high antioxidant activity by both methods. Also, antibacterial activity of5a–5hwas evaluated against gram-positive and gram-negative bacterial strains. None of the compounds inhibitedA. hydrophila, while they had moderate to low inhibitory activity against other tested bacterial strains. [ABSTRACT FROM AUTHOR]

The introduction of the cyclopropyl group in the structure of curcuminoids is a challenge by decreased reactivity in the methylene group, due to the existence of keto-enol equilibrium in these compounds. The development of this reaction is affected by the instability of curcuminoids in basic medium. Considering the possibility of developing alkylation reactions in aqueous medium using potassium carbonate as base and tetrabutylammonium bromide as a catalyst phase transfer to facilitate interaction of the reactants it was made double alkylation of five 5 5-pentatrienonas with 1,2-dibromoethane in molar ratio 1: 1, heating the reaction mixture for 12 h at 40 °C. They were obtained five cyclopropyl derivatives in yields ranging between 22 and 32 %. All obtained compounds are colored solids; they were characterized by NMR, quantitative elemental analysis and mass spectrometry. The procedure is presented as a novel method of cyclopropanation of curcuminoids that uses water as solvent; it also facilitates product separation because of its insolubility in the reaction medium, which gives environmental and economic value. [ABSTRACT FROM AUTHOR]

Carbene transfer to appropriate substrates is a highly versatile tool for the construction of carbon frameworks with increased functional and structural complexity. In this study, some novel cyclopropane derivatives were synthesized via carbenoid reactions and their further reactivities were investigated. (1 E)-Buta-1,3-dien-1-yl acetate was reacted with four different diazocarbonyl compounds, ethyl diazoacetate, dimethyl diazomalonate, 1-diazo-1-phenylpropan-2-one, and methyl (3 E)-2-diazo-4-phenylbut-3-enoate, in the presence of two catalysts. All synthesized substituted cyclopropanes were obtained chemoselectively with respect to less-hindered CC bonds. Under the applied conditions, while cyclopropanes 7a and 7d underwent further reactions, cyclopropanes 7b and 7c were stable enough. Cyclopropanes 7a and an additional equivalent of ethyl diazoacetate yielded polyfunctionalized cyclohexenes. Cyclopropanes from methyl (3 E)-2-diazo-4-phenylbut-3-enoate yielded polyfunctionalyzed cycloheptadiene isomers by Cope rearrangement. [ABSTRACT FROM AUTHOR]

The pairing of transition metal catalysis with the reagent Selectfluor (F-TEDA-BF4) has attracted considerable attention due to its utility in myriad CC and Cheteroatom bond-forming reactions. However, little mechanistic information is available for Selectfluor-mediated transition metal-catalyzed reactions and controversy surrounds the precise role of Selectfluor in these processes. We present herein a systematic investigation of homogeneous Au-catalyzed oxidative CO bond-forming reactions using density functional theory calculations. Currently, Selectfluor is thought to serve as an external oxidant in AuI/AuIII catalysis. However, our investigations suggest that these reactions follow a newly proposed mechanism in which Selectfluor functions as an electrophilic fluorinating reagent involved in a fluorination/defluorination cycle. We have also explored Selectfluor-mediated gold-catalyzed homocoupling reactions, which, when cyclopropyl propargylbenzoate is used as a substrate, lead to an unexpected byproduct. [ABSTRACT FROM AUTHOR]

The N-tosylaziridine 4 of (+)-2-carene 1 was prepared and subjected to solvolytic reactions with weak protic acids. For comparison, the solvolytic reactions of cis-3-carene- N-tosylaziridine 8 were also studied. The solvolyses of 4 were more rapid than those of 8, and both rings were opened in 4, whereas only the aziridine was opened in 8. This leads to the conclusion that the aziridine and cyclopropane rings in 4 can achieve a conjugated transition state. [ABSTRACT FROM AUTHOR]

Abstract: The consecutive treatment of 5-hydroxy-1-pentynyl 2,2-disubstituted-cyclopropyl ketones with Co2(CO)8 and BF3·OEt2 produced the corresponding Co2(CO)6-complexed dioxaspiro[4.6] derivatives. The one-carbon homologated substrates also afforded dioxaspiro[4.7]. It was found that this procedure can be applied to the substrates with gem-disubstituents as well as a mono-aryl substituent on the cyclopropane, but the mono-alkyl substituted cyclopropanes are insufficient. [Copyright &y& Elsevier]

Abstract: The (CO) elimination reaction of cyclopropylmethoxy (fluoro/chloro) carbenes (C–X, X=H, F, Cl) and its consequent rearrangement products are studied computationally using B3LYP/6-311++G** method. Results of this study show that the reaction proceeds via a first TS corresponding to the cyclopropylmethoxy (chloro/fluoro) carbenes (C–X, X=H, F, Cl). The negative mode of this TS species corresponds to the elimination of the CO molecule, consistent with the experimentally proposed mechanism. Effects of the X substitution on the electronic and energetic properties of this conversion which is an intermediate step of the conversion of 3-cyclopropylmethoxy-3-(fluoro/chloro) diazirines (D–X, X=H, F, Cl) to different products are also investigated. Calculations are also carried out for reactants and products of this reaction at the same level of theory. Nuclear quadrupole coupling constants and asymmetry parameter of the 35Cl and 14N nuclei have also been calculated and analyzed for reactants, TSs and products, as probes of the reaction coordinate. [Copyright &y& Elsevier]

Abstract: Methods for the synthesis of cyclopropyl glycosides and their use as glycosyl donors are described. Cyclopropyl glycosides containing different substituents were prepared by cyclopropanation of the corresponding vinyl glycosides, or by glycosidation of cyclopropyl alcohols that are synthesized by the Kulinkovich reaction. 1-Methyl- and 1-phenyl-substituted cyclopropyl glycosides undergo coupling to Fmoc-protected serine and threonine and to partially protected monosaccharides in the presence of TMS triflate to give glycosidated products. [Copyright &y& Elsevier]

Abstract: Recently, valley–ridge inflection points on the potential energy surface for the ring opening of the cyclopropyl radical have been determined using Newton trajectories (NTs) [W. Quapp, J.M. Bofill, A. Aguilar-Mogas, Theor. Chem. Acc. 129 (2011) 803]. This Letter is the report about the utilization of NTs for the search for conical intersection (CI) points. These points play a main role in the understanding of intersections of different electronic surfaces which open the door for photochemical reactions. We explain the reason why Newton trajectories can find CI points, and report a CI seam on the CASSCF (3,3) surface of the allyl radical ring closure. [Copyright &y& Elsevier]

The kinetics and equilibrium of the allyl radical reactionwithmolecular oxygen have been studied in direct measurements using temperature-controlledtubular flow reactor coupled to a laser photolysis/photoionizationmass spectrometer. In low-temperature experiments (T= 201–298 K), association kinetics were observed, and themeasured time-resolved C3H5radical signalsdecayed exponentially to the signal background. In this range, thedetermined rate coefficients exhibited a negative temperature dependenceand were observed to depend on the carrier-gas (He) pressure {p= 0.4–36 Torr, [He] = (1.7–118.0) ×1016cm–3}. The bimolecular rate coefficientsobtained vary in the range (0.88–11.6) × 10–13cm3s–1. In higher-temperature experiments(T= 320–420 K), the C3H5radical signal did not decay to the signal background, indicatingequilibration of the reaction. By measuring the radical decay rateunder these conditions as a function of temperature and followingtypical second- and third-law procedures, plotting the resulting ln Kpvalues versus 1/Tin a modifiedvan’t Hoff plot, the thermochemical parameters of the reactionwere extracted. The second-law treatment resulted in values of ΔH298°= −78.3 ± 1.1 kJ mol–1and ΔS298°= −129.9 ± 3.1 J mol–1K–1, with the uncertainties given as one standard error. When resultsfrom a previous investigation were taken into account and the third-lawmethod was applied, the reaction enthalpy was determined as ΔH298°= −75.6 ± 2.3 kJ mol–1. [ABSTRACT FROM AUTHOR]

Although they are highly strained, methylenecyclopropanes (MCPs) are readily accessible molecules that have served as useful building blocks in organic synthesis. MCPs can undergo a variety of ring-opening reactions because the release of cyclopropyl ring strain (40 kcal/mol) can provide a thermodynamic driving force for reactions and the π-character of the bonds within the cyclopropane can afford the kinetic opportunity to initiate the ring-opening. Since the 1970s, the chemistry of MCPs has been widely explored in the presence of transition metal catalysts, but less attention had been paid to the Lewis or Brønsted acid mediated chemistry of MCPs. During the past decade, significant developments have also been made in the Lewis or Brønsted acid mediated reactions of MCPs. This Account describes chemistry developed in our laboratory and by other researchers. [ABSTRACT FROM AUTHOR]

Abstract: Cyclopropyl analogues of melatonin can be readily synthesized in high yields by Rh(II)-catalysed decomposition of aryldiazoacetates in the presence of N-vinylacetamide or vinyl acetate. The reaction is highly trans selective. [Copyright &y& Elsevier]

A Fe-catalytic highly selective ring expansion reaction of alkynylcyclopropyl alkanols to alkynylcyclobutanols via a 1,2-carbon shift under mild conditions was developed. A new class of homogeneous FeCl2/O2 catalytic system was employed in these novel transformations. [ABSTRACT FROM AUTHOR]

The new cyclopropyl-triterpenoid is isolated along with four known compounds from the aerial parts of Ochradenus arabicus. [ABSTRACT FROM AUTHOR]

This method was deployed as key reaction in total synthesis of (+)-myrmicarin 217 (XXII). [ABSTRACT FROM AUTHOR]