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Heterogeneous catalytic hydrogenation of strained nitrile substituted spirocyclopropyl oxindoles in acetic anhydride, allowed to the regioselective formation of ring-opened 2-oxohomotryptamines accompanied by the ring-retained spirocyclopropyl acetamides as by products. The C3 C9 bond fission would be induced by H atom attack via the plausible intermediacy of a stabilized benzolactam carbon-centered radical. The substituent effects on the stability of such radicals were analyzed in terms of the energy of SOMO orbitals, showing good agreement with σ m Hammett constants. The theoretical results reflect experimental findings on the reactivity of the analyzed compounds. [ABSTRACT FROM AUTHOR]

The cyclopropyl (cPr) group, which is a well-known probe for detecting radical character at atoms to which it is connected, is tested as an indicator for aromaticity in the first ππ* triplet and singlet excited states (T1 and S1). Baird's rule says that the π-electron counts for aromaticity and antiaromaticity in the T1 and S1 states are opposite to Hückel's rule in the ground state (S0). Our hypothesis is that the cPr group, as a result of Baird's rule, will remain closed when attached to an excited-state aromatic ring, enabling it to be used as an indicator to distinguish excited-state aromatic rings from excited-state antiaromatic and nonaromatic rings. Quantum chemical calculations and photoreactivity experiments support our hypothesis; calculated aromaticity indices reveal that openings of cPr substituents on [4 n]annulenes ruin the excited-state aromaticity in energetically unfavorable processes. Yet, polycyclic compounds influenced by excited-state aromaticity (e.g., biphenylene), as well as 4 nπ-electron heterocycles with two or more heteroatoms represent limitations. [ABSTRACT FROM AUTHOR]

Computing the optical rotation of organic molecules can be a real challenge, and various theoretical approaches have been developed in this regard. A benchmark study of optical rotation of various classes of compounds was carried out by Density Functional Theory (DFT) methods. The aim of the present research study was to find out the best-suited functional and basis set to estimate the optical rotations of selected compounds with respect to experimental literature values. Six DFT functional LSDA, BVP86, CAM-B3LYP, B3PW91, and PBE were applied on 22 different compounds. Furthermore, six different basis sets, i.e., 3-21G, 6-31G, aug-cc-pVDZ, aug-cc-pVTZ, DGDZVP, and DGDZVP2 were also applied with the best-suited functional B3LYP. After rigorous effort, it can be safely said that the best combination of functional and basis set is B3LYP/aug-cc-pVTZ for the estimation of optical rotation for selected compounds. [ABSTRACT FROM AUTHOR]

Molecular topology was used to develop a mathematical model capable of classifying compounds according to antimicrobial activity against methicillin resistant Staphylococcus aureus (MRSA). Topological indices were used as structural descriptors and their relation to antimicrobial activity was determined by using linear discriminant analysis. This topological model establishes new structure activity relationships which show that the presence of cyclopropyl, chlorine and ramification pairs at a distance of two bonds favor this activity, while the presence of tertiary amines decreases it. This model was applied to a combinatorial library of a thousand and one 6-fluoroquinolones, from which 117 theoretical active molecules were obtained. The compound 10 and five new quinolones were tested against MRSA. They all showed some activity against MRSA, although compounds 6 , 8 and 9 showed anti -MRSA activity similar to ciprofloxacin. This model was also applied to 263 theoretical antibacterial agents described by us in a previous work, from which 34 were predicted as theoretically active. Anti -MRSA activity was found bibliographically in 9 of them (ensuring at least 26% of success), and from the rest, 3 compounds were randomly chosen and tested, finding mitomycin C to be more active than ciprofloxacin. The results demonstrate the utility of the molecular topology approaches for identifying new drugs active against MRSA. [ABSTRACT FROM AUTHOR]

A new series of functionalized ( Z )-3-(2-oxo-2-substituted ethylidene)-3,4-dihydro-2 H -benzo[ b ][1,4]oxazin-2-ones 23 – 26 , incorporating pharmaceutically privileged substructures such as cyclopropyl, naphthyl, biphenyl and cyclohexylphenyl were synthesized in excellent yields. All the synthesized compounds were screened for their in vitro antibacterial activity against gram-(+)ve and gram-(−)ve bacterial species i.e. S. griseus , S. aureus , B. subtillis and E. coli as well as in vitro antifungal activity against fungal species i.e. F. oxysporium , A. niger , P. funiculosum and T. reesei , respectively. In this study, compounds containing c yclopropyl and cyclohexylphenyl substructures were identified as promising antimicrobial agents than standard drugs, ampicillin and chloramphenicol as well as ketoconazole. SAR study illustrates that electron-withdrawing groups increases the antibacterial as well as antifungal activity of 2-oxo-benzo[1,4]oxazines and vice versa. Compounds 23e and 26e , the most active compounds of the series, displayed promising antibacterial activity than Ampicillin and Chloramphenicol. Moreover, compound 26d showed promising antifungal potency as compared to Ketoconazole. Cytotoxic studies of the active compounds i.e. 23c – e , 24e , 25d and 26d – e found to be non-toxic in nature in 3T 3 fibroblast cell lines using MTT assay. [ABSTRACT FROM AUTHOR]

Push-pull alkynylcyclopropane derivatives are claimed as suitable and active substrates for gold-catalyzed transformations. Thus, 2(3 H)-azepinones can be readily prepared from alkynylcyclopropanecarboxamides through a nucleophilic addition/cyclopropane ring-opening cascade process and, in this manuscript, the scope and the limitations of such reaction sequence are reported. The cascade reaction is general and occurs with complete regio- and quimioselection to form the seven-membered heterocycles with the exception of primary alkyl-substituted alkynylcyclopropanecarboxamides that render 4-methoxy-6-oxo-4-enenitriles in moderate yields. Additionally, less activated alkynylcyclopropylmethanols undergo regioselective cycloisomerization at low temperature leading to oxabicyclo[4.1.0]heptanes. Notably, the cyclopropane ring opening of these adducts takes place under thermal conditions to form dihydropyranones. [ABSTRACT FROM AUTHOR]

An organocatalytic Cloke-Wilson rearrangement of cyclopropyl ketones to 2,3-dihydrofurans is exploited utilizing the homoconjugate addition process. With 1,4-diazabicyclo[2.2.2]octane as the catalyst, the rearrangement in DMSO at 120 °C proceeded in generally high yields, exclusive regioselectivity, and a broad substrate scope. An examination of the mechanism including stereochemical analysis and intermediate isolation supports an SN1-type ring opening of the mechanism. [ABSTRACT FROM AUTHOR]

We conducted detailed studies on CO-assisted reductive chemistry with cyclopropyl ketones as a special type of substrate. Multiple factors influencing the outcome of the reaction have been studied for both ruthenium and rhodium catalysis. An unusual rearrangement of aminomethylcyclopropanes was found. We showed that some reductive reactions, which were believed to proceed through a water-gas shift reaction pathway, can nonetheless take place even without an external or internal water source, indicating a more interesting reaction mechanism. Cyclopropylketones were employed as bifunctional electrophiles and, depending on the conditions, the reaction with an amine can lead to a number of products, including aminoketones, cyclopropyl methylamines, pyrrolidines or 1,4-diaminopentanes. [ABSTRACT FROM AUTHOR]

Inter- and intramolecular cyclopropanations of a series of diazo Weinreb amides and trans-allylic diazo Weinreb amide derivatives have been achieved using chiral ruthenium(II)- Amm-Pheox catalyst to give the corresponding chiral cyclopropyl Weinreb amides in excellent yield (up to 99%) with excellent enantioselectivity (up to 99% ee). The chiral products could easily undergo useful synthetic transformations to give the corresponding aldehydes, alcohols and ketones in high yields and enantioselectivities. [ABSTRACT FROM AUTHOR]

A novel series of optically active 2,6-disubstituted alkylphenols with improved anesthetic profiles compared to widely used propofol were synthesized. The incorporation of the cyclopropyl group not only increased the steric effect but also introduced stereoselective effects over their anesthetic properties. Compounds 1, 2, and 6 were selected as potential candidates for further preclinical development including studies of their water-soluble prodrugs. Clinical studies of candidate compound 6 (Haisco HSK3486) as a general anesthetic are being performed in Australia and China. [ABSTRACT FROM AUTHOR]

In the scope of a broader study focused on glutamate receptors regulators, we have been engaged in synthesis, analysis and pharmacological characterization of rigid analogues of glutamic acid. These compounds exhibited the bioisosteric replacement of the distal carboxylic group with the sulfonic one. Besides the sophisticated synthetic approach, we targeted preparation of a series of cyclopropyl-containing sulfonyl amino acids and development of a chromatographic enantioselective method suitable for distinguishing and quantifying the resulting isomers. Due to chelating ability, the chiral ligand-exchange chromatography (CLEC) was used for diastereo- and enantioseparation of the synthesized compounds. The CLEC-based enantioseparation was achieved by using a chiral mobile phase (CMP) system with N,N-dimethyl-( S)-phenylalanine [(S)-DMP] as the chiral selector. Only one of the investigated enantiomeric pairs was undiscriminated with the employed CLEC-CMP system which, very importantly, produced the simultaneous diastereo- and enantioseparation of two compounds of the series. Furthermore, the large α and RS values computed for three enantiomer pairs could be a good basis for a successful scale-up to a semi-preparative level. [ABSTRACT FROM AUTHOR]

[Display omitted] We have used the M06-D3 flavor of density functional theory (DFT) to investigate the structures and free energies of initiation for a series of Hoveyda-Grubbs-like complexes in which the isopropoxy part replaced by selected saturated or unsaturated derivatives of cyclopropane, cyclobutane and cyclopentane. We show that the introduction of the double bond into this part of the complex weakens the ruthenium-oxygen bond, creating a series of potential catalysts capable of fast initiation metathesis. The addition to the nitro group in the para position of the benzylidene part of the complex also creates a potentially highly efficient ruthenium catalyst. We demonstrate that the Gibbs free energy of activation correlates with various structural and computational parameters of the precatalyst, including the Ru-O bond strength and partial charges on selected atoms. [ABSTRACT FROM AUTHOR]

General routes for the synthesis of 1,3-oxazin-4-ones are discussed, with particular attention paid to recent developments in the field. The syntheses of amine functionalised cyclopropyl carbinols via a hydride-mediated reduction of various 5-chloroethyl-1,3-oxazin-4-enones in moderate to good yield are disclosed. This new method provides an opportunity to access greater structural diversity within these useful synthetic building blocks. [ABSTRACT FROM AUTHOR]

CuF 2 ·2H 2 O/4,7-diphenyl-1,10-phenanthroline was found to be a highly efficient catalyst for the nucleophilic alkynylation of cyclopropyl trifluoromethyl ketone. The corresponding trifluoromethyl-substituted tertiary propargyl alcohols were synthesized in moderate to excellent yields under mild conditions. The catalyst system could also be applied to aromatic trifluoromethyl ketone as well as trifluoropyruvate. [ABSTRACT FROM AUTHOR]

A mechanistic study using a cyclopropylmethyl radical clock as a probe to investigate the formation of a macrolactam ring via an SmI2-mediated intramolecular Reformatsky reaction is experimentally explored. The results of our study indicate that the key SmIII-enolate intermediate is formed by cleavage of a C−Br bond in an anion-mediated β-elimination, and then eventually undergoes an intramolecular aldol condensation to form the macrolactam ring. [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]

Elevated triglycerides (TG) contribute towards increased risk for cardiovascular disease. Lipoprotein lipase (LPL) is an enzyme that is responsible for the metabolism of core triglycerides of very-low density lipoproteins (VLDL) and chylomicrons in the vasculature. In this study, we explored the structure-activity relationships of our lead compound (C10d) that we have previously identified as an LPL agonist. We found that the cyclopropyl moiety of C10d is not absolutely necessary for LPL activity. Several substitutions were found to result in loss of LPL activity. The compound C10d was also tested in vivo for its lipid lowering activity. Mice were fed a high-fat diet (HFD) for four months, and treated for one week at 10 mg/kg. At this dose, C10d exhibited in vivo biological activity as indicated by lower TG and cholesterol levels as well as reduced body fat content as determined by ECHO-MRI. Furthermore, C10d also reduced the HFD induced fat accumulation in the liver. Our study has provided insights into the structural and functional characteristics of this novel LPL activator. [ABSTRACT FROM AUTHOR]

The transient intermediate η²-cyclopropene/bicyclobutane niobium complex [TpMe2Nb(η²-c-C3H4)(MeCCMe)] A, generated by an intramolecular β-H abstraction of methane from the methyl cyclopropyl complex [TpMe2NbMe(c-C3H5)(MeCCMe)] (1), is able to cleave the CH bond of a variety of unsaturated hydrocarbons RH in a selective manner to give the corresponding hydrocarbyl complexes [TpMe2NbR(c-C3H5)(MeCCMe)] (R = 2-furyl, 2-thienyl, 1-alkynyl, 1-cyclopentenyl, 1-ferrocenyl (Fc), pentafluorophenyl). The activation of the C-H bond occurs stereospecifically via a 1,3-CH addition across the Nb(η²-cyclopropene) bond of A. Full characterization of several of these complexes includes multinuclear NMR spectroscopy, X-ray diffraction, UV/vis spectroscopy, and electrochemical data. A charge transfer between the ferrocenyl moiety and the niobium center is responsible for the characteristic purple color of the bimetallic complex [TpMe2NbFc(c-C3H5)(MeCCMe)]. The reactivity of these complexes with benzene follows qualitatively the strength and the pK a of the CH bond that is cleaved. The pentafluorophenyl complex [TpMe2Nb(C6F5)(c-C3H5)(MeCCMe)] undergoes cyclopropyl ring opening and alkyne coupling to give two isomeric η4-butadienyl complexes, with [TpMe2Nb(C6F5)(η4-CMeCMeCHCHMe)] as the major isomer. [ABSTRACT FROM AUTHOR]

Abstract: Two novel carbohydrate-derived pyridyl (PYOX)- and cyclopropyl (CYBOX)-substituted oxazoline ligands were prepared from D-glucosamine hydrochloride and 1,3,4,6-tetra-O-acetyl- 2-amino-2-deoxy-β-D-glucopyranose hydrochloride in two steps, respectively. The sugar-annulated PYOX ligand formed a stable metal complex with Pd(II), which was fully characterized by NMR spectroscopy and X-ray crystallography. NMR and X-ray analysis revealed a change of the conformation in the sugar moiety upon complexation with the palladium(II) species. Both glycosylated ligands resulted in high asymmetric induction (up to 98% ee) upon application as chiral ligands in the Pd-catalyzed allylic alkylation of rac-1,3-diphenylallyl acetate with dimethyl malonate (Tsuji-Trost reaction). Both ligands provided mainly the (R)-enantiomer of the alkylation product. [ABSTRACT FROM AUTHOR]

A convenient copper-catalyzed approach has been developed for the synthesis of substituted spiro-fused pyrazolin-5-ones from readily available cyclopropyl O-acyl ketoximes via an intramolecular NN bond formation reaction. These catalytic reactions proceed in excellent yields with a broad scope. [ABSTRACT FROM AUTHOR]

Glycoside hydrolases (GHs) have attracted considerable attention as targets for therapeutic agents, and thus mechanism-based inhibitors are of great interest. We report the first structural analysis of a carbocyclic mechanism-based GH inactivator, the results of which show that the two Michaelis complexes are in 2H3 conformations. We also report the synthesis and reactivity of a fluorinated analogue and the structure of its covalently linked intermediate (flattened 2H3 half-chair). We conclude that these inactivator reactions mainly involve motion of the pseudo-anomeric carbon atom, knowledge that should stimulate the design of new transition-state analogues for use as chemical biology tools. [ABSTRACT FROM AUTHOR]

The synthesis of chiral cyclopropyl carbocyclic purine nucleoside analogues via the highly enantioselective intramolecular cyclopropanation reactions has been reported. With a chiral ruthenium(II)-phenyloxazoline complex as the catalyst, cyclopropyl carbocyclic purine nucleoside analogues containing three contiguous stereocenters were obtained with up to 99% yield and 99% ee. Furthermore, a chiral cyclopropyl carbocyclic adenosine nucleoside having anti-BLV activity could be synthesized in a concise manner using this strategy. [ABSTRACT FROM AUTHOR]

Frankincense (olibanum) is one of the oldest aromatic materials used by humans, but the key molecular constituents contributing to its characteristic odor remained unknown. Reported herein is the discovery that (1 S,2 S)-(+)- trans- and (1 S,2 R)-(+)- cis-2-octylcyclopropyl-1-carboxylic acids are highly potent and substantive odorants occurring in ppm amounts in all of the frankincense samples analyzed, even those showing radically different volatile compositions. These cyclopropyl-derived acids provide the very characteristic old churchlike endnote of the frankincense odor. [ABSTRACT FROM AUTHOR]

Selective tissue factor-factor VIIa complex (TF-FVIIa) inhibitors are viewed as promising compounds for treating thrombotic disease. In this contribution, we describe multifaceted exploratory SAR studies of S1′-binding moieties within a macrocyclic chemotype aimed at replacing cyclopropyl sulfone P1′ group. Over the course of the optimization efforts, the 1-(1 H -tetrazol-5-yl)cyclopropane P1′ substituent emerged as an improved alternative, offering increased metabolic stability and lower clearance, while maintaining excellent potency and selectivity. [ABSTRACT FROM AUTHOR]

An efficient allylation and butenylation of N-alkoxycarbonyl-2-tributylstannyl-1,3-oxazolidines derived from ( S)-vinylglycinol or ( S)-styrylglycinol is described. After conversion of the stannylated azadienes into stannylated dienyl oxazolidinones, a ring-closing metathesis generates dehydropiperidine or dehydroazepane; both are interesting scaffolds for the synthesis of polyfunctionnalized piperidines or azepanes. Whereas the dehydropiperidine synthesis was found to be selective regardless of the Grubbs catalyst used, we found that Grubbs II catalyst induced partial double bond isomerization in the dehydroazepane series. In addition, when allyltrimethylsilane was used in the ring-opening reactions of N-alkoxycarbonyl-2-tributylstannyl-1,3-oxazolidines, cyclopropyl derivatives were selectively obtained. [ABSTRACT FROM AUTHOR]

Recently, there has been an increasing use of the cyclopropyl ring in drug development to transition drug candidates from the preclinical to clinical stage. Important features of the cyclopropane ring are, the (1) coplanarity of the three carbon atoms, (2) relatively shorter (1.51 Å) C-C bonds, (3) enhanced π-character of C-C bonds, and (4) C-H bonds are shorter and stronger than those in alkanes. The present review will focus on the contributions that a cyclopropyl ring makes to the properties of drugs containing it. Consequently, the cyclopropyl ring addresses multiple roadblocks that can occur during drug discovery such as (a) enhancing potency, (b) reducing off-target effects, (c) increasing metabolic stability, (d) increasing brain permeability, (e) decreasing plasma clearance, (f) contributing to an entropically more favorable binding to the receptor, (g) conformational restriction of peptides/peptidomimetics to prevent proteolytic hydrolysis, and (h) altering drug pKa to reduce its P-glycoprotein efflux ratio. [ABSTRACT FROM AUTHOR]

Poly(acrylic acid)s ( PAAs) with curable methacrylamide moieties as well as bisacrylamide crosslinkers are described as components for well-defined hydrogels with increased hydrolytic resistance. PAAs with tethered curing moieties of different alkyl spacer lengths (−( CH2) n−, n = 2, 3, 6 or 8) were prepared via copolymerization of one-sided methacrylated diamines with protected acrylic acid, followed by polymer-analogous methacrylation and deprotection. Bisacrylamide crosslinkers were synthesized by acrylation of diamines with different cores and N-substitutes like allyl, cyclopropyl or propyl groups. Both components were subsequently combined for the formation of novel amide based hydrogels. Network densities of the obtained gels were elucidated by rheokinetic investigations. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A highly efficient asymmetric ring-opening/cyclization/retro-Mannich reaction of cyclopropyl ketones with aryl 1,2-diamines has been realized using a chiral N, N′-dioxide/ScIII catalyst. Benzimidazoles containing chiral side chains were generated under mild reaction conditions in excellent outcomes (up to 99 % yield and 97 % ee). This method also provides efficient access to chiral benzimidazole-substituted amide and cycloheptene derivatives. [ABSTRACT FROM AUTHOR]

A direct route to chiral cyclopropylpyrimidine carbocyclic nucleoside analogues has been reported via highly enantioselective intermolecular cyclopropanation reactions of N1-vinylpyrimidines with α-diazoesters. With chiral ruthenium(II)-phenyloxazoline complex (2 mol %) as the catalyst, cyclopropyl pyrimidine nucleoside analogues could be obtained in good yields (71-96% yields) with high levels of diastereo- and enantioselectivities (10:1 to >20:1 dr and 96-99% ee) in 1 min. [ABSTRACT FROM AUTHOR]

A calcium-catalyzed, dehydrative, ring-opening cyclization of (hetero)aryl cyclopropyl carbinols is reported. The cyclopropyl carbinols are prepared directly from the corresponding donor-acceptor (D-A) cyclopropanes. The calcium catalyst catalyzes the formation of putative (hetero)aryl cyclopropyl carbinyl cations that undergo ring-opening to allylcarbinyl cations. Subsequent intramolecular Friedel-Crafts reaction affords (hetero)aryl-fused cyclohexa-1,3-dienes in up to 97% yield. This approach represents the first example of catalysis for this intramolecular, dehydrative ring-opening cyclization and outperforms the previous reports using stoichiometric Lewis acids. [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]

An efficient approach for the synthesis of highly functionalized pyrroles has been developed by a Pd(TFA)2-catalyzed tandem heterocyclization of 1-(1-alkynyl)cyclopropyl oxime derivatives under mild conditions. The reaction first proceeded via an intramolecular nucleophilic attack followed by a ring-opening process and then intermolecular nucleophilic attack as well as protonation to afford the desired products in moderate to excellent yields. [ABSTRACT FROM AUTHOR]

A novel and practical homoconjugate addition of alkenyl, alkynyl, heteroaryl, and aryl trifluoroborates to arylated cyclopropyl ketones to synthesize γ,γ-disubstituted ketones is reported. A preliminary mechanistic proposal involving ketone protonation, an intermediary carbocation, and intermolecular nucleophile addition has been made based on control studies. [ABSTRACT FROM AUTHOR]

Several isoxazole-containing series of FXR agonists have been published over the last 15 years, subsequent to the prototypical amphiphilic ‘hammerhead’-type structure that was originally laid out by GW4064, the first potent synthetic FXR agonist. A set of novel compounds where the hammerhead is connected to the terminal carboxylic acid-bearing aryl or heteroaryl moiety by either a cyclopropyl, a hydroxycyclobutyl or a hydroxyazetidinyl linker was synthesized in order to improve upon the ADME properties of such isoxazoles. The resulting compounds all demonstrated high potencies at the target receptor FXR but with considerable differences in their physicochemical and in vivo profiles. The structure–activity relationships for key chemical features that have a major impact on the in vivo pharmacology of this series are discussed. [ABSTRACT FROM AUTHOR]

pH--rate profiles for aqueous--organic protodeboronation of 18 boronic acids, many widely viewed as unstable, have been studied by NMR and DFT. Rates were pH-dependent, and varied substantially between the boronic acids, with rate maxima that varied over 6 orders of magnitude. A mechanistic model containing five general pathways (k1--k5) has been developed, and together with input of [B]tot, Kw, Ka, and KaH, the protodeboronation kinetics can be correlated as a function of pH (1-13) for all 18 species. Cyclopropyl and vinyl boronic acids undergo very slow protodeboronation, as do 3- and 4-pyridyl boronic acids (t0.5 > 1 week, pH 12, 70 °C). In contrast, 2-pyridyl and 5-thiazolyl boronic acids undergo rapid protodeboronation (t0.5 ≅ 25-50 s, pH 7, 70 °C), via fragmentation of zwitterionic intermediates. Lewis acid additives (e.g., Cu, Zn salts) can attenuate (2-pyridyl) or accelerate (5-thiazolyl and S-pyrazolyl) fragmentation. Two additional processes compete when the boronic acid and the boronate are present in sufficient proportions (pH = pKa ± 1.6): (i) self-/autocatalysis and (ii) sequential disproportionations of boronic acid to borinic acid and borane. [ABSTRACT FROM AUTHOR]

An efficient amidation method between readily available 1,1-dicyanoalkanes and either chiral or nonchiral amines was realized simply with molecular oxygen and a carbonate base. This oxidative protocol can be applied to both sterically and electronically challenging substrates in a highly chemoselective, practical, and rapid manner. The use of cyclopropyl and thioether substrates support the radical formation of α-peroxy malononitrile species, which can cyclize to dioxiranes that can monooxygenate malononitrile α-carbanions to afford activated acyl cyanides capable of reacting with amine nucleophiles. [ABSTRACT FROM AUTHOR]

An efficient amidation method between readily available 1,1-dicyanoalkanes and either chiral or nonchiral amines was realized simply with molecular oxygen and a carbonate base. This oxidative protocol can be applied to both sterically and electronically challenging substrates in a highly chemoselective, practical, and rapid manner. The use of cyclopropyl and thioether substrates support the radical formation of α-peroxy malononitrile species, which can cyclize to dioxiranes that can monooxygenate malononitrile α-carbanions to afford activated acyl cyanides capable of reacting with amine nucleophiles. [ABSTRACT FROM AUTHOR]

Hydrosilyl ethers, generated in situ by the dehydrogenative silylation of cyclopropylmethanols with diethylsilane, undergo asymmetric, intramolecular silylation of cyclopropyl C−H bonds in high yields and with high enantiomeric excesses in the presence of a rhodium catalyst derived from a rhodium precursor and the bisphosphine ( S)-DTBM-SEGPHOS. The resulting enantioenriched oxasilolanes are suitable substrates for the Tamao-Fleming oxidation to form cyclopropanols with conservation of the ee value from the C−H silylation. Preliminary mechanistic data suggest that C−H cleavage is likely to be the turnover-limiting and enantioselectivity-determining step. [ABSTRACT FROM AUTHOR]

Efavirenz is a non-nucleoside reverse transcriptase inhibitor used in the treatment of human immunodeficiency virus type-1 (HIV). (2S)-(2-Amino-5-chlorophenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol (AMCOL), used as an intermediate in the synthesis of efavirenz and a degradation impurity, has an aminoaryl derivative which is a well-known alerting function for genotoxic activity. Upon request from a regulatory agency, a selective and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for trace level quantitative determination of AMCOL related compound of efavirenz, for a risk assessment and comparison of impurity levels with the commercially available innovator product (brand name: Sustiva). The method provided excellent sensitivity at a typical target analyte level of <2.5 ppm, an established threshold of toxicological concern (TTC), when the drug substance and drug product samples were prepared at 15.0 mg/mL. The AMCOL sample was analyzed on a Luna C18 (2) (100 mm × 4.6 mm, 3 µm) column interfaced with a triple quadrupole tandem mass spectrometer operated in a multiple reaction monitoring (MRM) mode. Positive electrospray ionization (ESI) was employed as the ionization source and the mobile phase used was 5.0 mM ammonium acetate-methanol (35:65, v/v). The calibration curve showed good linearity over the concentration range of 0.2–5.0 ppm with a correlation coefficient of >0.999. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.07 and 0.2 ppm, respectively. The developed method was validated as per international council on harmonization (ICH) guidelines in terms of LOD, LOQ, linearity, precision, accuracy, specificity, and robustness [ABSTRACT FROM AUTHOR]

The crystal structures of 4-cyclopropyl-1-(1-methyl-4-nitro-1 H-imidazol-5-yl)-1 H-1,2,3-triazole, 1, and ethyl 1-(1-methyl-4-nitro-1 H-imidazol-5-yl)-1 H-1,2,3-triazole-4-carboxylate, 2, are reported. The two molecules are non-planar as indicated by the dihedral angles between the heteroaryl rings of 53.94 (7)° in 1 and 70.68 (12)° in 2. Considerable delocalization of π -electron density within the triazole ring is indicated by the pattern of bond distances in 1. By contrast to 1, localization of π -electron density within the triazole ring in 2 is apparent. In both molecules, the nitro group takes part in N-O···π(imidazole) interactions. Compound 1 crystallizes in the orthorhombic space group P222 with a = 7.8053(3) Å, b = 8.5264(3) Å, c = 15.7343(11) Å and Z = 4. Compound 2 crystallizes in the monoclinic space group, P2/ c wit h a = 5.2740(4) Å, b = 8.9695(5) Å, c = 26.0080(18) Å, β = 92.622(2)° and Z = 4. Graphical Abstract: The bond lengths indicate more bond fixation in the triazole rings of ethyl 1-(1-methyl-4-nitro-1 H-imidazol-5-yl)-1 H-1,2,3-triazole-4-carboxylate and more delocalization in 4-cyclopropyl-1-(1-methyl-4-nitro-1 H-imidazol-5-yl)-1 H-1,2,3-triazole. [ABSTRACT FROM AUTHOR]

A divergent approach to generate either 1-hydroxymethylindenes (which could then be converted to benzofulvenes through a dehydration reaction) or naphthalenes by the rearrangement of cycloprop[2,3]inden-1-ols is reported. The effect of the cyclopropyl ring substitution pattern on ring-opening/expansion rearrangements of the substrates was systemically studied. [ABSTRACT FROM AUTHOR]

We disclose a reaction cascade involving cyclopropylimine rearrangement and the Povarov reaction for the synthesis of hexahydropyrroloquinolines from anilines and cyclopropyl aldehydes. This method provides facile and convenient access to pharmacologically significant pyrrolo[3,2-c]quinoline derivatives which are not easily accessible using the existing methods. [ABSTRACT FROM AUTHOR]

A novel formal [3+2] cycloaddition of cyclopropylacetals and aldehydes was developed, and the resulting trisubstituted tetrahydrofurans display three new chiral centers formed with highly diastereoselectivity. This method is stereocomplementary to most previously reported cycloadditions of malonate diesters, relies on the transient generation of cyclopropyl oxocarbenium ions, proceeds under mild conditions, and is based on the concept of temporary activation of an otherwise inert protecting group. [ABSTRACT FROM AUTHOR]

A highly facile and efficient electrophilic bromolactonization of cyclopropylcarboxylic acids could be effected by a Lewis basic sulfide catalyst. Mechanistic studies performed revealed that the cyclopropane substrates could undergo radical bromination upon exposure to light, yielding a mixture of regioisomers. In stark contrast, the Lewis basic sulfide catalyst could promote the electrophilic bromolactonization and yield the Markovnikov product exclusively. [ABSTRACT FROM AUTHOR]

A transformation of cyclopropyl carbene generated from 2-cyclopropyl-2-diazoacetate via oxonium ylide was found by trapping the resulting ylide with imine. The asymmetric three-component reaction of cycloproyl diazoacetates, benzenemethanols and imines afforded a rapid and efficient method to synthesize complex cyclopropane derivatives with excellent diastereoselectivity and enantioselectivity. [ABSTRACT FROM AUTHOR]

The solvent effect on the reaction mechanism of the Pd( II)-catalyzed cycloisomerization of 4-aza-1-cyclopropyl-1,6-enyne toward 3-aza-bicyclo[4.1.0]heptene and homo-ene product was investigated via density functional theory. Four different Pd complexes, PdCl2 {P( OPh)3}, PdCl2 ( PPh3 ), Pd{P( OPh)3}, and Pd( PPh3 ) as hypothetical active catalyst species were applied to ( E)- N-(but-2-ynyl)- N-(3-cyclopropylallyl)amine model substrate in 1,4-dioxane and dichloroethane solvent environment. Reaction pathways toward ( Z)-3-(( Z)-buta-1,3-dien-1-yl)-4-ethylidenepyrrolidine (homo-ene product) and 7-cyclopropyl-6-methyl-3-azabicyclo[4.1.0]hept-4-ene were obtained and energetic differences were compared. The selective formation of 3-aza-bicyclo[4.1.0]heptenes in toluene at 130°C that was not reproduced in other solvents at lower temperatures was likely because of the catalyst effect rather than the solvent effect. [ABSTRACT FROM AUTHOR]

The addition of an alkynyl cyclopropyl mechanistic probe to a digermyne did not lead to any ring-opened rearrangement products indicating that the reaction pathway does not involve any vinylic radicals or cations and providing experimental insight into the addition of alkynes to digermynes. [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]

A series of electronically diverse imines were found to readily react with various donor-acceptor cyclopropyl acid chlorides, with complete regioselectivity, to form 1,3-oxazin-4-ones in moderate yields (25-48% over two steps). Select oxazinones underwent a base induced rearrangement to afford the corresponding cycloheptene-fused oxazinones in good yields (up to 70%). [ABSTRACT FROM AUTHOR]