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Graphical abstract Highlights • Synthesis of cyclopropyl silyl ketones possessing a hydrocarbon group at 1-position of three-membered ring. • Reaction of sulfoxonium ylide with α,β-unsaturated acylsilanes. • The Corey-Chaykovsky cyclopropanation and subsequent silylation of α,β-unsaturated aldehydes. Abstract The synthesis of cyclopropyl silyl ketones possessing a hydrocarbon group at 1-position of three-membered ring was investigated. The reaction of sulfoxonium ylide with α,β-unsaturated acylsilanes derived from α,β-unsaturated aldehydes did not afford the desired acylsilane derivatives. Instead, the corresponding silyl enol ethers were yielded exclusively. On the other hand, the Corey-Chaykovsky cyclopropanation of α-substituted α,β-unsaturated aldehydes proceeded well to give 1-substituted cyclopropyl aldehydes. The silyl substitution of formyl proton in the obtained aldehydes via umpolung of carbonyl group afforded the target acylsilanes. [ABSTRACT FROM AUTHOR]

Novel chiral gold(III) complexes, based on bisoxazoline (BOX) and 2‐pyridyl‐(–)menthol ligands, were prepared and characterised (X‐ray), and their catalytic properties in cyclopropanation reactions of propargyl esters with alkenes were explored. The BOX‐AuIII catalysts gave excellent results for fast cyclopropanation and subsequent in situ cis‐to‐trans vinylcyclopropyl isomerization. AuI and AuIII catalytic species showed different abilities to tune the reactions and transform the initially formed cis product into the isomerized trans product. The appropriate choice of gold(I) or gold(III) complex enabled highly stereoselective formation of cis or trans products (up to 99 % dr), in high yields (63–98 %). The pure cis isomers were used in isomerization studies, showing that rapid cis‐to‐trans isomerization took place at room temperature in the presence of BOX‐AuIII catalysts. [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]

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]

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]

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]

Propargyl acetates reacted with norbornene in the presence of a catalytic amount of tetrakis(tripheylphosphine)palladium to give cyclopropyl ketones. The reaction proceeded with high stereoselectivity, affording a single stereoisomer. The reaction of various substituted norbornenes gave the corresponding cyclopropanes in moderate to good yields. [ABSTRACT FROM AUTHOR]

A flexible method for synthesis of laurencione, a marine natural product, and its benzyl and tert-butyl-methylsilyl-protected precursors was developed utilizing 3-hydroxypropionic acid ethyl ester as a starting material. The synthetic route consists of Kulinkovich cyclopropanation of a hydroxyl-protected ester, followed by oxidation of the resulting cyclopropanol to the appropriate oxiranyl ketone and its MgBr∙OEt-catalyzed rearrangement to 1,2-diketone. [ABSTRACT FROM AUTHOR]

We report a facile approach to a cydopropyl-fused pyrrolidine, which contains four stereogenic centers, by employing the N--O tethered carbenoid methodology. The synthesis was facilitated by the development of a direct Mitsunobu reaction of alcohols with N-alkyl-N-hydroxyl amides to give diazo precursors, which upon intramoleoalar cydopropanation yielded a library of N--O containing cydopropyl-fused bicydic intermediates. Elaboration of the N--O moiety of one member of this library resulted in the formation of the desired pyrrolidine ring demonstrating the potential of this methodology for making cydopropyl-fused heterocydes. [ABSTRACT FROM AUTHOR]

A direct and much simpler way was developed for the diastereoselective synthesis of spiro cyclopropan-1,3′-oxindoles from indolin-2-one/ N-protected indolin-2-ones and bromonitroalkene. The fused restrained cyclopropanes were obtained with high diastereomeric ratios (upto >99:1) and in reasonable to high isolated chemical yields (upto 94%). [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the influence of stereochemistry on biological activities of cis-cyclopropyl combretastatin A4 (CA4) analogues, we have prepared several cyclopropyl compounds in their pure enantiomeric forms. The key reactions in our synthesis are the cyclopropanation of a (Z)-alkenylboron compound bearing a chiral auxiliary, and the cross-coupling of both enantiomeric cyclopropyl trifluoroborate salts with aryl and olefinic halides. Three pairs of cis-cyclopropyl CA4 analogues were evaluated for their potential antivascular activities. The diarylcyclopropyl compounds with SR-configuration (−)-1b, (−)-2b and the cyclopropylvinyl enantiomer (+)-3a with RR-configuration were the most potent tubulin polymerization inhibitors. A correlation was noted between anti-tubulin activity and rounding up activity of endothelial cells. The cytotoxic activity on B16 melanoma cells was in the submicromolar range for most compounds, but unlike the anti-tubulin activity, there was no difference in cytotoxic activity between racemic and enantiomerically pure forms for the three series of compounds. Molecular docking studies within the colchicine binding site of tubulin were in good agreement with the tubulin polymerization inhibitory data and confirmed the importance of the configuration of the synthesized cis-cyclopropyl CA4 analogues for potential antivascular activities. [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]

Copper(II)-mediated N-cyclopropylation of pyridinols involving copper(II) acetate, pyridine, and NaHMDS under microwave conditions in a dry air atmosphere is described. [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]

Abstract: Cyclopropyl moieties embedded in the long aliphatic side chains of imidazolium-type ionic liquids are shown to be highly effective in lowering the T m of such materials relative to counterparts bearing linear, saturated side chains. While not as efficient as olefins in bringing about this effect, ILs incorporating side-chain cyclopropanated modules are likely to be more resistant to aerobic degradation than those employing the former. [Copyright &y& Elsevier]

Abstract: The first efficient total syntheses of 3((1R,2R)- and 3((1S,2R)-2-(12-methyltridecyl)cyclopropyl)propanoic acid have been achieved following a chelation controlled modified Simmon–Smith cyclopropanation, Wittig reaction, Horner–Wadsworth–Emmons olefination, and p-toluenesulfonyl hydrazide catalyzed hydrogenation as key reactions in good overall yield. [Copyright &y& Elsevier]

trans-2-(Trifluoromethyl)cyclopropylamine was prepared on a multigram scale from readily accessible 4,4,4-trifluorobut-2-enoic acid in five steps. The key step was a high-yielding cyclopropane ring formation from 4,4,4-trifluorobut-2-enoic acid methoxymethyl amide under Corey-Chaykovsky reaction conditions. [ABSTRACT FROM AUTHOR]