Domino synthesis of indenols and alkyl-indene ethers under modified Vilsmeier conditions

Indenols are produced in high yields through domino reactions, when electron-rich trans-stilbenes and other trans aryl-alkyl olefins were subjected to Vilsmeier formylation in the presence of excess POCl₃ in a one-pot procedure. The method is even suitable for converting aryl-alkyl carbinols (precursors for olefins) directly into indenols. The corresponding indene ethers could be prepared in high yields directly when less reactive α,β-unsaturated aldehydes were subjected to cyclization in alcoholic HCl.     

Palladium-catalyzed highly regioselective and stereoselective decarboxylative arylation of unactivated olefins with aryl carboxylic acids

Palladium(II)-catalyzed highly regioselective and stereoselective decarboxylative arylation of unactivated olefins with aryl carboxylic acids has been developed. This method is applicable to a variety of unactivated olefins, including allylamides, long chain functionalized olefins and purely aliphatic olefins, leads to the formation of linear E-configured products in high yields. Both electron-rich and electron-deficient aryl carboxylic acids are suitable arylation reagents. It was found that the choice of solvent, catalyst precursor and oxidant had an important influence on reaction efficiency. As a co-solvent and ligand, DMSO is critical to catalysis. This chemistry expands the scope of decarboxylative arylation of olefins with aryl carboxylic acids, and provides a rapid access to useful linear arylation products of unactivated olefins.     

N,N′-Mono substituted acyclic thioureas: efficient ligands for the palladium catalyzed Heck reaction of deactivated aryl bromides

A series of N,N′-mono substituted acyclic thiourea ligands are found to be highly active phosphine-free catalysts for palladium catalyzed Heck reaction of aryl iodides and bromides with olefins. We have achieved high turnover numbers for aryl iodides with olefins (TONs up to 970,000 for the reaction of iodobenzene with styrene).     

A convenient synthesis of olefins via deacylation reaction

A convenient and environmentally-friendly synthetic method of olefins via deacylation reaction is described. The reaction gives olefins by condensation of aldehydes with a variety of 1,3-dicarbonyl compounds in the presence of anhydrous potassium carbonate at room temperature in high yields (70-90%) in one step. The synthetic potential of this strategy can be used as an alternative procedure to the Wittig, Wittig-Horner reactions. The stereochemistry of the resulted olefins was determined by NOE experiment with correct radio frequency and X-ray analysis. The E/Z selectivity of the deacylation reaction depends on the α-substituents of the 1,3-dicarbonyl compounds.     

Efficient conditions for the synthesis of C-glycosylidene derivatives: a direct and stereoselective route to C-glycosyl compounds

Efficient conditions for the synthesis of C-glycosylidene compounds from lactones based on Wittig reactions of cyanomethyl triphenylphosphoranylidene involving microwave heating are described: subsequent stereoselective reduction of the anomeric olefins gave the corresponding C-glycosides in good yields with high stereocontrol.     

Synthesis of monohalocyclopropane derivatives from olefins by the reaction with trihalomethanes and copper

Fluoro-, chloro-, bromo-, and iodocyclopropane derivatives were obtained in 10–80% yields by the reaction of FCHI₂, ClCHI₂, BrCHI₂, and CHI₃, respectively, with Cu in the presence of olefins. The reaction was electrophilic, and proceeded stereospecifically, i.e., cis and trans olefins afforded cyclopropane derivatives whose configurations with respect to the substituents from original olefins were cis and trans, respectively. Since isomeric olefins were not detected in the reaction mixture which would be expected from the insertion of the corresponding free monohalocarbenes into C—H bonds, the reaction seemed to proceed via organocopper intermediates rather than free monohalocarbenes. With respect to the configuration of the halogen introduced by the new reaction, the cis or endo isomers were generally obtained predominantly over the corresponding trans or exo isomers.     

Regioselective oxidation of internal olefins bearing neighboring oxygen functions by means of palladium catalysts. Preparation of β-alkoxy or acetoxy ketones from allyl and homoallyl ethers or esters

A new preparative method of β- and γ-alkoxy (acetoxy) ketones, which are important precursors of vinyl ketones and 1,4-diketones, respectively, is presented. With PdCl₂/CuCl/O₂ or PdCl₂/p-benzoquinone catalyst system, internal olefins bearing allylic alkoxy or acetoxy group underwent regioselective oxidation to form the corresponding β-alkoxy or β-acetoxy ketones. Similarly, γ-acetoxy ketones were obtained from homoallyl acetates having internal olefins with high regioselectivity.     

An easy and efficient synthesis of 3-nitrochromans

The reaction of nitro olefins reacted with (E)-(2-hydroxyphenyl)-1-nitroethylene in the presence of DABCO generates 3-nitrochroman with a high stereoselectivity. A possible reaction mechanism for the reaction and the transition states involved in producing the final product are proposed. The treatment of 3-nitrochromans with t-BuOK give alkenes.     

Homogeneous hydrogenation of alk-1-enes and alkynes catalyzed by the 1-[Ir(CO)(PhCN)(PPh3)]-7-C6H5-1,7-(σ-C2B10H10) complex

The complex [Ir(σ-carb)(CO)(PhCN)(PPh₃)], where carb = -7-C₆H₅-1,2C₂B₁₀H₁₀, was found to be an effective catalyst for homogeneous hydrogenation of terminal olefins and acetylenes at room temperature and atmospheric or subatmospheric hydrogen pressure. Internal olefins are not hydrogenated, but simple alk-1-enes are readily converted into the corresponding alkanes. Isomerization of the double bond catalyzed by the metal complex occurs at very small extent. Catalytic hydrogenation of olefins having carboxylate substituents on the unsaturated carbon atoms is prevented by the formation of thermally stable chelate hydridoalkyl complexes of the type I$\text{(H)}$(σ-CHRCHR′C(O)OR″) (σ-carb)(CO)(PPh₃)]. Acetylenes are hydrogenated to alkenes. The alk-1-enes formed in the hydrogenation of the alkynes HCCR in turn undergo the more slow reactions either of hydrogenation to alkanes or isomerization to internal olefins which cannot be further hydrogenated. Hydrogenation of alkynes of the type RCCR′ is stereospecifically cis, yielding cis- olefins. Catalyzed cis → trans isomerization reaction of these internal olefins occurs only to a negligeable extent.     

Enzymatic-like mediated olefins epoxidation by molecular oxygen under mild conditions

Highly efficient epoxidation of olefins by molecular oxygen with catalytic amount of manganese meso-tetraphenylporphyrin (Mn(TPP)) at the ppm level were reported. The catalyst conferred high activity and selectivity for the olefins epoxidation under ambient temperature and atmospheric pressure. The turnover number (TON) of the catalyst could reach up to 700 million, which is comparable to enzyme catalysis.     

Tunable dendritic ligands of chiral 1,2-diamine and their application in asymmetric transfer hydrogenation

Tunable dendritic N-mono-sulfonyl ligands have been designed and synthesized via direct N-mono-sulfonylization of the chiral dendritic vicinal diamines and their ruthenium complexes demonstrated high catalytic and recyclable activities with comparable enantioselectivities to Noyori–Ikariya’s TsDPEN-Ru in the asymmetric transfer hydrogenation of an extended range of substrates, such as ketones, keto esters, and olefins.     

The Effect of Substituents on Catalytic Performance of <Emphasis Type="Italic">bis</Emphasis>-Thiosemicarbazone Mo(VI) Complexes: Synthesis and Spectroscopic,Electrochemical, and Functional Properties

The preparation, characterization and electrochemical properties are reported for three new types of molybdenum(VI) complexes with bis-thiosemicarbazone ligands. All compounds were characterized by elemental analysis, electronic spectra, IR and ¹H NMR spectroscopies, thermogravimetric analysis, and cyclic voltammetry. The bis-thiosemicarbazone Mo(VI) complexes were tested as a catalyst for the homogeneous oxidation of olefins using tert-butyl hydrogen peroxide as an oxidant. The catalysts showed efficient reactivity in the olefins epoxidation reactions giving high yield and selectivity of the products, in most cases. Results showed that the bis-thiosemicarbazone ligands introduced both electronic and steric effects on catalytic performance of the prepared Mo(VI) complexes.     

A facile preparation of various N-heterocycles using amides and olefins

We herein report a one pot approach for the synthesis of various nitrogen containing heterocycles including: oxazolines, thiazolines, and dihydro dioxazines via the addition of amides to olefins in the presence of N-iodosuccinimide (NIS) and propionitrile at high temperatures. Thus, the reaction of aryl/heteroaryl amides, thioamides, N-hydroxybenzamide, and phenylurea with various olefins in the presence of NIS and propionitrile at 45 °C afforded the N-heterocycles in good to moderate yields. Reaction of the electron deficient tri-O-acetyl-d-glucal and tri-O-acetyl-d-galactal with benzamide and thiophene-2-carboxamide afforded the N-glycooxazolines in good yields. The newly made heterocycles were tested against various enzymes. Only 3,6-diphenyl-dihydro-1,4,2-dioxazine (1c) was found to moderately inhibit hexokinase II (hHK2).     

Chemical repercussions of orbital interactions through bond and through space The reactivity of the double bond in unsaturated cyclic sulphones towards aziridine formation and epoxidation

The ease of formation of aziridine and/or epoxides from a series of bicyclic olefins, where distant sulphonyl groups are present, is very variable. There is some correlation between reactivity of the vinyl group and its π-ionisation potential which is high in the present molecules relative to comparison olefins. This increase is thought to be due to the presence of orbital interactions through bonds and/or through space between the sulphone group and the double bond, making the latter electron deficient. The ionisation potentials were determined by UV-photoelectron spectroscopy and the assignments made by recourse to ab initio configuration interaction methods.     

Asymmetric catalysis of ene reactions with trifluoropyruvate catalyzed by dicationic palladium(II) complexes

Chiral dicationic SEGPHOS-Pd(II) complex achieves a high chemical yield, (E)-olefin selectivity, anti-diastereoselectivity, along with high enantioselectivity even with less reactive mono- and 1,2-disubstituted olefins in this much less reactive ketone-ene reactions. The high levels of enantioselectivity stem from the effective shielding with diphenyl groups on phosphines caused by the narrow dihedral angle of metal complexes with SEGPHOS.     

A first high enantiocontrol of an asymmetric tertiary carbon center attached with a fluoroalkyl group via Rh(I)-catalyzed conjugate addition reaction

Treatment of fluoroalkylated electron-deficient olefins with various boronic acids in the presence of a catalytic amount of Rh(I) coordinated with (S)-BINAP in toluene/H₂O at the reflux temperature for 3 h gave the corresponding conjugate addition products with high enantioselectivity in high yields.     

Toluene as a novel carrier of xanthates—preparation,use and surrogate of S-tri- and di-chloromethyl xanthates

Toluene has been identified as a novel carrier of xanthates. Their corresponding fragmentative precursors proved to behave efficiently in radical group transfer reactions. As examples, unprecedented S-tri/di-chloromethyl xanthates could be prepared, isolated and further used in radical additions to olefins. Their precursors (de-aromatized toluene upon which is grafted, at one end, a tri/di-chloromethyl-group and, at the other end, a dithiocarbonyl group) can also be used directly in the transfer of both groups to olefins. The re-aromatizing loss of toluene by radical initiated fragmentation of the precursors brings thus new opportunities to the chemistry of xanthates, exemplified here in the intermolecular additions to olefins of new S-tri/di-chloromethyl xanthates.     

Oxidation of olefins and sulfides with different oxidants catalyzed by meso-tetra(n-propyl)porphyrinatomanganese(III) acetate: comparison with meso-tetra(phenyl)porphyrinatomanganese(III) acetate

In this study, the catalytic activity of meso-tetra(n-propyl)porphyrinatomanganese(III) acetate, MnT(n-pr)(OAc) in oxidation of olefins and sulfides with tetra-n-butylammonium Oxone (TBAO), tetra-n-butylammonium periodate (TBAP), aqueous hydrogen peroxide, sodium periodate and Oxone in the presence of imidazole (ImH) has been studied. The comparison of catalytic performance of MnT(n-pr)P(OAc) and MnTPP(OAc) in oxidation of olefins with TBAP shows that while the latter is four times more efficient than the former, the extent of oxidative degradation of the former is ca. 3.5 times greater than the latter. The use of excess amount of styrene resulted in only a ca. 10 % increase in the catalyst stability, suggesting a mainly intramolecular mechanism for the catalyst degradation. On the other hand, in the case of TBAO, the oxidative degradation of the former is four times greater than the latter, but the catalytic performance of the latter for the oxidation of cyclohexene was only ca. 2 times larger than the former. This observation shows that the decreased catalytic performance of MnT(n-pr)P(OAc) relative to MnTPP(OAc) is essentially due to the high degree of degradation of the former. Due to the high degree of catalyst degradation, oxidation of olefins with periodate and Oxone in the presence of the two manganese porphyrins in aqueous solution (or with hydrogen peroxide in dichloromethane) gave little or no product. Oxidation of sulfides with TBAO and TBAP in the presence of MnT(n-pr)P(OAc) showed a conversion of ca. 15 % for the catalytic oxidation of sulfides to sulfones.     

Samarium triiodide-catalyzed conjugate addition of indoles with electron-deficient olefins

The SmI₃-catalyzed reaction of indoles with electron-deficient olefins generated the corresponding Michael adducts in high yields. The substitution on the indole nucleus occurred exclusively at the 3-position and N-alkylation products have not been observed.