Enantioselective Sulfur‐Michael Addition of Thioacetic Acid to Nitroalkenes Catalyzed by Bifunctional Amine‐Thiourea Catalysts

An enantioselective Michael addition of thioacetic acid (AcSH) to nitroalkenes, catalyzed by a leucine‐derived bifunctional amine? thiourea, was developed with high yields and moderate enantioselectivities. The thiourea‐ammonium salt formed in the reaction is identified as the active catalyst, and the multiple H‐bonding system is responsible for the stereocontrol. The resulting thioester products are useful intermediates for the synthesis of enantiomerically enriched S‐containing compounds.     

A three-component reaction between alkenes, secondary phosphanes, and elemental selenium: a novel, efficient, atom-economic synthesis of diselenophosphinic esters

A novel, convenient, atom-economic approach toward the synthesis of diselenophosphinic esters has been developed via the three-component reaction between aryl- or hetarylalkenes secondary phosphanes, and elemental selenium. The reaction proceeds without a catalyst (85 °C, 3 h, 1,4-dioxane) to afford the target compounds in good to high yields.     

Deconstructive Carboxylation of Activated Alkenes with Carbon Dioxide

Carboxylation with carbon dioxide (CO₂) represents one notable methodology to produce carboxylic acids. In contrast to carbon–heteroatom bonds, carbon–carbon bond cleavage for carboxylation with CO₂ is far more challenging due to their inherent and less favorable orbital directionality for interacting with transition metals. Here we report a photocatalytic protocol for the deconstructive carboxylation of alkenes with CO₂ to generate carboxylic acids in the absence of transition metals. It is emphasized that our protocol provides carboxylic acids with obviously unchanged carbon numbers when terminal alkenes were used. To show the power of this strategy, a variety of pharmaceutically relevant applications including the modular synthesis of propionate nonsteroidal anti-inflammatory drugs and the late-stage carboxylation of bioactive molecule derivatives are demonstrated.     

Retention indices of alkenes and the corresponding epoxides on a capillary column coated with cyanopropyl methyl silicone phase

Summary Retention indices or five 1-alkenes, seven branched alkenes and five cycloalkenes and the corresponding epoxides were determined at two temperatures on a fused-silica capillary column coated with cyanopropyl methyl siloxane to interpret their chromatographic behaviour. The standard deviation was 0.2 index units.     

Olefin cyclopropanation catalyzed by new diiminophosphorane and triiminophosphorane complexes of copper and palladium

Chelating diiminophosphorane and tripodal iminophosphorane copper and palladium complexes are found to efficiently catalyze the cyclopropanation of activated monosubstituted olefins with ethyl diazoacetate. Cycloolefins, and linear α-olefins are somewhat less reactive. The diastereoselectivities of the reactions are moderate and no major differences were seen when comparing the bidentate chelating ligand to the tripodal ligands.     

A simple and accurate approach for calculating the vibration spectra of molecules on surfaces: Comparisons to high resolution electron energy loss data for ethylene on silicon

Peak assignment is a complex but important task for analyzing the vibration spectra of surface-bound molecules. Here we describe a simple approach for calculating infrared and Raman spectra for surface-bound molecules using a cluster model approach with quantum capping potentials (QCPs). The utility of the approach is demonstrated by comparisons to the measured high resolution electron energy loss spectra for ethylene on clean silicon. By capping the silicon cluster with QCPs we computed spectra that agree very well with the HREEL spectrum, allowing us to easily assign the experimental peaks. QCPs are similar to effective core potentials, can be used with any ab initio technique and most computational chemistry packages, and their use requires no special expertise.     

A convenient preparation of mixed allylic and allenic thiosulfinates

The first successful preparation of propargylic and allylic chloroalkoxy disulfides in high yields is reported. Facile 1,4-electrophilic addition of these to 2,3-dimethyl-1,3-butadiene, followed by [2,3]-sigmatropic rearrangements affords mixed allyl allenic and bis-allylic thiosulfinates, respectively. Due to their similarity to allicin, the latter are of potential biological interest.     

Vinamidines and Vinamidinium Salts—Examples of Stabilized Push-Pull Alkenes

The name vinamidines has been proposed for 1,5-diazapentadienes: these compounds can be regarded as vinylogous amidines and at the same time as push-pull substituted (and thereby stabilized) alkenes. Vinamidine and vinamidinium structural elements may also form part of a ring system. Characteristic of this class of compounds are their reactivity toward electrophiles (at C_β) and nucleophiles (C_α) and their regenerative character, i.e. their tendency to undergo substitution instead of addition reactions. Reactions of vinamidinium salts with nucleophiles are of special preparative value: they lead e.g. to pyrazoles, oxazoles, pyrimidines, diazepines, quinolines, and quinolizines.     

The Reduction of Organic Compounds with Chromium(II) Salts

Chromium(II) salts can be used for a variety of reductions in organic chemistry; for example, alkyl halides and suitably substituted olefins may both be reduced to alkanes, and alkynes may be converted into trans-olefins. Several epoxyketones are reduced to α,β-unsaturated ketones or β-hydroxyketones, and a nitro steroid was found to give a hydroxy(hydroxyimino) compound. The reduction of alkyl halides is reported to proceed by a free-radical mechanism; the halogen atom that is set free forms a bridge between two chromium atoms.