Along came poly: A novel macroporous polymer‐supported chiral RuII/pheox catalyst (1, see SEM image) afforded excellent reactivity and enantioselectivity in inter‐ and intramolecular cyclopropanation ...reactions with a broad range of substrates. The catalyst showed no leaching and could be reused up to 11 times, even after storage.
Novel catalysis involving phosphonomethylation of N-methylaniline and asymmetric cyclopropylphosphonation reactions of N,N-diethylaniline derivatives with diazomethylphosphonates are reported. ...Optically active cyclopropylphosphonate derivatives were directly synthesized from diazomethylphosphonates and N,N-diethylaniline derivatives catalyzed by a Ru(II)-Pheox complex in one step in good yields and high diastereoselectivities (up to trans/cis = > 99:1<) and enantioselectivities (up to 99% ee). D-labeling mechanistic studies of phosphonomethylation and cyclopropylphosphonation suggested that an enamine or iminium intermediate was generated in the reaction process.
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.
Highly enantioselective Diels−Alder reactions of α-halo-α,β-unsaturated ketones with Lewis acid-activated chiral oxazaborolidine 1 are described. The reaction with α-fluoroenones provided the ...corresponding cyclohexane derivatives having a fluorinated quaternary stereogenic center with up to 99% de and 94% ee. The reaction with α-bromo cyclic enones provided the corresponding bromo bicyclic adducts with up to 99% de and 95% ee. A brominated cis-fused bicyclic adduct derived from 2-bromocyclopenten-1-one and Dane’s diene was converted to the trans-fused bicyclic system via reductive alkylation with the bulky aluminum reagent aluminum tris(2,6-diphenylphenoxide) (ATPH). With this process, formal syntheses of (+)-estrone and norgestrel have been demonstrated.
A single particle observation of quantum dots (QDs) was performed on lipid bilayers formed on graphene oxide (GO). The long-range fluorescence quenching of GO has been applied to biosensing for ...various biomolecules. We demonstrated the single particle observation of a QD on supported lipid bilayers in this study, aiming to detect the quenching efficiency of lipid and protein molecules in a lipid bilayer by fluorescence single particle tacking (SPT). A single lipid bilayer or double lipid bilayers were formed on GO flakes deposited on a thermally oxidized silicon substrate by the vesicle fusion method. The QDs were conjugated on the lipid bilayers, and single particle images of the QDs were obtained under the quenching effect of GO. The quenching efficiency of a single QD was evaluated from the fluorescence intensities on the regions with and without GO. The quenching efficiency reflecting the layer numbers of the lipid bilayers was obtained.
The practical synthesis of 4,4,4-trifluorocrotonaldehyde (1) and its application to enantioselective 1,4-additions are described. The organocatalytic 1,4-addition of 1 with several nucleophiles such ...as heteroaromatics, alkylthiols and aldoximes afforded the corresponding products, each bearing a trifluoromethylated stereogenic center with high optical purity. A resulting product was converted into an MAO-A inhibitor, befloxatone.
The diazo derivative of acetonyl acetate is a useful basic skeleton for the synthesis of cyclopropyl ketones. The intermolecular cyclopropanations of diazo acetoxy acetone with olefins are ...accomplished by using a novel p‐nitro‐Ru(II)‐diphenyl‐Pheox catalyst to give the corresponding optically active cyclopropane derivatives in good yields (up to 95%) with excellent diastereoselectivities (up to 99:1) and enantioselectivities (up to 98% ee).
Computational chemical analysis of Ru(II)‐Pheox–catalyzed highly enantioselective intramolecular cyclopropanation reactions was performed using density functional theory (DFT). In this study, ...cyclopropane ring–fused γ‐lactones, which are 5.8 kcal/mol more stable than the corresponding minor enantiomer, are obtained as the major product. The results of the calculations suggest that the enantioselectivity of the Ru(II)‐Pheox–catalyzed intramolecular cyclopropanation reaction is affected by the energy differences between the starting structures 5l and 5i. The reaction pathway was found to be a stepwise mechanism that proceeds through the formation of a metallacyclobutane intermediate. This is the first example of a computational chemical analysis of enantioselective control in an intramolecular carbene‐transfer reaction using C1‐symmetric catalysts.
An aggregation-induced emission chromophore, vinylpyrrole, was prepared from a formylpyrrole derivative, Meldrum's acid, and 1,3-dimethylbarbituric acid. The optical properties of the chromophore ...both in the solution and solid states were investigated by UV-vis and fluorescence spectroscopy. Single crystal X-ray diffraction measurements revealed that the dimethylbarbituric acid adduct formed a J-aggregate in the solid and resulted in higher fluorescence quantum yield compared to the Meldrum's acid adduct. Emission enhancement was found to occur by the restriction of molecular rotation in the solid state.
A cyclic ester and a cyclic amide functionalized monopyrroles show aggregation-induced emission (AIE) by the restriction of intramolecular rotation (RIR) mechanism.
A simultaneous immunosensor based on surface plasmon resonance (SPR) was developed for determination of 3 pesticides —boscalid, clothianidin and nitenpyram— instead of the direct competitive ...enzyme-linked immunosorbent assays (dcELISAs) widely used as individual determination methods. Carboxy groups that introduced compounds to their pesticides were designed, and conjugates of them and bovine serum albumin were immobilized onto separate channels of the same sensor chip. When a mixture of 3 monoclonal antibodies reacted to each pesticide, and 3 pesticides were injected into the SPR immunosensor, each channel showed specific reactivity at 15 – 93 ng mL−1 for boscalid, 6.7 – 27 ng mL−1 for clothianidin, and 7.3 – 62 ng mL−1 for nitenpyram. Recovery tests using vegetables spiked with a mixture of 3 pesticides showed good results: 75 – 90%, 88 – 104%, and 72 – 105%, respectively, with a high correlation to results of the dcELISAs. The SPR immunosensor would be useful for the determination of pesticide residues in vegetables.
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