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Some heterocyclic substrates, substituted at the ortho-position of a heteroatom with alkyl substituents bearing a site-selective methyl group, are successfully silylated with reagent (II).

Direct synthesis of 2,5-disubstituted pyrroles has been achieved via acceptorless dehydrogenative heterocyclization of 1,2-aminoalcohols and secondary alcohols by utilizing a heterogeneous carbon-supported Pt catalyst (Pt/C). The optimized method gave 92% yield of 2-ethyl-5-phenyl-1H-pyrrole as a desired product from 2-amino-1-butanol and 1-phenylethanol in the presence of 0.1 mol% of Pt/C and 1.1 equiv. of KOtBu. It has been revealed that Pt/C demonstrates superior catalytic activity to a number of catalysts tested in this study including other transition metal-loaded carbon and various metal-oxide-supported Pt catalysts. In addition, the turnover number (TON) obtained in the present system was found to be higher than those obtained in previously-reported catalytic systems. It is significant that the Pt/C catalyst could be recycled as a heterogeneous catalyst without significant loss in the activity and showed a wide substrate scope for the 2,5-disubstituted pyrrole forming process.

Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method.

Title catalyst is used for the dehydrogenation of sulfoxides to sulfides under solvent-free and mild conditions.

Selective oxidation of α,β-unsaturated aldehydes to α,β-unsaturated carboxylic acids was performed using O2 as the oxidant in the presence of a simple iron catalyst. The addition of an alkali metal...

For the hydrogenation of a tertiary amide (N-acetylpiperidine), Lewis acidic support materials (Nb2O5 and MoOx/TiO2) increase the catalytic activity of Pt metal nanoparticles by a factor of >100. In situ infrared (IR) study shows that coordination of the C=O group of amide to surface Lewis acid sites weakens the C=O bond, and the activated amide undergoes hydrogen transfer from H species on Pt sites. Among 19 types of heterogeneous catalysts tested, Pt/Nb2O5 shows the highest catalytic activity. Pt/Nb2O5 is generally effective for the selective hydrogenation of various tertiary amides and ɛ-caprolactam to the corresponding amines under additive-free and solventless conditions and shows an order of higher turnover number (TON) than previously reported catalysts. Pt-MoOx/TiO2 is the secondary most effective and is reusable 10 times after the reaction.

Five new labdane-type diterpenoids, sterebins Q1 (1), Q2 (2), Q3 (3), Q4 (4), and R (5), were isolated from Stevia rebaudiana fermented by Saccharomyces cerevisiae. The structures of these compounds were established using NMR, MS, and IR methods and their absolute configurations were determined by the ECD spectra of their benzoate derivatives. Through the structures of these new compounds, it was established that the fermentation process caused selective epoxidation and nucleophilic addition of water. Thus, fermentation is an effective way to develop new natural resources for use as drug candidates by enhancing the diversity of natural compounds.

An unprecedented method for the additive-free reductive dimerization of carboxylic acids to esters is developed using Pd-nanoparticles on SnO2 as reusable heterogeneous catalyst.

The first total synthesis of albaflavenone, a novel antibiotic sesquiterpene, has been accomplished via the concise construction of its zizaene skeleton utilizing sequential intramolecular aldol condensation followed by chemo- and diastereoselective reduction of the conjugated carbon–carbon double bond. This synthetic work was completed in nine steps from 2-cyclopenten-1-one as a starting material without the use of protecting groups and with high stereocontrol. In addition, the absolute configuration of naturally occurring albaflavenone was determined to be 1R,2S and 8S.

N-Alkylated indoles [(III) and (V)] are regioselectively synthesized by using Pt-loaded H+-exchanged BEA zeolite as catalyst.

The reaction of dicarboxylic acids and anhydrides with amines, hydroxylamine or ammonia is efficiently catalyzed by Nb2O5 to form a wide range of cyclic imides.

Chemoselective oxidation of allylic alcohols to α,β-unsaturated carbonyl compounds proceeded efficiently using hydrogen peroxide with iron-picolinate catalysts. The in situ generated [Fe(Me-Pic)3] (Me-Pic = 6-methylpicolinate) catalyzed oxidation of the alcohol moiety of primary allylic alcohols while the [Fe(Pic)3] (Pic = picolinate) and [Fe(Me-Pic)2(Pic)] did not show sufficient catalytic activity.

An MWW-type titanosilicate zeolite catalyst with interlayer-expanded structure exhibits the highest activity combined with good chemoselectivity.

A practical and environmental-friendly method was developed to convert vinyl ether into acetate by using a palladium complex with phosphine ligand and hydrogen peroxide. The only by-product is water.

Pt and MoOx co-loaded TiO2 is found to be highly effective for direct methylation of aliphatic and aromatic secondary amines by CO2 and H2 under solvent-free conditions.

Fe-catalyzed oxidation of styrenes to epoxides by H2O2 is achieved in good yields and realized on a 100-g scale.

Fe 3+ -exchanged montmorillonite is shown to be an effective and reusable heterogeneous catalyst for the transamidation of various amides and amines under solvent-free condition. The catalyst shows high yields and wide substrate scope.

The capacity of nanoparticular LiMn2O4 (LMO) spinel can be improved up to 220 mAh/g at a cutoff voltage of 2.5 V by coating with a few layers of graphitic basal planes.

The platinum rule: Heterogeneous, additive-free C-3 selective alkylation of indoles by aliphatic and aromatic alcohols proceeded under transfer hydrogenation conditions with the reusable Pt/θ-Al2 O3 catalyst (see scheme; TON=turnover number).

A selective hydrogen peroxide oxidation of sulfides to sulfoxides using Ti-MWW and Ti-IEZ-MWW catalysts was developed. This reaction was carried out under organic solvent-free conditions, and the only side-product was water. Improvement of catalytic activity toward bulky sulfides will be achieved by optimization of the topology in the Ti zeolite.

For asymmetric synthesis of α-substituted carboxylic acid derivatives, a variety of chiral auxiliaries have been used for the dynamic resolution of α-halo esters in nucleophilic substitution. 1 For example, L-lactamide-mediated dynamic kinetic resolution of α-bromo esters was successfully used for the asymmetric preparation of α-aryloxy carboxylic acids and oxazin-2-ones. 2 However, the application of Llactate as a chiral auxiliary was not effective for the dynamic resolution of α-halo esters. 3 In our continuous efforts to develop L-lactic acid as a chiral auxiliary for the dynamic resolution, we have recently found successful results with ethyl L-lactate. We herein report ethyl L-lactate-mediated dynamic kinetic resolution of α-bromo esters for the asymmetric preparation of α-amino acid derivatives. Treatment of racemic α-bromo-α-phenylacetic acid with ethyl L-lactate in the presence of DCC and DMAP provided α-bromo-α-phenyl ester (αRS)-1 with 50:50 diastereomeric ratio (dr) in 78% yield. When the diastereomeric mixture (αRS)-1 was treated with p-anisidine (p-MeOPhNH2, 1.5 equiv), tetrabutylammonium iodide (TBAI, 1.0 equiv) and diisopropylethylamine (DIEA, 1.0 equiv) in CH2Cl2 at room temperature for 24 h, the amino acid derivative 2 was produced in 86% yield with 97:3 dr as shown in Scheme 1. Following removal of L-lactate chiral auxiliary with Et3N in MeOH gave methyl phenylglycinate (R)-3 with 97:3 enantiomeric ratio (er) in 65% yield. 4 These results imply that α-bromo stereogenic center is configurationally labile with respect to the rate of substitution and (αRS)-1 is dynamically resolved in the substitution with the amine nucleophile. In a solvent screen, the reactions in CHCl3, ether, n-hexane and THF provided (αR)-2 with the same dr as in CH2Cl2, while the lower selectivities of 92:8 dr and 93:7 dr were observed in the reactions in DMF and CH3CN, respectively. In order to understand the asymmetric reaction pathway, we carried out two reactions with α-bromo-α-phenyl ester 1 of 67:33 dr. When 1 of 67:33 dr was allowed to reach thermodynamic equilibrium in the presence of DIEA, the diastereomeric ratio of recovered 1 was determined to be 49:51 dr. The result indicates that the thermodynamic stabilities of two diastereomers are almost the same, ruling out dynamic thermodynamic resolution as a primary pathway. In the reaction of 1 (67:33 dr) with p-anisidine under the same condition, 2 was obtained with the same stereoselectivity (97:3 dr) as in the reaction of 1 with 50:50 dr. In other words, the dr of product 2 is not dependent on the initial dr of 1. These preliminary results indicate that the epimerization is sufficiently fast with respect to the rate of substitution and the primary pathway of the asymmetric induction is a dynamic kinetic resolution. 1

A Co/TiO2 catalyst shows high activity in the dehydrogenation of various secondary alcohols (I) and (III) to afford the corresponding ketones.

Addition of a saturated amount of anhydrous sodium sulfate significantly improves the tungsten-catalyzed H2O2 epoxidation to give acid-labile epoxides in high yields.

The use of sodium sulfate as an additive in the oxidation of various terpenes with hydrogen peroxide allows the synthesis of acid-labile epoxides in high yields.

In some cases it is necessary to add an organic solvent to form the desired product or to increase the yield.

Two kinds of Pd-catalyzed cross-coupling reactions are employed to synthesize diarylphospholes (III) and (VII) (Stille coupling), and (X) (Negishi coupling).

Synthesis and biological evaluation of chrysophanol and menadione derivatives are described.

Conformational properties of methyl nicotinate and methyl isonicotinate have been studied by liquid crystal 1 H-NMR spectroscopy combined with ab initio calculations. The solvent used is a mixture of 80 mol.% of EBBA and 20 mol.% of MBBA.Ab initio calculations have been performed with 4-21G and MINI-4 basis sets to estimate molecular structures and the potential functions for internal rotation. Some structural parameters and the energy difference between rotational isomers have been refined by using observed dipolar coupling constants. The correlation between internal rotation and reorientational molecular motion has been taken into account according to the theory of Emsley, Luckhurst and Stockley. The parameters of the mean external potential are found to take similar values for methyl nicotinate and methyl isonicotinate. The energy difference of the two stable conformers of methyl nicotinate is in agreement with the analysis neglecting the correlation between the two motions.

A series of 2-(p-fluorobenzyl)-3-aryl-6-methoxybenzofurans has been prepared in good yields in a two-step sequence from the corresponding benzylidencoumaranones (aurones).

The reaction rate of Knoevenagel condensation can be dramatically enhanced by irradiating the reaction mixture containing an aldehyde, diethyl malonate, P2O5, piperidine, and chlorobenzene with a commercial microwave oven. Six Knoevenagel condensation products were synthesized within 5–15 min in good yields.