Search

The present study explores the solvothermal synthesis of the Sn-Na MOF composed of stannatranone cages interconnected through Na bridges. The MOF was used as a catalytic support to hold palladium nanoparticles. The nanopalladium-decorated Sn-Na MOF (Pd NPs/Sn-Na MOF) was characterized by FTIR, PXRD, SEM, TEM, NH3-TPD, and XPS analysis. The resulting composite Pd NPs/Sn-Na MOF demonstrated catalytic activity for the conversion of fructose to 5-hydroxymethylfurfural (5-HMF), which is a promising material for the production of various value-added chemicals. The catalyst shows rapid conversion (in 3 h), recyclability (up to 5 cycles), and a high yield of 5-HMF (92.4%) in an aqueous medium without the formation of the side product levullinic acid. Further, the successful conversion of stale and rotten apples to 5-HMF using the developed protocol justifies the scope to convert agrowaste sugars to value-added products with appreciable yield. [ABSTRACT FROM AUTHOR]

Density functional theory calculations and solvation effects are used for modeling each step in the Morita-Baylis-Hillman (MBH) reaction. The studies have shown the formation of the ammonium enolate and subsequent addition to the aldehyde, which is followed by rate-limiting proton transfer to give the MBH adduct.

The application and scope of chalcogenides as organocatalysts in ylide-mediated synthesis of enantioselective aziridines is reviewed. The chalcogenides can also used in asymmetric synthesis of carbonyl compounds such as indole alkaloids.

The salt-free Wittig reaction of non-, semi-, and stabilized ylides was investigated on realistic systems using density functional theory (DFT) calculations, including continuum salvation. The importance of including the two key steps of the process in the analysis for understanding selectivity in the Wittig reaction is demonstrated.

The reactions of a range of amide-stabilized sulfur ylides derived from camphor-derived sulfonium salts for the synthesis of glycidic amides are studied. Primary, secondary and tertiary amides are tested and it is found that the highest enantioselectives are observed with tertiary amides with exclusive trans selectivity, and the selective ring opening of the amides with a variety of nucleophiles is effected, followed by hydrolysis of the amide to yield the corresponding carboxylic acid.

Two catalytic methods are developed to chart the synthetic reaction of sulfur ylides with carbonyl compounds to give epoxides. The scope and application of these two methods is reviewed.

Varieties of metalated tosylhydrazone salts derived from benzaldehyde are prepared and reacted with benzaldehyde in the presence of tetrahydrothiophene (THT) (20 mol percent) and Rh2(OAc)(sub 4) (1 mol percent) to give stilbene oxide. A general process for the in situ generation of diazo compounds from from tosylhydrazone sodium salts is established and applied in sulfur-ylide mediated epoxidation reactions.

Amines were reported to catalyze the epoxidation of alkenes using oxone (2KHSO5+KHSO4+K2SO4), and significant levels to asymmetric induction were observed. From screening a series of amines based on 2-substituted pyrrolidines, it has been found that more consistent and reproducible results are achieved with HCI salt of the amine compared to the amine itself.

Research has been conducted on (R)-salbutamol. The results of enantioselective synthesis of this compound carried out via the use of chiral C (sub)2 symmetric acyl anion equivalent are presented.

The use of sophisticated computational methods to examine potential energy surfaces for the epoxidation of aldehydes by sulfur ylides is described. The mechanisms of the 'model' reaction and the reaction forming stilbene oxide are studied using the density functional theory calculations and flexible basis sets.

Research has been conducted on N-sulfonyl imines derived from aromatic, aliphatic, heteroaromatic and unsaturated aldehydes. The imines have been treated with trimethylsilyldiazomethane to produce C-silylaziridines and the synthetic potential of these C-silylaziridines has been investigated.

Research has been conducted on the Baylis-Hillman reaction between cyclohexenone and benzaldehyde. Results indicate the acceleration of this reaction when it is conducted in water and the origin of this acceleration rate is discussed.

A study was conducted to examine asymmetric oxidation of a series of 1,3-dithianes. Asymmetric induction was determined in the formation of the monoxide with all esters while the racemic oxidation of 2-carbethox-1,3-ithiane and a range of oxidants were also evaluated in the study. Results indicated that the oxidation of ethyl 1,3-dithiane-2-carboxylate can be effectively determined by the Modena oxidation protocol.

A study was conducted to analyze the catalysis of the Baylis-Hillman reaction associated with the coupling of an unsaturated carbonyl compound/nitrile with aldehydes. Reactions were carried out utilizing tert-butyl acrylate and benzaldehyde with various Lewis acids. Results indicated that the use of catalytic amounts of oxygen-rich donor ligands supported an increase in reaction rate.

Chiral sulfides were designed and optimized for use in catalyzing the synthesis of nonracemic epoxides. The highest yield and enantioselectivity in the epoxidation process were obtained for the acetaldehyde (1R,4R,6R,8R)-4,11,11-trimethyl-5-oxa-3-thia-tricyclo-{6.2.1.0(super 1,6)}undecane. Results also showed that the solvent and metal catalyst used had no effect on the enantioselectivity. Moreover, high enantioselectivities and diastereoselectivities were obtained when the optimum conditions were used for different aldehydes.

Research was conducted to examine the 1,3-dipolar cycloaddition reactions of trans-2-methylene-1,3-dithiolane 1,3-dioxide with nitrones. The existence of a C2 symmetry element in (1R,3R)-2-methylene-1,3-dithiolane 1,3-dioxide to a diene are symmetry related and, thus, identical, which reduces the number of competing transition states in the reaction. (1R,3R)-2-methylene-1,3-dithiolane 1,3-dioxide revealed very high reactivity and stereoselectivity in Diels-Alder reactions with a range of dienes.

Aziridination, cyclopropanation, epoxidation, olefination and rearrangement are asymmetric ylide reactions. Previous studies have demonstrated such reactions on heteroatom ylides O, S, Se, P, N and As and their derivatives. Further studies, however, are needed before the potential of the asymmetric ylide approach is truly realized in synthesis. Research should focus on catalytic asymmetric processes and carbonyl compound dynamic kinetic resolution.

The synthesis of C-4-substituted 2-oxabicyclo[3.3.0]oct-7-en-ones and their reactivity in palladium-mediated substitution reactions was reported. Reaction rates were found directly related with increasing electron-withdrawing ability of the substituent(X). A strong correlation between rate and pKa of the corresponding substituted acetic acids(XCH2CO2H), with the exception of X=OH was also observed.

The reactions of metalated trans-1,3-dithiolane 1,3-dioxide with aldehydes were investigated. The results showed that the anion of the compound is sufficiently stable and reacted with different aldehydes to form secondary alcohols with moderate to high selectivity. The use of 2.4 equiv of lithium hexamethyldisilazide at -78 degrees C, resulted in higher diastereoselectivity.

A short, asymmetric method for the synthesis of carbocylic analogues of nikkomycins and polyoxins is described. The scheme involves the palladium-catalyzed substitution reaction of an unsaturated lactone as the key step. The reaction conditions for the stereospecific total synthesis of the carboxylic analogue of uracil polyoxin C are presented.

A study of the anion chemistry of 1,3-dithiane 1,3-dioxide with aldehydes and ketones shows that it undergoes selective addition reactions with aromatic aldehydes under equilibrium-controlled conditions. Li, Mg, Al, Ce and Ti exhibit reduced selectivity but Zn4 provided improved selectivity with aromatic aldehydes. The model developed to explain the disteroselectivity of aldehydes includes complexation of metal alkoxides with axial sulfoxide.