The mechanism of lipase-catalyzed synthesis of food flavoring ethyl butyrate in a solvent-free system

Immobilized Lipase-B from Candida antarctica catalyzed the esterification of butyric acid and ethanol under anhydrous solvent-free reaction conditions toward the synthesis of ethyl butyrate, a compound significant as food and perfume flavoring, as well as biofuel. The proton inventory technique was efficiently applied in mixtures of the anhydrous polar solvents ethanol and deuterated ethanol (CH3CH2OD). Subsequently, and by suitable analysis of the experimental data, the aforementioned synthetic procedure seems likely to follow the kinetic mechanism ordered bi-bi involving single substrate dead-end inhibition by ethanol, whereas were estimated values of important parameters. So far is the first experimental evidence that the synthesis of ethyl butyrate, which is catalyzed by immobilized lipase, it follows an entirely different mechanism when it is performed in anhydrous solvent-free system vs. that in anhydrous n-hexane; then it may be constructive for the industrial production of fixed quality of ethyl butyrate.

Dealkenylative Thiylation of C(sp3)–C(sp2) Bonds

Carbon–carbon bond fragmentations are useful methods for the functionalization of molecules. The value of such cleavage events is maximized when paired with a subsequent bond formation. Herein we report a protocol for the cleavage of a C(sp³)–C(sp²) bond, followed by the formation of a new C(sp³)–S bond. This reaction is performed in non-anhydrous solvent and open to the air, employs common starting materials, and can be used to rapidly diversify natural products. We have also subjected the thiylated products to various synthetic transformations, demonstrating their utility as synthetic intermediates.

Dealkenylative Thiylation of C(sp3)–C(sp2) Bonds

Carbon–carbon bond fragmentations are useful methods for the functionalization of molecules. The value of such cleavage events is maximized when paired with a subsequent bond formation. Herein we report a protocol for the cleavage of a C(sp³)–C(sp²) bond, followed by the formation of a new C(sp³)–S bond. This reaction is performed in non-anhydrous solvent and open to the air, employs common starting materials, and can be used to rapidly diversify natural products. We have also subjected the thiylated products to various synthetic transformations, demonstrating their utility as synthetic intermediates.

Unravelling Factors Affecting Directed Lithiation of Acylamino­aromatics

Ureas, pivalamides, and carbamates are widely used as directing metalation groups (DMGs) due to their good directing ability, low cost, ease of access, and ease of removal. Lithiation of substituted benzenes having such directing metalation groups using various alkyllithiums in anhydrous solvent at low temperature provides the corresponding lithium intermediates, but lithiation may take place at various sites. Reactions of the lithium reagents obtained in situ with various electrophiles give the corresponding derivatives, typically substituted at the site(s) where initial lithiation occurred, often in high yields. However, it is often difficult to predict what reagents and/or conditions might be needed to give specific products or to draw general conclusions about the factors that influence the reactions, especially when the reagents, temperature, and solvents used in reported reactions are not directly comparable. In this review, therefore, we attempt to unravel the various factors that influence the lithiation of various simple aromatic compounds containing urea, pivalamide, and carbamate groups.1 Introduction2 Lithiation with DMG Attached Directly to the Phenyl Ring2.1 Influence of the DMG2.2 Influence of Substitution on the Phenyl Ring3 Lithiation with the DMG Separated by a CH2 Group from the Phenyl­ Ring3.1 Effect of the DMG3.2 Influence of Substitution on the Phenyl Ring4 Lithiation with the Phenyl Ring and DMG Separated by Two or More CH2 Groups4.1 Effect of the DMG and Its Distance from the Phenyl Group4.2 Effect of Substituents on the Phenyl Ring5 Conclusions

Palladium/N-Heterocyclic Carbene Catalyzed Mono- and Double-Cyanation of Aryl Halides Using Potassium Ferrocyanide Trihydrate under Aerobic Conditions

A practical palladium/N-heterocyclic carbene catalyzed procedure for the mono- and double-cyanation of aryl halides is described using inexpensive, easy-to-handle and nontoxic potassium ferrocyanide trihydrate {K4[Fe(CN)6]·3H2O} as the cyanating agent. The reaction does not require an anhydrous solvent, or the exclusion of air or moisture. A variety of electron-rich and electron-deficient aryl halides are efficiently converted into their corresponding nitriles and dicarbonitriles.

Role of important parameters in ring opening polymerization of polylactide

Different parameters, namely polymerization temperature, polymerization time, monomer/initiator ratio, nature of the initiator, amount of water or other impurities etc. are very significant for polymerization reactions either in bulk or solution. Monomer to initiator ratio has a very significant role in polymerization reactions and a value ranging from 50 to 5000 that has been reported by different researchers. Recrystallization of the monomer removes the meso compounds from the monomer, which absorbs the moisture and effects polymerization reaction. So, it is necessary to recrystallize the monomer with any anhydrous solvent like dry toluene, ethyl acetate etc. Prolonged reaction time cannot increase the polymer yield; it generally causes the decrease of molecular weight and broadening of molecular weight distribution of formed polymers. This is probably due to the transesterification side reaction in polymerization, intensifying at prolonged time periods. Several groups like hydroxyl and carboxylic acid affect the polymerization rate.