One example of a syn adduct from an (E)-silicon enolate and two examples of anti adducts from (Z)-silicon enolates are reported (J. ), Kobayashi and co-workers published an efficient (up to 94% yield) enantio- and diastereoselective (syn/anti 8-92 to 92-8, 67-95% ee) protocol for Mannich-type reactions of a hydrazono ester with silicon enolates in aqueous medium. Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work! It is the process by which many substances important to daily life are obtained.
We synthesise natural products and their structural analogues, applying new methodology we develop.
Our synthetic targets are bioactive macrocyclic natural products and their analogues, and those that can be made through reactions of cyclopropanes.
The present Highlight presents a brief selection of different organic reactions run in an aqueous medium from the literature of the past two years. Chemoselectivity (no overoxidation to sulphones) is explained by the formation of reversible host-guest complexes between the sulphoxide and catalytic amounts of β-cyclodextrin (Tetrahedron Lett. Commercial Glucose Oxidase (GOx) is used to produce in situ hydrogen peroxide via the enzymic oxidation of glucose. The reaction proceeds with high yield (99%) and enantioselection (85-97% ee) using an aqueous solution of formic acid and Et Nano-palladium particles (ARP-Pd) supported on an amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin was found to effect the hydrogenation of styrene and cinnamic derivatives in high yield (81-99% yield).
An excellent review about stereoselective organic reactions in water have been recently published (Chem. The addition of catalytic amounts of sodium bicarbonate/manganese sulphate increases the rate and the yield of the process. Uozumi and co-workers found also that this catalytic system can be used in the hydrodechlorination of chloroarenes (81-99% yield), providing a recyclable, clean and safe protocol for the detoxification of aqueous pollutants (Org.
In the case of lipophilic alkenes, sodium dodecyl sulphate (SDS) was used as a surfactant (Tetrahedron 2005, 61, 6009. A highly efficient (88-98% yield) aerobic oxidation of benzylic alcohols, to the corresponding aldehydes or ketones, was developed by Hu and co-workers.
This is a TEMPO (1)-catalysed system using DBDMH (2) and Na NO as oxidant (a stable, cheap and easy to handle salt) in an aqueous surfactant solution of dimethyldodecylamine N-oxide (DDAO) (Eur.
For many compounds, it is possible to establish alternative synthetic routes.
The ones actually used depend on many factors, such as cost and availability of starting materials, the amount of energy needed to make the reaction proceed at a satisfactory rate, and the cost of separating and purifying the end products.
Chemical synthesis and the extraction of natural products from plants, algae and bacteria are complementary methods for discovering novel and bioactive molecules.
Natural compounds produced by the organism for defence or other biological processes often have interesting bioactivity based on the structure of the compounds.