Current Organic Synthesis - Volume 1, Issue 2, 2004

The reaction of α-haloesters and carbonyl compounds in the presence of metallic zinc to give β- hydroxy esters represents a powerful synthetic tool for carbon-carbon bond formation. Since its discovery by Reformatsky, this reaction has been undergoing several improvements and its scope and selectivity have been considerably extended. To this purpose many parameters, such as metal activation, reaction temperature, solvent, properly designed reactants and substrates have been investigated. Furthermore, reactions are not restricted to the use of zinc, but include a variety of other metals or metal derivatives. Among them, transition metals may offer important advantages in terms of milder conditions, higher reproducibility and stereoselectivity.

Recent advance of solvent-free oxidation of alcohols to the corresponding carbonyl compounds is reviewed. The usefulness of different kinds of oxidizing reagents for this transformation, mainly concentrated on chromium- and manganese-based compounds, is discussed.

The syntheses and transformations of 1-(α-aminobenzyl)-2-naphthol (Betti base) derivatives are reviewed. Special attention is paid to the applications of enantiopure Betti base derivatives as chiral ligands in asymmetric transformations.

Natural retinoids, especially retinol, are present in all living organisms and are known as fundamental mediators for many biological processes. Recently, protective effects of carotenoids against severe diseases have encouraged exhaustive chemical and biochemical researches. The emphasis for the past twenty years has been the stereoselective syntheses of economically important retinoids and carotenoids, such as retinol, retinal, RAs, β-carotene, astaxanthin, lycopene etc. This review covers the major developments of synthetic chemistry on natural retinoids and carotenoids from 1990 to the present.