Stereoselective synthesis of 1,2-difunctional compounds through the addition of organometallic reagents to chiral masked forms of glyoxal

Chiral masked forms of glyoxal can be prepared from cheap aqueous solution of glyoxal or its simple achiral derivatives by one- or multi-step sequences involving the transformation of one or preferably both carbonyl groups, while maintaining the oxidation state of the pre-existing carbons, by reaction with chiral enantiopure compounds, such as alcohols, amines, hydrazines, 1,2-diols, 1,2-aminoalcohols and 1,2-diainines. In most cases, these chiral synthons, constituted of two equal or different functions, have been submitted to organometallic reagents. Thus, taking advantage of the auxiliary-induced asymmetric induction, optically enriched or pure 1,2-difunctional compounds have been prepared, including alpha-hydroxy- and alpha-aminoaldehydes (and the corresponding carboxylic acids by subsequent oxidation), 1,2-diols, 1,2-aminoalcohols and 1,2-diamines. On the other hand, the addition of chiral organometallic reagents to glyoxal has been seldom described. The reaction pathways, mechanisms and stereochemical models or transition states involved in the described routes are herein critically discussed.