Formaldehyde N,N-dialkylhydrazones as C-1 building-blocks in asymmetric synthesis

The aza-enamine character of formaldehyde N,N-dialkylhydrazones can be exploited for their use as d(1)'-synthons in the addition reaction to a variety of electrophilic substrates, including Michael accepters and carbonyl compounds. Using readily available proline-derived chiral forms of these reagents, a variety of bifunctional adducts can be obtained with high optical purity. The availability of racemization-free cleavage methods for the transformation of these hydrazones into the corresponding aldehydes and nitriles makes these reagents to appear as a new class of chiral, neutral formyl anion and cyanide equivalents.