Homogeneous Strecker synthesis

Asymmetric cyanation of imines, a modified Strecker synthesis, affords enantiomerically enriched a-aminonitriles, which can be converted into a-amino acids. Seayad and Ramahngam reported a homogeneous catalyst system that was derived... 

Keywords Strecker reaction, a-aminonitriles, carbonyl compounds, TMSCN, Zr0Cl2.8H20, homogeneous catalyst, one-pot synthesis, multicomponent reaction (MCR), solvent-free, room temperature... 

For better enantiopurities with aliphatic substrates, structural elements crucial for a high stereoinduction were revised by library screening on a solid phase. It was found that the presence of a bulky substituent at both the amino acid and at the 3-position of the salicylimine moiety were key elements responsible for high enantioselectivity. By employing of a pivaloyl substituent at the 5-position of the salicylaldehyde moiety, 24 was found to be a superior catalyst for the Strecker reaction of aliphatic imines 23 (Scheme 30.5) [16]. By adaptation of solid-supported 24 to homogenous conditions, the thiourea was replaced with a urea moiety because of the more convenient synthesis. By applying the so-synthesized catalyst 25, Strecker adducts 26 were obtained in high ee s and yields. Transformation of 3,4-dihydroisoquinoline, a fixed (Z)-imine, into the Strecker adduct (in 88% yield ... 

---