Isocyanide and Related Aldol Reactions

Cyanopropionates have also been employed in catalytic aldol reactions. The enolisation of the nucleophile (7.98) by the rhodium complex of TRAP ligand (7.99) is the basis for the catalysis. The use of bulky esters affords high selectivity in the aldol reaction with formaldehyde (7.100), although only moderate antitsyn selectivity was observed when alternative aldehydes were employed. 

Another approach to the synthesis of p hydroxy-a-amino acids is by aldol reaction of imines derived from amino adds. The benzophenone imine of glycine (7.102) undergoes highly enantioselective aldol addition with a range of aliphatic aldehydes, including (7.71) xmder phase-transfer conditions in the presence of the bromide salt of phase-transfer catalyst (7.103). A similar transformation is catalysed, in low to moderate ee, by the bimetallic catalysts developed by Shibasaki and CO workers.  

---