Aliphatic dialdehydes are prepared in good yield from the corresponding acid chlorides by reduction with hydrogen and a palladium catalyst in the presence of a tertiary amide.
Dihalobutyraldehydes of formula I ##STR1## wherein X and Y are each independently of the other Cl or Br, are obtainable at high rates of conversion and with excellent selectivities by catalytic dehalogenation with hydrogen by carrying out the reaction with appropriate .alpha.,.alpha.-dihalobutyraldehydes in an organic aprotic solvent. The dihalobutyraldehydes are intermediates for the synthesis of herbicidal acyl cyclohexanediones.
