2 From nitriles and esters
Nitriles are reduced to corresponding imine with stannous chloride
in the presence of hydrochloric acid, which on hydrolysis give
corresponding aldehyde This reaction is called Stephen reaction Alternatively, 
nitriles 
are 
selectively 
reduced 
by
diisobutylaluminium hydride, (DIBAL-H) to imines followed by
hydrolysis to aldehydes:
8