Imines are widely used as intermediates in the synthesis of heterocycles.  
*Aromatic imines react with an enol ether to a quinoline in the Povarov reaction.  
*Imines react, thermally, with ketenes in [2+2] cycloadditions to form β-lactams in the Staudinger synthesis.  Several variants have been described.
*Imine react with dienes in the Imine Diels-Alder reaction to a tetrahydropyridine.
*tosylimines react with α,β-unsaturated carbonyl compound to give allylic amines in the Aza-Baylis–Hillman reaction.