Wadsworth-Emmons reactions between different aldehydes including aliphatic, aromatic, cyclic and heterocyclic with various phosphonates affords alpha,beta-unsaturated nitriles and esters under mild conditions without the formation of by-products such as Michael or Knoevenagel products using a nanocrystalline MgO catalyst. (c) 2005 Elsevier B.V. All rights reserved.