Synthesis of highly-functionalised pyridines via hetero-Diels-Alder methodology: reaction of 3-siloxy-1-aza-1,3-butadienes with electron deficient acetylenes

The hetero-Diels-Alder reaction between 1-aza-3-siloxy-1,3-butadienes and electron deficient acetylenes is described. The reactivity of a range of alpha,beta-unsaturated oximes and hydrazones is assessed in the synthesis of tri- and tetra-substituted pyridines bearing an oxygen functionality at C-3. Microwave irradiation has been employed to decrease the extended reaction times and increase the poor yields often associated with this reaction. (c) 2006 Elsevier Ltd. All rights reserved.