A three-component synthesis of β-alkoxy-β-keto-enamides—flexible precursors for 4-hydroxypyridine derivatives and their palladium-catalysed reactions

The flexible three-component reaction of lithiated alkoxyallenes with nitriles and carboxylic acids provided a series of highly functionalised β-alkoxy-β-ketoenamide derivatives. Upon base induced cyclisation and conversion to 4-pyridyl nonaflates various palladium-catalysed coupling reactions could be employed. The efficacy of this approach to functionalised pyridine derivatives was demonstrated by a fairly short route to a key intermediate suitable for a Glenvastatin synthesis. After Sonogashira couplings of alkynes with 4-pyridyl nonaflates subsequent cyclisations led to highly fluorescent [2,3c]furopyridine derivatives, whereas Suzuki reactions afforded 4-pyridyl stilbenes and by photocyclisation a highly substituted benzoisoquinoline derivative.