Abstract Aldehydes react with triacetic acid lactone, 1, in the presence of piperidine to afford the pyrones 3a-d and 5. The intermediacy of quinone-methides of type 2a-e has been postulated, and experimental evidence for their existence has been achieved by generation by thiophenol elimination from 7 and subsequent trapping in Diels-Alder reactions. Two examples are given in reactivity of 7 at the sluggish C-5 position.