New linear polyimides 11 were synthesized via Diels‐Alder addition polymerization of α‐pyrones 9 with bismaleimides 10. The number‐average molecular weights Mn range from 10 000 to 34 000 g. mol (gel‐permeation chromatography). The chemical structure of these polymers is supported by X‐ray crystallography, NMR spectra and model reactions. The Diels‐Alder addition occurred with high endo selectivity.