close to those calculated for the Danishefsky−Kitahara and Rawal dienes. In fact, 4-alkenylthiazoles behave as all-carbon dienes in Diels−Alderreactions with the participation of the formal C−C double bond of the thiazole ring and the side-chain double bond. The reactions with N-substituted maleimides, maleic anhydride, and naphthoquinone take place with high levels of stereocontrol to give the corresponding