Alkenylthiazolines, 3, have been synthesized in two steps by reacting 2-methylthiazoline, 1, with different aldehydes followed by dehydration. Acid chlorides react with alkenylthiazolines, 3, to produce the corresponding N-acylation adducts, 4. The Diels-Alder reactions of alkenylthiazolines 3 to generate heterocycles, such as 5 containing cyclic ketene-N,S-acetal structures, have also been explored.