Methyl (Z)-3-aminocrotonate is a good example of the molecular choreography behind heterocycle synthesis. It doesn't look dramatic. Just five carbons, one nitrogen, one double bond, and an ester. But those groups are already arranged in a useful order.
The amino group and double bond give the molecule enamine character. The ester provides a carbonyl. Together, they create a small molecular fragment that is ready to fold into something more complicated.
Global Chemical Database