Ring shaped molecules containing nitrogen and oxygen (as well as sulfur) are called "heterocycles" and they are an extremely common building block of pharmaceuticals. They are found in 8 of the top 10 best selling drugs in the USA: Lipitor, Plavix, Nexium, Abilify, Seroquel, Singulair, Crestor, and Cymbalta. Combined sales of these 8 pharmaceuticals were worth $43.2 billion in 2011. http://www.businessinsider.com/10-best-selling-blockbuster-d...

So developing reliable reactions that build these molecules is, indeed, a useful exercise.