Regio- and stereoselective 1,3-dipolar cycloaddition of indenoquinoxalinone azomethine ylides to β-nitrostyrenes: synthesis of spiro[indeno[1,2-b]quinoxaline-11,3'-pyrrolizidines] and spiro[indeno[1,2-b]quinoxaline-11,2'-pyrrolidines]

 Azomethine ylides obtained in situ from proline or sarcosine and indenoquinoxalinones reacted with nitrostyrenes upon heating in isopropanol for 4–5 days, resulting in the formation of spiro[indeno[1,2-b]quinoxaline-11,3'-pyrrolizidines] and spiro[indeno[1,2-b]-quinoxaline-11,2'-pyrrolidines] with various regiochemistry.