Complex sentence: The 1,3-dipolar cycloaddition or Huisgen cycloaddition or Huisgen reaction is an organic chemical reaction belonging to the larger class of cycloadditions, between a 1,3-dipole and a dipolarophile mostly a substituted alkene to form a substituted five-membered ring.
Split into simpler sentences: The 1,3-dipolar cycloaddition, also known as the Huisgen cycloaddition or Huisgen reaction, is an organic chemical reaction belonging to the larger class of cycloadditions. It is the reaction between a 1,3-dipole and a dipolarophile, most of which are substituted alkenes, to form a five-membered ring.