Remarkable Solvent Effect of Fluorinated Alcohols on Azo-Ene Reactions.

Despite the long history of the ene reaction between 1,2,4-triazoline-3,5-diones (TADs) and alkenes, its efficiency has always been hampered by competing side reactions, including the overreaction of ene adducts. In this communication, we demonstrate that this inherent limitation can be overcome by using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the solvent. HFIP uniquely facilitates the desired azo-ene process between alkene with TADs presumably through hydrogen-bonding interactions. In addition to TADs, diethyl azodicarboxylate is a competent azo compound that undergoes a sluggish ene reaction with terminal alkenes.