Combining topochemical [2+2] photoreactions and hydrothermal isomerisation for the regioselective and quantitative preparation of rtct-pyridylcyclobutanes

A non-photochemical route for the regioselective and quantitative preparation of rtct-pyridylcyclobutane isomers is achieved from the combination of solid state [2+2] photoreactions and controlled isomerisations promoted either by Lewis or Bronsted acids under hydrothermal conditions.