Diastereoselective guest-shape dependent [2+2]-photodimerization of 2-cyclopenten-1-one trapped within a metal-organic framework.

UV-induced [2+2] dimerization of 2-cyclopenten-1-one and 2-methyl-2-cyclopenten-1-one was successfully carried out in a single-crystal-to-single-crystal manner within a porous metal-organic framework. Intermolecular contacts direct the orientation of the α,β-enone molecules within the host channels, which drives the subsequent photoaddition reaction in a facile and diastereoselective fashion, yielding head-to-tail anti dimers only.