Stereoselective Solid-State Synthesis of Substituted Cyclobutanes Assisted by Pseudorotaxane-like MOFs
Fei-Long Hu1,2, YanMi2, Chen Zhu1, Brendan F. Abrahams3, Pierre Braunstein4, and Jian-Ping Lang*,1（郎建平）
1 College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, P. R. China
3 School of Chemistry, University of Melbourne, Victoria, Australia
4 Institut de Chimie (UMR 7177 CNRS), Université de Strasbourg, Strasbourg, France
Angew. Chem. Int. Ed. 2018, 57, 12696 --12701
Regioselective photodimerization of trans‐4‐styrylpyridine (4‐spy) derivatives is performed using pseudorotaxane‐like Zn‐based metal organic frameworks MOFs as templates. The formation of rctt‐HT (head‐to‐tail) dimers is achieved by confining pairs of coordinated 4‐spy derivative ligands within hexagonal windows and then irradiating them with UV light. It is also possible to achieve a photodimerization reaction where two different substituted 4‐spy ligands are included in such a MOF material. The ether bond formation is employed to protect the sensitive ‐OH group of HO‐spy and the methyl group of CH3O‐spy is subsequently removed after the formation of cyclobutane derivative in the CH3O‐spy‐based MOF. Introducing substituents at the 2‐ or 3‐position of the phenyl group of 4‐spy does not significantly affect the rate of the dimerization process except in the case of the strongly electron‐withdrawing nitro group where the rate is significantly decreased. These results are in striking contrast to the mixtures of photoproducts and low yields obtained by untemplated photodimerization in organic solvents.