Novel solid-state synthesis of dimeric 4-aryl-1,4-dihydropyridines

Article abstract of DOI:10.1002/jhet.5570350217

On irradiation in the solid state the 4-aryl-1,4-dihydroypridines 1 undergo [2+2] cycloadditon to centro-symmetric head-to-tail dimers 3 and 4a. The almost exclusive formation of the cage dimers 3 via the C₂-symmetric syn-dimers 2 takes place in nearly quantitative yields, in contrast with the cycloaddition reaction of the anti-dimer 4a, which is accomplished by photooxidation to pyridine 5a.