Synthesis, Structure, and Thermolysis of Tetracoordinated 1λ4,2‐Selenazetidines Bearing Two Chiral Centers at the 3‐ and 4‐Positions

The title trans and cis isomers (trans-3 and cis-3) were successfully synthesized as stable compounds by taking advantage of the Martin ligand. The X-ray crystallographic analysis of trans-3 showed that it has a distorted pseudotrigonal bipyramidal structure, and that the two phenyl groups at the 3- and 4-positions are cis to each other. The thermolysis of trans-3 in the presence of excess dimethyl acetylenedicarboxylate (DMAD) gave a mixture of the corresponding aziridines (trans-7 and cis-7) and cycloadducts (11a and 11b) of the azomethine ylides formed by ring opening of the aziridines with DMAD. Heating of cis-7 and excess DMAD under the same conditions gave diastereomeric mixtures of both the aziridines and the cycloadducts, which means that the stereochemistry of the aziridine formation from the 1,2-selenazetidine cannot be determined in this system.