Synthesis and reactions of a symmetric paramagnetic pyrrolidine diene

Symmetric paramagnetic diene 6 was prepared and proved to be a useful inter mediate in 1,4-addition, cheletropic, and Diels-Alder reactions. These meth ods were used for the synthesis of both aromatic 10, 12 heteroaromatic 15, 23 and heterocyclic ring fused nitroxide rings 7, 14, 16, 25a, 25b. The sym metric dibromo compound 20 led to homobifunctional spin label reagents 21, 22b, 24a, 24b, 27a, 27b heterobifunctional reagents 26a, 28a and to double sensor reagents 26b, 28b.