1,4,7,10-Tetraazacyclododecane was synthesized through 4 steps by using easily available diphenylsulfonium
triflate as a key annulation reagent. The reaction condition was very mild and the yield was high. After oxidation and hydrolysis,
1,4,7,10-Tetraazacyclododecane, which had been proven to be the pivotal precursor for a wide range of MRI
contrast reagents, was produced in an overall yield of 31%.