A NEW APPROACH TO THE SYNTHESIS OF 1,4,7, 10-TETRAAZACYCLODODECANE

A new and simplified method for synthesis 1,4,7,10-tetraazacyclododeca ne (cyclen) has been proposed by two steps in this paper, The first st ep deals with cyclic condensation of triethylenetetramine and diethyl oxalate in methanolic solution, giving the twelve-numbered cyclic oxam ide, i. e., 1,4,7,10-tetraazacyclododecane-2,3-dione, The pure product was obtained as a crystalline precipitate in 39% yield on addition of ethanol to the concentrated solution of the reaction mixture, Subsequ ently, in the second step, the cyclic oxamide was reduced in THF with diborane produced in situ from potassium borohydride and boron trifluo ride etherate and extracted by CH2Cl2 from the basic aqueous solution of the solvent free residue, giving cyclen in 56% yield after removing the solvent.