Process for mono- and 1,7-bis-N- beta -hydroxyalkylation of cyclene; N- beta -hydroxyalkyl-1,4,7,10-tetraazacyclododecane-lithium-salt complexes and the use of the complexes for the production of gadobutrol and analogs

The invention relates to the process for mono- and 1,7-bis-N- beta -hydroxyalkylation of cyclene, the corresponding mono- and 1,7-bis-N- beta -hydroxyalkyl-1,4,7,10-tetraazacyclododecane-Li-salt complexes as intermediate products in the process and the use of the N-(6-hydroxy-2,3-dimethyl-1,3-dioxepan-5-yl)-1,4,7,10-tetraazacyclododecane-LiCl complex for the production of gadobutrol [Gd ocmplex of N-(1-hydroxy-methyl-2,3-dihydroxypropyl)-1,4,7-triscarboxymethyl-1,4,7,10-tetraazacyclododecane].