Rapid Removal of Benzyloxycarbonyl Groups from 1,4,7,10-Tetraazacyclododecane Derivatives by Catalytic Transfer Hydrogenation

Abstract

We report that N-benzyloxycarbonyl groups can be conveniently removed from 1,4,7,10-tetraazacyclododecanes by catalytic transfer hydrogenation with cyclohexene and 5% palladium–carbon catalyst. The process is rapid, selective, inexpensive, and is high yielding.

Keywords:

• 1,4,7,10-Tetraazacyclododecane (cyclen)
• Catalytic transfer hydrogenation
• Benzyloxycarbonyl

Acknowledgments

The financial support of the Whitaker foundation and the Dow Chemical Company are acknowledged. Contributions from John Griffin are gratefully acknowledged.

Notes

^aAll compounds were characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, and CHN analysis.