Cyclic carbonates have not need in activation to nucleophilic attack - they reacts mostly as 2-hydroxyalkylating agents:

http://pubs.rsc.org/en/content/articlelanding/2010/ob/c0ob00105h#!divAbstract

Urethane direction is known for non-cyclic carbonates - isolated yields with best catalyst are in order 90-95%

Dear Rogoza,

Thank you for your suggestion but I already read this article. My target is urethanes using cyclic carbonates not 2-hydroxyalkylating agents and aminoalcohols. I don't want to loss CO2...I need that for urethane synthesis.

Problem is that when I am trying to prepare urethane most of amine convert into dimer like dicyclohexylamine.

Some catalysts can activate carbonyl carbon to nucleophilic attack, have a look at

1) "Carbamate synthesis from amines and dimethyl carbonate under ytterbium triflate catalysis",Tetrahedron Letters 43 (2002) 4895–4897

2) "Catalytic Transamidation under Moderate Conditions", J. AM. CHEM. SOC. 2003, 125, 3422-3423

Thanks rogoza....

That articles didn't helped in my case...but solved my problem....with a simple metal salt...