CO2-catalysed carbamation of aminofunctional silanes

Abstract

Under mild conditions (348 K), carbon dioxide (P CO = 0.1 MPa) catalytically promotes the carbamation of the following industrially relevant aminofunctional silanes: H 2 N(CH 2 ) 3 Si (OMe) 3 , H 2 N(CH 2 ) 3 Si(OEt) 3 and H 2 N(CH 2 ) 2 NH (CH 2 ) 3 Si(OMe) 3 . These, upon reaction with dimethylcarbonate, are selectively converted into the methyl carbamate esters MeO(O) CNH(CH 2 ) 3 Si(OMe) 3 , MeO(O)CNH(CH 2 ) 3 Si (OEt) 3 and MeO(O)CNH(CH 2 ) 2 NH(CH 2 ) 3 Si (OMe) 3 respectively. Carbamate MeO(O)CNH (CH 2 ) 3 Si(OEt) 3 is accompanied by MeO(O)CNH (CH 2 ) 3 Si(OMe) x (OEt) 3 - x formed via transesterification of the triethoxysilyl group by the co-produced methanol. The carbamation process is very selective and N-methylated species are formed in trace amounts. Conversely, the ureidofunctional silane H 2 NC(O)NH (CH 2 ) 2 NH(CH 2 ) 3 Si(OMe) 3 shows a poor reactivity towards carbamation, and, under the above conditions, N-methyl derivatives are preferably formed.