Halogen-Free Synthesis of Carbamates from CO2 and Amines Using Titanium Alkoxides
A direct synthesis of carbamates from amines and carbon dioxide in the presence of Ti(OR)4 (R=nBu (1), Me (2), Et (3), nPr (4)) was investigated. Aniline was reacted with titanium n-butoxide (1) in the presence of carbon dioxide (5 MPa) to give the corresponding n-butyl N-phenylcarbamate (BPC) in nearly quantitative yield (99 %) within 20 min. Furthermore, 1 could be regenerated upon reaction with n-butanol during water removal. The recovered 1 could then be reused in a subsequent reaction.
N-Substituted carbamates are prepared by reacting a carbamate with an olefin in the presence of a cation exchanger containing sulfonic acid groups and of from 0.1 to 50 g of an alcohol per mole of starting material II. The N-substituted carbamates obtainable by the process of the invention are active ingredients and useful starting materials for the preparation of dyes, pesticides and drugs.
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(2008/06/13)
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