Abstract
An indium triflate-catalyzed synthesis of primary carbamates from alcohols and urea
as an ecofriendly carbonyl source has been developed. Various linear, branched, and
cyclic alcohols were converted into the corresponding carbamates in good to excellent
yields. This method also provided access to N-substituted ureas by carbamoylation
of amines. All the products were obtained by simple filtration or crystallization,
without the need for chromatographic purification. Mechanistic investigations suggest
that the carbamoylation reaction proceeds through activation of urea by O-coordination
with indium, followed by nucleophilic attack by the alcohol or amine on the carbonyl
center of urea. The inexpensive and easily available starting materials and catalyst,
the short reaction times, and the ease of product isolation highlight the inherent
practicality of the developed method.
Key words
carbamates - alcohols - ureas - indium catalysis - nucleophilic substitution
