| Abstract
| - New methods for the synthesis of 2-oxazolone-4-carboxylates from 3-nosyloxy- and 3-bromo-2-ketoesters are described. Condensation of 3-nosyloxy-2-ketoesters with methyl carbamate inrefluxing toluene in the presence of p-TSA provided 2-oxazolone-4-carboxylates in good yields (41−80%). Alternatively, bromination of α-ketoesters with CuBr2 provided 3-bromo-2-ketoesters whichcondensed with methyl carbamate in the presence of p-TSA and AgOTf under similar conditions toprovide 2-oxazolone-4-carboxylates in comparable yields (30−79%). The 2-oxazolone-4-carboxylatesbear functionality that can be elaborated to a variety of potentially useful compounds. For example,some of these heterocycles were readily N-acylated, reduced to alcohols, or saponified and coupledwith amino acids.
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